draft-ietf-tsvwg-diffserv-service-classes-01.txt   draft-ietf-tsvwg-diffserv-service-classes-02.txt 
TSVWG J. Babiarz TSVWG J. Babiarz
Internet-Draft K. Chan Internet-Draft K. Chan
Expires: January 16, 2006 Nortel Networks Expires: August 20, 2006 Nortel Networks
F. Baker F. Baker
Cisco Systems Cisco Systems
July 15, 2005 February 16, 2006
Configuration Guidelines for DiffServ Service Classes Configuration Guidelines for DiffServ Service Classes
draft-ietf-tsvwg-diffserv-service-classes-01 draft-ietf-tsvwg-diffserv-service-classes-02
Status of this Memo Status of this Memo
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This Internet-Draft will expire on January 16, 2006. This Internet-Draft will expire on August 20, 2006.
Copyright Notice Copyright Notice
Copyright (C) The Internet Society (2005). Copyright (C) The Internet Society (2006).
Abstract Abstract
This paper summarizes the recommended correlation between service This document describes service classes configured with Diffserv,
classes and their usage, with references to their corresponding recommends how they can be used and how to construct them using
recommended Differentiated Service Code Points (DSCP), traffic Differentiated Service Code Points (DSCP), traffic conditioners, Per-
conditioners, Per-Hop Behaviors (PHB) and Active Queue Management Hop Behaviors (PHB), and Active Queue Management (AQM) mechanisms.
(AQM) mechanism. There is no intrinsic requirement that particular There is no intrinsic requirement that particular DSCPs, traffic
DSCPs, traffic conditioner PHBs and AQM be used for a certain service conditioners, PHBs, and AQM be used for a certain service class, but
class, but as a policy it is useful that they be applied consistently as a policy and for interoperability it is useful to apply them
across the network. consistently.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1 Requirements Notation . . . . . . . . . . . . . . . . . . 4 1.1. Requirements Notation . . . . . . . . . . . . . . . . . . 5
1.2 Expected use in the Network . . . . . . . . . . . . . . . 4 1.2. Expected use in the Network . . . . . . . . . . . . . . . 5
1.3 Service Class Definition . . . . . . . . . . . . . . . . . 5 1.3. Service Class Definition . . . . . . . . . . . . . . . . . 5
1.4 Key Differentiated Services Concepts . . . . . . . . . . . 5 1.4. Key Differentiated Services Concepts . . . . . . . . . . . 6
1.4.1 Queuing . . . . . . . . . . . . . . . . . . . . . . . 6 1.4.1. Queuing . . . . . . . . . . . . . . . . . . . . . . . 6
1.4.1.1 Priority Queuing . . . . . . . . . . . . . . . . . 6 1.4.1.1. Priority Queuing . . . . . . . . . . . . . . . . . 7
1.4.1.2 Rate Queuing . . . . . . . . . . . . . . . . . . . 6 1.4.1.2. Rate Queuing . . . . . . . . . . . . . . . . . . . 7
1.4.2 Active Queue Management . . . . . . . . . . . . . . . 7 1.4.2. Active Queue Management . . . . . . . . . . . . . . . 7
1.4.3 Traffic Conditioning . . . . . . . . . . . . . . . . . 7 1.4.3. Traffic Conditioning . . . . . . . . . . . . . . . . . 8
1.4.4 Differentiated Services Code Point (DSCP) . . . . . . 8 1.4.4. Differentiated Services Code Point (DSCP) . . . . . . 9
1.4.5 Per-Hop Behavior (PHB) . . . . . . . . . . . . . . . . 8 1.4.5. Per-Hop Behavior (PHB) . . . . . . . . . . . . . . . . 9
1.5 Key Service Concepts . . . . . . . . . . . . . . . . . . . 8 1.5. Key Service Concepts . . . . . . . . . . . . . . . . . . . 9
1.5.1 Default Forwarding (DF) . . . . . . . . . . . . . . . 9 1.5.1. Default Forwarding (DF) . . . . . . . . . . . . . . . 9
1.5.2 Assured Forwarding (AF) . . . . . . . . . . . . . . . 9 1.5.2. Assured Forwarding (AF) . . . . . . . . . . . . . . . 10
1.5.3 Expedited Forwarding (EF) . . . . . . . . . . . . . . 10 1.5.3. Expedited Forwarding (EF) . . . . . . . . . . . . . . 10
1.5.4 Class Selector (CS) . . . . . . . . . . . . . . . . . 10 1.5.4. Class Selector (CS) . . . . . . . . . . . . . . . . . 11
1.5.5 Admission Control . . . . . . . . . . . . . . . . . . 11 1.5.5. Admission Control . . . . . . . . . . . . . . . . . . 11
2. Service Differentiation . . . . . . . . . . . . . . . . . . . 11 2. Service Differentiation . . . . . . . . . . . . . . . . . . . 12
2.1 Service Classes . . . . . . . . . . . . . . . . . . . . . 11 2.1. Service Classes . . . . . . . . . . . . . . . . . . . . . 12
2.2 Categorization of User Service Classes . . . . . . . . . . 13 2.2. Categorization of User Service Classes . . . . . . . . . . 13
2.3 Service Class Characteristics . . . . . . . . . . . . . . 16 2.3. Service Class Characteristics . . . . . . . . . . . . . . 17
2.4 Deployment Scenarios . . . . . . . . . . . . . . . . . . . 21 2.4. Deployment Scenarios . . . . . . . . . . . . . . . . . . . 22
2.4.1 Example 1 . . . . . . . . . . . . . . . . . . . . . . 21 2.4.1. Example 1 . . . . . . . . . . . . . . . . . . . . . . 22
2.4.2 Example 2 . . . . . . . . . . . . . . . . . . . . . . 22 2.4.2. Example 2 . . . . . . . . . . . . . . . . . . . . . . 23
2.4.3 Example 3 . . . . . . . . . . . . . . . . . . . . . . 25 2.4.3. Example 3 . . . . . . . . . . . . . . . . . . . . . . 26
3. Network Control Traffic . . . . . . . . . . . . . . . . . . . 27 3. Network Control Traffic . . . . . . . . . . . . . . . . . . . 27
3.1 Current Practice in The Internet . . . . . . . . . . . . . 27 3.1. Current Practice in The Internet . . . . . . . . . . . . . 28
3.2 Network Control Service Class . . . . . . . . . . . . . . 27 3.2. Network Control Service Class . . . . . . . . . . . . . . 28
3.3 OAM Service Class . . . . . . . . . . . . . . . . . . . . 29 3.3. OAM Service Class . . . . . . . . . . . . . . . . . . . . 30
4. User Traffic . . . . . . . . . . . . . . . . . . . . . . . . . 30 4. User Traffic . . . . . . . . . . . . . . . . . . . . . . . . . 31
4.1 Telephony Service Class . . . . . . . . . . . . . . . . . 31 4.1. Telephony Service Class . . . . . . . . . . . . . . . . . 32
4.2 Signaling Service Class . . . . . . . . . . . . . . . . . 32 4.2. Signaling Service Class . . . . . . . . . . . . . . . . . 33
4.3 Multimedia Conferencing Service Class . . . . . . . . . . 34 4.3. Multimedia Conferencing Service Class . . . . . . . . . . 35
4.4 Real-time Interactive Service Class . . . . . . . . . . . 37 4.4. Real-time Interactive Service Class . . . . . . . . . . . 38
4.5 Multimedia Streaming Service Class . . . . . . . . . . . . 38 4.5. Multimedia Streaming Service Class . . . . . . . . . . . . 39
4.6 Broadcast Video Service Class . . . . . . . . . . . . . . 40 4.6. Broadcast Video Service Class . . . . . . . . . . . . . . 41
4.7 Low Latency Data Service Class . . . . . . . . . . . . . . 42 4.7. Low Latency Data Service Class . . . . . . . . . . . . . . 43
4.8 High Throughput Data Service Class . . . . . . . . . . . . 44 4.8. High Throughput Data Service Class . . . . . . . . . . . . 45
4.9 Standard Service Class . . . . . . . . . . . . . . . . . . 46 4.9. Standard Service Class . . . . . . . . . . . . . . . . . . 47
4.10 Low Priority Data . . . . . . . . . . . . . . . . . . . . 47 4.10. Low Priority Data . . . . . . . . . . . . . . . . . . . . 48
5. Additional Information on Service Class Usage . . . . . . . . 48 5. Additional Information on Service Class Usage . . . . . . . . 49
5.1 Mapping for Signaling . . . . . . . . . . . . . . . . . . 48 5.1. Mapping for Signaling . . . . . . . . . . . . . . . . . . 49
5.2 Mapping for NTP . . . . . . . . . . . . . . . . . . . . . 48 5.2. Mapping for NTP . . . . . . . . . . . . . . . . . . . . . 49
5.3 VPN Service Mapping . . . . . . . . . . . . . . . . . . . 49 5.3. VPN Service Mapping . . . . . . . . . . . . . . . . . . . 50
6. Security Considerations . . . . . . . . . . . . . . . . . . . 49 6. Security Considerations . . . . . . . . . . . . . . . . . . . 50
7. Summary of Changes from Previous Draft . . . . . . . . . . . . 50 7. Summary of Changes from Previous Version . . . . . . . . . . . 51
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 51 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 54
9. Appendix A . . . . . . . . . . . . . . . . . . . . . . . . . . 51 9. Appendix A . . . . . . . . . . . . . . . . . . . . . . . . . . 54
9.1 Explanation of Ring Clipping . . . . . . . . . . . . . . . 51 9.1. Explanation of Ring Clipping . . . . . . . . . . . . . . . 54
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 52 10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 55
10.1 Normative References . . . . . . . . . . . . . . . . . . . 52 10.1. Normative References . . . . . . . . . . . . . . . . . . . 55
10.2 Informative References . . . . . . . . . . . . . . . . . . 53 10.2. Informative References . . . . . . . . . . . . . . . . . . 56
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 54 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 58
Intellectual Property and Copyright Statements . . . . . . . . 56 Intellectual Property and Copyright Statements . . . . . . . . . . 59
1. Introduction 1. Introduction
This paper summarizes the recommended correlation between service For understanding the role of this document we use an useful analogy,
classes and their usage, with references to their corresponding starting from the fact that the Differentiated Services
recommended Differentiated Service Code Points (DSCP), traffic specifications are fundamentally a toolkit - the specifications
conditioners, Per-Hop Behaviors (PHB) and Active Queue Management provide the equivalent of band saws, planers, drill presses, etc. In
(AQM) mechanisms. There is no intrinsic requirement that particular the hands of an expert, there's no limit to what can be built, but
DSCPs, traffic conditioner PHBs and AQM be used for a certain service such a toolkit can be intimidating to the point of inaccessible to a
class, but as a policy it is useful that they be applied consistently non-expert who just wants to build a bookcase. This document should
across the network. be viewed as a set of "project plans" for building all the (diffserv)
furniture that one might want. The user may choose what to build
(e.g., perhaps our non-expert doesn't need a china cabinet right
now), and how to go about building it (e.g., plans for a non-expert
probably won't employ mortise/tenon construction, but that absence
does not imply that mortise/tenon construction is forbidden or
unsound). The authors hope that these diffserv "project plans" will
provide a useful guide to Network Administrators in the use of
diffserv techniques to implement quality of service measures
appropriate for their network's traffic.
This document describes service classes configured with Diffserv,
recommends how they can be used and how to construct them using
Differentiated Service Code Points (DSCP), traffic conditioners, Per-
Hop Behaviors (PHB), and Active Queue Management (AQM) mechanisms.
There is no intrinsic requirement that particular DSCPs, traffic
conditioners, PHBs, and AQM be used for a certain service class, but
as a policy and for interoperability it is useful to apply them
consistently.
Service classes are defined based on the different traffic Service classes are defined based on the different traffic
characteristics and required performance of the applications/ characteristics and required performance of the applications/
services. This approach allows us to map current and future services. This approach allows us to map current and future
applications/services of similar traffic characteristics and applications/services of similar traffic characteristics and
performance requirements into the same service class. Since the performance requirements into the same service class. Since the
applications'/services' characteristics and required performance are applications'/services' characteristics and required performance are
end to end, the service class notion needs to be preserved end to end to end, the service class notion needs to be preserved end to
end. With this approach, a limited set of service classes is end. With this approach, a limited set of service classes is
required. For completeness, we have defined twelve different service required. For completeness, we have defined twelve different service
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are used for service differentiation in IP networks. Section 2, is are used for service differentiation in IP networks. Section 2, is
an overview of how service classes are constructed to provide service an overview of how service classes are constructed to provide service
differentiation with examples of deployment scenarios. Section 3, differentiation with examples of deployment scenarios. Section 3,
provides configuration guidelines of service classes that are used provides configuration guidelines of service classes that are used
for stable operation and administration of the network. Section 4, for stable operation and administration of the network. Section 4,
provides configuration guidelines of service classes that are used provides configuration guidelines of service classes that are used
for differentiation of user/subscriber traffic. Section 5, provides for differentiation of user/subscriber traffic. Section 5, provides
additional guidance on mapping different applications/protocol to additional guidance on mapping different applications/protocol to
service classes. Section 6, address security considerations. service classes. Section 6, address security considerations.
1.1 Requirements Notation 1.1. Requirements Notation
The key words "SHOULD", "SHOULD NOT", "REQUIRED", "SHALL", "SHALL The key words "SHOULD", "SHOULD NOT", "REQUIRED", "SHALL", "SHALL
NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in
this document are to be interpreted as described in [RFC2119]. this document are to be interpreted as described in [RFC2119].
