draft-ietf-bess-service-chaining-00.txt   draft-ietf-bess-service-chaining-01.txt 
BGP Enabled Services (bess) R. Fernando BGP Enabled Services (bess) R. Fernando
INTERNET-DRAFT Cisco INTERNET-DRAFT Cisco
Intended status: Standards Track S. Mackie Intended status: Standards Track S. Mackie
Expires: October 2016 Juniper Expires: May 3, 2017 Juniper
D. Rao D. Rao
Cisco Cisco
B. Rijsman B. Rijsman
Juniper Juniper
M. Napierala M. Napierala
AT&T AT&T
T. Morin October 30, 2016
Orange Orange
April 13, 2016
Service Chaining using Virtual Networks with BGP VPNs Service Chaining using Virtual Networks with BGP VPNs
draft-ietf-bess-service-chaining-00 draft-ietf-bess-service-chaining-01
Abstract Abstract
This document describes how service function chains (SFC) can be This document describes how service function chains (SFC) can be
applied to traffic flows using routing in a virtual (overlay) applied to traffic flows using routing in a virtual (overlay) network
network to steer traffic between service nodes. Chains can include to steer traffic between service nodes. Chains can include services
services running in routers, on physical appliances or in virtual running in routers, on physical appliances or in virtual machines.
machines. Service chains have applicability at the subscriber edge, Service chains have applicability at the subscriber edge, business
business edge and in multi-tenant datacenters. The routing function edge and in multi-tenant datacenters. The routing function into SFCs
into SFCs and between service functions within an SFC can be and between service functions within an SFC can be performed by
performed by physical devices (routers), be virtualized inside physical devices (routers), be virtualized inside hypervisors, or run
hypervisors, or run as part of a host OS. as part of a host OS.
A BGP control plane for route distribution is used to create virtual A BGP control plane for route distribution is used to create virtual
networks implemented using IP MPLS, VXLAN or other suitable networks implemented using IP MPLS, VXLAN or other suitable
encapsulation, where the routes within the virtual networks cause encapsulation, where the routes within the virtual networks cause
traffic to flow through a sequence of service nodes that apply traffic to flow through a sequence of service nodes that apply packet
packet processing functions to the flows. processing functions to the flows.
Two techniques are described: in one the service chain is Two techniques are described: in one the service chain is implemented
implemented as a sequence of distinct VPNs between sets of service as a sequence of distinct VPNs between sets of service nodes that
nodes that apply each service function; in the other, the routes apply each service function; in the other, the routes within a VPN
within a VPN are modified through the use of special route targets are modified through the use of special route targets and modified
and modified next-hop resolution to achieve the desired result. next-hop resolution to achieve the desired result.
In both techniques, service chains can be created by manual In both techniques, service chains can be created by manual
configuration of routes and route targets in routing systems, or configuration of routes and route targets in routing systems, or
through the use of a controller which contains a topological model through the use of a controller which contains a topological model of
of the desired service chains. the desired service chains.
This document also contains discussion of load balancing between This document also contains discussion of load balancing between
network functions, symmetric forward and reverse paths when stateful network functions, symmetric forward and reverse paths when stateful
services are involved, and use of classifiers to direct traffic into services are involved, and use of classifiers to direct traffic into
a service chain. a service chain.
Status of this Memo Status of this Memo
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Copyright Notice and License Notice Copyright Notice and License Notice
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Table of Contents Table of Contents
1 Introduction ...................................................4 1 Introduction ...................................................4
1.1 Terminology................................................5 1.1 Terminology................................................5
2 Service Function Chain Architecture Using Virtual Networking ...8 2 Service Function Chain Architecture Using Virtual Networking ...8
2.1 High Level Architecture....................................9 2.1 High Level Architecture....................................9
2.2 Service Function Chain Logical Model......................10 2.2 Service Function Chain Logical Model......................10
2.3 Service Function Implemented in a Set of SF Instances.....11 2.3 Service Function Implemented in a Set of SF Instances.....11
2.4 SF Instance Connections to VRFs...........................13 2.4 SF Instance Connections to VRFs...........................13
skipping to change at page 3, line 44 skipping to change at page 3, line 44
3.4 Forward and Reverse Flow Load Balancing...................29 3.4 Forward and Reverse Flow Load Balancing...................29
3.4.1 Issues with Equal Cost Multi-Path Routing............29 3.4.1 Issues with Equal Cost Multi-Path Routing............29
3.4.2 Modified ECMP with Consistent Hash...................29 3.4.2 Modified ECMP with Consistent Hash...................29
3.4.3 ECMP with Flow Table.................................30 3.4.3 ECMP with Flow Table.................................30
3.4.4 Dealing with different hash algorithms in an SFC.....32 3.4.4 Dealing with different hash algorithms in an SFC.....32
4 Steering into SFCs Using a Classifier .........................32 4 Steering into SFCs Using a Classifier .........................32
5 External Domain Co-ordination .................................34 5 External Domain Co-ordination .................................34
6 Fine-grained steering using BGP Flow-Spec .....................35 6 Fine-grained steering using BGP Flow-Spec .....................35
7 Controller Federation .........................................35 7 Controller Federation .........................................35
8 Coordination Between SF Instances and Controller using BGP ....35 8 Coordination Between SF Instances and Controller using BGP ....35
9 BGP Attributes ................................................36 9 BGP Extended Communities ......................................36
10 Summary and Conclusion........................................38 10 Summary and Conclusion........................................38
11 Security Considerations.......................................38 11 Security Considerations.......................................38
12 IANA Considerations...........................................38 12 IANA Considerations...........................................38
13 Informative References........................................38 13 Informative References........................................38
14 Acknowledgments...............................................40 14 Acknowledgments...............................................40
1 Introduction 1 Introduction
The purpose of networks is to allow computing systems to communicate The purpose of networks is to allow computing systems to communicate
with each other. Requests are usually made from the client or with each other. Requests are usually made from the client or
customer side of a network, and responses are generated by customer side of a network, and responses are generated by
applications residing in a datacenter. Over time, the network applications residing in a datacenter. Over time, the network between
between the client and the application has become more complex, and the client and the application has become more complex, and traffic
traffic between the client and the application is acted on by between the client and the application is acted on by intermediate
intermediate systems that apply network services. Some of these systems that apply network services. Some of these activities, like
activities, like firewall filtering, subscriber attachment and firewall filtering, subscriber attachment and network address
network address translation are generally carried out in network translation are generally carried out in network devices along the
devices along the traffic path, while others are carried out by traffic path, while others are carried out by dedicated appliances,
dedicated appliances, such as media proxy and deep packet inspection such as media proxy and deep packet inspection (DPI). Deployment of
(DPI). Deployment of these in-network services is complex, time- these in-network services is complex, time- consuming and costly,
consuming and costly, since they require configuration of devices since they require configuration of devices with vendor-specific
with vendor-specific operating systems, sometimes with co-processing operating systems, sometimes with co-processing cards, or deployment
cards, or deployment of physical devices in the network, which of physical devices in the network, which requires cabling and
requires cabling and configuration of the devices that they connect configuration of the devices that they connect to. Additionally,
to. Additionally, other devices in the network need to be configured other devices in the network need to be configured to ensure that
to ensure that traffic is correctly steered through the systems that traffic is correctly steered through the systems that services are
services are running on. running on.
The current mode of operations does not easily allow common The current mode of operations does not easily allow common
operational processes to be applied to the lifecycle of services in operational processes to be applied to the lifecycle of services in
the network, or for steering of traffic through them. the network, or for steering of traffic through them.
The recent emergence of Network Functions Virtualization (NFV) The recent emergence of Network Functions Virtualization (NFV)
[NFVE2E] to provide a standard deployment model for network services [NFVE2E] to provide a standard deployment model for network services
as software appliances, combined with Software Defined Networking as software appliances, combined with Software Defined Networking
(SDN) for more dynamic traffic steering can provide foundational (SDN) for more dynamic traffic steering can provide foundational
elements that will allow network services to be deployed and managed elements that will allow network services to be deployed and managed
far more efficiently and with more agility than is possible today. far more efficiently and with more agility than is possible today.
This document describes how the combination of several existing This document describes how the combination of several existing
technologies can be used to create chains of functions, while technologies can be used to create chains of functions, while
preserving the requirements of scale, performance and reliability preserving the requirements of scale, performance and reliability for
for service provider networks. The technologies employed are: service provider networks. The technologies employed are:
o Traffic flow between service functions described by routing and o Traffic flow between service functions described by routing and
network policies rather than by static physical or logical network policies rather than by static physical or logical
connectivity connectivity
o Packet header encapsulation in order to create virtual private o Packet header encapsulation in order to create virtual private
networks using network overlays networks using network overlays
o VRFs on both physical devices and in hypervisors to implement o VRFs on both physical devices and in hypervisors to implement
forwarding policies that are specific to each virtual network forwarding policies that are specific to each virtual network
o Optional use of a controller to calculate routes to be installed o Optional use of a controller to calculate routes to be installed
in routing systems to form a service chain. The controller uses a in routing systems to form a service chain. The controller uses a
topological model that stores service function instance topological model that stores service function instance
connectivity to network devices and intended connectivity between connectivity to network devices and intended connectivity between
service functions. service functions.
o MPLS or other labeling to facilitate identification of the next o MPLS or other labeling to facilitate identification of the next
interface to send packets to in a service function chain interface to send packets to in a service function chain
o BGP or BGP-style signaling to distribute routes in order to o BGP or BGP-style signaling to distribute routes in order to create
create service function chains service function chains
o Distributed load balancing between service functions performed in o Distributed load balancing between service functions performed in
the VRFs that service function instance connect to. the VRFs that service function instance connect to.
Virtualized environments can be supported without necessarily Virtualized environments can be supported without necessarily running
running BGP or MPLS natively. Messaging protocols such as NC/YANG, BGP or MPLS natively. Messaging protocols such as NC/YANG, XMPP or
XMPP or OpenFlow may be used to signal forwarding information. OpenFlow may be used to signal forwarding information. Encapsulation
Encapsulation mechanisms such as VXLAN or GRE may be used for mechanisms such as VXLAN or GRE may be used for overlay transport.
overlay transport. The term 'BGP-style', above, refers to this type The term 'BGP-style', above, refers to this type of signaling.
of signaling.
