draft-ietf-tsvwg-ecn-encap-guidelines-01.txt   draft-ietf-tsvwg-ecn-encap-guidelines-02.txt 
Transport Area Working Group B. Briscoe Transport Area Working Group B. Briscoe
Internet-Draft BT Internet-Draft BT
Updates: 3819 (if approved) J. Kaippallimalil Updates: 3819 (if approved) J. Kaippallimalil
Intended status: Best Current Practice Huawei Intended status: Best Current Practice Huawei
Expires: May 20, 2015 P. Thaler Expires: September 27, 2015 P. Thaler
Broadcom Corporation Broadcom Corporation
November 16, 2014 March 26, 2015
Guidelines for Adding Congestion Notification to Protocols that Guidelines for Adding Congestion Notification to Protocols that
Encapsulate IP Encapsulate IP
draft-ietf-tsvwg-ecn-encap-guidelines-01 draft-ietf-tsvwg-ecn-encap-guidelines-02
Abstract Abstract
The purpose of this document is to guide the design of congestion The purpose of this document is to guide the design of congestion
notification in any lower layer or tunnelling protocol that notification in any lower layer or tunnelling protocol that
encapsulates IP. The aim is for explicit congestion signals to encapsulates IP. The aim is for explicit congestion signals to
propagate consistently from lower layer protocols into IP. Then the propagate consistently from lower layer protocols into IP. Then the
IP internetwork layer can act as a portability layer to carry IP internetwork layer can act as a portability layer to carry
congestion notification from non-IP-aware congested nodes up to the congestion notification from non-IP-aware congested nodes up to the
transport layer (L4). Following these guidelines should assure transport layer (L4). Following these guidelines should assure
skipping to change at page 1, line 42 skipping to change at page 1, line 42
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on May 20, 2015. This Internet-Draft will expire on September 27, 2015.
Copyright Notice Copyright Notice
Copyright (c) 2014 IETF Trust and the persons identified as the Copyright (c) 2015 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . 5 1.1. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 6 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 6
3. Modes of Operation . . . . . . . . . . . . . . . . . . . . . 7 3. Guidelines in All Cases . . . . . . . . . . . . . . . . . . . 7
3.1. Feed-Forward-and-Up Mode . . . . . . . . . . . . . . . . 8 4. Modes of Operation . . . . . . . . . . . . . . . . . . . . . 7
3.2. Feed-Up-and-Forward Mode . . . . . . . . . . . . . . . . 9 4.1. Feed-Forward-and-Up Mode . . . . . . . . . . . . . . . . 8
3.3. Feed-Backward Mode . . . . . . . . . . . . . . . . . . . 10 4.2. Feed-Up-and-Forward Mode . . . . . . . . . . . . . . . . 10
3.4. Null Mode . . . . . . . . . . . . . . . . . . . . . . . . 12 4.3. Feed-Backward Mode . . . . . . . . . . . . . . . . . . . 10
4. Feed-Forward-and-Up Mode: Guidelines for Adding Congestion 4.4. Null Mode . . . . . . . . . . . . . . . . . . . . . . . . 12
5. Feed-Forward-and-Up Mode: Guidelines for Adding Congestion
Notification . . . . . . . . . . . . . . . . . . . . . . . . 12 Notification . . . . . . . . . . . . . . . . . . . . . . . . 12
4.1. IP-in-IP Tunnels with Tightly Coupled Shim Headers . . . 13 5.1. IP-in-IP Tunnels with Tightly Coupled Shim Headers . . . 13
4.2. Wire Protocol Design: Indication of ECN Support . . . . . 13 5.2. Wire Protocol Design: Indication of ECN Support . . . . . 13
4.3. Encapsulation Guidelines . . . . . . . . . . . . . . . . 15 5.3. Encapsulation Guidelines . . . . . . . . . . . . . . . . 15
4.4. Decapsulation Guidelines . . . . . . . . . . . . . . . . 17 5.4. Decapsulation Guidelines . . . . . . . . . . . . . . . . 17
4.5. Sequences of Similar Tunnels or Subnets . . . . . . . . . 18 5.5. Sequences of Similar Tunnels or Subnets . . . . . . . . . 18
4.6. Reframing and Congestion Markings . . . . . . . . . . . . 19 5.6. Reframing and Congestion Markings . . . . . . . . . . . . 19
5. Feed-Up-and-Forward Mode: Guidelines for Adding Congestion 6. Feed-Up-and-Forward Mode: Guidelines for Adding Congestion
Notification . . . . . . . . . . . . . . . . . . . . . . . . 19 Notification . . . . . . . . . . . . . . . . . . . . . . . . 19
6. Feed-Backward Mode: Guidelines for Adding Congestion 7. Feed-Backward Mode: Guidelines for Adding Congestion
Notification . . . . . . . . . . . . . . . . . . . . . . . . 21 Notification . . . . . . . . . . . . . . . . . . . . . . . . 21
7. IANA Considerations (to be removed by RFC Editor) . . . . . . 22 8. IANA Considerations (to be removed by RFC Editor) . . . . . . 22
8. Security Considerations . . . . . . . . . . . . . . . . . . . 22 9. Security Considerations . . . . . . . . . . . . . . . . . . . 22
9. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . 22 10. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . 22
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 23 11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 23
11. Comments Solicited . . . . . . . . . . . . . . . . . . . . . 23 12. Comments Solicited . . . . . . . . . . . . . . . . . . . . . 23
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 23 13. References . . . . . . . . . . . . . . . . . . . . . . . . . 23
12.1. Normative References . . . . . . . . . . . . . . . . . . 23 13.1. Normative References . . . . . . . . . . . . . . . . . . 23
12.2. Informative References . . . . . . . . . . . . . . . . . 24 13.2. Informative References . . . . . . . . . . . . . . . . . 24
Appendix A. Outstanding Document Issues . . . . . . . . . . . . 27 Appendix A. Outstanding Document Issues . . . . . . . . . . . . 27
Appendix B. Changes in This Version (to be removed by RFC Appendix B. Changes in This Version (to be removed by RFC
Editor) . . . . . . . . . . . . . . . . . . . . . . 27 Editor) . . . . . . . . . . . . . . . . . . . . . . 27
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 29
1. Introduction 1. Introduction
The benefits of Explicit Congestion Notification (ECN) described The benefits of Explicit Congestion Notification (ECN) described
below can only be fully realised if support for ECN is added to the below can only be fully realised if support for ECN is added to the
relevant subnetwork technology, as well as to IP. When a lower layer relevant subnetwork technology, as well as to IP. When a lower layer
buffer drops a packet obviously it does not just drop at that layer; buffer drops a packet obviously it does not just drop at that layer;
the packet disappears from all layers. In contrast, when a lower the packet disappears from all layers. In contrast, when a lower
layer marks a packet with ECN, the marking needs to be explicitly layer marks a packet with ECN, the marking needs to be explicitly
propagated up the layers. The same is true if a buffer marks the propagated up the layers. The same is true if a buffer marks the
skipping to change at page 5, line 11 skipping to change at page 5, line 11
used in preference to 'MUST' or 'MUST NOT', because it is difficult used in preference to 'MUST' or 'MUST NOT', because it is difficult
to know the compromises that will be necessary in each protocol to know the compromises that will be necessary in each protocol
design. If a particular protocol design chooses to contradict a design. If a particular protocol design chooses to contradict a
'SHOULD (NOT)' given in the advice below, it MUST include a sound 'SHOULD (NOT)' given in the advice below, it MUST include a sound
justification. justification.