1.2 Expected use in the Network 1.2. Expected use in the Network
In the Internet today, corporate LANs and ISP WANs are generally not In the Internet today, corporate LANs and ISP WANs are generally not
heavily utilized - they are commonly 10% utilized at most. For this heavily utilized - they are commonly 10% utilized at most. For this
reason, congestion, loss, and variation in delay within corporate reason, congestion, loss, and variation in delay within corporate
LANs and ISP backbones is virtually unknown. This clashes with user LANs and ISP backbones is virtually unknown. This clashes with user
perceptions, for three very good reasons. perceptions, for three very good reasons.
o The industry moves through cycles of bandwidth boom and bandwidth o The industry moves through cycles of bandwidth boom and bandwidth
bust, depending on prevailing market conditions and the periodic bust, depending on prevailing market conditions and the periodic
deployment of new bandwidth-hungry applications. deployment of new bandwidth-hungry applications.
o In access networks, the state is often different. This may be o In access networks, the state is often different. This may be
because throughput rates are artificially limited, or are over because throughput rates are artificially limited, or are over
subscribed, or because of access network design trade-offs. subscribed, or because of access network design trade-offs.
o Other characteristics, such as database design on web servers o Other characteristics, such as database design on web servers
(that may create contention points, e.g. in filestore), and (that may create contention points, e.g. in filestore), and
configuration of firewalls and routers, often look externally like configuration of firewalls and routers, often look externally like
a bandwidth limitation. a bandwidth limitation.
The intent of this document is to provide a consistent marking, The intent of this document is to provide a consistent marking,
conditioning and packet treatment strategy so that it can be conditioning, and packet treatment strategy so that it can be
configured and put into service on any link which itself is configured and put into service on any link which itself is
congested. congested.
1.3 Service Class Definition 1.3. Service Class Definition
A "service class" represents a set of traffic that requires specific A "service class" represents a set of traffic that requires specific
delay, loss and jitter characteristics from the network for which a delay, loss, and jitter characteristics from the network.
consistent and defined per-hop behavior (PHB) [RFC2474] applies.
Conceptually, a service class pertains to applications with similar Conceptually, a service class pertains to applications with similar
characteristics and performance requirements, such as a "High characteristics and performance requirements, such as a "High
Throughput Data" service class for applications like the web and Throughput Data" service class for applications like the web and
electronic mail, or a "Telephony" service class for real-time traffic electronic mail, or a "Telephony" service class for real-time traffic
such as voice and other telephony services. Such service class may such as voice and other telephony services. Such service class may
be defined locally in a Differentiated Services domain, or across be defined locally in a Differentiated Services domain, or across
multiple DS domains, including possibly extending end to end. multiple DS domains, including possibly extending end to end.
A Service Class as defined here is essentially a statement of the A service class as defined here is essentially a statement of the
required characteristics of a traffic aggregate; the actual required characteristics of a traffic aggregate. The required
characteristics of these traffic aggregates can be realized by the
use of defined per-hop behavior (PHB) [RFC2474]. The actual
specification of the expected treatment of a traffic aggregate within specification of the expected treatment of a traffic aggregate within
a domain may also be defined as a Per Domain Behavior [RFC3086]. a domain may also be defined as a per domain behavior (PDB)
[RFC3086].
Each domain may choose to implement different service classes, or use
different behaviors to implement the service classes, or aggregate
different kinds of traffic into the aggregates and still achieve
their required characteristics. For example, low delay, loss, and
jitter may be realized using the EF PHB, or with an over provisioned
AF PHB. This must be done with care as it may disrupt the end to end
performance required by the applications/services. This document
provides recommendations on usage of PHBs for specific service
classes for their consistent implementation, these recommendations
are not to be construed as prohibiting use of other PHBs that realize
behaviors sufficient for the relevant class of traffic.
The Default Forwarding "Standard" service class is REQUIRED, all The Default Forwarding "Standard" service class is REQUIRED, all
other service classes are OPTIONAL. It is expected that network other service classes are OPTIONAL. It is expected that network
administrators will choose the level of service differentiation that administrators will choose the level of service differentiation that
they will support based on their need, starting off with three or they will support based on their need, starting off with three or
four service classes for user traffic and add others as the need four service classes for user traffic and add others as the need
arises. arises.
1.4 Key Differentiated Services Concepts 1.4. Key Differentiated Services Concepts
The reader SHOULD be familiar with the principles of the The reader SHOULD be familiar with the principles of the
Differentiated Services Architecture [RFC2474]. However, we Differentiated Services Architecture [RFC2474]. We recapitulate key
recapitulate key concepts here to save searching. concepts here only to provide convenience for the reader, with the
referenced RFCs providing the authoritative definitions.
1.4.1 Queuing 1.4.1. Queuing
A queue is a data structure that holds packets that are awaiting A queue is a data structure that holds packets that are awaiting
transmission. The packets may be delayed while in the queue, transmission. The packets may be delayed while in the queue,
possibly due to lack of bandwidth, or because it is low in priority. possibly due to lack of bandwidth, or because it is low in priority.
There are a number of ways to implement a queue, a simple model of a There are a number of ways to implement a queue, a simple model of a
queuing system, however, is a set of data structures for packet data, queuing system, however, is a set of data structures for packet data,
which we will call queues and a mechanism for selecting the next which we will call queues and a mechanism for selecting the next
packet from among them, which we call a scheduler. packet from among them, which we call a scheduler.
1.4.1.1 Priority Queuing 1.4.1.1. Priority Queuing
A priority queuing system is a combination of a set of queues and a A priority queuing system is a combination of a set of queues and a
scheduler that empties them in priority sequence. When asked for a scheduler that empties them in priority sequence. When asked for a
packet, the scheduler inspects the highest priority queue, and if packet, the scheduler inspects the highest priority queue, and if
there is data present returns a packet from that queue. Failing there is data present returns a packet from that queue. Failing
that, it inspects the next highest priority queue, and so on. A that, it inspects the next highest priority queue, and so on. A
freeway onramp with a stoplight for one lane, but which allows freeway onramp with a stoplight for one lane, but which allows
vehicles in the high occupancy vehicle lane to pass, is an example of vehicles in the high occupancy vehicle lane to pass, is an example of
a priority queuing system; the high occupancy vehicle lane represents a priority queuing system; the high occupancy vehicle lane represents
the "queue" having priority. the "queue" having priority.
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the amount of data remaining to be serialized when the packet arrived the amount of data remaining to be serialized when the packet arrived
plus the volume of the data already queued ahead of it in the same plus the volume of the data already queued ahead of it in the same
queue. The technical reason for using a priority queue relates queue. The technical reason for using a priority queue relates
exactly to this fact: it limits delay and variations in delay, and exactly to this fact: it limits delay and variations in delay, and
should be used for traffic which has that requirement. should be used for traffic which has that requirement.
A priority queue or queuing system needs to avoid starvation of lower A priority queue or queuing system needs to avoid starvation of lower
priority queues. This may be achieved through a variety of means priority queues. This may be achieved through a variety of means
such as admission control, rate control, or network engineering. such as admission control, rate control, or network engineering.
1.4.1.2 Rate Queuing 1.4.1.2. Rate Queuing
Similarly, a rate-based queuing system is a combination of a set of Similarly, a rate-based queuing system is a combination of a set of
queues and a scheduler that empties each at a specified rate. An queues and a scheduler that empties each at a specified rate. An
example of a rate based queuing system is a road intersection with a example of a rate based queuing system is a road intersection with a
stoplight - the stoplight acts as a scheduler, giving each lane a stoplight - the stoplight acts as a scheduler, giving each lane a
certain opportunity to pass traffic through the intersection. certain opportunity to pass traffic through the intersection.
In a rate-based queuing system, such as WFQ or WRR, the delay that a In a rate-based queuing system, such as WFQ or WRR, the delay that a
packet in any given queue will experience is dependant on the packet in any given queue will experience is dependant on the
parameters and occupancy of its queue and the parameters and parameters and occupancy of its queue and the parameters and
occupancy of the queues it is competing with. A queue whose traffic occupancy of the queues it is competing with. A queue whose traffic
arrival rate is much less than the rate at which it lets traffic arrival rate is much less than the rate at which it lets traffic
depart will tend to be empty and packets in it will experience depart will tend to be empty and packets in it will experience
nominal delays. A queue whose traffic arrival rate approximates or nominal delays. A queue whose traffic arrival rate approximates or
exceeds its departure rate will tend to be not empty, and packets in exceeds its departure rate will tend to be not empty, and packets in
it will experience greater delay. Such a scheduler can impose a it will experience greater delay. Such a scheduler can impose a
minimum rate, a maximum rate, or both, on any queue it touches. minimum rate, a maximum rate, or both, on any queue it touches.
1.4.2 Active Queue Management 1.4.2. Active Queue Management
"Active queue management" or AQM is a generic name for any of a "Active queue management" or AQM is a generic name for any of a
variety of procedures that use packet dropping or marking to manage variety of procedures that use packet dropping or marking to manage
the depth of a queue. The canonical example of such a procedure is the depth of a queue. The canonical example of such a procedure is
Random Early Detection, in that a queue is assigned a minimum and Random Early Detection, in that a queue is assigned a minimum and
maximum threshold, and the queuing algorithm maintains a moving maximum threshold, and the queuing algorithm maintains a moving
average of the queue depth. While the mean queue depth exceeds the average of the queue depth. While the mean queue depth exceeds the
maximum threshold, all arriving traffic is dropped. While the mean maximum threshold, all arriving traffic is dropped. While the mean
queue depth exceeds the minimum threshold but not the maximum queue depth exceeds the minimum threshold but not the maximum
threshold, a randomly selected subset of arriving traffic is marked threshold, a randomly selected subset of arriving traffic is marked
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approximate the minimum threshold. approximate the minimum threshold.
A variation of the algorithm is applied in Assured Forwarding PHB A variation of the algorithm is applied in Assured Forwarding PHB
[RFC2597], in that the behavior aggregate consists of traffic with [RFC2597], in that the behavior aggregate consists of traffic with
multiple DSCP marks, which are intermingled in a common queue. multiple DSCP marks, which are intermingled in a common queue.
Different minima and maxima are configured for the several DSCPs Different minima and maxima are configured for the several DSCPs
separately, such that traffic that exceeds a stated rate at ingress separately, such that traffic that exceeds a stated rate at ingress
is more likely to be dropped or marked than traffic that is within is more likely to be dropped or marked than traffic that is within
its contracted rate. its contracted rate.
1.4.3 Traffic Conditioning 1.4.3. Traffic Conditioning
Additionally, at the first router in a network that a packet crosses, Additionally, at the first router in a network that a packet crosses,
arriving traffic may be measured, and dropped or marked according to arriving traffic may be measured, and dropped or marked according to
a policy, or perhaps shaped on network ingress as in A Rate Adaptive a policy, or perhaps shaped on network ingress as in A Rate Adaptive
Shaper for Differentiated Services [RFC2963]. This may be used to Shaper for Differentiated Services [RFC2963]. This may be used to
bias feedback loops, such as is done in Assured Forwarding PHB bias feedback loops, such as is done in Assured Forwarding PHB
[RFC2597], or to limit the amount of traffic in a system, as is done [RFC2597], or to limit the amount of traffic in a system, as is done
in Expedited Forwarding PHB [RFC3246]. Such measurement procedures in Expedited Forwarding PHB [RFC3246]. Such measurement procedures
are collectively referred to as "traffic conditioners". Traffic are collectively referred to as "traffic conditioners". Traffic
conditioners are normally built using token bucket meters, for conditioners are normally built using token bucket meters, for
skipping to change at page 8, line 14 skipping to change at page 8, line 49
bucket meter to achieve multiple levels of conformance used by bucket meter to achieve multiple levels of conformance used by
Assured Forwarding PHB [RFC2597]. Multiple rates and burst sizes can Assured Forwarding PHB [RFC2597]. Multiple rates and burst sizes can
be realized using multiple levels of token buckets or more complex be realized using multiple levels of token buckets or more complex
token buckets, these are implementation details. Some traffic token buckets, these are implementation details. Some traffic
conditioners that may be used in deployment of differentiated conditioners that may be used in deployment of differentiated
services are: services are:
o For Class Selector (CS) PHBs, a single token bucket meter to o For Class Selector (CS) PHBs, a single token bucket meter to
provide a rate plus burst size control provide a rate plus burst size control
o For Expedited Forwarding (EF) PHB, a single token bucket meter to o For Expedited Forwarding (EF) PHB, a single token bucket meter to
provide a rate plus burst size control provide a rate plus burst size control
o For Assured Forwarding (AF) PHBs, usually two token buckets meters o For Assured Forwarding (AF) PHBs, usually two token bucket meters
configured to provide behavior as outlined in Two Rate Three Color configured to provide behavior as outlined in Two Rate Three Color
Marker (trTCM) [RFC2698] or the Single Rate Three Color Marker Marker (trTCM) [RFC2698] or the Single Rate Three Color Marker
(srTCM) [RFC2697]. The two rate three color marker is used to (srTCM) [RFC2697]. The two rate three color marker is used to
enforce two rates whereas, the single rate three color marker is enforce two rates whereas, the single rate three color marker is
used to enforce a committed rate with two burst lengths. used to enforce a committed rate with two burst lengths.
1.4.4 Differentiated Services Code Point (DSCP) 1.4.4. Differentiated Services Code Point (DSCP)
The DSCP is a number in the range 0..63, that is placed into an IP The DSCP is a number in the range 0..63, that is placed into an IP
packet to mark it according to the class of traffic it belongs in. packet to mark it according to the class of traffic it belongs in.
Half of these values are earmarked for standardized services, and the Half of these values are earmarked for standardized services, and the
other half of them are available for local definition. other half of them are available for local definition.