Traffic can be directed into service function chains using IP Traffic can be directed into service function chains using IP routing
routing at each end of the service function chain, or be directed at each end of the service function chain, or be directed into the
into the chain by a classifier function that can determine which chain by a classifier function that can determine which service chain
service chain a traffic flow should pass through based on deep a traffic flow should pass through based on deep packet inspection
packet inspection (DPI) and/or subscriber identity. (DPI) and/or subscriber identity.
The techniques can support an evolution from services implemented in The techniques can support an evolution from services implemented in
physical devices attached to physical forwarding systems (routers) physical devices attached to physical forwarding systems (routers) to
to fully virtualized implementations as well as intermediate hybrid fully virtualized implementations as well as intermediate hybrid
implementations. implementations.
1.1 Terminology 1.1 Terminology
This document uses the following acronyms and terms. This document uses the following acronyms and terms.
Terms Meaning Terms Meaning
----- ----------------------------------------------- ----- -----------------------------------------------
AS Autonomous System AS Autonomous System
ASBR Autonomous System Border Router ASBR Autonomous System Border Router
CE Customer Edge
FW Firewall FW Firewall
I2RS Interface to the Routing System I2RS Interface to the Routing System
L3VPN Layer 3 VPN L3VPN Layer 3 VPN
LB Load Balancer LB Load Balancer
NLRI Network Layer Reachability Information [RFC4271] NLRI Network Layer Reachability Information [RFC4271]
P Provider backbone router P Provider backbone router
proxy-arp proxy-Address Resolution Protocol proxy-arp proxy-Address Resolution Protocol
RR Route Reflector RR Route Reflector
RT Route Target RT Route Target
SDN Software Defined Network SDN Software Defined Network
skipping to change at page 6, line 41 skipping to change at page 6, line 36
composite built from several service functions executed in one or composite built from several service functions executed in one or
more pre-determined sequences and delivered by software executing more pre-determined sequences and delivered by software executing
in physical or virtual devices. in physical or virtual devices.
Classification: Customer/network/service policy used to identify and Classification: Customer/network/service policy used to identify and
select traffic flow(s) requiring certain outbound forwarding select traffic flow(s) requiring certain outbound forwarding
actions, in particular, to direct specific traffic flows into the actions, in particular, to direct specific traffic flows into the
ingress of a particular service function chain, or causing ingress of a particular service function chain, or causing
branching within a service function chain. branching within a service function chain.
Virtual Network: A logical overlay network built using virtual Virtual Network: A logical overlay network built using virtual links
links or packet encapsulation, over an existing network (the or packet encapsulation, over an existing network (the underlay).
underlay).
Service Function Chain (SFC): A service function chain defines an Service Function Chain (SFC): A service function chain defines an
ordered set of service functions that must be applied to packets ordered set of service functions that must be applied to packets
and/or frames selected as a result of classification. An SFC may and/or frames selected as a result of classification. An SFC may be
be either a linear chain or a complex service graph with multiple either a linear chain or a complex service graph with multiple
branches. The term 'Service Chain' is often used in place of branches. The term 'Service Chain' is often used in place of
'Service Function Chain'.
SFC Set: The pair of SFCs through which the forward and reverse SFC Set: The pair of SFCs through which the forward and reverse
directions of a given classified flow will pass. directions of a given classified flow will pass.
Service Function (SF): A logical function that is applied to Service Function (SF): A logical function that is applied to
packets. A service function can act at the network layer or other packets. A service function can act at the network layer or other
OSI layers. A service function can be embedded in one or more OSI layers. A service function can be embedded in one or more
physical network elements, or can be implemented in one or more physical network elements, or can be implemented in one or more
software instances running on physical or virtual hosts. One or software instances running on physical or virtual hosts. One or
multiple service functions can be embedded in the same network multiple service functions can be embedded in the same network
skipping to change at page 7, line 28 skipping to change at page 7, line 20
A non-exhaustive list of services includes: firewalls, DDOS A non-exhaustive list of services includes: firewalls, DDOS
protection, anti-malware/ant-virus systems, WAN and application protection, anti-malware/ant-virus systems, WAN and application
acceleration, Deep Packet Inspection (DPI), server load balancers, acceleration, Deep Packet Inspection (DPI), server load balancers,
network address translation, HTTP Header Enrichment functions, network address translation, HTTP Header Enrichment functions,
video optimization, TCP optimization, etc. video optimization, TCP optimization, etc.
SF Instance: An instance of software that implements the packet SF Instance: An instance of software that implements the packet
processing of a service function processing of a service function
SF Instance Set: A group of SF instances that, in parallel, SF Instance Set: A group of SF instances that, in parallel, implement
implement a service function in an SFC. a service function in an SFC.
Routing System: A hardware or software system that performs layer 3 Routing System: A hardware or software system that performs layer 3
routing and/or forwarding functions. The term includes physical routing and/or forwarding functions. The term includes physical
routers as well as hypervisor or Host OS implementations of the routers as well as hypervisor or Host OS implementations of the
forwarding plane of a conventional router. forwarding plane of a conventional router.
Gateway: A routing system attached to the source or destination Gateway: A routing system attached to the source or destination
network that peers with the controller, or with the routing system network that peers with the controller, or with the routing system
at one end of an SFC. A source network gateway directs traffic at one end of an SFC. A source network gateway directs traffic from
from the source network into an SFC, while a destination network the source network into an SFC, while a destination network gateway
gateway distributes traffic towards destinations. The routing distributes traffic towards destinations. The routing systems at
systems at each end of an SFC can themselves act as gateways and each end of an SFC can themselves act as gateways and in a
in a bidirectional SF instance set, gateways can act in both bidirectional SF instance set, gateways can act in both directions
directions
VRF: A subsystem within a routing system as defined in [RFC4364] VRF: A subsystem within a routing system as defined in [RFC4364] that
that contains private routing and forwarding tables and has contains private routing and forwarding tables and has physical
physical and/or logical interfaces associated with it. In the case and/or logical interfaces associated with it. In the case of
of hypervisor/Host OS implementations, the term refers only to the hypervisor/Host OS implementations, the term refers only to the
forwarding function of a VRF, and this will be referred to as a forwarding function of a VRF, and this will be referred to as a
'VPN forwarder.' 'VPN forwarder.'
Ingress VRF: A VRF containing an ingress interface of a SF instance Ingress VRF: A VRF containing an ingress interface of a SF instance
Egress VRF: A VRF containing an egress interface of a SF instance Egress VRF: A VRF containing an egress interface of a SF instance
Note that in this document the terms 'ingress' and 'egress' are used Note that in this document the terms 'ingress' and 'egress' are used
with respect to SF instances rather than the tunnels that connect SF with respect to SF instances rather than the tunnels that connect SF
instances. This is different usage than in VPN literature in instances. This is different usage than in VPN literature in general.
general.
Entry VRF: A VRF through which traffic enters the SFC from the Entry VRF: A VRF through which traffic enters the SFC from the source
source network. This VRF may be used to advertise the destination network. This VRF may be used to advertise the destination
network's routes to the source network. It could be placed on a network's routes to the source network. It could be placed on a
gateway router or be collocated with the first ingress VRF. gateway router or be collocated with the first ingress VRF.
Exit VRF: A VRF through which traffic exits the SFC into the Exit VRF: A VRF through which traffic exits the SFC into the
destination network. This VRF contains the routes from the destination network. This VRF contains the routes from the
destination network and could be located on a gateway router. destination network and could be located on a gateway router.
Alternatively, the egress VRF attached to the last SF instance may Alternatively, the egress VRF attached to the last SF instance may
also function as the exit VRF. also function as the exit VRF.
2 Service Function Chain Architecture Using Virtual Networking 2 Service Function Chain Architecture Using Virtual Networking
The techniques described in this document use virtual networks to The techniques described in this document use virtual networks to
implement service function chains. Service function chains can be implement service function chains. Service function chains can be
implemented on devices that support existing MPLS VPN and BGP implemented on devices that support existing MPLS VPN and BGP
standards [RFC4364, RFC4271, RFC4760], as well as other standards [RFC4364, RFC4271, RFC4760], as well as other
encapsulations, such as VXLAN [RFC7348]. Similarly, equivalent encapsulations, such as VXLAN [RFC7348]. Similarly, equivalent
control plane protocols such as BGP-EVPN with type-2 and type-5 control plane protocols such as BGP-EVPN with type-2 and type-5 route
route types can also be used where supported. The set of techniques types can also be used where supported. The set of techniques
described in this document represent one implementation approach to described in this document represent one implementation approach to
realize the SFC architecture described in [sfc-arch]. realize the SFC architecture described in [sfc-arch].
The following sections detail the building blocks of the SFC The following sections detail the building blocks of the SFC
architecture, and outline the processes of route installation and architecture, and outline the processes of route installation and
subsequent route exchange to create an SFC. subsequent route exchange to create an SFC.
2.1 High Level Architecture 2.1 High Level Architecture
Service function chains can be deployed with or without a Service function chains can be deployed with or without a classifier.
classifier. Use cases where SFCs may be deployed without a Use cases where SFCs may be deployed without a classifier include
classifier include multi-tenant data centers, private and public multi-tenant data centers, private and public cloud and virtual CPE
cloud and virtual CPE for business services. Classifiers will for business services. Classifiers will primarily be used in mobile
primarily be used in mobile and wireline subscriber edge use cases. and wireline subscriber edge use cases. Use of a classifier is
Use of a classifier is discussed in Section 4. discussed in Section 4.
A high-level architecture diagram of an SFC without a classifier, A high-level architecture diagram of an SFC without a classifier,
where traffic is routed into and out of the SFC, is shown in Figure where traffic is routed into and out of the SFC, is shown in Figure
1, below. An optional controller is shown that contains a 1, below. An optional controller is shown that contains a topological
topological model of the SFC and which configures the network model of the SFC and which configures the network resources to
resources to implement the SFC. implement the SFC.