It has not been possible to give common guidelines for all lower It has not been possible to give common guidelines for all lower
layer technologies, because they do not all fit a common pattern. layer technologies, because they do not all fit a common pattern.
Instead they have been divided into a few distinct modes of Instead they have been divided into a few distinct modes of
operation: feed-forward-and-upward; feed-upward-and-forward; feed- operation: feed-forward-and-upward; feed-upward-and-forward; feed-
backward; and null mode. These modes are described in Section 3, backward; and null mode. These modes are described in Section 4,
then in the following sections separate guidelines are given for each then in the following sections separate guidelines are given for each
mode. mode.
This document updates the advice to subnetwork designers about ECN in This document updates the advice to subnetwork designers about ECN in
Section 13 of [RFC3819]. Section 13 of [RFC3819].
1.1. Scope 1.1. Scope
This document only concerns wire protocol processing of explicit This document only concerns wire protocol processing of explicit
notification of congestion and makes no changes or recommendations notification of congestion and makes no changes or recommendations
skipping to change at page 7, line 34 skipping to change at page 7, line 34
the load" deliberately includes a transport that doesn't actually the load" deliberately includes a transport that doesn't actually
control the load but ideally it ought to (e.g. a sending control the load but ideally it ought to (e.g. a sending
application without congestion control that uses UDP). application without congestion control that uses UDP).
Congestion Baseline: The location of the function on the path that Congestion Baseline: The location of the function on the path that
initialised the values of all congestion notification fields in a initialised the values of all congestion notification fields in a
sequence of packets, before any are set to the congestion sequence of packets, before any are set to the congestion
experienced (CE) codepoint if they experience congestion further experienced (CE) codepoint if they experience congestion further
downstream. Typically the original data source at layer-4. downstream. Typically the original data source at layer-4.
3. Modes of Operation 3. Guidelines in All Cases
RFC 3168 specifies that the ECN field in the IP header is intended to
be marked by active queue management algorithms. Any congestion
notification from an algorithm that does not conform to the
recommendations in [I-D.ietf-aqm-recommendation] MUST NOT be
propagated from a lower layer into the ECN field in IP.
4. Modes of Operation
This section sets down the different modes by which congestion This section sets down the different modes by which congestion
information is passed between the lower layer and the higher one. It information is passed between the lower layer and the higher one. It
acts as a reference framework for the following sections, which give acts as a reference framework for the following sections, which give
normative guidelines for designers of explicit congestion normative guidelines for designers of explicit congestion
notification protocols, taking each mode in turn: notification protocols, taking each mode in turn:
Feed-Forward-and-Up: Nodes feed forward congestion notification Feed-Forward-and-Up: Nodes feed forward congestion notification
towards the egress within the lower layer then up and along the towards the egress within the lower layer then up and along the
layers towards the end-to-end destination at the transport layer. layers towards the end-to-end destination at the transport layer.
skipping to change at page 8, line 13 skipping to change at page 8, line 20
egress of a subnet. egress of a subnet.
Feed-Backward: Nodes feed back congestion signals towards the Feed-Backward: Nodes feed back congestion signals towards the
ingress of the lower layer and (optionally) attempt to control ingress of the lower layer and (optionally) attempt to control
congestion within their own layer. congestion within their own layer.
Null: Nodes cannot experience congestion at the lower layer except Null: Nodes cannot experience congestion at the lower layer except
at ingress nodes (which are IP-aware or equivalently higher-layer- at ingress nodes (which are IP-aware or equivalently higher-layer-
aware). aware).
3.1. Feed-Forward-and-Up Mode 4.1. Feed-Forward-and-Up Mode
Like IP and MPLS, many subnet technologies are based on self- Like IP and MPLS, many subnet technologies are based on self-
contained protocol data units (PDUs) or frames sent unreliably. They contained protocol data units (PDUs) or frames sent unreliably. They
provide no feedback channel at the subnetwork layer, instead relying provide no feedback channel at the subnetwork layer, instead relying
on higher layers (e.g. TCP) to feed back loss signals. on higher layers (e.g. TCP) to feed back loss signals.
In these cases, ECN may best be supported by standardising explicit In these cases, ECN may best be supported by standardising explicit
notification of congestion into the lower layer protocol that carries notification of congestion into the lower layer protocol that carries
the data forwards. It will then also be necessary to define how the the data forwards. It will then also be necessary to define how the
egress of the lower layer subnet propagates this explicit signal into egress of the lower layer subnet propagates this explicit signal into
skipping to change at page 9, line 43 skipping to change at page 10, line 5
Note that the FECN (forward ECN) bit in Frame Relay and the explicit Note that the FECN (forward ECN) bit in Frame Relay and the explicit
forward congestion indication (EFCI [ITU-T.I.371]) bit in ATM user forward congestion indication (EFCI [ITU-T.I.371]) bit in ATM user
data cells follow a feed-forward pattern. However, in ATM, this is data cells follow a feed-forward pattern. However, in ATM, this is
only as part of a feed-forward-and-backward pattern at the lower only as part of a feed-forward-and-backward pattern at the lower
layer, not feed-forward-and-up out of the lower layer--the intention layer, not feed-forward-and-up out of the lower layer--the intention
was never to interface to IP ECN at the subnet egress. To our was never to interface to IP ECN at the subnet egress. To our
knowledge, Frame Relay FECN is solely used to detect where more knowledge, Frame Relay FECN is solely used to detect where more
capacity should be provisioned [Buck00]. capacity should be provisioned [Buck00].