1.4.5 Per-Hop Behavior (PHB) 1.4.5. Per-Hop Behavior (PHB)
In the end, the mechanisms described above are combined to form a In the end, the mechanisms described above are combined to form a
specified set of characteristics for handling different kinds of specified set of characteristics for handling different kinds of
traffic, depending on the needs of the application. This document traffic, depending on the needs of the application. This document
seeks to identify useful traffic aggregates and specify what PHB seeks to identify useful traffic aggregates and specify what PHB
should be applied to them. should be applied to them.
1.5 Key Service Concepts 1.5. Key Service Concepts
While Differentiated Services is a general architecture that may be While Differentiated Services is a general architecture that may be
used to implement a variety of services, three fundamental forwarding used to implement a variety of services, three fundamental forwarding
behaviors have been defined and characterized for general use. These behaviors have been defined and characterized for general use. These
are basic Default Forwarding (DF) behavior for elastic traffic, the are basic Default Forwarding (DF) behavior for elastic traffic, the
Assured Forwarding (AF) behavior, and the Expedited Forwarding (EF) Assured Forwarding (AF) behavior, and the Expedited Forwarding (EF)
behavior for real-time (inelastic) traffic. The facts that four code behavior for real-time (inelastic) traffic. The facts that four code
points are recommended for AF, and that one code point is recommended points are recommended for AF, and that one code point is recommended
for EF, are arbitrary choices, and the architecture allows any for EF, are arbitrary choices, and the architecture allows any
reasonable number of AF and EF classes simultaneously. The choice of reasonable number of AF and EF classes simultaneously. The choice of
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arbitrary, and operators MAY choose to operate more or fewer of arbitrary, and operators MAY choose to operate more or fewer of
either. either.
The terms "elastic" and "real-time" are defined in [RFC1633] Section The terms "elastic" and "real-time" are defined in [RFC1633] Section
3.1, as a way of understanding broad brush application requirements. 3.1, as a way of understanding broad brush application requirements.
This document should be reviewed to obtain a broad understanding of This document should be reviewed to obtain a broad understanding of
the issues in quality of service, just as [RFC2475] should be the issues in quality of service, just as [RFC2475] should be
reviewed to understand the data plane architecture used in today's reviewed to understand the data plane architecture used in today's
Internet. Internet.
1.5.1 Default Forwarding (DF) 1.5.1. Default Forwarding (DF)
The basic forwarding behavior applied to any class of traffic are The basic forwarding behavior applied to any class of traffic are
those described in [RFC2474] and [RFC2309]. Best Effort service may those described in [RFC2474] and [RFC2309]. Best Effort service may
be summarized as "I will accept your packets", and is typically be summarized as "I will accept your packets", and is typically
configured with some bandwidth guarantee. Packets in transit may be configured with some bandwidth guarantee. Packets in transit may be
lost, reordered, duplicated, or delayed at random. Generally, lost, reordered, duplicated, or delayed at random. Generally,
networks are engineered to limit this behavior, but changing traffic networks are engineered to limit this behavior, but changing traffic
loads can push any network into such a state. loads can push any network into such a state.
Application traffic in the internet which uses default forwarding is Application traffic in the internet which uses default forwarding is
expected to be "elastic" in nature. By this, we mean that the sender expected to be "elastic" in nature. By this, we mean that the sender
of traffic will adjust its transmission rate in response to changes of traffic will adjust its transmission rate in response to changes
in available rate, loss, or delay. in available rate, loss, or delay.
For the basic best effort service, a single DSCP value is provided to For the basic best effort service, a single DSCP value is provided to
identify the traffic, a queue to store it, and active queue identify the traffic, a queue to store it, and active queue
management to protect the network from it and to limit delays. management to protect the network from it and to limit delays.
1.5.2 Assured Forwarding (AF) 1.5.2. Assured Forwarding (AF)
The Assured Forwarding PHB [RFC2597] behavior is explicitly modeled The Assured Forwarding PHB [RFC2597] behavior is explicitly modeled
on Frame Relay's DE flag or ATM's CLP capability, and is intended for on Frame Relay's DE flag or ATM's CLP capability, and is intended for
networks that offer average-rate SLAs (as FR and ATM networks do). networks that offer average-rate SLAs (as FR and ATM networks do).
This is an enhanced best effort service; traffic is expected to be This is an enhanced best effort service; traffic is expected to be
"elastic" in nature. The receiver will detect loss or variation in "elastic" in nature. The receiver will detect loss or variation in
delay in the network and provide feedback such that the sender delay in the network and provide feedback such that the sender
adjusts its transmission rate to approximate available capacity. adjusts its transmission rate to approximate available capacity.
For such behaviors, multiple DSCP values are provided (two or three, For such behaviors, multiple DSCP values are provided (two or three,
perhaps more using local values) to identify the traffic, a common perhaps more using local values) to identify the traffic, a common
queue to store the aggregate and active queue management to protect queue to store the aggregate and active queue management to protect
the network from it and to limit delays. Traffic is metered as it the network from it and to limit delays. Traffic is metered as it
enters the network, and traffic is variously marked depending on the enters the network, and traffic is variously marked depending on the
arrival rate of the aggregate. The premise is that it is normal for arrival rate of the aggregate. The premise is that it is normal for
users to occasionally use more capacity than their contract users to occasionally use more capacity than their contract
stipulates, perhaps up to some bound. However, if traffic SHOULD be stipulates, perhaps up to some bound. However, if traffic should be
lost or marked to manage the queue, this excess traffic will be marked or lost to manage the queue, this excess traffic will be
marked or lost first. marked or lost first.
1.5.3 Expedited Forwarding (EF) 1.5.3. Expedited Forwarding (EF)
Expedited Forwarding PHB [RFC3246] behavior was originally proposed The intent of Expedited Forwarding PHB [RFC3246] is to provide a
as a way to implement a virtual wire, and can be used in such a building block for low loss, low delay, and low jitter services. It
manner. It is an enhanced best effort service: traffic remains can be used to build an enhanced best effort service: traffic remains
subject to loss due to line errors and reordering during routing subject to loss due to line errors and reordering during routing
changes. However, using queuing techniques, the probability of delay changes. However, using queuing techniques, the probability of delay
or variation in delay is minimized. For this reason, it is generally or variation in delay is minimized. For this reason, it is generally
used to carry voice and for transport of data information that used to carry voice and for transport of data information that
requires "wire like" behavior through the IP network. Voice is an requires "wire like" behavior through the IP network. Voice is an
inelastic "real-time" application that sends packets at the rate the inelastic "real-time" application that sends packets at the rate the
codec produces them, regardless of availability of capacity. As codec produces them, regardless of availability of capacity. As
such, this service has the potential to disrupt or congest a network such, this service has the potential to disrupt or congest a network
if not controlled. It also has the potential for abuse. if not controlled. It also has the potential for abuse.
To protect the network, at minimum one SHOULD police traffic at To protect the network, at minimum one SHOULD police traffic at
various points to ensure that the design of a queue is not over-run, various points to ensure that the design of a queue is not over-run,
and then the traffic SHOULD be given a low delay queue (often using and then the traffic SHOULD be given a low delay queue (often using
priority, although it is asserted that a rate-based queue can do priority, although it is asserted that a rate-based queue can do
this) to ensure that variation in delay is not an issue, to meet this) to ensure that variation in delay is not an issue, to meet
application needs. application needs.
1.5.4 Class Selector (CS) 1.5.4. Class Selector (CS)
Class Selector provides support for historical codepoint definitions Class Selector provides support for historical codepoint definitions
and PHB requirement. The Class Selector DS field provides a limited and PHB requirement. The Class Selector DS field provides a limited
backward compatibility with legacy (pre DiffServ) practice, as backward compatibility with legacy (pre DiffServ) practice, as
described in [RFC2474] Section 4. Backward compatibility is described in [RFC2474] Section 4. Backward compatibility is
addressed in two ways. First, there are per-hop behaviors that are addressed in two ways. First, there are per-hop behaviors that are
already in widespread use (e.g. those satisfying the IPv4 Precedence already in widespread use (e.g. those satisfying the IPv4 Precedence
queuing requirements specified in [RFC1812], and we wish to permit queuing requirements specified in [RFC1812], and we wish to permit
their continued use in DS-compliant networks. In addition, there are their continued use in DS-compliant networks. In addition, there are
some codepoints that correspond to historical use of the IP some codepoints that correspond to historical use of the IP
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or TOS bits of the IPv4 TOS octet, as defined in [RFC0791]and or TOS bits of the IPv4 TOS octet, as defined in [RFC0791]and
[RFC1349]. [RFC1349].
A DS-compliant network can be deployed with a set of one or more A DS-compliant network can be deployed with a set of one or more
Class Selector compliant PHB groups. As well, network administrator Class Selector compliant PHB groups. As well, network administrator
may configure the network nodes to map codepoints to PHBs may configure the network nodes to map codepoints to PHBs
irrespective of bits 3-5 of the DSCP field to yield a network that is irrespective of bits 3-5 of the DSCP field to yield a network that is
compatible with historical IP Precedence use. Thus, for example, compatible with historical IP Precedence use. Thus, for example,
codepoint '011000' would map to the same PHB as codepoint '011010'. codepoint '011000' would map to the same PHB as codepoint '011010'.
1.5.5 Admission Control 1.5.5. Admission Control
Admission control including refusal when policy thresholds are Admission control including refusal when policy thresholds are
crossed, can assure high quality communication by ensuring the crossed, can assure high quality communication by ensuring the
availability of bandwidth to carry a load. Inelastic real-time flows availability of bandwidth to carry a load. Inelastic real-time flows
like VoIP (telephony) or video conferencing services can benefit from like VoIP (telephony) or video conferencing services can benefit from
use of admission control mechanism, as generally the telephony use of admission control mechanism, as generally the telephony
service is configured with over subscription, meaning that some service is configured with over subscription, meaning that some
user(s) may not be able to make a call during peak periods. user(s) may not be able to make a call during peak periods.
For VoIP (telephony) service, a common approach is to use signaling For VoIP (telephony) service, a common approach is to use signaling
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support to provide the appropriate level of behaviors and performance support to provide the appropriate level of behaviors and performance
needed by current and future applications and services. The defined needed by current and future applications and services. The defined
structure for providing services allows several applications having structure for providing services allows several applications having
similar traffic characteristics and performance requirements to be similar traffic characteristics and performance requirements to be
grouped into the same service class. This approach provides a lot of grouped into the same service class. This approach provides a lot of
flexibility in providing the appropriate level of service flexibility in providing the appropriate level of service
differentiation for current and new yet unknown applications without differentiation for current and new yet unknown applications without
introducing significant changes to routers or network configurations introducing significant changes to routers or network configurations
when a new traffic type is added to the network. when a new traffic type is added to the network.
2.1 Service Classes 2.1. Service Classes
Traffic flowing in a network can be classified in many different Traffic flowing in a network can be classified in many different
ways. We have chosen to divide it into two groupings, network ways. We have chosen to divide it into two groupings, network
control and user/subscriber traffic. To provide service control and user/subscriber traffic. To provide service
differentiation, different service classes are defined in each differentiation, different service classes are defined in each
grouping. The network control traffic group can further be divided grouping. The network control traffic group can further be divided
into two service classes (see Section 3 for detailed definition of into two service classes (see Section 3 for detailed definition of
each service class): each service class):
o "Network Control" for routing and network control function. o "Network Control" for routing and network control function.
o "OAM" (Operations, Administration and Management) for network o "OAM" (Operations, Administration and Management) for network
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broadcast TV and live events, video surveillance and security. broadcast TV and live events, video surveillance and security.
o Low Latency Data service class is best suited for data processing o Low Latency Data service class is best suited for data processing
applications where a human is waiting for output, such as web- applications where a human is waiting for output, such as web-
based ordering, Enterprise Resource Planning (ERP) application, based ordering, Enterprise Resource Planning (ERP) application,
etc. etc.
o High Throughput Data service class is best suited for store and o High Throughput Data service class is best suited for store and
forward applications such as FTP, billing record transfer, etc. forward applications such as FTP, billing record transfer, etc.
o Standard service class is for traffic that has not been identified o Standard service class is for traffic that has not been identified
as requiring differentiated treatment and is normally referred as as requiring differentiated treatment and is normally referred as
best effort. best effort.
o Low Priority Data service class is intended for packet flows where o Low Priority Data service class is intended for packet flows where
bandwidth assurance is not required. bandwidth assurance is not required.
2.2 Categorization of User Service Classes 2.2. Categorization of User Service Classes
The ten defined user/subscriber services classes listed above can be The ten defined user/subscriber service classes listed above can be
grouped into a small number of application categories. For some grouped into a small number of application categories. For some
application categories, it was felt that more than one service class application categories, it was felt that more than one service class
was needed to provide service differentiation within that category was needed to provide service differentiation within that category
due to the different traffic characteristic of the applications, due to the different traffic characteristic of the applications,
control function and the required flow behavior. Figure 1 provides control function and the required flow behavior. Figure 1 provides
summary of service class grouping into four application categories. summary of service class grouping into four application categories.
Application Control category: Application Control category:
o The Signaling service class is intended to be used to control o The Signaling service class is intended to be used to control
applications or user endpoints. Examples of protocols that would applications or user endpoints. Examples of protocols that would
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and SIP or IGMP for control of broadcast TV service to and SIP or IGMP for control of broadcast TV service to
subscribers. Although user signaling flows have similar subscribers. Although user signaling flows have similar
performance requirements as Low Latency Data they need to be performance requirements as Low Latency Data they need to be
distinguished and marked with a different DSCP. The essential distinguished and marked with a different DSCP. The essential
distinction is something like "administrative control and distinction is something like "administrative control and
management" of the traffic affected as the protocols in this class management" of the traffic affected as the protocols in this class
tend to be tied to the media stream/session they signal and tend to be tied to the media stream/session they signal and
control. control.