+-------------------------+ +-------------------------+
|--- Data plane connection| |--- Data plane connection|
|=== Encapsulation tunnel | |=== Encapsulation tunnel |
| O VRF | | O VRF |
+-------------------------+ +-------------------------+
Control +------------------------------------------------+ Control +------------------------------------------------+
Plane | Controller | Plane | Controller |
....... +-+------------+----------+----------+---------+-+ ....... +-+------------+----------+----------+---------+-+
skipping to change at page 10, line 16 skipping to change at page 10, line 14
SFC composed of SF instances, SF1, SF2 and SF3. Routing system R-A SFC composed of SF instances, SF1, SF2 and SF3. Routing system R-A
contains a VRF (shown as 'O' symbol) that is the SFC entry point. contains a VRF (shown as 'O' symbol) that is the SFC entry point.
This VRF will advertise a route to reach Network-B into Network-A This VRF will advertise a route to reach Network-B into Network-A
causing any traffic from a source in Network-A with a destination in causing any traffic from a source in Network-A with a destination in
Network-B to arrive in this VRF. The forwarding table in the VRF in Network-B to arrive in this VRF. The forwarding table in the VRF in
R-A will direct traffic destined for Network-B into an encapsulation R-A will direct traffic destined for Network-B into an encapsulation
tunnel with destination R-1 and a label that identifies the ingress tunnel with destination R-1 and a label that identifies the ingress
(left) interface of SF1 that R-1 should send the packets out on. The (left) interface of SF1 that R-1 should send the packets out on. The
packets are processed by service instance SF-1 and arrive in the packets are processed by service instance SF-1 and arrive in the
egress (right) VRF in R-1. The forwarding entries in the egress VRF egress (right) VRF in R-1. The forwarding entries in the egress VRF
direct traffic to the next ingress VRF using encapsulation direct traffic to the next ingress VRF using encapsulation tunneling.
tunneling. The process is repeated for each service instance in the The process is repeated for each service instance in the SFC until
SFC until packets arrive at the SFC exit VRF (in R-B). This VRF is packets arrive at the SFC exit VRF (in R-B). This VRF is peered with
peered with Network-B and routes packets towards their destinations Network-B and routes packets towards their destinations in the user
in the user data plane. In this example, routing systems R-A and R-B data plane. In this example, routing systems R-A and R-B are gateway
are gateway routing systems. routing systems.
In the example, each pair of ingress and egress VRFs are configured In the example, each pair of ingress and egress VRFs are configured
in separate routing systems, but such pairs could be collocated in in separate routing systems, but such pairs could be collocated in
the same routing system, and it is possible for the ingress and the same routing system, and it is possible for the ingress and
egress VRFs for a given SF instance to be in different routing egress VRFs for a given SF instance to be in different routing
systems. The SFC entry and exit VRFs can be collocated in the same systems. The SFC entry and exit VRFs can be collocated in the same
routing system, and the service instances can be local or remote routing system, and the service instances can be local or remote from
from either or both of the routing systems containing the entry and either or both of the routing systems containing the entry and exit
exit VRFs, and from each other. It is also possible that the ingress VRFs, and from each other. It is also possible that the ingress and
and egress VRFs are implemented using alternative mechanisms. egress VRFs are implemented using alternative mechanisms.
The controller is responsible for configuring the VRFs in each The controller is responsible for configuring the VRFs in each
routing system, installing the routes in each of the VRFs to routing system, installing the routes in each of the VRFs to
implement the SFC, and, in the case of virtualized services, may implement the SFC, and, in the case of virtualized services, may
instantiate the service instances. instantiate the service instances.
2.2 Service Function Chain Logical Model 2.2 Service Function Chain Logical Model
A service function chain is a set of logically connected service A service function chain is a set of logically connected service
functions through which traffic can flow. Each egress interface of functions through which traffic can flow. Each egress interface of
skipping to change at page 11, line 20 skipping to change at page 11, line 17
In Figure 2, above, a service function chain has been created that In Figure 2, above, a service function chain has been created that
connects Network-A to Network-B, such that traffic from a host in connects Network-A to Network-B, such that traffic from a host in
Network-A to a host in Network-B will traverse the service function Network-A to a host in Network-B will traverse the service function
chain. chain.
As defined in [sfc-arch], a service function chain can be uni- As defined in [sfc-arch], a service function chain can be uni-
directional or bi-directional. In this document, in order to allow directional or bi-directional. In this document, in order to allow
for the possibility that the forward and reverse paths may not be for the possibility that the forward and reverse paths may not be
symmetrical, SFCs are defined as uni-directional, and the term 'SFC symmetrical, SFCs are defined as uni-directional, and the term 'SFC
set' is used to refer to a pair of forward and reverse direction set' is used to refer to a pair of forward and reverse direction SFCs
SFCs for some set of routed or classified traffic. for some set of routed or classified traffic.
2.3 Service Function Implemented in a Set of SF Instances 2.3 Service Function Implemented in a Set of SF Instances
A service function instance is a software system that acts on A service function instance is a software system that acts on packets
packets that arrive on an ingress interface of that software system. that arrive on an ingress interface of that software system. Service
Service function instances may run on a physical appliance or in a function instances may run on a physical appliance or in a virtual
virtual machine. A service function instance may be transparent at machine. A service function instance may be transparent at layer 2
layer 2 and/or layer 3, and may support branching across multiple and/or layer 3, and may support branching across multiple egress
egress interfaces and may support aggregation across ingress interfaces and may support aggregation across ingress interfaces. For
interfaces. For simplicity, the examples in this document have a simplicity, the examples in this document have a single ingress and a
single ingress and a single egress interface. single egress interface.
Each service function in a chain can be implemented by a single Each service function in a chain can be implemented by a single
service function instance, or by a set of instances in order to service function instance, or by a set of instances in order to
provide scale and resilience. provide scale and resilience.
+------------------------------------------------------------------+ +------------------------------------------------------------------+
| Logical Service Functions Connected in a Chain | | Logical Service Functions Connected in a Chain |
| | | |
| +--------+ +--------+ | | +--------+ +--------+ |
| Net-A--->| SF-1 |----------->| SF-2 |--->Net-B | | Net-A--->| SF-1 |----------->| SF-2 |--->Net-B |
skipping to change at page 12, line 36 skipping to change at page 12, line 36
| '''''' '''''' | | '''''' '''''' |
+------------------------------------------------------------------+ +------------------------------------------------------------------+
Figure 3 - Service Functions Are Composed of SF Instances Connected Figure 3 - Service Functions Are Composed of SF Instances Connected
Via Virtual Networks Via Virtual Networks
In Figure 3, service function SF-1 is implemented in three service In Figure 3, service function SF-1 is implemented in three service
function instances, SFI-11, SFI-12, and SFI-13. Service function SF- function instances, SFI-11, SFI-12, and SFI-13. Service function SF-
2 is implemented in two SF instances. The service function instances 2 is implemented in two SF instances. The service function instances
are connected to the next service function in the chain using a are connected to the next service function in the chain using a
virtual network, VN-2. Additionally, a virtual network (VN-1) is virtual network, VN-2. Additionally, a virtual network (VN-1) is used
used to enter the SFC and another (VN-3) is used at the exit. to enter the SFC and another (VN-3) is used at the exit.
The logical connection between two service functions is implemented The logical connection between two service functions is implemented
using a virtual network that contains egress interfaces for using a virtual network that contains egress interfaces for instances
instances of one service function, and ingress interfaces of of one service function, and ingress interfaces of instances of the
instances of the next service function. Traffic is directed across next service function. Traffic is directed across the virtual network
the virtual network between the two sets of service function between the two sets of service function instances using layer 3
instances using layer 3 forwarding (e.g. an MPLS VPN) or layer 2 forwarding (e.g. an MPLS VPN) or layer 2 forwarding (e.g. a VXLAN).
forwarding (e.g. a VXLAN).
The virtual networks could be described as "directed half-mesh", in The virtual networks could be described as "directed half-mesh", in
that the egress interface of each SF instance of one service that the egress interface of each SF instance of one service function
function can reach any ingress interface of the SF instances of the can reach any ingress interface of the SF instances of the connected
connected service function. service function.
Details on how routing across virtual networks is achieved, and Details on how routing across virtual networks is achieved, and
requirements on load balancing across ingress interfaces are requirements on load balancing across ingress interfaces are
discussed in later sections of this document. discussed in later sections of this document.
2.4 SF Instance Connections to VRFs 2.4 SF Instance Connections to VRFs
SF instances can be deployed as software running on physical SF instances can be deployed as software running on physical
appliances, or in virtual machines running on a hypervisor. These appliances, or in virtual machines running on a hypervisor. These two
two types are described in more detail in the following sections. types are described in more detail in the following sections.
2.4.1 SF Instance in Physical Appliance 2.4.1 SF Instance in Physical Appliance
The case of a SF instance running on a physical appliance is shown The case of a SF instance running on a physical appliance is shown in
in Figure 4, below. Figure 4, below.
+---------------------------------+ +---------------------------------+
| | | |
| +-----------------------------+ | | +-----------------------------+ |
| | Service Function Instance | | | | Service Function Instance | |
| +-------^-------------|-------+ | | +-------^-------------|-------+ |
| | Host | | | | Host | |
+---------|-------------|---------+ +---------|-------------|---------+
| | | |
+------ |-------------|-------+ +------ |-------------|-------+
skipping to change at page 14, line 40 skipping to change at page 14, line 40
| | | Routing System | | | | | | Routing System | | |
| | +-----------------------------+ | | | | +-----------------------------+ | |
| | Hypervisor or Host OS | | | | Hypervisor or Host OS | |
| +---------------------------------+ | | +---------------------------------+ |
| Host | | Host |
+-------------------------------------+ +-------------------------------------+
Figure 5 - Ingress and Egress VRFs for a Virtual Routing System and Figure 5 - Ingress and Egress VRFs for a Virtual Routing System and
Virtualized SF Instance Virtualized SF Instance
When more than one instance of an SF is running on a hypervisor, When more than one instance of an SF is running on a hypervisor, they
they can be connected to the same VRF for scale out of an SF within can be connected to the same VRF for scale out of an SF within an
an SFC. SFC.