3.2. Feed-Up-and-Forward Mode 4.2. Feed-Up-and-Forward Mode
Ethernet is particularly difficult to extend incrementally to support Ethernet is particularly difficult to extend incrementally to support
explicit congestion notification. One way to support ECN in such explicit congestion notification. One way to support ECN in such
cases has been to use so called 'layer-3 switches'. These are cases has been to use so called 'layer-3 switches'. These are
Ethernet switches that bury into the Ethernet payload to find an IP Ethernet switches that bury into the Ethernet payload to find an IP
header and manipulate or act on certain IP fields (specifically header and manipulate or act on certain IP fields (specifically
Diffserv & ECN). For instance, in Data Center TCP [DCTCP], layer-3 Diffserv & ECN). For instance, in Data Center TCP [DCTCP], layer-3
switches are configured to mark the ECN field of the IP header within switches are configured to mark the ECN field of the IP header within
the Ethernet payload when their output buffer becomes congested. the Ethernet payload when their output buffer becomes congested.
With respect to switching, a layer-3 switch acts solely on the With respect to switching, a layer-3 switch acts solely on the
skipping to change at page 10, line 36 skipping to change at page 10, line 46
Figure 2: Feed-Up-and-Forward Mode Figure 2: Feed-Up-and-Forward Mode
By comparing Figure 2 with Figure 1, it can be seen that subnet E By comparing Figure 2 with Figure 1, it can be seen that subnet E
(perhaps a subnet of layer-3 Ethernet switches) works in feed-up-and- (perhaps a subnet of layer-3 Ethernet switches) works in feed-up-and-
forward mode by notifying congestion directly into L3 at the point of forward mode by notifying congestion directly into L3 at the point of
congestion, even though the congested switch does not otherwise act congestion, even though the congested switch does not otherwise act
at L3. In this example, the technology in subnet F (e.g. MPLS) does at L3. In this example, the technology in subnet F (e.g. MPLS) does
support ECN natively, so when the router adds the layer-2 header it support ECN natively, so when the router adds the layer-2 header it
copies the ECN marking from L3 to L2 as well. copies the ECN marking from L3 to L2 as well.
3.3. Feed-Backward Mode 4.3. Feed-Backward Mode
In some layer 2 technologies, explicit congestion notification has In some layer 2 technologies, explicit congestion notification has
been defined for use internally within the subnet with its own been defined for use internally within the subnet with its own
feedback and load regulation, but typically the interface with IP for feedback and load regulation, but typically the interface with IP for
ECN has not been defined. ECN has not been defined.
For instance, for the available bit-rate (ABR) service in ATM, the For instance, for the available bit-rate (ABR) service in ATM, the
relative rate mechanism was one of the more popular mechanisms for relative rate mechanism was one of the more popular mechanisms for
managing traffic, tending to supersede earlier designs. In this managing traffic, tending to supersede earlier designs. In this
approach ATM switches send special resource management (RM) cells in approach ATM switches send special resource management (RM) cells in
skipping to change at page 12, line 11 skipping to change at page 12, line 21
which it signals forwards on later data packets at layer 3 (e.g. which it signals forwards on later data packets at layer 3 (e.g.
packet W). Note that the forward signal from the middle router is packet W). Note that the forward signal from the middle router is
not triggered directly by the backward signal. Rather, it is not triggered directly by the backward signal. Rather, it is
triggered by congestion resulting from the middle router's mismatched triggered by congestion resulting from the middle router's mismatched
rate response to the backward signal. rate response to the backward signal.
In response to this later forward signalling, end-to-end feedback at In response to this later forward signalling, end-to-end feedback at
layer-4 finally completes the tortuous path of congestion indications layer-4 finally completes the tortuous path of congestion indications
back to the origin data source, as before. back to the origin data source, as before.
3.4. Null Mode 4.4. Null Mode
Often link and physical layer resources are 'non-blocking' by design. Often link and physical layer resources are 'non-blocking' by design.
In these cases congestion notification may be implemented but it does In these cases congestion notification may be implemented but it does
not need to be deployed at the lower layer; ECN in IP would be not need to be deployed at the lower layer; ECN in IP would be
sufficient. sufficient.
A degenerate example is a point-to-point Ethernet link. Excess A degenerate example is a point-to-point Ethernet link. Excess
loading of the link merely causes the queue from the higher layer to loading of the link merely causes the queue from the higher layer to
back up, while the lower layer remains immune to congestion. Even a back up, while the lower layer remains immune to congestion. Even a
whole meshed subnetwork can be made immune to interior congestion by whole meshed subnetwork can be made immune to interior congestion by
limiting ingress capacity and careful sizing of links, particularly limiting ingress capacity and careful sizing of links, particularly
if multi-path routing is used to ensure even worst-case patterns of if multi-path routing is used to ensure even worst-case patterns of
load cannot congest any link. load cannot congest any link.
4. Feed-Forward-and-Up Mode: Guidelines for Adding Congestion 5. Feed-Forward-and-Up Mode: Guidelines for Adding Congestion
Notification Notification
Feed-forward-and-up is the mode already used for signalling ECN up Feed-forward-and-up is the mode already used for signalling ECN up
the layers through MPLS into IP [RFC5129] and through IP-in-IP the layers through MPLS into IP [RFC5129] and through IP-in-IP
tunnels [RFC6040]. These RFCs take a consistent approach and the tunnels [RFC6040]. These RFCs take a consistent approach and the
following guidelines are designed to ensure this consistency following guidelines are designed to ensure this consistency
continues as ECN support is added to other protocols that encapsulate continues as ECN support is added to other protocols that encapsulate
IP. The guidelines are also designed to ensure compliance with the IP. The guidelines are also designed to ensure compliance with the
more general best current practice for the design of alternate ECN more general best current practice for the design of alternate ECN
schemes given in [RFC4774]. schemes given in [RFC4774].
The rest of this section is structured as follows: The rest of this section is structured as follows:
o Section 4.1 addresses the most straightforward cases, where o Section 5.1 addresses the most straightforward cases, where
[RFC6040] can be applied directly to add ECN to tunnels that are [RFC6040] can be applied directly to add ECN to tunnels that are
effectively the same as IP-in-IP tunnels. effectively the same as IP-in-IP tunnels.
o The subsequent sections give guidelines for adding ECN to a subnet o The subsequent sections give guidelines for adding ECN to a subnet
technology that uses feed-forward-and-up mode like IP, but it is technology that uses feed-forward-and-up mode like IP, but it is
not so similar to IP that [RFC6040] rules can be applied directly. not so similar to IP that [RFC6040] rules can be applied directly.
Specifically: Specifically:
* Sections 4.2, 4.3 and 4.4 respectively address how to add ECN * Sections 5.2, 5.3 and 5.4 respectively address how to add ECN
support to the wire protocol and to the encapsulators and support to the wire protocol and to the encapsulators and
decapsulators at the ingress and egress of the subnet. decapsulators at the ingress and egress of the subnet.