Media-Oriented category: Due to the vest number of new (in process of Media-Oriented category: Due to the vest number of new (in process of
being deployed) and already in uses media-oriented services in IP being deployed) and already in use media-oriented services in IP
networks, five service classes have been defined. networks, five service classes have been defined.
o Telephony service class is intended for IP telephony (VoIP) o Telephony service class is intended for IP telephony (VoIP)
service as well it may be used for other applications that meet service as well it may be used for other applications that meet
the defined traffic characteristics and performance requirements. the defined traffic characteristics and performance requirements.
o Real-time Interactive service class is intended for inelastic o Real-time Interactive service class is intended for inelastic
video flows from such application like SIP based desktop video video flows from such application like SIP based desktop video
conferencing applications and for interactive gaming. conferencing applications and for interactive gaming.
o Multimedia Conferencing service class is for video conferencing o Multimedia Conferencing service class is for video conferencing
solutions that have the ability to reduce their transmission rate solutions that have the ability to reduce their transmission rate
on detection of congestion, therefore these flows can be on detection of congestion, therefore these flows can be
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classified as rate adaptive. As currently there are both types of classified as rate adaptive. As currently there are both types of
video conferencing equipment used in IP networks, ones that video conferencing equipment used in IP networks, ones that
generate inelastic and ones that generate rate adaptive traffic, generate inelastic and ones that generate rate adaptive traffic,
therefore two service class are needed. Real-time Interactive therefore two service class are needed. Real-time Interactive
service class should be used for equipment that generate inelastic service class should be used for equipment that generate inelastic
video flows and Multimedia Conferencing service class for video flows and Multimedia Conferencing service class for
equipment that generate rate adaptive video flows. equipment that generate rate adaptive video flows.
o Broadcast Video service class is to be used for inelastic traffic o Broadcast Video service class is to be used for inelastic traffic
flows which is intended for broadcast TV service and for transport flows which is intended for broadcast TV service and for transport
of live video and audio events. of live video and audio events.
o Multimedia Streaming service class is to be used for elastic o Multimedia Streaming service class is to be used for elastic
multimedia traffic flows. This multimedia content is typically multimedia traffic flows. This multimedia content is typically
stored before being transmitted, as well it is buffered at the stored before being transmitted, as well it is buffered at the
receiving end before being played out. The buffering is receiving end before being played out. The buffering is
sufficient large to accommodate any variation in transmission rate sufficiently large to accommodate any variation in transmission
that is encountered in the network. Multimedia entertainment over rate that is encountered in the network. Multimedia entertainment
IP delivery services that are being developed can generate both over IP delivery services that are being developed can generate
elastic and/or inelastic traffic flows, therefore two service both elastic and/or inelastic traffic flows, therefore two service
classes are defined to address this space. classes are defined to address this space.
Data category: The data category is divided into three service Data category: The data category is divided into three service
classes. classes.
o Low Latency Data for applications/services that require low delay o Low Latency Data for applications/services that require low delay
or latency for bursty but short lived flows. or latency for bursty but short lived flows.
o High Throughput Data for applications/services that require good o High Throughput Data for applications/services that require good
throughput for long lived bursty flows. High Throughput and throughput for long lived bursty flows. High Throughput and
Multimedia Steaming are close in their traffic flow Multimedia Steaming are close in their traffic flow
characteristics with High Throughput being a bit more bursty and characteristics with High Throughput being a bit more bursty and
not as long lived as Multimedia Steaming. not as long lived as Multimedia Streaming.
o Low Priority Data for applications or services that can tolerate o Low Priority Data for applications or services that can tolerate
short or long interruptions of packet flows. Low Priority Data short or long interruptions of packet flows. Low Priority Data
service class can be viewed as don't care to some degree. service class can be viewed as don't care to some degree.
Best Effort category: Best Effort category:
o All traffic that is not differentiated in the network falls into o All traffic that is not differentiated in the network falls into
this category and is mapped into the Standard service class. If a this category and is mapped into the Standard service class. If a
packet is marked with a DSCP value that is not supported in the packet is marked with a DSCP value that is not supported in the
network, it SHOULD be forwarded using the Standard service class. network, it SHOULD be forwarded using the Standard service class.
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| Best Effort | Standard | Not Specified |Non-critical| | Best Effort | Standard | Not Specified |Non-critical|
----------------------------------------------------------------- -----------------------------------------------------------------
Note: N.A. = Not Applicable. Note: N.A. = Not Applicable.
Figure 1: User/Subscriber Service Classes Grouping Figure 1: User/Subscriber Service Classes Grouping
Here is a short explanation of end user QoS category as defined in Here is a short explanation of end user QoS category as defined in
ITU-T Recommendation G.1010. User traffic is divided into four ITU-T Recommendation G.1010. User traffic is divided into four
different categories, namely, interactive, responsive, timely, and different categories, namely, interactive, responsive, timely, and
non-critical. An example of interactive traffic is between two non-critical. An example of interactive traffic is between two
humans and is most sensitive to delay, loss and jitter. Another humans and is most sensitive to delay, loss, and jitter. Another
example of interactive traffic is between two servers where very low example of interactive traffic is between two servers where very low
delay and loss is needed. Responsive traffic is typically between a delay and loss is needed. Responsive traffic is typically between a
human and a server but also can be between two servers. Responsive human and a server but also can be between two servers. Responsive
traffic is less affected by jitter and can tolerate longer delays traffic is less affected by jitter and can tolerate longer delays
than interactive traffic. Timely traffic is either between servers than interactive traffic. Timely traffic is either between servers
or servers and humans and the delay tolerance is significantly longer or servers and humans and the delay tolerance is significantly longer
than responsive traffic. Non-critical traffic is normally between than responsive traffic. Non-critical traffic is normally between
servers/machines where delivery may be delay for period of time. servers/machines where delivery may be delay for period of time.
2.3 Service Class Characteristics 2.3. Service Class Characteristics
This draft provides guidelines for network administrator in This document provides guidelines for network administrator in
configuring their network for the level of service differentiation configuring their network for the level of service differentiation
that is appropriate in their network to meet their QoS needs. It is that is appropriate in their network to meet their QoS needs. It is
expected that network operators will configure and provide in their expected that network operators will configure and provide in their
networks a subset of the defined service classes. Our intent is to networks a subset of the defined service classes. Our intent is to
provide guidelines for configuration of Differentiated Services for a provide guidelines for configuration of Differentiated Services for a
wide variety of applications, services and network configurations. wide variety of applications, services and network configurations.
Additionally, network administrators may choose to define and deploy Additionally, network administrators may choose to define and deploy
in their network other service classes. in their network other service classes.
Figure 2 provides a behavior view for traffic serviced by each Figure 2 provides a behavior view for traffic serviced by each
service class. The traffic characteristics column defines the service class. The traffic characteristics column defines the
characteristics and profile of flows serviced and the tolerance to characteristics and profile of flows serviced and the tolerance to
loss, delay and jitter columns define the treatment the flows will loss, delay and jitter columns define the treatment the flows will
receive. End-to-end quantitative performance requirements may be receive. End-to-end quantitative performance requirements may be
obtained from ITU-T Recommendation Y.1541 and Y.1540. There is also obtained from ITU-T Recommendation Y.1541 and Y.1540.
new work currently underway in ITU-T that applies to the service
classes defined in this document.
------------------------------------------------------------------- -------------------------------------------------------------------
|Service Class | | Tolerance to | |Service Class | | Tolerance to |
| Name | Traffic Characteristics | Loss |Delay |Jitter| | Name | Traffic Characteristics | Loss |Delay |Jitter|
|===============+==============================+======+======+======| |===============+==============================+======+======+======|
| Network |Variable size packets, mostly | | | | | Network |Variable size packets, mostly | | | |
| Control |inelastic short messages, but | Low | Low | Yes | | Control |inelastic short messages, but | Low | Low | Yes |
| | traffic can also burst (BGP) | | | | | | traffic can also burst (BGP) | | | |
|---------------+------------------------------+------+------+------| |---------------+------------------------------+------+------+------|
| | Fixed size small packets, | Very | Very | Very | | | Fixed size small packets, | Very | Very | Very |
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Note: A "Yes" in the jitter-tolerant column implies that data is Note: A "Yes" in the jitter-tolerant column implies that data is
buffered in the endpoint, and a moderate level of network-induced buffered in the endpoint, and a moderate level of network-induced
variation in delay will not affect the application. Applications variation in delay will not affect the application. Applications
that use TCP as a transport are generally good examples. Routing that use TCP as a transport are generally good examples. Routing
protocols and peer-to-peer signaling also fall in this class; while protocols and peer-to-peer signaling also fall in this class; while
loss can create problems in setting up calls, a moderate level of loss can create problems in setting up calls, a moderate level of
jitter merely makes call placement a little less predictable in jitter merely makes call placement a little less predictable in
duration. duration.
Service classes indicate the required traffic forwarding treatment in Service classes indicate the required traffic forwarding treatment in
order to meet user, application or network expectations. Section 3in order to meet user, application or network expectations. Section 3
this document defines the service classes that MAY be used for in this document defines the service classes that MAY be used for
forwarding network control traffic and Section 4 defines the service forwarding network control traffic and Section 4 defines the service
classes that MAY be used for forwarding user traffic with examples of classes that MAY be used for forwarding user traffic with examples of
intended application types mapped into each service class. Note that intended application types mapped into each service class. Note that
the application types are only examples and are not meant to be all- the application types are only examples and are not meant to be all-
inclusive or prescriptive. Also it should be noted that the service inclusive or prescriptive. Also it should be noted that the service
class naming or ordering does not imply any priority ordering. They class naming or ordering does not imply any priority ordering. They
are simply reference names that are used in this document with are simply reference names that are used in this document with
associated QoS behaviors that are optimized for the particular associated QoS behaviors that are optimized for the particular
application types they support. Network administrators MAY choose to application types they support. Network administrators MAY choose to
assign different service class names, to the service classes that assign different service class names, to the service classes that
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|Broadcast Video| CS3 | 011000 |Broadcast TV & live events| |Broadcast Video| CS3 | 011000 |Broadcast TV & live events|
|---------------+---------+-------------+--------------------------| |---------------+---------+-------------+--------------------------|
| Low Latency |AF21,AF22|010010,010100|Client/server transactions| | Low Latency |AF21,AF22|010010,010100|Client/server transactions|
| Data | AF23 | 010110 | Web-based ordering | | Data | AF23 | 010110 | Web-based ordering |
|---------------+---------+-------------+--------------------------| |---------------+---------+-------------+--------------------------|
| OAM | CS2 | 010000 | OAM&P | | OAM | CS2 | 010000 | OAM&P |
|---------------+---------+-------------+--------------------------| |---------------+---------+-------------+--------------------------|
|High Throughput|AF11,AF12|001010,001100| Store and forward | |High Throughput|AF11,AF12|001010,001100| Store and forward |
| Data | AF13 | 001110 | applications | | Data | AF13 | 001110 | applications |
|---------------+---------+-------------+--------------------------| |---------------+---------+-------------+--------------------------|
| Standard | DF,(CS0)| 000000 | Undifferentiated | | Standard | DF (CS0)| 000000 | Undifferentiated |
| | | | applications | | | | | applications |
|---------------+---------+-------------+--------------------------| |---------------+---------+-------------+--------------------------|
| Low Priority | CS1 | 001000 | Any flow that has no BW | | Low Priority | CS1 | 001000 | Any flow that has no BW |
| Data | | | assurance | | Data | | | assurance |
------------------------------------------------------------------ ------------------------------------------------------------------
Figure 3: DSCP to Service Class Mapping Figure 3: DSCP to Service Class Mapping
Note for Figure 3: Note for Figure 3:
o Default Forwarding (DF) and Class Selector 0 (CS0) provide o Default Forwarding (DF) and Class Selector 0 (CS0) provide
skipping to change at page 21, line 30 skipping to change at page 22, line 30
scheduler. scheduler.
o In network segments that use IP precedence marking, only one of o In network segments that use IP precedence marking, only one of
the two service classes can be supported, High Throughput Data or the two service classes can be supported, High Throughput Data or
Low Priority Data. We RECOMMEND that the DSCP value(s) of the Low Priority Data. We RECOMMEND that the DSCP value(s) of the
unsupported service class to be changed to 000xx1 on ingress and unsupported service class to be changed to 000xx1 on ingress and
changed back to original value(s) on egress of the network segment changed back to original value(s) on egress of the network segment
that uses precedence marking. For example, if Low Priority Data that uses precedence marking. For example, if Low Priority Data
is mapped to Standard service class, then 000001 DSCP marking MAY is mapped to Standard service class, then 000001 DSCP marking MAY
be used to distinguish it from Standard marked packets on egress. be used to distinguish it from Standard marked packets on egress.
2.4 Deployment Scenarios 2.4. Deployment Scenarios
It is expected that network administrators will choose the service It is expected that network administrators will choose the service
classes that they will support based on their need, starting off with classes that they will support based on their need, starting off with
three or four service classes for user traffic and add more service three or four service classes for user traffic and add more service
classes as the need arises. In this section we provide three classes as the need arises. In this section we provide three
examples of possible deployment scenarios. examples of possible deployment scenarios.