The routing mechanisms in the VRFs into and between service function The routing mechanisms in the VRFs into and between service function
instances, and the encapsulation tunneling between routing systems instances, and the encapsulation tunneling between routing systems
are identical in the physical and virtual implementations of SFCs are identical in the physical and virtual implementations of SFCs and
and routing systems described in this document. Physical and virtual routing systems described in this document. Physical and virtual
service functions can be mixed as needed with different combinations service functions can be mixed as needed with different combinations
of physical and virtual routing systems, within a single service
chain. chain.
The SF instances are attached to the routing systems via physical, The SF instances are attached to the routing systems via physical,
virtual or logical (e.g, 802.1q) interfaces, and are assumed to virtual or logical (e.g, 802.1q) interfaces, and are assumed to
perform basic L3 or L2 forwarding. perform basic L3 or L2 forwarding.
A single SF instance can be part of multiple service chains. In this A single SF instance can be part of multiple service chains. In this
case, the SF instance will have dedicated interfaces (typically case, the SF instance will have dedicated interfaces (typically
logical) and forwarding contexts associated with each service chain. logical) and forwarding contexts associated with each service chain.
skipping to change at page 15, line 27 skipping to change at page 15, line 26
instances in the chain and, when a classifier is not used, from the instances in the chain and, when a classifier is not used, from the
originating network into the SFC and from the SFC into the originating network into the SFC and from the SFC into the
destination network. destination network.
The tunnels can be MPLS over GRE [RFC4023], MPLS over UDP [draft- The tunnels can be MPLS over GRE [RFC4023], MPLS over UDP [draft-
ietf-mpls-in-udp], MPLS over MPLS [RFC3031], VXLAN [RFC7348], or ietf-mpls-in-udp], MPLS over MPLS [RFC3031], VXLAN [RFC7348], or
another suitable encapsulation methods. another suitable encapsulation methods.
Tunneling capabilities may be enabled in each routing system as part Tunneling capabilities may be enabled in each routing system as part
of a base configuration or may be configured by the controller. of a base configuration or may be configured by the controller.
Tunnel encapsulations may be programmed by the controller or Tunnel encapsulations may be programmed by the controller or signaled
signaled using BGP. The encapsulation to be used for a given route using BGP. The encapsulation to be used for a given route is signaled
is signaled in BGP using the procedures described in [draft-rosen- in BGP using the procedures described in [draft-rosen-
idr-tunnel-encaps], i.e. typically relying on the BGP Tunnel idr-tunnel-encaps], i.e. typically relying on the BGP Tunnel
Encapsulation Extended Community. Encapsulation Extended Community.
2.6 SFC Creation Procedure 2.6 SFC Creation Procedure
This section describes how service chains are created using two This section describes how service chains are created using two
methods: methods:
o Sequential VPNs - where a conventional VPN is created between o Sequential VPNs - where a conventional VPN is created between each
each set of SF instances to create the links in the SFC set of SF instances to create the links in the SFC
o Route Modification - where each routing system modifies o Route Modification - where each routing system modifies advertised
advertised routes that it receives, to realize the links in an routes that it receives, to realize the links in an SFC on the
SFC on the basis of a special service topology RT and a route- basis of a special service topology RT and a route- policy that
policy that describes the service chain logical topology describes the service chain logical topology
In both cases the controller, when present, is responsible for In both cases the controller, when present, is responsible for
creating ingress and egress VRFs, configuring the interfaces creating ingress and egress VRFs, configuring the interfaces
connected to SF instances in each VRF, and allocating and connected to SF instances in each VRF, and allocating and configuring
configuring import and export RTs for each VRF. Additionally, in the import and export RTs for each VRF. Additionally, in the second
second method, the controller also sends the route-policy containing method, the controller also sends the route-policy containing the
the service chain logical topology to each routing system. If a service chain logical topology to each routing system. If a
controller is not used, these procedures will require to be controller is not used, these procedures will require to be performed
performed manually or through scripting, for instance. manually or through scripting, for instance.
The source and destination networks' prefixes can be configured in The source and destination networks' prefixes can be configured in
the controller, or may be automatically learned through peering the controller, or may be automatically learned through peering
between the controller and each network's gateway. This is further between the controller and each network's gateway. This is further
described in Section 2.8.5 and Section 5. described in Section 2.8.5 and Section 5.
The following sub-sections describe how RT configuration, local The following sub-sections describe how RT configuration, local route
route installation and route distribution occur in each of the installation and route distribution occur in each of the methods.
methods.
It should be noted that depending on the capabilities of the routing It should be noted that depending on the capabilities of the routing
systems, a controller can use one or more techniques to realize systems, a controller can use one or more techniques to realize
forwarding along the service chain, ranging from fully centralized forwarding along the service chain, ranging from fully centralized to
to fully distributed. The goal of describing the following two fully distributed. The goal of describing the following two methods
methods is to illustrate the broad approaches and as a base for is to illustrate the broad approaches and as a base for various
various optimization options. optimization options.
Interoperability between a controller implementing one method and a Interoperability between a controller implementing one method and a
controller implementing a different method is achieved by relying on controller implementing a different method is achieved by relying on
the techniques described in section 5 and section 8, that describe the techniques described in section 5 and section 8, that describe
the use of BGP-style service chaining within domains that are the use of BGP-style service chaining within domains that are
interconnected using standard BGP VPN route exchanges. interconnected using standard BGP VPN route exchanges.
2.6.1 SFC Provisioning Using Sequential VPNs 2.6.1 SFC Provisioning Using Sequential VPNs
The task of the controller in this method of SFC provisioning is to The task of the controller in this method of SFC provisioning is to
create a set of VPNs that carry traffic to the destination network create a set of VPNs that carry traffic to the destination network
through instances of each service function in turn. This is achieved through instances of each service function in turn. This is achieved
by allocating and configuring RTs such that the egress VRFs of one by allocating and configuring RTs such that the egress VRFs of one
set of SF instances import an RT that is an export RT for the set of SF instances import an RT that is an export RT for the ingress
ingress VRFs of the next, logically connected, set of SF instances. VRFs of the next, logically connected, set of SF instances.
The process of SFC creation is as follows: The process of SFC creation is as follows:
1. Controller creates a VRF in each routing system that is 1. Controller creates a VRF in each routing system that is
connected to a service instance that will be used in the connected to a service instance that will be used in the SFC
SFC
2. Controller configures each VRF to contain the logical 2. Controller configures each VRF to contain the logical
interface that connects to a SF instance. interface that connects to a SF instance.
3. Controller implements route target import and export 3. Controller implements route target import and export
policies in the VRFs using the same route targets for the policies in the VRFs using the same route targets for the
egress VRFs of a service function and the ingress VRFs of egress VRFs of a service function and the ingress VRFs of
the next logically connected service function in the SFC. the next logically connected service function in the SFC.
4. Controller installs a static route in each ingress VRF 4. Controller installs a static route in each ingress VRF whose
whose next hop is the interface that a SF instance is next hop is the interface that a SF instance is connected
connected to. The prefix for the route is the destination to. The prefix for the route is the destination network to
network to be reached by passing through the SFC. The be reached by passing through the SFC. The following
following sections describe variations that can be used. sections describe variations that can be used.
5. Routing systems advertise the static routes via BGP as VPN 5. Routing systems advertise the static routes via BGP as VPN
routes with next hop being the IP address of the router, routes with next hop being the IP address of the router,
with an encapsulation specified and a label that identifies with an encapsulation specified and a label that identifies
the service instance interface. the service instance interface.
6. Routing systems containing VRFs with matching route targets 6. Routing systems containing VRFs with matching route targets
receive the updates. receive the updates.
7. Routes are installed in egress VRFs with matching import 7. Routes are installed in egress VRFs with matching import
targets. The egress VRFs of each SF instance will now targets. The egress VRFs of each SF instance will now
contain VPN routes to one or more routers containing contain VPN routes to one or more routers containing ingress
ingress VRFs for SF instances of the next service function VRFs for SF instances of the next service function in the
in the SFC. SFC.
Routes to the destination network via the first set of SF instances Routes to the destination network via the first set of SF instances
are advertised into the source network, and the egress VRFs of the are advertised into the source network, and the egress VRFs of the
last SF instance set have routes into the destination network. last SF instance set have routes into the destination network.
As discussed further in Section 3, egress VRFs can load balance As discussed further in Section 3, egress VRFs can load balance
across the multiple next hops advertised from the next set of across the multiple next hops advertised from the next set of ingress
ingress VRFs. VRFs.
2.6.2 Modified-Route SFC Creation 2.6.2 Modified-Route SFC Creation
In this method of SFC configuration, all the VRFs connected to SF In this method of SFC configuration, all the VRFs connected to SF
instances for a given SFC are configured with same import and export instances for a given SFC are configured with same import and export
RT, so they form a VPN-connected mesh between the SF instance RT, so they form a VPN-connected mesh between the SF instance
interfaces. This is termed the 'Service VPN'. A route is configured interfaces. This is termed the 'Service VPN'. A route is configured
or learnt in each VRF with destination being the IP address of a or learnt in each VRF with destination being the IP address of a
connected SF instance via an interface configured in the VRF. The connected SF instance via an interface configured in the VRF. The
interface may be a physical or logical interface. The routing system interface may be a physical or logical interface. The routing system
that hosts such a VRF advertises a VPN route for each locally that hosts such a VRF advertises a VPN route for each locally
connected SF instance, with a forwarding label that enables it to connected SF instance, with a forwarding label that enables it to
forward incoming traffic from other routing systems to the connected forward incoming traffic from other routing systems to the connected
SF instance. The VPN routes may be advertised via an RR or the SF instance. The VPN routes may be advertised via an RR or the
controller, which sends these updates to all the other routing controller, which sends these updates to all the other routing
systems that have VRFs with the service VPN RT. At this point all systems that have VRFs with the service VPN RT. At this point all the
the VRFs have a route to reach every SF instance. The same virtual VRFs have a route to reach every SF instance. The same virtual IP
IP address may be used for each SF instance in a set, enabling load- address may be used for each SF instance in a set, enabling load-
balancing among multiple SF instances in the set. balancing among multiple SF instances in the set.