* Section 4.5 deals with the special, but common, case of * Section 5.5 deals with the special, but common, case of
sequences of tunnels or subnets that all use the same sequences of tunnels or subnets that all use the same
technology technology
* Section 4.6 deals with the question of reframing when IP * Section 5.6 deals with the question of reframing when IP
packets do not map 1:1 into lower layer frames. packets do not map 1:1 into lower layer frames.
4.1. IP-in-IP Tunnels with Tightly Coupled Shim Headers 5.1. IP-in-IP Tunnels with Tightly Coupled Shim Headers
A common pattern for many tunnelling protocols is to encapsulate an A common pattern for many tunnelling protocols is to encapsulate an
inner IP header with shim header(s) then an outer IP header. In many inner IP header with shim header(s) then an outer IP header. In many
cases the shim header(s) always have to be tightly coupled to the cases the shim header(s) always have to be tightly coupled to the
outer IP header because they are not sufficient as outer headers in outer IP header because they are not sufficient as outer headers in
their own right. In such cases the shim header(s) and the outer IP their own right. In such cases the shim header(s) and the outer IP
header are always added (or removed) in the same operation. header are always added (or removed) in the same operation.
Therefore, in all such tightly coupled IP-in-IP tunnelling protocols, Therefore, in all such tightly coupled IP-in-IP tunnelling protocols,
the rules in [RFC6040] for propagating the ECN field between the two the rules in [RFC6040] for propagating the ECN field between the two
IP headers SHOULD be applied directly. IP headers SHOULD be applied directly.
skipping to change at page 13, line 37 skipping to change at page 13, line 46
o L2TP [RFC2661] o L2TP [RFC2661]
o GRE [RFC1701], [RFC2784] o GRE [RFC1701], [RFC2784]
o PPTP [RFC2637] o PPTP [RFC2637]
o GTP [GTPv1], [GTPv1-U], [GTPv2-C] o GTP [GTPv1], [GTPv1-U], [GTPv2-C]
o VXLAN [RFC7348]. o VXLAN [RFC7348].
4.2. Wire Protocol Design: Indication of ECN Support 5.2. Wire Protocol Design: Indication of ECN Support
This section is intended to guide the redesign of any lower layer This section is intended to guide the redesign of any lower layer
protocol that encapsulate IP to add native ECN support at the lower protocol that encapsulate IP to add native ECN support at the lower
layer. It reflects the approaches used in [RFC6040] and in layer. It reflects the approaches used in [RFC6040] and in
[RFC5129]. Therefore IP-in-IP tunnels or IP-in-MPLS or MPLS-in-MPLS [RFC5129]. Therefore IP-in-IP tunnels or IP-in-MPLS or MPLS-in-MPLS
encapsulations that already comply with [RFC6040] or [RFC5129] will encapsulations that already comply with [RFC6040] or [RFC5129] will
already satisfy this guidance. already satisfy this guidance.
A lower layer (or subnet) congestion notification system: A lower layer (or subnet) congestion notification system:
skipping to change at page 15, line 9 skipping to change at page 15, line 19
whether the PDU is destined for a transport that will understand whether the PDU is destined for a transport that will understand
them. Nonetheless, this is made safe by requiring that the network them. Nonetheless, this is made safe by requiring that the network
operator upgrades all decapsulating edges of a whole domain at once, operator upgrades all decapsulating edges of a whole domain at once,
as soon as even one switch within the domain is configured to mark as soon as even one switch within the domain is configured to mark
rather than drop during congestion. Therefore, any edge node that rather than drop during congestion. Therefore, any edge node that
might decapsulate a packet will be capable of checking whether the might decapsulate a packet will be capable of checking whether the
higher layer transport is ECN-capable. When decapsulating a CE- higher layer transport is ECN-capable. When decapsulating a CE-
marked packet, if the decapsulator discovers that the higher layer marked packet, if the decapsulator discovers that the higher layer
(inner header) indicates the transport is not ECN-capable, it drops (inner header) indicates the transport is not ECN-capable, it drops
the packet--effectively on behalf of the earlier congested node (see the packet--effectively on behalf of the earlier congested node (see
Decapsulation Guideline 1 in Section 4.4). Decapsulation Guideline 1 in Section 5.4).
It was only appropriate to define such an incremental deployment It was only appropriate to define such an incremental deployment
strategy because MPLS is targeted solely at professional operators, strategy because MPLS is targeted solely at professional operators,
who can be expected to ensure that a whole subnetwork is consistently who can be expected to ensure that a whole subnetwork is consistently
configured. This strategy might not be appropriate for other link configured. This strategy might not be appropriate for other link
technologies targeted at zero-configuration deployment or deployment technologies targeted at zero-configuration deployment or deployment
by the general public (e.g. Ethernet). For such 'plug-and-play' by the general public (e.g. Ethernet). For such 'plug-and-play'
environments it will be necessary to invent a failsafe approach that environments it will be necessary to invent a failsafe approach that
ensures congestion markings will never fall into black holes, no ensures congestion markings will never fall into black holes, no
matter how inconsistently a system is put together. Alternatively, matter how inconsistently a system is put together. Alternatively,
skipping to change at page 15, line 31 skipping to change at page 15, line 41
be confined to flavours of Ethernet intended only for professional be confined to flavours of Ethernet intended only for professional
network operators, such as IEEE 802.1ah Provider Backbone Bridges network operators, such as IEEE 802.1ah Provider Backbone Bridges
(PBB). (PBB).
QCN [IEEE802.1Qau] provides another example of how to indicate to QCN [IEEE802.1Qau] provides another example of how to indicate to
lower layer devices that the end-points will not understand ECN. An lower layer devices that the end-points will not understand ECN. An
operator can define certain 802.1p classes of service to indicate operator can define certain 802.1p classes of service to indicate
non-QCN frames and an ingress bridge is required to map arriving not- non-QCN frames and an ingress bridge is required to map arriving not-
QCN-capable IP packets to one of these non-QCN 802.1p classes. QCN-capable IP packets to one of these non-QCN 802.1p classes.
4.3. Encapsulation Guidelines 5.3. Encapsulation Guidelines
This section is intended to guide the redesign of any node that This section is intended to guide the redesign of any node that
encapsulates IP with a lower layer header when adding native ECN encapsulates IP with a lower layer header when adding native ECN
support to the lower layer protocol. It reflects the approaches used support to the lower layer protocol. It reflects the approaches used
in [RFC6040] and in [RFC5129]. Therefore IP-in-IP tunnels or IP-in- in [RFC6040] and in [RFC5129]. Therefore IP-in-IP tunnels or IP-in-
MPLS or MPLS-in-MPLS encapsulations that already comply with MPLS or MPLS-in-MPLS encapsulations that already comply with
[RFC6040] or [RFC5129] will already satisfy this guidance. [RFC6040] or [RFC5129] will already satisfy this guidance.