2.4.1 Example 1 2.4.1. Example 1
A network administrator determined that they need to provide A network administrator determined that they need to provide
different performance levels (quality of service) in their network different performance levels (quality of service) in their network
for the services that they will be offering to their customers. They for the services that they will be offering to their customers. They
need to enable their network to provide: need to enable their network to provide:
o Reliable VoIP (telephony) service, equivalent to PSTN o Reliable VoIP (telephony) service, equivalent to PSTN
o A low delay assured bandwidth data service o A low delay assured bandwidth data service
o As well, support current Internet services o As well, support current Internet services
For this example, the network administrator's needs are addressed For this example, the network administrator's needs are addressed
skipping to change at page 22, line 14 skipping to change at page 23, line 14
o Standard service class for all traffic that will receive normal o Standard service class for all traffic that will receive normal
(undifferentiated) forwarding treatment through their network for (undifferentiated) forwarding treatment through their network for
support of current Internet service support of current Internet service
o Telephony service class for VoIP (telephony) bearer traffic o Telephony service class for VoIP (telephony) bearer traffic
o Signaling service class for Telephony signaling to control the o Signaling service class for Telephony signaling to control the
VoIP service VoIP service
o Low Latency Data service class for the low delay assured bandwidth o Low Latency Data service class for the low delay assured bandwidth
differentiated data service differentiated data service
o OAM service class for operation and management of the network o OAM service class for operation and management of the network
Figure 5, provides a summary of the mechanisms need for delivery of Figure 5, provides a summary of the mechanisms needed for delivery of
service differentiation for Example 1. service differentiation for Example 1.
------------------------------------------------------------------- -------------------------------------------------------------------
| Service | DSCP | Conditioning at | PHB | | | | Service | DSCP | Conditioning at | PHB | | |
| Class | | DS Edge | Used | Queuing| AQM| | Class | | DS Edge | Used | Queuing| AQM|
|===============+=======+===================+=========+========+====| |===============+=======+===================+=========+========+====|
|Network Control| CS6 | See Section 3.1 | RFC2474 | Rate | Yes| |Network Control| CS6 | See Section 3.1 | RFC2474 | Rate | Yes|
|---------------+-------+-------------------+---------+--------+----| |---------------+-------+-------------------+---------+--------+----|
| Telephony | EF |Police using sr+bs | RFC3246 |Priority| No | | Telephony | EF |Police using sr+bs | RFC3246 |Priority| No |
|---------------+-------+-------------------+---------+--------+----| |---------------+-------+-------------------+---------+--------+----|
| Signaling | CS5 |Police using sr+bs | RFC2474 | Rate | No | | Signaling | CS5 |Police using sr+bs | RFC2474 | Rate | No |
skipping to change at page 22, line 47 skipping to change at page 23, line 47
Notes for Figure 5: Notes for Figure 5:
o "sr+bs" represents a policing mechanism that provides single rate o "sr+bs" represents a policing mechanism that provides single rate
with burst size control. with burst size control.
o The single rate three color marker (srTCM) behavior SHOULD be o The single rate three color marker (srTCM) behavior SHOULD be
equivalent to RFC 2697. equivalent to RFC 2697.
o Any packet that is marked with DSCP value that is not represented o Any packet that is marked with DSCP value that is not represented
by the supported service classes, SHOULD be forwarded using the by the supported service classes, SHOULD be forwarded using the
Standard service class. Standard service class.
2.4.2 Example 2 2.4.2. Example 2
With this example we show how network operators with Example 1 With this example we show how network operators with Example 1
capabilities can evolve their service offering to provide three new capabilities can evolve their service offering to provide three new
additional services to their customers. The new additional service additional services to their customers. The new additional service
capabilities that are to be added are: capabilities that are to be added are:
o SIP based desktop video conference capability to complement VoIP o SIP based desktop video conference capability to complement VoIP
(telephony) service (telephony) service
o Provide TV and on demand movie viewing service to residential o Provide TV and on demand movie viewing service to residential
subscribers subscribers
o Provide network based data storage and file backup service to o Provide network based data storage and file backup service to
skipping to change at page 25, line 5 skipping to change at page 26, line 5
Notes for Figure 6: Notes for Figure 6:
o "sr+bs" represents a policing mechanism that provides single rate o "sr+bs" represents a policing mechanism that provides single rate
with burst size control. with burst size control.
o The single rate three color marker (srTCM) behavior SHOULD be o The single rate three color marker (srTCM) behavior SHOULD be
equivalent to RFC 2697 and the two rate three color marker (trTCM) equivalent to RFC 2697 and the two rate three color marker (trTCM)
behavior SHOULD be equivalent to RFC 2698. behavior SHOULD be equivalent to RFC 2698.
o Any packet that is marked with DSCP value that is not represented o Any packet that is marked with DSCP value that is not represented
by the supported service classes, SHOULD be forwarded using the by the supported service classes, SHOULD be forwarded using the
Standard service class. Standard service class.
2.4.3 Example 3 2.4.3. Example 3
An enterprise network administrator determined that they need to An enterprise network administrator determined that they need to
provide different performance levels (quality of service) in their provide different performance levels (quality of service) in their
network for the new services that are being offered to corporate network for the new services that are being offered to corporate
users. The enterprise network needs to: users. The enterprise network needs to:
o Provide reliable corporate VoIP service o Provide reliable corporate VoIP service
o Provide video conferencing service to selected Conference Rooms o Provide video conferencing service to selected Conference Rooms
o Support on demand distribution of prerecorded audio and video o Support on demand distribution of prerecorded audio and video
information to large number of users information to large number of users
o Provide a priority data transfer capability for engineering teams o Provide a priority data transfer capability for engineering teams
skipping to change at page 25, line 35 skipping to change at page 26, line 35
is needed for reliable operation of the enterprise network is needed for reliable operation of the enterprise network
o OAM service class for operation and management of the network o OAM service class for operation and management of the network
o Standard service class for all traffic that will receive normal o Standard service class for all traffic that will receive normal
(undifferentiated) forwarding treatment (undifferentiated) forwarding treatment
o Telephony service class for VoIP (telephony) bearer traffic o Telephony service class for VoIP (telephony) bearer traffic
o Signaling service class for Telephony signaling to control the o Signaling service class for Telephony signaling to control the
VoIP service VoIP service
o Multimedia Conferencing service class for support of inter o Multimedia Conferencing service class for support of inter
Conference Room video conferencing service using H.323/V2 or Conference Room video conferencing service using H.323/V2 or
similar equipment. similar equipment.
o Multimedia Steaming service class for transfer of prerecorded o Multimedia Streaming service class for transfer of prerecorded
audio and video information audio and video information
o High Throughput Data service class to provide bandwidth assurance o High Throughput Data service class to provide bandwidth assurance
for timely transfer of large engineering files for timely transfer of large engineering files
o Low Priority Data service class for selected background o Low Priority Data service class for selected background
applications where data transfer can be delayed or suspended for a applications where data transfer can be delayed or suspended for a
period of time during peak network load conditions period of time during peak network load conditions
Figure 7, provides a summary of the mechanisms need for delivery of Figure 7, provides a summary of the mechanisms need for delivery of
service differentiation for Example 3. service differentiation for Example 3.
skipping to change at page 26, line 39 skipping to change at page 27, line 39
| Low Priority | CS1 | Not applicable | RFC3662 | Rate | Yes| | Low Priority | CS1 | Not applicable | RFC3662 | Rate | Yes|
| Data | | | | | | | Data | | | | | |
|---------------+-------+-------------------+---------+--------+----| |---------------+-------+-------------------+---------+--------+----|
| Standard |DF(CS0)| Not applicable | RFC2474 | Rate | Yes| | Standard |DF(CS0)| Not applicable | RFC2474 | Rate | Yes|
| | +other| | | | | | | +other| | | | |
------------------------------------------------------------------- -------------------------------------------------------------------
Figure 7: Enterprise Network Configuration Example Figure 7: Enterprise Network Configuration Example
Notes for Figure 7: Notes for Figure 7:
o The Administrative service class MAY be implemented using Rate
queuing method as long as sufficient amount of bandwidth is
guaranteed and latency of scheduler is sufficiently low to meet
the requirement.
o "sr+bs" represents a policing mechanism that provides single rate o "sr+bs" represents a policing mechanism that provides single rate
with burst size control. with burst size control.
o The single rate three color marker (srTCM) behavior SHOULD be o The single rate three color marker (srTCM) behavior SHOULD be
equivalent to RFC 2697 and the two rate three color marker (trTCM) equivalent to RFC 2697 and the two rate three color marker (trTCM)
behavior SHOULD be equivalent to RFC 2698. behavior SHOULD be equivalent to RFC 2698.
o Any packet that is marked with DSCP value that is not represented o Any packet that is marked with DSCP value that is not represented
by the supported service classes, SHOULD be forwarded using the by the supported service classes, SHOULD be forwarded using the
Standard service class. Standard service class.
3. Network Control Traffic 3. Network Control Traffic
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for stable operation of the administered network as well for for stable operation of the administered network as well for
information that may be exchanged between neighboring networks across information that may be exchanged between neighboring networks across
a peering point where SLAs are in place. Network control traffic is a peering point where SLAs are in place. Network control traffic is
different from user application control (signaling) that may be different from user application control (signaling) that may be
generated by some applications or services. Network control traffic generated by some applications or services. Network control traffic
is mostly between routers and network nodes that are used for is mostly between routers and network nodes that are used for
operating, administering, controlling or managing the network operating, administering, controlling or managing the network
segments. Network Control Traffic may be split into two service segments. Network Control Traffic may be split into two service
classes, i.e. Network Control and OAM. classes, i.e. Network Control and OAM.
3.1 Current Practice in The Internet 3.1. Current Practice in The Internet
Based on today's routing protocols and network control procedures Based on today's routing protocols and network control procedures
that are used in The Internet, we have determined that CS6 DSCP value that are used in The Internet, we have determined that CS6 DSCP value
SHOULD be used for routing and control and that CS7 DSCP value be SHOULD be used for routing and control and that CS7 DSCP value be
reserved for future use, potentially for future routing and/or reserved for future use, potentially for future routing and/or
control protocols. Network administrator MAY use a Local/ control protocols. Network administrator MAY use a Local/
Experimental DSCP therefore a locally defined service class within Experimental DSCP therefore a locally defined service class within
their network to further differentiate their routing and control their network to further differentiate their routing and control
traffic. traffic.
RECOMMENDED Network Edge Conditioning for CS7 DSCP marked packets: RECOMMENDED Network Edge Conditioning for CS7 DSCP marked packets:
o Drop or remark CS7 marked packets at ingress to DiffServ network o Drop or remark CS7 marked packets at ingress to DiffServ network
domain. domain.
o CS7 marked packets SHOULD NOT be sent across peering points. o CS7 marked packets SHOULD NOT be sent across peering points.
Exchange of control information across peering points SHOULD be Exchange of control information across peering points SHOULD be
done using CS6 DSCP, using Network Control service class. done using CS6 DSCP, using Network Control service class.
3.2 Network Control Service Class 3.2. Network Control Service Class
The Network Control service class is used for transmitting packets The Network Control service class is used for transmitting packets
between network devices (routers) that require control (routing) between network devices (routers) that require control (routing)
information to be exchanged between nodes within the administrative information to be exchanged between nodes within the administrative
domain as well across a peering point between different domain as well across a peering point between different
administrative domains. Traffic transmitted in this service class is administrative domains. Traffic transmitted in this service class is
very important as it keeps the network operational and needs to be very important as it keeps the network operational and needs to be
forwarded in a timely manner. forwarded in a timely manner.
The Network Control service class SHOULD be configured using the The Network Control service class SHOULD be configured using the
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If RED [RFC2309] is used as an AQM algorithm, the min-threshold If RED [RFC2309] is used as an AQM algorithm, the min-threshold
specifies a target queue depth, and the max-threshold specifies the specifies a target queue depth, and the max-threshold specifies the
queue depth above which all traffic is dropped or ECN marked. Thus, queue depth above which all traffic is dropped or ECN marked. Thus,
in this service class, the following inequality should hold in queue in this service class, the following inequality should hold in queue
configurations: configurations:
o min-threshold CS6 < max-threshold CS6 o min-threshold CS6 < max-threshold CS6
o max-threshold CS6 <= memory assigned to the queue o max-threshold CS6 <= memory assigned to the queue
Note: Many other AQM algorithms exist and are used; they should be Note: Many other AQM algorithms exist and are used; they should be
configured to achieve a similar result. configured to achieve a similar result.
3.3 OAM Service Class 3.3. OAM Service Class
The OAM (Operations, Administration and Management) service class is The OAM (Operations, Administration and Management) service class is
RECOMMENDED for OAM&P (Operations, Administration and Management and RECOMMENDED for OAM&P (Operations, Administration and Management and
Provisioning) using protocols such as SNMP, TFTP, FTP, Telnet, COPS, Provisioning) using protocols such as SNMP, TFTP, FTP, Telnet, COPS,
etc. Applications using this service class require a low packet loss etc. Applications using this service class require a low packet loss
but are relatively not sensitive to delay. This service class is but are relatively not sensitive to delay. This service class is
configured to provide good packet delivery for intermittent flows. configured to provide good packet delivery for intermittent flows.
The OAM service class SHOULD use the Class Selector (CS) PHB defined The OAM service class SHOULD use the Class Selector (CS) PHB defined
in [RFC2474]. This service class SHOULD be configured to provide a in [RFC2474]. This service class SHOULD be configured to provide a
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the above for service differentiation, mapping of applications that the above for service differentiation, mapping of applications that
have the matching traffic characteristics that fit the traffic have the matching traffic characteristics that fit the traffic
profile and performance requirements of the defined service classes. profile and performance requirements of the defined service classes.