The controller builds a route-policy for the routing systems in the The controller builds a route-policy for the routing systems in the
VPN, that describes the logical topology of each service chain that VPN, that describes the logical topology of each service chain that
it belongs to. The route-policy contains entries in the form of a it belongs to. The route-policy contains entries in the form of a
tuple for each service chain: tuple for each service chain:
{Service-topology-name, Service-topology-RT, Service-node- {Service-topology-name, Service-topology-RT, Service-node-
sequence} sequence}
skipping to change at page 19, line 22 skipping to change at page 19, line 20
modification of behavior in the routing systems allows the automatic modification of behavior in the routing systems allows the automatic
and constrained flow of traffic through the service chain. and constrained flow of traffic through the service chain.
Each routing system in the service VPN will process the VPN route to Each routing system in the service VPN will process the VPN route to
Network-B via R-B as follows: Network-B via R-B as follows:
1. If the routing system contains VRFs that import the 1. If the routing system contains VRFs that import the
Service-topology-RT, continue, otherwise ignore the route. Service-topology-RT, continue, otherwise ignore the route.
2. The routing system identifies the position and role 2. The routing system identifies the position and role
(ingress/egress) of each of its VRFs in the SFC by (ingress/egress) of each of its VRFs in the SFC by comparing
comparing the IP address of the route in the VRF to the the IP address of the route in the VRF to the connected SF
connected SF instance with those in the Service-node- instance with those in the Service-node- sequence in the
sequence in the route-policy. Alternatively, the controller route-policy. Alternatively, the controller may provision
may provision the specific service node IP to be used as the specific service node IP to be used as the next-hop in
the next-hop in each VRF, in the route-policy for the VRF. each VRF, in the route-policy for the VRF.
3. The routing system modifies the next-hop of the imported 3. The routing system modifies the next-hop of the imported
route with the Service-topology-RT, to select the route with the Service-topology-RT, to select the
appropriate next-hop as per the route-policy. It ignores appropriate next-hop as per the route-policy. It ignores the
the next-hop and label in the received route. It resolves next-hop and label in the received route. It resolves the
the selected next-hop in the local VRF routing table. selected next-hop in the local VRF routing table.
a. The imported route to Network-B in the ingress VRF is a. The imported route to Network-B in the ingress VRF is
modified to have a next-hop of the IP address of the modified to have a next-hop of the IP address of the
logically connected SF instance. logically connected SF instance.
b. The imported route to Network-B in the egress VRF is b. The imported route to Network-B in the egress VRF is
modified to have a next hop of the IP address of the modified to have a next hop of the IP address of the
next SF instance in the SFC. next SF instance in the SFC.
4. The egress VRFs for the last service function install the 4. The egress VRFs for the last service function install the
skipping to change at page 20, line 13 skipping to change at page 20, line 13
the various intermediate routing systems in the SFC. the various intermediate routing systems in the SFC.
2.6.3 Common SFC provisioning considerations 2.6.3 Common SFC provisioning considerations
In both the methods, for physical routers, the creation and In both the methods, for physical routers, the creation and
configuration of VRFs, interfaces and local static routes can be configuration of VRFs, interfaces and local static routes can be
performed programmatically using Netconf; and BGP route distribution performed programmatically using Netconf; and BGP route distribution
can use a route reflector (which may be part of the controller). In can use a route reflector (which may be part of the controller). In
the virtualized case, where a VPN forwarder is present, creation and the virtualized case, where a VPN forwarder is present, creation and
configuration of VRFs, interfaces and installation of routes may configuration of VRFs, interfaces and installation of routes may
instead be performed using a single protocol like XMPP, NC/YANG or instead be performed using a single protocol like XMPP, NC/YANG or an
an equivalent programmatic interface. equivalent programmatic interface.
Also in the virtualized case, the actual forwarding table entries to Also in the virtualized case, the actual forwarding table entries to
be installed in the ingress and egress VRFs may be calculated by the be installed in the ingress and egress VRFs may be calculated by the
controller based on its internal knowledge of the required SFC controller based on its internal knowledge of the required SFC
topology and the connectivity of SF instances to routing systems. In topology and the connectivity of SF instances to routing systems. In
this case, the routes may be directly installed in the forwarders this case, the routes may be directly installed in the forwarders
using the programmatic interface and no BGP route advertisement is using the programmatic interface and no BGP route advertisement is
necessary, except when coordination with external domains (Section necessary, except when coordination with external domains (Section 5)
5) or federation between controller domains is employed (Section 7). or federation between controller domains is employed (Section 7).
Note however that this is just one typical model for a virtual Note however that this is just one typical model for a virtual
forwarding based system. In general, physical and virtual routing forwarding based system. In general, physical and virtual routing
systems can be treated exactly the same if they have the same systems can be treated exactly the same if they have the same
capabilities. capabilities.
In both the methods, the SF instance may also need to be set up In both the methods, the SF instance may also need to be set up
appropriately to forward traffic between it's input and output appropriately to forward traffic between it's input and output
interfaces, either via static, dynamic or policy-based routing. If interfaces, either via static, dynamic or policy-based routing. If
the service function is a transparent L2 service, then the static the service function is a transparent L2 service, then the static
route installed in the ingress VRF will have a next-hop of the IP route installed in the ingress VRF will have a next-hop of the IP
address of the routing system interface that the service instance is address of the routing system interface that the service instance is
attached to on its other interface. attached to on its other interface.
2.7 Controller Function 2.7 Controller Function
The purpose of the controller is to manage instantiation of SFCs in The purpose of the controller is to manage instantiation of SFCs in
networks and datacenters. When an SFC is to be instantiated, a model networks and datacenters. When an SFC is to be instantiated, a model
of the desired topology (service functions, number of instances, of the desired topology (service functions, number of instances,
connectivity) is built in the controller either via an API or GUI. connectivity) is built in the controller either via an API or GUI.
The controller then selects resources in the infrastructure that The controller then selects resources in the infrastructure that will
will support the SFC and configures them. This can involve support the SFC and configures them. This can involve instantiation
instantiation of SF instances to implement each service function, of SF instances to implement each service function, the instantiation
the instantiation of VRFs that will form virtual networks between SF of VRFs that will form virtual networks between SF instances, and
instances, and installation of routes to cause traffic to flow into installation of routes to cause traffic to flow into and between SF
and between SF instances. It can also include provisioning the instances. It can also include provisioning the necessary static,
necessary static, dynamic or policy based forwarding on the service dynamic or policy based forwarding on the service function instance
function instance to enable it to forward traffic. to enable it to forward traffic.
For simplicity, in this document, the controller is assumed to For simplicity, in this document, the controller is assumed to
contain all the required features for management of SFCs. In actual contain all the required features for management of SFCs. In actual
implementations, these features may be distributed among multiple implementations, these features may be distributed among multiple
inter-connected systems. E.g. An overarching orchestrator might inter-connected systems. E.g. An overarching orchestrator might
manage the overall SFC model, sending instructions to a separate manage the overall SFC model, sending instructions to a separate
virtual machine manager to instantiate service function instances, virtual machine manager to instantiate service function instances,
and to a virtual network manager to set up the service chain and to a virtual network manager to set up the service chain
connections between them. connections between them.
skipping to change at page 21, line 28 skipping to change at page 21, line 26
2.8 Variations on Setting Prefixes in an SFC 2.8 Variations on Setting Prefixes in an SFC
The SFC Creation section above described the basic procedures for a The SFC Creation section above described the basic procedures for a
couple of SFC creation methods. This section describes some couple of SFC creation methods. This section describes some
techniques that can extend and provide optimizations on top of the techniques that can extend and provide optimizations on top of the
basic procedures. basic procedures.
2.8.1 Using a Default Route 2.8.1 Using a Default Route
In the methods described above, it can be noted that only the In the methods described above, it can be noted that only the gateway
gateway routing systems need the specific network prefixes to steer routing systems need the specific network prefixes to steer traffic
traffic in and out of the SFC. The intermediate systems can direct in and out of the SFC. The intermediate systems can direct traffic in
traffic in the ingress and egress VRFs by using only a default the ingress and egress VRFs by using only a default route. Hence, it
route. Hence, it is possible to avoid installing the network is possible to avoid installing the network prefixes in the
prefixes in the intermediate systems. This can be done by splitting intermediate systems. This can be done by splitting the SFC into two
the SFC into two sections - one linking the entry and exit VRFs and sections - one linking the entry and exit VRFs and the other
the other including the intermediate systems. For instance, this may including the intermediate systems. For instance, this may be
be achieved by using two different Service-topology-RTs in the achieved by using two different Service-topology-RTs in the second
second method. method.
2.8.2 Using a Default Route and a Large Prefix 2.8.2 Using a Default Route and a Large Prefix
In the configuration methods described above, the network prefixes In the configuration methods described above, the network prefixes
for each network (Network-A and Network-B in the example above) for each network (Network-A and Network-B in the example above)
connected to the SFC are used in the routes that direct traffic connected to the SFC are used in the routes that direct traffic
through the SFC. This creates an operational linkage between the
implementation of the SFC and the insertion of the SFC into a implementation of the SFC and the insertion of the SFC into a
network. network.
For instance, subscriber network prefixes will normally be segmented For instance, subscriber network prefixes will normally be segmented
across subscriber attachment points such as broadband or mobile across subscriber attachment points such as broadband or mobile
gateways. This means that each SFC would have to be configured with gateways. This means that each SFC would have to be configured with
the subscriber network prefixes whose traffic it is handling. the subscriber network prefixes whose traffic it is handling.