1. Egress Capability Check: A subnet ingress needs to be sure that 1. Egress Capability Check: A subnet ingress needs to be sure that
the corresponding egress of a subnet will propagate any the corresponding egress of a subnet will propagate any
skipping to change at page 17, line 5 skipping to change at page 17, line 13
markings while others copy incoming CE markings into the outer. markings while others copy incoming CE markings into the outer.
Most information can be extracted if the Congestion Baseline is Most information can be extracted if the Congestion Baseline is
standardised at the node that is regulating the load (the Load standardised at the node that is regulating the load (the Load
Regulator--typically the data source). Then the operator can Regulator--typically the data source). Then the operator can
measure both congestion since the Load Regulator, and congestion measure both congestion since the Load Regulator, and congestion
since the subnet ingress. The latter might be measurable by since the subnet ingress. The latter might be measurable by
subtracting the level of CE markings on inner headers from that subtracting the level of CE markings on inner headers from that
on outer headers (see Appendix C of [RFC6040]). on outer headers (see Appendix C of [RFC6040]).
4.4. Decapsulation Guidelines 5.4. Decapsulation Guidelines
This section is intended to guide the redesign of any node that This section is intended to guide the redesign of any node that
decapsulates IP from within a lower layer header when adding native decapsulates IP from within a lower layer header when adding native
ECN support to the lower layer protocol. It reflects the approaches ECN support to the lower layer protocol. It reflects the approaches
used in [RFC6040] and in [RFC5129]. Therefore IP-in-IP tunnels or used in [RFC6040] and in [RFC5129]. Therefore IP-in-IP tunnels or
IP-in-MPLS or MPLS-in-MPLS encapsulations that already comply with IP-in-MPLS or MPLS-in-MPLS encapsulations that already comply with
[RFC6040] or [RFC5129] will already satisfy this guidance. [RFC6040] or [RFC5129] will already satisfy this guidance.
A subnet egress SHOULD NOT simply copy congestion notification from A subnet egress SHOULD NOT simply copy congestion notification from
outer headers to the forwarded header. It SHOULD calculate the outer headers to the forwarded header. It SHOULD calculate the
skipping to change at page 18, line 10 skipping to change at page 18, line 19
levels in IP or MPLS [RFC6660]. levels in IP or MPLS [RFC6660].
If the arriving inner header is an ECN-PDU, where the inner and If the arriving inner header is an ECN-PDU, where the inner and
outer headers carry indications of congestion of different outer headers carry indications of congestion of different
severity, the more severe indication SHOULD be forwarded in severity, the more severe indication SHOULD be forwarded in
preference to the less severe. preference to the less severe.
5. The inner and outer headers might carry a combination of 5. The inner and outer headers might carry a combination of
congestion notification fields that should not be possible given congestion notification fields that should not be possible given
any currently used protocol transitions. For instance, if any currently used protocol transitions. For instance, if
Encapsulation Guideline 3 in Section 4.3 had been followed, it Encapsulation Guideline 3 in Section 5.3 had been followed, it
should not be possible to have a less severe indication of should not be possible to have a less severe indication of
congestion in the outer than in the inner. It MAY be appropriate congestion in the outer than in the inner. It MAY be appropriate
to log unexpected combinations of headers and possibly raise an to log unexpected combinations of headers and possibly raise an
alarm. alarm.
If a safe outgoing codepoint can be defined for such a PDU, the If a safe outgoing codepoint can be defined for such a PDU, the
PDU SHOULD be forwarded rather than dropped. Some implementers PDU SHOULD be forwarded rather than dropped. Some implementers
discard PDUs with currently unused combinations of headers just discard PDUs with currently unused combinations of headers just
in case they represent an attack. However, an approach using in case they represent an attack. However, an approach using
alarms and policy-mediated drop is preferable to hard-coded drop, alarms and policy-mediated drop is preferable to hard-coded drop,
so that operators can keep track of possible attacks but so that operators can keep track of possible attacks but
currently unused combinations are not precluded from future use currently unused combinations are not precluded from future use
through new standards actions. through new standards actions.
4.5. Sequences of Similar Tunnels or Subnets 5.5. Sequences of Similar Tunnels or Subnets
In some deployments, particularly in 3GPP networks, an IP packet may In some deployments, particularly in 3GPP networks, an IP packet may
traverse two or more IP-in-IP tunnels in sequence that all use traverse two or more IP-in-IP tunnels in sequence that all use
identical technology (e.g. GTP). identical technology (e.g. GTP).
In such cases, it would be sufficient for every encapsulation and In such cases, it would be sufficient for every encapsulation and
decapsulation in the chain to comply with RFC 6040. Alternatively, decapsulation in the chain to comply with RFC 6040. Alternatively,
as an optimisation, a node that decapsulates a packet and immediately as an optimisation, a node that decapsulates a packet and immediately
re-encapsulates it for the next tunnel MAY copy the incoming outer re-encapsulates it for the next tunnel MAY copy the incoming outer
ECN field directly to the outgoing outer and the incoming inner ECN ECN field directly to the outgoing outer and the incoming inner ECN
skipping to change at page 19, line 9 skipping to change at page 19, line 15
monitor the whole sequence of tunnels, but only if the above monitor the whole sequence of tunnels, but only if the above
optimisation were used consistently along the sequence of tunnels, in optimisation were used consistently along the sequence of tunnels, in
order to make it appear as a single tunnel. Therefore, tunnel order to make it appear as a single tunnel. Therefore, tunnel
endpoint implementations SHOULD allow the operator to configure endpoint implementations SHOULD allow the operator to configure
whether this optimisation is enabled. whether this optimisation is enabled.
When ECN support is added to a subnet technology, consideration When ECN support is added to a subnet technology, consideration
SHOULD be given to a similar optimisation between subnets in sequence SHOULD be given to a similar optimisation between subnets in sequence
if they all use the same technology. if they all use the same technology.
4.6. Reframing and Congestion Markings 5.6. Reframing and Congestion Markings
The guidance in this section is worded in terms of framing The guidance in this section is worded in terms of framing
boundaries, but it applies equally whether the protocol data units boundaries, but it applies equally whether the protocol data units
are frames, cells or packets. are frames, cells or packets.