Network administrators can categorize their applications based on the Network administrators can categorize their applications based on the
type of behavior that they require and MAY choose to support all or type of behavior that they require and MAY choose to support all or
subset of the defined service classes. Figure 3 provides some common subset of the defined service classes. Figure 3 provides some common
applications and the forwarding service class that best supports them applications and the forwarding service class that best supports them
based on their performance requirements. based on their performance requirements.
4.1 Telephony Service Class 4.1. Telephony Service Class
The Telephony service class is RECOMMENDED for applications that The Telephony service class is RECOMMENDED for applications that
require real-time, very low delay, very low jitter and very low require real-time, very low delay, very low jitter, and very low
packet loss for relatively constant-rate traffic sources (inelastic packet loss for relatively constant-rate traffic sources (inelastic
traffic sources). This service class SHOULD be used for IP telephony traffic sources). This service class SHOULD be used for IP telephony
service. service.
The fundamental service offered to traffic in the Telephony service The fundamental service offered to traffic in the Telephony service
class is minimum jitter, delay and packet loss service up to a class is minimum jitter, delay, and packet loss service up to a
specified upper bound. Operation is in some respect similar to an specified upper bound. Operation is in some respect similar to an
ATM CBR service, which has guaranteed bandwidth and which, if it ATM CBR service, which has guaranteed bandwidth and which, if it
stays within the negotiated rate, experiences nominal delay and no stays within the negotiated rate, experiences nominal delay and no
loss. The EF PHB has a similar guarantee. loss. The EF PHB has a similar guarantee.
Typical configurations negotiate the setup of telephone calls over IP Typical configurations negotiate the setup of telephone calls over IP
using protocols such as H.248, MEGACO, H.323, or SIP. When a user using protocols such as H.248, MEGACO, H.323, or SIP. When a user
has been authorized to send telephony traffic, the call admission has been authorized to send telephony traffic, the call admission
procedure should have verified that the newly admitted flow will be procedure should have verified that the newly admitted flow will be
within the capacity of the Telephony service class forwarding within the capacity of the Telephony service class forwarding
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admission control mechanism between peering points. admission control mechanism between peering points.
The fundamental service offered to "Telephony" traffic is enhanced The fundamental service offered to "Telephony" traffic is enhanced
best effort service with controlled rate, very low delay and very low best effort service with controlled rate, very low delay and very low
loss. The service MUST be engineered so that EF marked packet flows loss. The service MUST be engineered so that EF marked packet flows
have sufficient bandwidth in the network to provide guaranteed have sufficient bandwidth in the network to provide guaranteed
delivery. Normally traffic in this service class does not respond delivery. Normally traffic in this service class does not respond
dynamically to packet loss. As such, Active Queue Management dynamically to packet loss. As such, Active Queue Management
[RFC2309] SHOULD NOT be applied to EF marked packet flows. [RFC2309] SHOULD NOT be applied to EF marked packet flows.
4.2 Signaling Service Class 4.2. Signaling Service Class
The Signaling service class is RECOMMENDED for delay sensitive The Signaling service class is RECOMMENDED for delay sensitive
client-server (traditional telephony) and peer-to-peer application client-server (traditional telephony) and peer-to-peer application
signaling. Telephony signaling includes signaling between IP phone signaling. Telephony signaling includes signaling between IP phone
and soft-switch, soft-client and soft-switch, media gateway and soft- and soft-switch, soft-client and soft-switch, media gateway and soft-
switch as well as peer-to-peer using various protocols. This service switch as well as peer-to-peer using various protocols. This service
class is intended to be used for control of sessions and class is intended to be used for control of sessions and
applications. Applications using this service class requiring a applications. Applications using this service class requiring a
relatively fast response as there are typically several message of relatively fast response as there are typically several message of
different size sent for control of the session. This service class different size sent for control of the session. This service class
skipping to change at page 34, line 36 skipping to change at page 35, line 34
to the Service Level Agreement (SLA). to the Service Level Agreement (SLA).
The fundamental service offered to "Signaling" traffic is enhanced The fundamental service offered to "Signaling" traffic is enhanced
best effort service with controlled rate and delay. The service best effort service with controlled rate and delay. The service
SHOULD be engineered so that CS5 marked packet flows have sufficient SHOULD be engineered so that CS5 marked packet flows have sufficient
bandwidth in the network to provide high assurance of delivery and bandwidth in the network to provide high assurance of delivery and
low delay. Normally traffic in this service class does not respond low delay. Normally traffic in this service class does not respond
dynamically to packet loss. As such, Active Queue Management dynamically to packet loss. As such, Active Queue Management
[RFC2309] SHOULD NOT be applied to CS5 marked packet flows. [RFC2309] SHOULD NOT be applied to CS5 marked packet flows.
4.3 Multimedia Conferencing Service Class 4.3. Multimedia Conferencing Service Class
The Multimedia Conferencing service class is RECOMMENDED for The Multimedia Conferencing service class is RECOMMENDED for
applications that require real-time service for rate adaptive applications that require real-time service for rate adaptive
traffic. H.323/V2 and later versions of video conferencing equipment traffic. H.323/V2 and later versions of video conferencing equipment
with dynamic bandwidth adjustment is such an application. The with dynamic bandwidth adjustment is such an application. The
traffic sources (applications) in this service class have the traffic sources (applications) in this service class have the
capability to dynamically change their transmission rate based on capability to dynamically change their transmission rate based on
feedback received from the receiving end, within bounds of packet feedback received from the receiving end, within bounds of packet
loss by the receiver is sent using the applications control stream to loss by the receiver is sent using the applications control stream to
the transmitter as an indication of possible congestion; the the transmitter as an indication of possible congestion; the
skipping to change at page 37, line 15 skipping to change at page 38, line 12
o min-threshold AF43 < max-threshold AF43 o min-threshold AF43 < max-threshold AF43
o max-threshold AF43 <= min-threshold AF42 o max-threshold AF43 <= min-threshold AF42
o min-threshold AF42 < max-threshold AF42 o min-threshold AF42 < max-threshold AF42
o max-threshold AF42 <= min-threshold AF41 o max-threshold AF42 <= min-threshold AF41
o min-threshold AF41 < max-threshold AF41 o min-threshold AF41 < max-threshold AF41
o max-threshold AF41 <= memory assigned to the queue o max-threshold AF41 <= memory assigned to the queue
Note: This configuration tends to drop AF43 traffic before AF42 and Note: This configuration tends to drop AF43 traffic before AF42 and
AF42 before AF41. Many other AQM algorithms exist and are used; they AF42 before AF41. Many other AQM algorithms exist and are used; they
should be configured to achieve a similar result. should be configured to achieve a similar result.
4.4 Real-time Interactive Service Class 4.4. Real-time Interactive Service Class
The Real-time Interactive service class is RECOMMENDED for The Real-time Interactive service class is RECOMMENDED for
applications that require low loss, jitter and very low delay for applications that require low loss, jitter and very low delay for
variable rate inelastic traffic sources. Interactive gaming and variable rate inelastic traffic sources. Interactive gaming and
video conferencing applications that do not have the ability to video conferencing applications that do not have the ability to
change encoding rates or mark packets with different importance change encoding rates or mark packets with different importance
indications are such applications. The traffic sources in this indications are such applications. The traffic sources in this
traffic class does not have the ability to reduce their transmission traffic class does not have the ability to reduce their transmission
rate based on feedback received from the receiving end. rate based on feedback received from the receiving end.
skipping to change at page 38, line 44 skipping to change at page 39, line 41
to the Service Level Agreement (SLA). to the Service Level Agreement (SLA).
The fundamental service offered to "Real-time Interactive" traffic is The fundamental service offered to "Real-time Interactive" traffic is
enhanced best effort service with controlled rate and delay. The enhanced best effort service with controlled rate and delay. The
service SHOULD be engineered so that CS4 marked packet flows have service SHOULD be engineered so that CS4 marked packet flows have
sufficient bandwidth in the network to provide high assurance of sufficient bandwidth in the network to provide high assurance of
delivery. Normally traffic in this service class does not respond delivery. Normally traffic in this service class does not respond
dynamically to packet loss. As such, Active Queue Management dynamically to packet loss. As such, Active Queue Management
[RFC2309] SHOULD NOT be applied to CS4 marked packet flows. [RFC2309] SHOULD NOT be applied to CS4 marked packet flows.
4.5 Multimedia Streaming Service Class 4.5. Multimedia Streaming Service Class
The Multimedia Streaming service class is RECOMMENDED for The Multimedia Streaming service class is RECOMMENDED for
applications that require near-real-time packet forwarding of applications that require near-real-time packet forwarding of
variable rate elastic traffic sources that are not as delay sensitive variable rate elastic traffic sources that are not as delay sensitive
as applications using the Multimedia Conferencing service class. as applications using the Multimedia Conferencing service class.
Such applications include streaming audio and video, some video Such applications include streaming audio and video, some video
(movies) on demand applications and Web casts. In general, the (movies) on demand applications and Web casts. In general, the
Multimedia Streaming service class assumes that the traffic is Multimedia Streaming service class assumes that the traffic is
buffered at the source/destination and therefore, is less sensitive buffered at the source/destination and therefore, is less sensitive
to delay and jitter. to delay and jitter.
skipping to change at page 40, line 39 skipping to change at page 41, line 35
o min-threshold AF33 < max-threshold AF33 o min-threshold AF33 < max-threshold AF33
o max-threshold AF33 <= min-threshold AF32 o max-threshold AF33 <= min-threshold AF32
o min-threshold AF32 < max-threshold AF32 o min-threshold AF32 < max-threshold AF32
o max-threshold AF32 <= min-threshold AF31 o max-threshold AF32 <= min-threshold AF31
o min-threshold AF31 < max-threshold AF31 o min-threshold AF31 < max-threshold AF31
o max-threshold AF31 <= memory assigned to the queue o max-threshold AF31 <= memory assigned to the queue
Note: This configuration tends to drop AF33 traffic before AF32 and Note: This configuration tends to drop AF33 traffic before AF32 and
AF32 before AF31. Many other AQM algorithms exist and are used; they AF32 before AF31. Many other AQM algorithms exist and are used; they
should be configured to achieve a similar result. should be configured to achieve a similar result.
4.6 Broadcast Video Service Class 4.6. Broadcast Video Service Class
The Broadcast Video service class is RECOMMENDED for applications The Broadcast Video service class is RECOMMENDED for applications
that require near-real-time packet forwarding with very low packet that require near-real-time packet forwarding with very low packet
loss of constant and variable rate inelastic traffic sources that are loss of constant and variable rate inelastic traffic sources that are
not as delay sensitive as applications using the Real-time not as delay sensitive as applications using the Real-time
Interactive service class. Such applications include broadcast TV, Interactive service class. Such applications include broadcast TV,
streaming of live audio and video events, some video on demand streaming of live audio and video events, some video on demand
applications and video surveillance. In general, the Broadcast Video applications and video surveillance. In general, the Broadcast Video
service class assumes that the destination end point has a dejitter service class assumes that the destination end point has a dejitter
buffer, for video application usually a 2 - 8 video frames buffer (66 buffer, for video application usually a 2 - 8 video frames buffer (66
skipping to change at page 42, line 22 skipping to change at page 43, line 18
to the Service Level Agreement (SLA). to the Service Level Agreement (SLA).
The fundamental service offered to "Broadcast Video" traffic is The fundamental service offered to "Broadcast Video" traffic is
enhanced best effort service with controlled rate and delay. The enhanced best effort service with controlled rate and delay. The
service SHOULD be engineered so that CS3 marked packet flows have service SHOULD be engineered so that CS3 marked packet flows have
sufficient bandwidth in the network to provide high assurance of sufficient bandwidth in the network to provide high assurance of
delivery. Normally traffic in this service class does not respond delivery. Normally traffic in this service class does not respond
dynamically to packet loss. As such, Active Queue Management dynamically to packet loss. As such, Active Queue Management
[RFC2309] SHOULD NOT be applied to CS3 marked packet flows. [RFC2309] SHOULD NOT be applied to CS3 marked packet flows.
4.7 Low Latency Data Service Class 4.7. Low Latency Data Service Class
The Low Latency Data service class is RECOMMENDED for elastic and The Low Latency Data service class is RECOMMENDED for elastic and
responsive typically client/server based applications. Applications responsive typically client/server based applications. Applications
forwarded by this service class are those requiring a relatively fast forwarded by this service class are those requiring a relatively fast
response and typically have asymmetrical bandwidth need, i.e. the response and typically have asymmetrical bandwidth need, i.e. the
client typically sends a short message to the server and the server client typically sends a short message to the server and the server
responds with a much larger data flow back to the client. The most responds with a much larger data flow back to the client. The most
common example of this is when a user clicks a hyperlink (~few dozen common example of this is when a user clicks a hyperlink (~few dozen
bytes) on a web page resulting in a new web page to be loaded (Kbytes bytes) on a web page resulting in a new web page to be loaded (Kbytes
of data). This service class is configured to provide good response of data). This service class is configured to provide good response
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The fundamental service offered to "Low Latency Data" traffic is The fundamental service offered to "Low Latency Data" traffic is
enhanced best effort service with controlled rate and delay. The enhanced best effort service with controlled rate and delay. The
service SHOULD be engineered so that AF21 marked packet flows have service SHOULD be engineered so that AF21 marked packet flows have
sufficient bandwidth in the network to provide high assurance of sufficient bandwidth in the network to provide high assurance of
delivery. Since the AF2x traffic is elastic and responds dynamically delivery. Since the AF2x traffic is elastic and responds dynamically
to packet loss, Active Queue Management [RFC2309] SHOULD be used to packet loss, Active Queue Management [RFC2309] SHOULD be used
primarily to control TCP flow rates at congestion points by dropping primarily to control TCP flow rates at congestion points by dropping
packet from TCP flows that have large burst size. The probability of packet from TCP flows that have large burst size. The probability of
loss of AF21 traffic MUST NOT exceed the probability of loss of AF22 loss of AF21 traffic MUST NOT exceed the probability of loss of AF22
traffic, which in turn MUST NOT exceed the probability of loss of traffic, which in turn MUST NOT exceed the probability of loss of
AF23. Active queue management MAY also be implemented using Explicit AF23. Explicit Congestion Notification (ECN) [RFC3168] MAY also be
Congestion Notification (ECN) [RFC3168]. used with Active Queue Management.