In a variation of the SFC configuration method described above, the In a variation of the SFC configuration method described above, the
prefixes used in each direction can be such that they include all prefixes used in each direction can be such that they include all
possible addresses at each side of the SFC. For example, in Figure possible addresses at each side of the SFC. For example, in Figure 1,
1, the prefix for Network-A could include all subscriber IP the prefix for Network-A could include all subscriber IP addresses
addresses and the prefix for Network-B could be the default route, and the prefix for Network-B could be the default route, 0/0.
0/0.
Using this technique, the same routes can be installed in all Using this technique, the same routes can be installed in all
instances of an SFC that serve different groups of subscribers in instances of an SFC that serve different groups of subscribers in
different geographic locations. different geographic locations.
The routes forwarding traffic into a SF instance and to the next SF The routes forwarding traffic into a SF instance and to the next SF
instance are installed when an SFC is initially built, and each time instance are installed when an SFC is initially built, and each time
a SF instance is connected into the SFC, but there is no requirement a SF instance is connected into the SFC, but there is no requirement
for VRFs to be reconfigured when traffic from different networks for VRFs to be reconfigured when traffic from different networks pass
pass through the service chain, so long as their prefix is included through the service chain, so long as their prefix is included in the
in the prefixes in the VRFs along the SFC. prefixes in the VRFs along the SFC.
In this variation, it is assumed that no subscriber-originated In this variation, it is assumed that no subscriber-originated
traffic will enter the SFC destined for an IP address also in the traffic will enter the SFC destined for an IP address also in the
subscriber network address range. This will not be a restriction in subscriber network address range. This will not be a restriction in
many cases. many cases.
2.8.3 Disaggregated Gateway Routers 2.8.3 Disaggregated Gateway Routers
As a slight variation of the above, a network prefix may be As a slight variation of the above, a network prefix may be
disaggregated and spread out among various gateway routers, for disaggregated and spread out among various gateway routers, for
instance, in the case of virtual machines in a data-center. In order instance, in the case of virtual machines in a data-center. In order
to reduce the scaling requirements on the routing systems along the to reduce the scaling requirements on the routing systems along the
SFC, the SFC can again be split into two sections as described SFC, the SFC can again be split into two sections as described above.
above. In addition, the last egress VRF may act as the exit VRF and In addition, the last egress VRF may act as the exit VRF and install
install the destination network's disaggregated routes. If the the destination network's disaggregated routes. If the destination
destination network's prefixes can be aggregated, for instance into network's prefixes can be aggregated, for instance into a subnet
a subnet prefix, then the aggregate prefix may be advertised and prefix, then the aggregate prefix may be advertised and installed in
installed in the entry VRF. the entry VRF.
2.8.4 Optimizing VRF usage 2.8.4 Optimizing VRF usage
It may be desirable to avoid using distinct ingress and egress VRFs It may be desirable to avoid using distinct ingress and egress VRFs
for the service instances in order to make more efficient use of VRF for the service instances in order to make more efficient use of VRF
resources, especially on physical routing systems. The ingress VRF resources, especially on physical routing systems. The ingress VRF
and egress VRF may be treated as conceptual entities and the and egress VRF may be treated as conceptual entities and the
forwarding realized using one or more options described in this forwarding realized using one or more options described in this
section, combined with the methods described earlier. section, combined with the methods described earlier.
skipping to change at page 23, line 29 skipping to change at page 23, line 29
specific network prefixes may be installed in the intermediate specific network prefixes may be installed in the intermediate
service VRFs to direct traffic towards the attached service service VRFs to direct traffic towards the attached service
instances. instances.
Similarly, a per-interface policy-based-routing rule applied to an Similarly, a per-interface policy-based-routing rule applied to an
access interface can serve to direct traffic coming in from attached access interface can serve to direct traffic coming in from attached
service instances towards the next SF set. service instances towards the next SF set.
2.8.5 Dynamic Entry and Exit Signaling 2.8.5 Dynamic Entry and Exit Signaling
When either of the methods of the previous sections are employed, When either of the methods of the previous sections are employed, the
the prefixes of the attached networks at each end of an SFC can be prefixes of the attached networks at each end of an SFC can be
signaled into the corresponding VRFs dynamically. This requires that signaled into the corresponding VRFs dynamically. This requires that
a BGP session is configured either from the network device at each a BGP session is configured either from the network device at each
end of the SFC into each network or from the controller. end of the SFC into each network or from the controller.
If dynamic signaling is performed, and a bidirectional SFC set is If dynamic signaling is performed, and a bidirectional SFC set is
configured, and the gateways to the networks connected via the SFC configured, and the gateways to the networks connected via the SFC
exchange routes, steps must be taken to ensure that routes to both exchange routes, steps must be taken to ensure that routes to both
networks do not get advertised from both ends of the SFC set by re- networks do not get advertised from both ends of the SFC set by re-
origination. This can be achieved if a new BGP Extended Community is origination. This can be achieved if a new BGP Extended Community is
implemented to control re-origination. When a route is re- implemented to control re-origination. When a route is re-originated,
originated, the RTs of the re-originated routes are appended to the the RTs of the re-originated routes are appended to the new Route-
new RT-Record Extended Community, and if the RT for the route Target Record Extended Community, and if the RT for the route already
already exists in the Extended Community, the route is not re- exists in the Extended Community, the route is not re-originated (see
originated (see Section 9.1). Section 9.1).
2.8.6 Dynamic Re-Advertisements in Intermediate systems 2.8.6 Dynamic Re-Advertisements in Intermediate systems
The intermediate routing systems attached to the service instances The intermediate routing systems attached to the service instances
may also use the dynamic signaling technique from the previous may also use the dynamic signaling technique from the previous
section to re-advertise received routes up the chain. In this case, section to re-advertise received routes up the chain. In this case,
the ingress and egress VRFs are combined into one; and a local the ingress and egress VRFs are combined into one; and a local
route-policy ensures the re-advertised routes are associated with route-policy ensures the re-advertised routes are associated with
labels that direct incoming traffic directly to the attached service labels that direct incoming traffic directly to the attached service
instances on that routing system. instances on that routing system.
2.9 Layer-2 Virtual Networks and Service Functions 2.9 Layer-2 Virtual Networks and Service Functions
There are SFs that operate at layer-2, in a transparent mode, and There are SFs that operate at layer-2, in a transparent mode, and
forward traffic based on the MAC DA. When such a SF is present in forward traffic based on the MAC DA. When such a SF is present in the
the SFC, the procedures at the routing system are modified slightly. SFC, the procedures at the routing system are modified slightly. In
In this case, the IP address associated with the SF instance (and this case, the IP address associated with the SF instance (and used
used as the next-hop of routes in the above procedures) is actually as the next-hop of routes in the above procedures) is actually the
the one assigned to the routing system interface attached to the one assigned to the routing system interface attached to the other
other end of the SF instance, or it could be a virtual IP address end of the SF instance, or it could be a virtual IP address logically
logically associated with the service function with a next-hop of associated with the service function with a next-hop of the other
the other routing system interface. The routing system interface routing system interface. The routing system interface uses distinct
uses distinct interface MAC addresses. This allows the current interface MAC addresses. This allows the current scheme to be
scheme to be supported, while allowing the transparent service supported, while allowing the transparent service function to work
function to work using its existing behavior. using its existing behavior.
A SFC may be also be set up between end systems or network segments A SFC may be also be set up between end systems or network segments
within the same Layer-2 bridged network. In this case, applying the within the same Layer-2 bridged network. In this case, applying the
procedures described earlier, the segments or groups of end systems procedures described earlier, the segments or groups of end systems
are placed in distinct Layer-2 virtual networks, which are then then are placed in distinct Layer-2 virtual networks, which are then then
inter-connected via a sequence of intermediate Layer-2 virtual inter-connected via a sequence of intermediate Layer-2 virtual
networks that form the links in the SFC. Each virtual network maps networks that form the links in the SFC. Each virtual network maps to
to a pair of ingress and egress MAC VRFs on the routing systems to a pair of ingress and egress MAC VRFs on the routing systems to which
which the SF instances are attached. The routing systems at the ends the SF instances are attached. The routing systems at the ends of the
of the SFC will advertise the locally learnt or installed MAC SFC will advertise the locally learnt or installed MAC entries using
entries using BGP-EVPN type-2 routes, which will get installed in BGP-EVPN type-2 routes, which will get installed in the MAC VRFs at
the MAC VRFs at the other end. The intermediate systems may use the other end. The intermediate systems may use default MAC routes
default MAC routes installed in the ingress and egress MAC VRFs, or installed in the ingress and egress MAC VRFs, or the other variations
the other variations described earlier in this document. described earlier in this document.
2.10 Header Transforming Service Functions 2.10 Header Transforming Service Functions
If a service function performs an action that changes the source If a service function performs an action that changes the source
address in the packet header (e.g., NAT), the routes that were address in the packet header (e.g., NAT), the routes that were
installed as described above may not support reverse flow traffic. installed as described above may not support reverse flow traffic.
The solution to this is for the controller modify the routes in the The solution to this is for the controller modify the routes in the
reverse direction to direct traffic into instances of the reverse direction to direct traffic into instances of the
transforming service function. The original routes with a source transforming service function. The original routes with a source
skipping to change at page 25, line 26 skipping to change at page 25, line 26
address could be mapped to. In the case of network address address could be mapped to. In the case of network address
translation, this would correspond to the NAT pool. translation, this would correspond to the NAT pool.
3 Load Balancing Along a Service Function Chain 3 Load Balancing Along a Service Function Chain
One of the key concepts driving NFV [NFVE2E]is the idea that each One of the key concepts driving NFV [NFVE2E]is the idea that each
service function along an SFC can be separately scaled by changing service function along an SFC can be separately scaled by changing
the number of service function instances that implement it. This the number of service function instances that implement it. This
requires that load balancing be performed before entry into each requires that load balancing be performed before entry into each
service function. In this architecture, load balancing is performed service function. In this architecture, load balancing is performed
in either or both of egress and ingress VRFs depending on the type in either or both of egress and ingress VRFs depending on the type of
of load balancing being performed, and if more than one service load balancing being performed, and if more than one service instance
instance is connected to the same ingress VRF. is connected to the same ingress VRF.