Where framing boundaries are different between two layers, congestion Where framing boundaries are different between two layers, congestion
indications SHOULD be propagated on the basis that a congestion indications SHOULD be propagated on the basis that a congestion
indication on a PDU applies to all the octets in the PDU. On indication on a PDU applies to all the octets in the PDU. On
average, an encapsulator or decapsulator SHOULD approximately average, an encapsulator or decapsulator SHOULD approximately
preserve the number of marked octets arriving and leaving (counting preserve the number of marked octets arriving and leaving (counting
skipping to change at page 19, line 36 skipping to change at page 19, line 42
no bigger than the outstanding marked octets--which might involve a no bigger than the outstanding marked octets--which might involve a
long wait. long wait.
For instance, an algorithm for marking departing frames could For instance, an algorithm for marking departing frames could
maintain a counter representing the balance of arriving marked octets maintain a counter representing the balance of arriving marked octets
minus departing marked octets. It adds the size of every marked minus departing marked octets. It adds the size of every marked
frame that arrives and if the counter is positive it marks the next frame that arrives and if the counter is positive it marks the next
frame to depart and subtracts its size from the counter. This will frame to depart and subtracts its size from the counter. This will
often leave a negative remainder in the counter, which is deliberate. often leave a negative remainder in the counter, which is deliberate.
5. Feed-Up-and-Forward Mode: Guidelines for Adding Congestion 6. Feed-Up-and-Forward Mode: Guidelines for Adding Congestion
Notification Notification
The guidance in this section is applicable when IP packets: The guidance in this section is applicable when IP packets:
o are encapsulated in Ethernet headers; o are encapsulated in Ethernet headers;
o are forwarded by the eNode-B (base station) of a 3GPP radio access o are forwarded by the eNode-B (base station) of a 3GPP radio access
network, which is required to apply ECN marking during congestion network, which is required to apply ECN marking during congestion
[LTE-RA]. [LTE-RA].
skipping to change at page 21, line 5 skipping to change at page 21, line 7
an IP header is not found soon enough, or an unrecognised or an IP header is not found soon enough, or an unrecognised or
unreadable header is encountered, the switch SHOULD resort to an unreadable header is encountered, the switch SHOULD resort to an
alternative means of signalling congestion (e.g. drop, or the alternative means of signalling congestion (e.g. drop, or the
native lower layer mechanism if available). native lower layer mechanism if available).
3. It is sufficient to use the first IP header found in the stack; 3. It is sufficient to use the first IP header found in the stack;
the egress of the relevant tunnel can propagate congestion the egress of the relevant tunnel can propagate congestion
notification upwards to any more deeply encapsulated IP headers notification upwards to any more deeply encapsulated IP headers
later. later.
6. Feed-Backward Mode: Guidelines for Adding Congestion Notification 7. Feed-Backward Mode: Guidelines for Adding Congestion Notification
It can be seen from Section 3.3 that congestion notification in a It can be seen from Section 4.3 that congestion notification in a
subnet using feed-backward mode has generally not been designed to be subnet using feed-backward mode has generally not been designed to be
directly coupled with IP layer congestion notification. The subnet directly coupled with IP layer congestion notification. The subnet
attempts to minimise congestion internally, and if the incoming load attempts to minimise congestion internally, and if the incoming load
at the ingress exceeds the capacity somewhere through the subnet, the at the ingress exceeds the capacity somewhere through the subnet, the
layer 3 buffer into the ingress backs up. Thus, a feed-backward mode layer 3 buffer into the ingress backs up. Thus, a feed-backward mode
subnet is in some sense similar to a null mode subnet, in that there subnet is in some sense similar to a null mode subnet, in that there
is no need for any direct interaction between the subnet and higher is no need for any direct interaction between the subnet and higher
layer congestion notification. Therefore no detailed protocol design layer congestion notification. Therefore no detailed protocol design
guidelines are appropriate. Nonetheless, a more general guideline is guidelines are appropriate. Nonetheless, a more general guideline is
appropriate: appropriate:
skipping to change at page 22, line 5 skipping to change at page 22, line 7
Quantised congestion notification (QCN--also known as backward Quantised congestion notification (QCN--also known as backward
congestion notification or BCN) [IEEE802.1Qau] uses a feed-backward congestion notification or BCN) [IEEE802.1Qau] uses a feed-backward
mode structurally similar to ATM's relative rate mechanism. However, mode structurally similar to ATM's relative rate mechanism. However,
QCN confines its applicability to scenarios such as some data centres QCN confines its applicability to scenarios such as some data centres
where all endpoints are directly attached by the same Ethernet where all endpoints are directly attached by the same Ethernet
technology. If a QCN subnet were later connected into a wider IP- technology. If a QCN subnet were later connected into a wider IP-
based internetwork (e.g. when attempting to interconnect multiple based internetwork (e.g. when attempting to interconnect multiple
data centres) it would suffer the inefficiency shown Figure 3. data centres) it would suffer the inefficiency shown Figure 3.
7. IANA Considerations (to be removed by RFC Editor) 8. IANA Considerations (to be removed by RFC Editor)
This memo includes no request to IANA. This memo includes no request to IANA.
8. Security Considerations 9. Security Considerations
If a lower layer wire protocol is redesigned to include explicit If a lower layer wire protocol is redesigned to include explicit
congestion signalling in-band in the protocol header, care SHOULD be congestion signalling in-band in the protocol header, care SHOULD be
take to ensure that the field used is specified as mutable during take to ensure that the field used is specified as mutable during
transit. Otherwise interior nodes signalling congestion would transit. Otherwise interior nodes signalling congestion would
invalidate any authentication protocol applied to the lower layer invalidate any authentication protocol applied to the lower layer
header--by altering a header field that had been assumed as header--by altering a header field that had been assumed as
immutable. immutable.
The redesign of protocols that encapsulate IP in order to propagate The redesign of protocols that encapsulate IP in order to propagate
skipping to change at page 22, line 42 skipping to change at page 22, line 44
o A test with the same goals as the ECN nonce, but without the need o A test with the same goals as the ECN nonce, but without the need
for the receiver to co-operate with the protocol for the receiver to co-operate with the protocol
[I-D.moncaster-tcpm-rcv-cheat]. [I-D.moncaster-tcpm-rcv-cheat].
Given these end-to-end approaches are already being specified, it Given these end-to-end approaches are already being specified, it
would make little sense to attempt to design hop-by-hop congestion would make little sense to attempt to design hop-by-hop congestion
signal integrity into a new lower layer protocol, because end-to-end signal integrity into a new lower layer protocol, because end-to-end
integrity inherently achieves hop-by-hop integrity. integrity inherently achieves hop-by-hop integrity.