If RED [RFC2309] is used as an AQM algorithm, the min-threshold If RED [RFC2309] is used as an AQM algorithm, the min-threshold
specifies a target queue depth for each DSCP, and the max-threshold specifies a target queue depth for each DSCP, and the max-threshold
specifies the queue depth above which all traffic with such a DSCP is specifies the queue depth above which all traffic with such a DSCP is
dropped or ECN marked. Thus, in this service class, the following dropped or ECN marked. Thus, in this service class, the following
inequality should hold in queue configurations: inequality should hold in queue configurations:
o min-threshold AF23 < max-threshold AF23 o min-threshold AF23 < max-threshold AF23
o max-threshold AF23 <= min-threshold AF22 o max-threshold AF23 <= min-threshold AF22
o min-threshold AF22 < max-threshold AF22 o min-threshold AF22 < max-threshold AF22
o max-threshold AF22 <= min-threshold AF21 o max-threshold AF22 <= min-threshold AF21
o min-threshold AF21 < max-threshold AF21 o min-threshold AF21 < max-threshold AF21
o max-threshold AF21 <= memory assigned to the queue o max-threshold AF21 <= memory assigned to the queue
Note: This configuration tends to drop AF23 traffic before AF22 and Note: This configuration tends to drop AF23 traffic before AF22 and
AF22 before AF21. Many other AQM algorithms exist and are used; they AF22 before AF21. Many other AQM algorithms exist and are used; they
should be configured to achieve a similar result. should be configured to achieve a similar result.
4.8 High Throughput Data Service Class 4.8. High Throughput Data Service Class
The High Throughput Data service class is RECOMMENDED for elastic The High Throughput Data service class is RECOMMENDED for elastic
applications that require timely packet forwarding of variable rate applications that require timely packet forwarding of variable rate
traffic sources and more specifically is configured to provide good traffic sources and more specifically is configured to provide good
throughput for TCP longer lived flows. TCP [RFC1633] or a transport throughput for TCP longer lived flows. TCP [RFC1633] or a transport
with a consistent Congestion Avoidance Procedure [RFC2581] [RFC2582] with a consistent Congestion Avoidance Procedure [RFC2581] [RFC2582]
normally will drive as high a data rate as it can obtain over a long normally will drive as high a data rate as it can obtain over a long
period of time. The FTP protocol is a common example, although one period of time. The FTP protocol is a common example, although one
cannot definitively say that all FTP transfers are moving data in cannot definitively say that all FTP transfers are moving data in
bulk. bulk.
skipping to change at page 46, line 5 skipping to change at page 46, line 50
and packets traversing congested links may experience higher queuing and packets traversing congested links may experience higher queuing
delays and/or packet loss. Since the AF1x traffic is elastic and delays and/or packet loss. Since the AF1x traffic is elastic and
responds dynamically to packet loss, Active Queue Management responds dynamically to packet loss, Active Queue Management
[RFC2309] SHOULD be used primarily to control TCP flow rates at [RFC2309] SHOULD be used primarily to control TCP flow rates at
congestion points by dropping packet from TCP flows that have higher congestion points by dropping packet from TCP flows that have higher
rates first. The probability of loss of AF11 traffic MUST NOT exceed rates first. The probability of loss of AF11 traffic MUST NOT exceed
the probability of loss of AF12 traffic, which in turn MUST NOT the probability of loss of AF12 traffic, which in turn MUST NOT
exceed the probability of loss of AF13. In such a case, if one exceed the probability of loss of AF13. In such a case, if one
network customer is driving significant excess and another seeks to network customer is driving significant excess and another seeks to
use the link, any losses will be experienced by the high rate user, use the link, any losses will be experienced by the high rate user,
causing him to reduce his rate. Active queue management MAY also be causing him to reduce his rate. Explicit Congestion Notification
implemented using Explicit Congestion Notification (ECN) [RFC3168]. (ECN) [RFC3168] MAY also be used with Active Queue Management.
If RED [RFC2309] is used as an AQM algorithm, the min-threshold If RED [RFC2309] is used as an AQM algorithm, the min-threshold
specifies a target queue depth for each DSCP, and the max-threshold specifies a target queue depth for each DSCP, and the max-threshold
specifies the queue depth above which all traffic with such a DSCP is specifies the queue depth above which all traffic with such a DSCP is
dropped or ECN marked. Thus, in this service class, the following dropped or ECN marked. Thus, in this service class, the following
inequality should hold in queue configurations: inequality should hold in queue configurations:
o min-threshold AF13 < max-threshold AF13 o min-threshold AF13 < max-threshold AF13
o max-threshold AF13 <= min-threshold AF12 o max-threshold AF13 <= min-threshold AF12
o min-threshold AF12 < max-threshold AF12 o min-threshold AF12 < max-threshold AF12
o max-threshold AF12 <= min-threshold AF11 o max-threshold AF12 <= min-threshold AF11
o min-threshold AF11 < max-threshold AF11 o min-threshold AF11 < max-threshold AF11
o max-threshold AF11 <= memory assigned to the queue o max-threshold AF11 <= memory assigned to the queue
Note: This configuration tends to drop AF13 traffic before AF12 and Note: This configuration tends to drop AF13 traffic before AF12 and
AF12 before AF11. Many other AQM algorithms exist and are used; they AF12 before AF11. Many other AQM algorithms exist and are used; they
should be configured to achieve a similar result. should be configured to achieve a similar result.
4.9 Standard Service Class 4.9. Standard Service Class
The Standard service class is RECOMMENDED for traffic that has not The Standard service class is RECOMMENDED for traffic that has not
been classified into one of the other supported forwarding service been classified into one of the other supported forwarding service
classes in the DiffServ network domain. This service class provides classes in the DiffServ network domain. This service class provides
the Internet's "best effort" forwarding behavior. This service class the Internet's "best effort" forwarding behavior. This service class
typically has minimum bandwidth guarantee. typically has minimum bandwidth guarantee.
The Standard service class MUST use the Default Forwarding (DF) PHB The Standard service class MUST use the Default Forwarding (DF) PHB
defined in [RFC2474] and SHOULD be configured to receive at least a defined in [RFC2474] and SHOULD be configured to receive at least a
small percentage of forwarding resources as a guaranteed minimum. small percentage of forwarding resources as a guaranteed minimum.
skipping to change at page 47, line 19 skipping to change at page 48, line 15
If RED [RFC2309] is used as an AQM algorithm, the min-threshold If RED [RFC2309] is used as an AQM algorithm, the min-threshold
specifies a target queue depth, and the max-threshold specifies the specifies a target queue depth, and the max-threshold specifies the
queue depth above which all traffic is dropped or ECN marked. Thus, queue depth above which all traffic is dropped or ECN marked. Thus,
in this service class, the following inequality should hold in queue in this service class, the following inequality should hold in queue
configurations: configurations:
o min-threshold DF < max-threshold DF o min-threshold DF < max-threshold DF
o max-threshold DF <= memory assigned to the queue o max-threshold DF <= memory assigned to the queue
Note: Many other AQM algorithms exist and are used; they should be Note: Many other AQM algorithms exist and are used; they should be
configured to achieve a similar result. configured to achieve a similar result.
4.10 Low Priority Data 4.10. Low Priority Data
The Low Priority Data service class serves applications that run over The Low Priority Data service class serves applications that run over
TCP [RFC0793] or a transport with consistent congestion avoidance TCP [RFC0793] or a transport with consistent congestion avoidance
procedure [RFC2581] [RFC2582], and which the user is willing to procedure [RFC2581] [RFC2582], and which the user is willing to
accept service without guarantees. This service class is specified accept service without guarantees. This service class is specified
in [QBSS] and [RFC3662]. in [QBSS] and [RFC3662].
The following applications MAY use the Low Priority Data service The following applications MAY use the Low Priority Data service
class: class:
o Any TCP based application/packet flow transported through the o Any TCP based application/packet flow transported through the
skipping to change at page 48, line 19 skipping to change at page 49, line 16
o max-threshold CS1 <= memory assigned to the queue o max-threshold CS1 <= memory assigned to the queue
Note: Many other AQM algorithms exist and are used; they should be Note: Many other AQM algorithms exist and are used; they should be
configured to achieve a similar result. configured to achieve a similar result.
5. Additional Information on Service Class Usage 5. Additional Information on Service Class Usage
In this section we provide additional information on how some In this section we provide additional information on how some
specific applications should be configured to use the defined service specific applications should be configured to use the defined service
classes. classes.
5.1 Mapping for Signaling 5.1. Mapping for Signaling
There are many different signaling protocols, ways that signaling is There are many different signaling protocols, ways that signaling is
used and performance requirements from applications that are used and performance requirements from applications that are
controlled by these protocols. We believe that different signaling controlled by these protocols. We believe that different signaling
protocols should use the service class that best meet the objectives protocols should use the service class that best meet the objectives
of application or service they control. The following mapping is of application or service they control. The following mapping is
recommended: recommended:
o Peer-to-peer signaling using SIP/H.323 are marked with CS5 DSCP o Peer-to-peer signaling using SIP/H.323 are marked with CS5 DSCP
(use Signaling service class). (use Signaling service class).
o Client-server signaling as used in many implementation for IP o Client-server signaling as used in many implementation for IP
skipping to change at page 48, line 48 skipping to change at page 49, line 45
the same queue (service class) and marked with the same DSCP value the same queue (service class) and marked with the same DSCP value
as application data that it is controlling. This may also apply as application data that it is controlling. This may also apply
to the "on-path" NSIS signaling protocol. to the "on-path" NSIS signaling protocol.
o IGMP (Internet Group Management Protocol). If used for multicast o IGMP (Internet Group Management Protocol). If used for multicast
session control such as channel changing in IPTV systems, then session control such as channel changing in IPTV systems, then
IGMP packets should be marked with CS5 DSCP (use Signaling service IGMP packets should be marked with CS5 DSCP (use Signaling service
class). When IGMP is used only for the normal multicast routing class). When IGMP is used only for the normal multicast routing
purpose, it should be marked with CS6 DSCP (use Network Control purpose, it should be marked with CS6 DSCP (use Network Control
service class). service class).
5.2 Mapping for NTP 5.2. Mapping for NTP
From tests that were performed, indications are that precise time From tests that were performed, indications are that precise time
distribution requires a very low packet delay variation (jitter) distribution requires a very low packet delay variation (jitter)
transport. Therefore we suggest the following guidelines for NTP transport. Therefore we suggest the following guidelines for NTP
(Network Time Protocol) be used: (Network Time Protocol) be used:
o When NTP is used for providing high accuracy timing within o When NTP is used for providing high accuracy timing within
administrator's (carrier's) network or to end users/clients, the administrator's (carrier's) network or to end users/clients, the
Telephony service class should be used and NTP packets be marked Telephony service class should be used and NTP packets be marked
with EF DSCP value. with EF DSCP value.
o For applications that require "wall clock" timing accuracy, the o For applications that require "wall clock" timing accuracy, the
Standard service class should be used and packets should be marked Standard service class should be used and packets should be marked
with DF DSCP. with DF DSCP.
5.3 VPN Service Mapping 5.3. VPN Service Mapping
Differentiated Services and Tunnels [RFC2983] considers the Differentiated Services and Tunnels [RFC2983] considers the
interaction of DiffServ architecture with IP tunnels of various interaction of DiffServ architecture with IP tunnels of various
forms. Further to guidelines provided in RFC 2983, below are forms. Further to guidelines provided in RFC 2983, below are
additional guidelines for mapping service classes that are supported additional guidelines for mapping service classes that are supported
in one part of the network into a VPN connection. This discussion is in one part of the network into a VPN connection. This discussion is
limit only to VPNs that use DiffServ technology for traffic limit only to VPNs that use DiffServ technology for traffic
differentiation. differentiation.
o The DSCP value(s) that is/are used to represent a PHB or a PHB o The DSCP value(s) that is/are used to represent a PHB or a PHB
group should be the same for the networks at both ends of the VPN group should be the same for the networks at both ends of the VPN
skipping to change at page 50, line 32 skipping to change at page 51, line 31
way to respond to an unauthenticated data stream using service that way to respond to an unauthenticated data stream using service that
it is not intended to use, and such is the nature of the Internet. it is not intended to use, and such is the nature of the Internet.
The use of a service class by a user is not an issue when the SLA The use of a service class by a user is not an issue when the SLA
between the user and the network permits him to use it, or to use it between the user and the network permits him to use it, or to use it
up to a stated rate. In such cases, simple policing is used in the up to a stated rate. In such cases, simple policing is used in the
Differentiated Services Architecture. Some service classes, such as Differentiated Services Architecture. Some service classes, such as
Network Control, are not permitted to be used by users at all; such Network Control, are not permitted to be used by users at all; such
traffic should be dropped or remarked by ingress filters. Where traffic should be dropped or remarked by ingress filters. Where
service classes are available under the SLA only to an authenticated service classes are available under the SLA only to an authenticated
user rather than to the entire population of users, AAA services such user rather than to the entire population of users, authentication
as described in [I-D.iab-auth-mech] are required. and authorization services are required, such as those surveyed in
[I-D.iab-auth-mech].