3.1 SF Instances Connected to Separate VRFs 3.1 SF Instances Connected to Separate VRFs
If SF instances implementing a service in an SFC are each connected If SF instances implementing a service in an SFC are each connected
to separate VRFs(e.g. instances are connected to different routers to separate VRFs(e.g. instances are connected to different routers or
or are running on different hosts), load balancing is performed in are running on different hosts), load balancing is performed in the
the egress VRFs of the previous service, or in the VRF that is the egress VRFs of the previous service, or in the VRF that is the entry
entry to the SFC. The controller distributes BGP multi-path routes to the SFC. The controller distributes BGP multi-path routes to the
to the egress VRFs. The destination prefix of each route is the egress VRFs. The destination prefix of each route is the ultimate
ultimate destination network, or its representative aggregate or destination network, or its representative aggregate or default. The
default. The next-hops in the ECMP set are BGP next-hops of the next-hops in the ECMP set are BGP next-hops of the service instances
service instances attached to ingress VRFs of the next service in attached to ingress VRFs of the next service in the SFC. The load
the SFC. The load balancing corresponds to BGP Multipath, which balancing corresponds to BGP Multipath, which requires that the route
requires that the route distinguishers for each route are distinct distinguishers for each route are distinct in order to recognize that
in order to recognize that distinct paths should be used. Hence, distinct paths should be used. Hence, each VRF in a distributed, SFC
each VRF in a distributed, SFC environment should have a unique environment should have a unique route distinguisher.
route distinguisher.
+------+ +-------------------------+ +------+ +-------------------------+
O----|SFI-11|---O |--- Data plane connection| O----|SFI-11|---O |--- Data plane connection|
// +------+ \\ |=== Encapsulation tunnel | // +------+ \\ |=== Encapsulation tunnel |
// \\ | O VRF | // \\ | O VRF |
// \\ | * Load balancer | // \\ | * Load balancer |
// \\ +-------------------------+ // \\ +-------------------------+
// +------+ \\ // +------+ \\
Net-A-->O*====O----|SFI-12|---O====O-->Net-B Net-A-->O*====O----|SFI-12|---O====O-->Net-B
\\ +------+ // \\ +------+ //
\\ // \\ //
\\ // \\ //
\\ // \\ //
skipping to change at page 26, line 27 skipping to change at page 26, line 25
\\ +------+ // \\ +------+ //
O----|SFI-13|---O O----|SFI-13|---O
+------+ +------+
Figure 6 - Egress VRF Load Balancing across SF Instances Connected Figure 6 - Egress VRF Load Balancing across SF Instances Connected
to Different VRFs to Different VRFs
In the diagram, above, a service function is implemented in three In the diagram, above, a service function is implemented in three
service instances each connected to separate VRFs. Traffic from service instances each connected to separate VRFs. Traffic from
Network-A arrives at VRF at the start of the SFC, and is load Network-A arrives at VRF at the start of the SFC, and is load
balanced across the service instances using a set of ECMP routes balanced across the service instances using a set of ECMP routes with
with next hops being the addresses of the routing systems containing next hops being the addresses of the routing systems containing the
the ingress VRFs and with labels that identify the ingress ingress VRFs and with labels that identify the ingress interfaces of
interfaces of the service instances. the service instances.
3.2 SF Instances Connected to the Same VRF 3.2 SF Instances Connected to the Same VRF
When SF instances implementing a service in an SFC are connected to When SF instances implementing a service in an SFC are connected to
the same ingress VRF, load balancing is performed in the ingress VRF the same ingress VRF, load balancing is performed in the ingress VRF
across the service instances connected to it. The controller will across the service instances connected to it. The controller will
install routes in the ingress VRF to the destination network with install routes in the ingress VRF to the destination network with the
the interfaces connected to each service instance as next hops. The interfaces connected to each service instance as next hops. The
ingress VRF will then use ECMP to load balance across the service ingress VRF will then use ECMP to load balance across the service
instances. instances.
+------+ +-------------------------+ +------+ +-------------------------+
|SFI-11| |--- Data plane connection| |SFI-11| |--- Data plane connection|
+------+ |=== Encapsulation tunnel | +------+ |=== Encapsulation tunnel |
/ \ | O VRF | / \ | O VRF |
/ \ | * Load balancer | / \ | * Load balancer |
/ \ +-------------------------+ / \ +-------------------------+
/ +------+ \ / +------+ \
skipping to change at page 27, line 25 skipping to change at page 27, line 25
\ / \ /
\ / \ /
+------+ +------+
|SFI-13| |SFI-13|
+------+ +------+
Figure 7 - Ingress VRF Load Balancing across SF Instances Figure 7 - Ingress VRF Load Balancing across SF Instances
Connected to the Same VRF Connected to the Same VRF
In the diagram, above, a service is implemented by three service In the diagram, above, a service is implemented by three service
instances that are connected to the same ingress and egress VRFs. instances that are connected to the same ingress and egress VRFs. The
The ingress VRF load balances across the ingress interfaces using ingress VRF load balances across the ingress interfaces using ECMP,
ECMP, and the egress traffic is aggregated in the egress VRF. and the egress traffic is aggregated in the egress VRF.
If forwarding labels that identify each SFI ingress interface are If forwarding labels that identify each SFI ingress interface are
used, and if the routes to each SF instance are advertised with used, and if the routes to each SF instance are advertised with
different route distinguishers, then it is possible to perform ECMP different route distinguishers, then it is possible to perform ECMP
load balancing at the routing instance at the beginning of the load balancing at the routing instance at the beginning of the
encapsulation tunnel (which could be the egress VRF of the previous encapsulation tunnel (which could be the egress VRF of the previous
SF in the SFC). SF in the SFC).
3.3 Combination of Egress and Ingress VRF Load Balancing 3.3 Combination of Egress and Ingress VRF Load Balancing
skipping to change at page 28, line 29 skipping to change at page 28, line 29
Net-A-->O*====O----|SFI-13|---O*====O---|SFI-22|---O====O-->Net-B Net-A-->O*====O----|SFI-13|---O*====O---|SFI-22|---O====O-->Net-B
+------+ +------+ +------+ +------+
^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^
| | | | | | | | | | | |
| Ingress Egress | | | | Ingress Egress | | |
| Ingress Egress | | Ingress Egress |
SFC Entry SFC Exit SFC Entry SFC Exit
Figure 8 - Load Balancing across SF Instances Figure 8 - Load Balancing across SF Instances
In Figure 8, above, an SFC is composed of two services implemented In Figure 8, above, an SFC is composed of two services implemented by
by three service instances and two service instances, respectively. three service instances and two service instances, respectively. The
The service instances SFI-11 and SFI-12 are connected to the same service instances SFI-11 and SFI-12 are connected to the same ingress
ingress and egress VRFs, and all the other service instances are and egress VRFs, and all the other service instances are connected to
connected to separate VRFs. separate VRFs.
Traffic entering the SFC from Network-A is load balanced across the Traffic entering the SFC from Network-A is load balanced across the
ingress VRFs of the first service function by the chain entry VRF, ingress VRFs of the first service function by the chain entry VRF,
and then load balanced again across the ingress interfaces of SFI-11 and then load balanced again across the ingress interfaces of SFI-11
and SFI-12 by the shared ingress VRF. Note that use of standard ECMP and SFI-12 by the shared ingress VRF. Note that use of standard ECMP
will lead to an uneven distribution of traffic between the three will lead to an uneven distribution of traffic between the three
service instances (25% to SFI-11, 25% to SFI-12, and 50% to SFI-13). service instances (25% to SFI-11, 25% to SFI-12, and 50% to SFI-13).
This issue can be mitigated through the use of BGP link bandwidth This issue can be mitigated through the use of BGP link bandwidth
extended community [draft-ietf-idr-link-bandwidth]. As described in extended community [draft-ietf-idr-link-bandwidth]. As described in
the previous section, if a next-hop forwarding label is used, the previous section, if a next-hop forwarding label is used, another
another way to mitigate this effect would be to advertise routes to way to mitigate this effect would be to advertise routes to each SF
each SF instance connected to a VRF with a different route instance connected to a VRF with a different route distinguisher.
distinguisher.
After traffic passes through the first set of service instances, it After traffic passes through the first set of service instances, it
is load balanced in each of the egress VRFs of the first set of is load balanced in each of the egress VRFs of the first set of
service instances across the ingress VRFs of the next set of service service instances across the ingress VRFs of the next set of service
instances. instances.
3.4 Forward and Reverse Flow Load Balancing 3.4 Forward and Reverse Flow Load Balancing
This section discusses requirements in load balancing for forward This section discusses requirements in load balancing for forward and
and reverse paths when stateful service functions are deployed. reverse paths when stateful service functions are deployed.
3.4.1 Issues with Equal Cost Multi-Path Routing 3.4.1 Issues with Equal Cost Multi-Path Routing
As discussed in the previous sections, load balancing in the forward As discussed in the previous sections, load balancing in the forward
SFC in the above example can automatically occur with standard BGP, SFC in the above example can automatically occur with standard BGP,
if multiple equal cost routes to Network-B are installed into all if multiple equal cost routes to Network-B are installed into all the
the ingress VRFs, and each route directs traffic through a different ingress VRFs, and each route directs traffic through a different
service function instance in the next set. The multiple BGP routes service function instance in the next set. The multiple BGP routes in
in the routing table will translate to Equal Cost Multi-Path in the the routing table will translate to Equal Cost Multi-Path in the
forwarding table. The hash used in the load balancing algorithm (per forwarding table. The hash used in the load balancing algorithm (per
packet, per flow or per prefix) is implementation specific. packet, per flow or per prefix) is implementation specific.