9. Conclusions 10. Conclusions
Following the guidance in the document enables ECN support to be Following the guidance in the document enables ECN support to be
extended to numerous protocols that encapsulate IP (v4 & v6) in a extended to numerous protocols that encapsulate IP (v4 & v6) in a
consistent way, so that IP continues to fulfil its role as an end-to- consistent way, so that IP continues to fulfil its role as an end-to-
end interoperability layer. This includes: end interoperability layer. This includes:
o A wide range of tunnelling protocols with various forms of shim o A wide range of tunnelling protocols with various forms of shim
header between two IP headers; header between two IP headers;
o A wide range of subnet technologies, particularly those that work o A wide range of subnet technologies, particularly those that work
skipping to change at page 23, line 19 skipping to change at page 23, line 22
Guidelines have been defined for supporting propagation of ECN Guidelines have been defined for supporting propagation of ECN
between Ethernet and IP on so-called Layer-3 Ethernet switches, using between Ethernet and IP on so-called Layer-3 Ethernet switches, using
a 'feed-up-an-forward' mode. This approach could enable other subnet a 'feed-up-an-forward' mode. This approach could enable other subnet
technologies to pass ECN signals into the IP layer, even if they do technologies to pass ECN signals into the IP layer, even if they do
not support ECN natively. not support ECN natively.
Finally, attempting to add ECN to a subnet technology in feed- Finally, attempting to add ECN to a subnet technology in feed-
backward mode is deprecated except in special cases, due to its backward mode is deprecated except in special cases, due to its
likely sluggish response to congestion. likely sluggish response to congestion.
10. Acknowledgements 11. Acknowledgements
Thanks to Gorry Fairhurst for extensive reviews. Thanks also to the Thanks to Gorry Fairhurst for extensive reviews. Thanks also to the
following reviewers: Ingemar Johansson and Piers O'Hanlon and Michael following reviewers: Ingemar Johansson and Piers O'Hanlon and Michael
Welzl, who pointed out that lower layer congestion notification Welzl, who pointed out that lower layer congestion notification
signals may have different semantics to those in IP. signals may have different semantics to those in IP.
Bob Briscoe was part-funded by the European Community under its Bob Briscoe was part-funded by the European Community under its
Seventh Framework Programme through the Trilogy project (ICT-216372) Seventh Framework Programme through the Trilogy project (ICT-216372)
for initial drafts and through the Reducing Internet Transport for initial drafts and through the Reducing Internet Transport
Latency (RITE) project (ICT-317700) subsequently. The views Latency (RITE) project (ICT-317700) subsequently. The views
expressed here are solely those of the authors. expressed here are solely those of the authors.
11. Comments Solicited 12. Comments Solicited
Comments and questions are encouraged and very welcome. They can be Comments and questions are encouraged and very welcome. They can be
addressed to the IETF Transport Area working group mailing list addressed to the IETF Transport Area working group mailing list
<tsvwg@ietf.org>, and/or to the authors. <tsvwg@ietf.org>, and/or to the authors.
12. References 13. References
12.1. Normative References 13.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3168] Ramakrishnan, K., Floyd, S., and D. Black, "The Addition [RFC3168] Ramakrishnan, K., Floyd, S., and D. Black, "The Addition
of Explicit Congestion Notification (ECN) to IP", RFC of Explicit Congestion Notification (ECN) to IP", RFC
3168, September 2001. 3168, September 2001.
[RFC3819] Karn, P., Bormann, C., Fairhurst, G., Grossman, D., [RFC3819] Karn, P., Bormann, C., Fairhurst, G., Grossman, D.,
Ludwig, R., Mahdavi, J., Montenegro, G., Touch, J., and L. Ludwig, R., Mahdavi, J., Montenegro, G., Touch, J., and L.
skipping to change at page 24, line 15 skipping to change at page 24, line 20
[RFC4774] Floyd, S., "Specifying Alternate Semantics for the [RFC4774] Floyd, S., "Specifying Alternate Semantics for the
Explicit Congestion Notification (ECN) Field", BCP 124, Explicit Congestion Notification (ECN) Field", BCP 124,
RFC 4774, November 2006. RFC 4774, November 2006.
[RFC5129] Davie, B., Briscoe, B., and J. Tay, "Explicit Congestion [RFC5129] Davie, B., Briscoe, B., and J. Tay, "Explicit Congestion
Marking in MPLS", RFC 5129, January 2008. Marking in MPLS", RFC 5129, January 2008.
[RFC6040] Briscoe, B., "Tunnelling of Explicit Congestion [RFC6040] Briscoe, B., "Tunnelling of Explicit Congestion
Notification", RFC 6040, November 2010. Notification", RFC 6040, November 2010.
12.2. Informative References 13.2. Informative References
[ATM-TM-ABR] [ATM-TM-ABR]
Cisco, "Understanding the Available Bit Rate (ABR) Service Cisco, "Understanding the Available Bit Rate (ABR) Service
Category for ATM VCs", Design Technote 10415, June 2005. Category for ATM VCs", Design Technote 10415, June 2005.
[Buck00] Buckwalter, J., "Frame Relay: Technology and Practice", [Buck00] Buckwalter, J., "Frame Relay: Technology and Practice",
Pub. Addison Wesley ISBN-13: 978-0201485240, 2000. Pub. Addison Wesley ISBN-13: 978-0201485240, 2000.
[DCTCP] Alizadeh, M., Greenberg, A., Maltz, D., Padhye, J., Patel, [DCTCP] Alizadeh, M., Greenberg, A., Maltz, D., Padhye, J., Patel,
P., Prabhakar, B., Sengupta, S., and M. Sridharan, "Data P., Prabhakar, B., Sengupta, S., and M. Sridharan, "Data
Center TCP (DCTCP)", ACM SIGCOMM CCR 40(4)63--74, October Center TCP (DCTCP)", ACM SIGCOMM CCR 40(4)63--74, October
2010, <http://portal.acm.org/citation.cfm?id=1851192>. 2010, <http://portal.acm.org/citation.cfm?id=1851192>.
[GTPv1] 3GPP, "GPRS Tunnelling Protocol (GTP) across the Gn and Gp [GTPv1] 3GPP, "GPRS Tunnelling Protocol (GTP) across the Gn and Gp
interface", Technical Specification TS 29.060, . interface", Technical Specification TS 29.060.
[GTPv1-U] 3GPP, "General Packet Radio System (GPRS) Tunnelling [GTPv1-U] 3GPP, "General Packet Radio System (GPRS) Tunnelling
Protocol User Plane (GTPv1-U)", Technical Specification TS Protocol User Plane (GTPv1-U)", Technical Specification TS
29.281, . 29.281.