7. Summary of Changes from Previous Draft 7. Summary of Changes from Previous Version
NOTE TO RFC EDITOR: Please remove this section during the publication NOTE TO RFC EDITOR: Please remove this section during the publication
process. process.
Changes made to draft-ietf-tsvwg-diffserv-service-classes-00 based on Changes made to draft-ietf-tsvwg-diffserv-service-classes-01 from
minor typos on review by Mike Fidler. Following typos were fixed. review by David Black, Kathie Nichols, and Charlie Liu:
1. In Abstract section on page 1, and Section 1 Introduction on
1. page 20 first paragraph, "than 000001 DSCP marking" should be page 4 first paragraph.
"then 000001 DSCP marking" Old Text: This paper summarizes the recommended correlation
between service classes and their usage, with references to
2. page 22 last sentence of third bullet "than the Broadcast Video their corresponding recommended Differentiated Service Code
service class" should be "then the Broadcast..." Points (DSCP), traffic conditioners, Per-Hop Behaviors (PHB)
and Active Queue Management (AQM) mechanism. There is no
3. page 29 third bullet "than CS2 marked packet" should be "then CS2 intrinsic requirement that particular DSCPs, traffic
marked packets" (note plural also) conditioner PHBs and AQM be used for a certain service class,
4. page 40 second sentence of second bullet under "RECOMMENDED DSCP but as a policy it is useful that they be applied
marking" "If so, than" should be "If so, then" consistently across the network.
New Text: This document describes service classes configured
with Diffserv, recommends how they can be used and how to
construct them using Differentiated Service Code Points
(DSCP), traffic conditioners, Per-Hop Behaviors (PHB), and
Active Queue Management (AQM) mechanisms. There is no
intrinsic requirement that particular DSCPs, traffic
conditioners, PHBs, and AQM be used for a certain service
class, but as a policy and for interoperability it is useful
to apply them consistently.
2. In Section 1 Introduction on page 4. Added new first paragraph:
For understanding the role of this document we use an useful
analogy, starting from the fact that the Differentiated
Services specifications are fundamentally a toolkit - the
specifications provide the equivalent of band saws, planers,
drill presses, etc. In the hands of an expert, there's no
limit to what can be built, but such a toolkit can be
intimidating to the point of inaccessible to a non-expert who
just wants to build a bookcase. This document should be
viewed as a set of "project plans" for building all the
(diffserv) furniture that one might want. The user may
choose what to build (e.g., perhaps our non-expert doesn't
need a china cabinet right now), and how to go about building
it (e.g., plans for a non-expert probably won't employ
mortise/tenon construction, but that absence does not imply
that mortise/tenon construction is forbidden or unsound).
The authors hope that these diffserv "project plans" will
provide a useful guide to Network Administrators in the use
of diffserv techniques to implement quality of service
measures appropriate for their network's traffic.
3. In Section 1.3 first paragraph on page 5.
Old Text: A "service class" represents a set of traffic that
requires specific delay, loss, and jitter characteristics
from the network for which a consistent and defined per-hop-
behavior (PHB) applies.
New Text: A "service class" represents a set of traffic that
requires specific delay, loss, and jitter characteristics
from the network.
4. In Section 1.3 second paragraph on page 5.
Old Text: A Service Class as defined here is essentially a
statement of the required characteristics of a traffic
aggregate; the actual specification of the expected treatment
of a traffic aggregate within a domain may also be defined as
a Per Domain Behavior [RFC3086].
5. page 47 section 5.1 fourth bullet "than it needs to be forwarded" New Text: A service class as defined here is essentially a
should be "then it needs to be forwarded" statement of the required characteristics of a traffic
aggregate. The required characteristics of these traffic
aggregates can be realized by the use of defined per-hop
behavior (PHB) [RFC2474]. The actual specification of the
expected treatment of a traffic aggregate within a domain may
also be defined as a per domain behavior (PDB) [RFC3086].
5. In Section 1.3 third paragraph on page 5.
Added New Paragraph: Each domain may choose to implement
different service classes, or use different behaviors to
implement the service classes, or aggregate different kinds
of traffic into the aggregates and still achieve their
required characteristics. For example, low delay, loss, and
jitter may be realized using the EF PHB, or with an over
provisioned AF PHB. This must be done with care as it may
disrupt the end to end performance required by the
applications/services. This document provides
recommendations on usage of PHBs for specific service classes
for their consistent implementation, these recommendations
are not to be construed as prohibiting use of other PHBs that
realize behaviors sufficient for the relevant class of
traffic.
6. In Section 1.4 first paragraph on page 5.
Old Text: The reader SHOULD be familiar with the principles of
the Differentiated Services Architecture [RFC2474]. However,
we recapitulate key concepts here to save searching.
New Text: The reader SHOULD be familiar with the principles of
the Differentiated Services Architecture [RFC2474]. We
recapitulate key concepts here only to provide convenience
for the reader, with the referenced RFCs providing the
authoritative definitions.
7. In Section 1.5.3 first paragraph first sentence on page 10.
Old Text: Expedited Forwarding PHB [RFC3246] behavior was
originally proposed as a way to implement a virtual wire, and
can be used in such a manner. It is an enhanced best effort
service:
New Text: The intent of Expedited Forwarding PHB [RFC3246] is to
provide a building block for low loss, low delay, and low
jitter services. It can be used to build an enhanced best
effort service:
8. In Section 2.3 second paragraph on page 16. Deleted the last
sentence:
There is also new work currently underway in ITU-T that
applies to the service classes defined in this document.
9. In Section 2.4.3 Example 3, on page 25. Fixed typo: "Multimedia
Steaming", changed it to "Multimedia Streaming".
6. page 48 section 5.3 second bullet "Service classes are than 10. In Section 2.4.3 Example 3, on page 26. Deleted the first note
mapped" should be "Service classes are then mapped" under Notes for Figure 7: Deleted text "The Administrative
service class MAY be implemented using Rate queuing method as
long as sufficient amount of bandwidth is guaranteed and latency
of scheduler is sufficiently low to meet the requirement. "
11. In Section 10 on page 53. Moving the first reference:
[I-D.iab-auth-mech] Rescorla, E., "A Survey of Authentication
Mechanisms", draft-iab-auth-mech-04 (work in progress),
September 2005.
From Normative References section to Informative References
section.
8. Acknowledgements 8. Acknowledgements
The authors thank the TSVWG reviewers, David Black, Brian E Carpenter The authors thank the TSVWG reviewers, David Black, Brian E Carpenter
and Alan O'Neill for their review and input to this draft. and Alan O'Neill for their review and input to this draft.
The authors acknowledge great many inputs, most notably from Bruce The authors acknowledge great many inputs, most notably from Bruce
Davie, Dave Oran, Ralph Santitoro, Gary Kenward, Francois Audet, Davie, Dave Oran, Ralph Santitoro, Gary Kenward, Francois Audet,
Morgan Littlewood, Robert Milne, John Shuler, Nalin Mistry, Al Morgan Littlewood, Robert Milne, John Shuler, Nalin Mistry, Al
Morton, Mike Pierce, Ed Koehler Jr., Tim Rahrer, Fil Dickinson and Morton, Mike Pierce, Ed Koehler Jr., Tim Rahrer, Fil Dickinson, Mike
Shane Amante. Kimberly King, Joe Zebarth and Alistair Munroe each Fidler and Shane Amante. Kimberly King, Joe Zebarth and Alistair
did a thorough proof-reading, and the document is better for their Munroe each did a thorough proof-reading, and the document is better
contributions. for their contributions.
9. Appendix A 9. Appendix A
9.1 Explanation of Ring Clipping 9.1. Explanation of Ring Clipping
The term "ring clipping" refers to those instances where the front The term "ring clipping" refers to those instances where the front
end of a ringing signal is altered because the bearer channel is not end of a ringing signal is altered because the bearer channel is not
made available in time to carry all of the audible ringing signal. made available in time to carry all of the audible ringing signal.
This condition may occur due to a race condition between when the This condition may occur due to a race condition between when the
tone generator located in the circuit switch Exchange is turn on and tone generator located in the circuit switch Exchange is turn on and
when the bearer path through the IP network is enabled. To reduce when the bearer path through the IP network is enabled. To reduce
ring clipping from occurring, delay of signaling path needs to be ring clipping from occurring, delay of signaling path needs to be
minimized. Below is a more detailed explanation. minimized. Below is a more detailed explanation.
skipping to change at page 52, line 24 skipping to change at page 55, line 29
maximum value. Service administrators are free to choose specific maximum value. Service administrators are free to choose specific
IAM delay values based on their own preferences (i.e., they may wish IAM delay values based on their own preferences (i.e., they may wish
to set a very low mean delay objective for strategic reasons to to set a very low mean delay objective for strategic reasons to
differentiate themselves from other providers). In summary, out of differentiate themselves from other providers). In summary, out of
the 240ms delay budget, 200ms is allocated as cross-Exchange delay the 240ms delay budget, 200ms is allocated as cross-Exchange delay
(soft-switch and media gateway) and 40ms for network delay (queuing (soft-switch and media gateway) and 40ms for network delay (queuing
and distance). and distance).
10. References 10. References
10.1 Normative References 10.1. Normative References
[I-D.iab-auth-mech]
Rescorla, E., "A Survey of Authentication Mechanisms",
draft-iab-auth-mech-03 (work in progress), March 2004.
[RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791, [RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791,
September 1981. September 1981.
[RFC0793] Postel, J., "Transmission Control Protocol", STD 7, [RFC0793] Postel, J., "Transmission Control Protocol", STD 7,
RFC 793, September 1981. RFC 793, September 1981.
[RFC1349] Almquist, P., "Type of Service in the Internet Protocol [RFC1349] Almquist, P., "Type of Service in the Internet Protocol
Suite", RFC 1349, July 1992. Suite", RFC 1349, July 1992.
skipping to change at page 53, line 26 skipping to change at page 56, line 27
[RFC3246] Davie, B., Charny, A., Bennet, J., Benson, K., Le Boudec, [RFC3246] Davie, B., Charny, A., Bennet, J., Benson, K., Le Boudec,
J., Courtney, W., Davari, S., Firoiu, V., and D. J., Courtney, W., Davari, S., Firoiu, V., and D.
Stiliadis, "An Expedited Forwarding PHB (Per-Hop Stiliadis, "An Expedited Forwarding PHB (Per-Hop
Behavior)", RFC 3246, March 2002. Behavior)", RFC 3246, March 2002.
[RFC3662] Bless, R., Nichols, K., and K. Wehrle, "A Lower Effort [RFC3662] Bless, R., Nichols, K., and K. Wehrle, "A Lower Effort
Per-Domain Behavior (PDB) for Differentiated Services", Per-Domain Behavior (PDB) for Differentiated Services",
RFC 3662, December 2003. RFC 3662, December 2003.
10.2 Informative References 10.2. Informative References
[I-D.iab-auth-mech]
Rescorla, E., "A Survey of Authentication Mechanisms",
draft-iab-auth-mech-04 (work in progress), September 2005.
[QBSS] "QBone Scavenger Service (QBSS) Definition", Internet2 [QBSS] "QBone Scavenger Service (QBSS) Definition", Internet2
Technical Report Proposed Service Definition, March 2001. Technical Report Proposed Service Definition, March 2001.
[RFC1633] Braden, B., Clark, D., and S. Shenker, "Integrated [RFC1633] Braden, B., Clark, D., and S. Shenker, "Integrated
Services in the Internet Architecture: an Overview", Services in the Internet Architecture: an Overview",
RFC 1633, June 1994. RFC 1633, June 1994.
[RFC2205] Braden, B., Zhang, L., Berson, S., Herzog, S., and S. [RFC2205] Braden, B., Zhang, L., Berson, S., Herzog, S., and S.
Jamin, "Resource ReSerVation Protocol (RSVP) -- Version 1 Jamin, "Resource ReSerVation Protocol (RSVP) -- Version 1
skipping to change at page 54, line 46 skipping to change at page 58, line 24
Fax: +1-613-765-7462 Fax: +1-613-765-7462
Email: babiarz@nortel.com Email: babiarz@nortel.com
Kwok Ho Chan Kwok Ho Chan
Nortel Networks Nortel Networks
600 Technology Park Drive 600 Technology Park Drive
Billerica, MA 01821 Billerica, MA 01821
US US
Phone: +1-978-288-8175 Phone: +1-978-288-8175
Fax: +1-978-288-4690 Fax: +1-978-288-8700
Email: khchan@nortel.com Email: khchan@nortel.com
Fred Baker Fred Baker
Cisco Systems Cisco Systems
1121 Via Del Rey 1121 Via Del Rey
Santa Barbara, CA 93117 Santa Barbara, CA 93117
US US
Phone: +1-408-526-4257 Phone: +1-408-526-4257
Fax: +1-413-473-2403 Fax: +1-413-473-2403
Email: fred@cisco.com Email: fred@cisco.com
skipping to change at page 56, line 41 skipping to change at page 59, line 41
This document and the information contained herein are provided on an This document and the information contained herein are provided on an
"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Copyright Statement Copyright Statement
Copyright (C) The Internet Society (2005). This document is subject Copyright (C) The Internet Society (2006). This document is subject
to the rights, licenses and restrictions contained in BCP 78, and to the rights, licenses and restrictions contained in BCP 78, and
except as set forth therein, the authors retain all their rights. except as set forth therein, the authors retain all their rights.
Acknowledgment Acknowledgment
Funding for the RFC Editor function is currently provided by the Funding for the RFC Editor function is currently provided by the
Internet Society. Internet Society.
 End of changes. 88 change blocks. 
190 lines changed or deleted 314 lines changed or added

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