[GTPv2-C] 3GPP, "Evolved General Packet Radio Service (GPRS) [GTPv2-C] 3GPP, "Evolved General Packet Radio Service (GPRS)
Tunnelling Protocol for Control plane (GTPv2-C)", Tunnelling Protocol for Control plane (GTPv2-C)",
Technical Specification TS 29.274, . Technical Specification TS 29.274.
[I-D.ietf-aqm-recommendation]
Baker, F. and G. Fairhurst, "IETF Recommendations
Regarding Active Queue Management", draft-ietf-aqm-
recommendation-11 (work in progress), February 2015.
[I-D.ietf-conex-abstract-mech] [I-D.ietf-conex-abstract-mech]
Mathis, M. and B. Briscoe, "Congestion Exposure (ConEx) Mathis, M. and B. Briscoe, "Congestion Exposure (ConEx)
Concepts, Abstract Mechanism and Requirements", draft- Concepts, Abstract Mechanism and Requirements", draft-
ietf-conex-abstract-mech-13 (work in progress), October ietf-conex-abstract-mech-13 (work in progress), October
2014. 2014.
[I-D.ietf-trill-rfc7180bis] [I-D.ietf-trill-rfc7180bis]
Eastlake, D., Zhang, M., Perlman, R., Banerjee, A., Eastlake, D., Zhang, M., Perlman, R., Banerjee, A.,
Ghanwani, A., and S. Gupta, "TRILL: Clarifications, Ghanwani, A., and S. Gupta, "TRILL: Clarifications,
Corrections, and Updates", draft-ietf-trill-rfc7180bis-00 Corrections, and Updates", draft-ietf-trill-rfc7180bis-04
(work in progress), November 2014. (work in progress), March 2015.
[I-D.moncaster-tcpm-rcv-cheat] [I-D.moncaster-tcpm-rcv-cheat]
Moncaster, T., Briscoe, B., and A. Jacquet, "A TCP Test to Moncaster, T., Briscoe, B., and A. Jacquet, "A TCP Test to
Allow Senders to Identify Receiver Non-Compliance", draft- Allow Senders to Identify Receiver Non-Compliance", draft-
moncaster-tcpm-rcv-cheat-03 (work in progress), July 2014. moncaster-tcpm-rcv-cheat-03 (work in progress), July 2014.
[IEEE802.1Qah] [IEEE802.1Qah]
IEEE, "IEEE Standard for Local and Metropolitan Area IEEE, "IEEE Standard for Local and Metropolitan Area
Networks--Virtual Bridged Local Area Networks--Amendment Networks--Virtual Bridged Local Area Networks--Amendment
6: Provider Backbone Bridges", IEEE Std 802.1Qah-2008, 6: Provider Backbone Bridges", IEEE Std 802.1Qah-2008,
skipping to change at page 25, line 37 skipping to change at page 25, line 49
[ITU-T.I.371] [ITU-T.I.371]
ITU-T, "Traffic Control and Congestion Control in B-ISDN", ITU-T, "Traffic Control and Congestion Control in B-ISDN",
ITU-T Rec. I.371 (03/04), March 2004, ITU-T Rec. I.371 (03/04), March 2004,
<http://ieeexplore.ieee.org/xpl/ <http://ieeexplore.ieee.org/xpl/
mostRecentIssue.jsp?punumber=5454061>. mostRecentIssue.jsp?punumber=5454061>.
[LTE-RA] 3GPP, "Evolved Universal Terrestrial Radio Access (E-UTRA) [LTE-RA] 3GPP, "Evolved Universal Terrestrial Radio Access (E-UTRA)
and Evolved Universal Terrestrial Radio Access Network and Evolved Universal Terrestrial Radio Access Network
(E-UTRAN); Overall description; Stage 2", Technical (E-UTRAN); Overall description; Stage 2", Technical
Specification TS 36.300, . Specification TS 36.300.
[RFC1323] Jacobson, V., Braden, B., and D. Borman, "TCP Extensions [RFC1323] Jacobson, V., Braden, B., and D. Borman, "TCP Extensions
for High Performance", RFC 1323, May 1992. for High Performance", RFC 1323, May 1992.
[RFC1701] Hanks, S., Li, T., Farinacci, D., and P. Traina, "Generic [RFC1701] Hanks, S., Li, T., Farinacci, D., and P. Traina, "Generic
Routing Encapsulation (GRE)", RFC 1701, October 1994. Routing Encapsulation (GRE)", RFC 1701, October 1994.
[RFC2003] Perkins, C., "IP Encapsulation within IP", RFC 2003, [RFC2003] Perkins, C., "IP Encapsulation within IP", RFC 2003,
October 1996. October 1996.
skipping to change at page 27, line 17 skipping to change at page 27, line 17
1. [GF] Concern that certain guidelines warrant a MUST (NOT) rather 1. [GF] Concern that certain guidelines warrant a MUST (NOT) rather
than a SHOULD (NOT). Given the guidelines say that if any SHOULD than a SHOULD (NOT). Given the guidelines say that if any SHOULD
(NOT)s are not followed, a strong justification will be needed, (NOT)s are not followed, a strong justification will be needed,
they have been left as SHOULD (NOT) pending further list they have been left as SHOULD (NOT) pending further list
discussion. In particular: discussion. In particular:
* If inner is a Not-ECN-PDU and Outer is CE (or highest severity * If inner is a Not-ECN-PDU and Outer is CE (or highest severity
congestion level), MUST (not SHOULD) drop? congestion level), MUST (not SHOULD) drop?
2. Consider whether an IETF Standard Track doc will be needed to 2. Consider whether an IETF Standard Track doc will be needed to
Update the IP-in-IP protocols listed in Section 4.1--at least Update the IP-in-IP protocols listed in Section 5.1--at least
those that the IET those that the IET
Appendix B. Changes in This Version (to be removed by RFC Editor) Appendix B. Changes in This Version (to be removed by RFC Editor)
From ietf-01 to ietf-02:
* Added Section for guidelines that are applicable in all cases.
* Updated references.
From ietf-00 to ietf-01: Updated references. From ietf-00 to ietf-01: Updated references.
From briscoe-04 to ietf-00: Changed filename following tsvwg From briscoe-04 to ietf-00: Changed filename following tsvwg
adoption. adoption.
From briscoe-03 to 04: From briscoe-03 to 04:
* Re-arranged the introduction to describe the purpose of the * Re-arranged the introduction to describe the purpose of the
document first before introducing ECN in more depth. And document first before introducing ECN in more depth. And
clarified the introduction throughout. clarified the introduction throughout.
 End of changes. 47 change blocks. 
64 lines changed or deleted 85 lines changed or added

This html diff was produced by rfcdiff 1.42. The latest version is available from http://tools.ietf.org/tools/rfcdiff/