If a service function is stateful, it is required that forward flows If a service function is stateful, it is required that forward flows
and reverse flows always pass through the same service function and reverse flows always pass through the same service function
instance. Standard ECMP does not provide this capability, since the instance. Standard ECMP does not provide this capability, since the
hash calculation will see different input data for the same flow in hash calculation will see different input data for the same flow in
the forward and reverse directions (since the source and destination the forward and reverse directions (since the source and destination
fields are reversed). fields are reversed).
Additionally, if the number of SF instances changes, either Additionally, if the number of SF instances changes, either
increasing to expand capacity, or decreases (planned, or due to a SF increasing to expand capacity, or decreases (planned, or due to a SF
instance failure), the hash table in ECMP is recalculated, and most instance failure), the hash table in ECMP is recalculated, and most
flows will be directed to a different SF instance and user sessions flows will be directed to a different SF instance and user sessions
will be disrupted. will be disrupted.
There are a number of ways to satisfy the requirements of symmetric There are a number of ways to satisfy the requirements of symmetric
forward/reverse paths for flows and minimal disruption when SF forward/reverse paths for flows and minimal disruption when SF
instances are added to or removed from a set. Two techniques that instances are added to or removed from a set. Two techniques that can
can be employed are described in the following sections. be employed are described in the following sections.
3.4.2 Modified ECMP with Consistent Hash 3.4.2 Modified ECMP with Consistent Hash
Symmetric forwarding into each side of an SF instance set can be Symmetric forwarding into each side of an SF instance set can be
achieved with a small modification to ECMP if the packet headers are achieved with a small modification to ECMP if the packet headers are
preserved after passing through the SF instance set and assuming preserved after passing through the SF instance set and assuming that
that the same hash function, same hash salt and same ordering the same hash function, same hash salt and same ordering association
association of hash buckets to ECMP routes is used in both of hash buckets to ECMP routes is used in both
directions. Each packet's 5-tuple data is used to calculate which
hash bucket, and therefore which service instance, that the packet hash bucket, and therefore which service instance, that the packet
will be sent to, but the source and destination IP address and port will be sent to, but the source and destination IP address and port
information are swapped in the calculation in the reverse direction. information are swapped in the calculation in the reverse direction.
This method only requires that the list of available service This method only requires that the list of available service function
function instances is consistently maintained in load balance tables instances is consistently maintained in load balance tables in all
in all the routing systems rather than maintaining flow tables. This the routing systems rather than maintaining flow tables. This
requirement can be met by the use of a distinct VPN route for each requirement can be met by the use of a distinct VPN route for each
instance. instance.
In the SFC architecture described in this document, when SF In the SFC architecture described in this document, when SF instances
instances are added or removed, the controller is required to are added or removed, the controller is required to install (or
install (or remove) routes to the SF instances. The controller could remove) routes to the SF instances. The controller could configure
configure the load balancing function in VRFs that connect to each the load balancing function in VRFs that connect to each added (or
added (or removed) SF instance as part of the same network removed) SF instance as part of the same network transaction as route
transaction as route updates to ensure that the load balancer updates to ensure that the load balancer configuration is
configuration is synchronized with the set of SF instances. synchronized with the set of SF instances.
The consistent ordering among ECMP routes in the routing systems The consistent ordering among ECMP routes in the routing systems
could be achieved through configuration of the routing systems by could be achieved through configuration of the routing systems by the
the controller using, for instance, Netconf; or when the routes are controller using, for instance, Netconf; or when the routes are
signaled using BGP by the controller or a routing system, the order signaled using BGP by the controller or a routing system, the order
for a given instance can be sent in a new 'Consistent Hash Sort for a given instance can be sent in a new 'Consistent Hash Sort
Order' BGP Extended Community (defined in Section 9.2). Order' BGP Extended Community (defined in Section 9.2).
The effect of rehashing when SF instances are added or removed can The effect of rehashing when SF instances are added or removed can be
be minimized, or even eliminated using variations of the technique minimized, or even eliminated using variations of the technique of
of consistent hashing [consistent-hash]. Details are outside the consistent hashing [consistent-hash]. Details are outside the scope
scope of this document. of this document.
3.4.3 ECMP with Flow Table 3.4.3 ECMP with Flow Table
A second refinement that can ensure forward/reverse flow A second refinement that can ensure forward/reverse flow consistency,
consistency, and also provides stability when the number of SF and also provides stability when the number of SF instances changes
instances changes ('flow-stickiness'), is the use of dynamically ('flow-stickiness'), is the use of dynamically configured IP flow
configured IP flow tables in the VRFs. In this technique, flow tables in the VRFs. In this technique, flow tables are used to ensure
tables are used to ensure that existing flows are unaffected if the that existing flows are unaffected if the number of ECMP routes
number of ECMP routes changes, and that forward and reverse traffic changes, and that forward and reverse traffic passes through the same
passes through the same SF instance in each set of SF instances SF instance in each set of SF instances implementing a service
implementing a service function. function.
The flow tables are set up as follows: The flow tables are set up as follows:
1. User traffic with a new 5-tuple enters an egress VRF from a 1. User traffic with a new 5-tuple enters an egress VRF from a
connected SF instance. connected SF instance.
2. The VRF calculates the ECMP hash across available routes 2. The VRF calculates the ECMP hash across available routes
(i.e., ECMP group) to the ingress interfaces of the SF (i.e., ECMP group) to the ingress interfaces of the SF
instances in the next SF instance set. The consistent hash instances in the next SF instance set. The consistent hash
technique described in section 3.4.2 must be used here and technique described in section 3.4.2 must be used here and
in subsequent steps. in subsequent steps.
3. The VRF creates a new flow entry for the 5-tuple of the new 3. The VRF creates a new flow entry for the 5-tuple of the new
traffic with the next-hop being the chosen downstream ECMP traffic with the next-hop being the chosen downstream ECMP
group member (determined in the step 2. above) . All group member (determined in the step 2. above) . All
subsequent packets for the same flow will be forwarded subsequent packets for the same flow will be forwarded using
using flow lookup and, hence, will use the same next-hop. flow lookup and, hence, will use the same next-hop.
4. The encapsulated packet arrives in the routing system that 4. The encapsulated packet arrives in the routing system that
hosts the ingress VRF for the selected SF instance. hosts the ingress VRF for the selected SF instance.
5. The ingress VRF of the next service instance determines if 5. The ingress VRF of the next service instance determines if
the packet came from a routing system that is in an ECMP the packet came from a routing system that is in an ECMP
group in the reverse direction(i.e., from this ingress VRF group in the reverse direction(i.e., from this ingress VRF
back to the previous set of SF instances). back to the previous set of SF instances).
6. If an ECMP group is found, the ingress VRF creates a flow 6. If an ECMP group is found, the ingress VRF creates a flow
entry for the reversed 5-tuple with next-hop of the tunnel entry for the reversed 5-tuple with next-hop of the tunnel
on which traffic arrived. This is for the traffic in the on which traffic arrived. This is for the traffic in the
reverse direction. reverse direction.
7. If multiple SF instances are connected to the ingress VRF, 7. If multiple SF instances are connected to the ingress VRF,
the ECMP consistent hash is used to choose which one to the ECMP consistent hash is used to choose which one to send
send the traffic into. the traffic into.
8. A forward flow table entry is created for the traffic's 5- 8. A forward flow table entry is created for the traffic's 5-
tuple with next hop of the interface of the SF instance tuple with next hop of the interface of the SF instance
chosen in the previous step. chosen in the previous step.
9. The packet is sent into the selected SF instance. 9. The packet is sent into the selected SF instance.
The above method ensures that forward and reverse flows pass through The above method ensures that forward and reverse flows pass through
the same SF instances, and that if the number of ECMP routes changes the same SF instances, and that if the number of ECMP routes changes
when SF instances are added or removed, all existing flows will when SF instances are added or removed, all existing flows will
continue to flow through the same SF instances, but new flows will continue to flow through the same SF instances, but new flows will
use the new ECMP hash. The only flows affected will be those that use the new ECMP hash. The only flows affected will be those that
were passing through an SF instance that was removed, and those will were passing through an SF instance that was removed, and those will
be spread among the remaining SF instances using the updated ECMP be spread among the remaining SF instances using the updated ECMP
hash. hash.
If the consistent hash algorithm is used in both directions, then If the consistent hash algorithm is used in both directions, then
only the forwarding flow entries would be required, and would be only the forwarding flow entries would be required, and would be
built independently in each direction. If distinct VPN routes with next-hop forwarding labels are used, then only the flow table in step
next-hop forwarding labels are used, then only the flow table in 3 is sufficient to provide flow stickiness.
step 3 is sufficient to provide flow stickiness.
3.4.4 Dealing with different hash algorithms in an SFC 3.4.4 Dealing with different hash algorithms in an SFC
In some cases, there will be two or more hash algorithms in In some cases, there will be two or more hash algorithms in
forwarders along an SFC. E.g. when a physical router is at the entry forwarders along an SFC. E.g. when a physical router is at the entry
and exit of the chain, and virtual forwarders are used within the and exit of the chain, and virtual forwarders are used within the
chain. Forward and reverse flows will mostly not pass through the chain. Forward and reverse flows will mostly not pass through the
same SF instances of the first SF, and the SFC will not operate as same SF instances of the first SF, and the SFC will not operate as
intended if the first SF is stateful. It may be impractical, or intended if the first SF is stateful. It may be impractical, or
prohibitively expensive to implement the flow table-based methods prohibitively expensive to implement the flow table-based methods
described above to achieve flow stability and symmetry. This issue described above to achieve flow stability and symmetry. This issue
can be mitigated by ensuring that the first SF is not stateful, or can be mitigated by ensuring that the first SF is not stateful, or by
by placing a null SF between the physical router and the first placing a null SF between the physical router and the first actual SF
actual SF in the SFC. This ensures that the hash method on both in the SFC. This ensures that the hash method on both sides of
sides of stateful service instances is the same, and the SFC will stateful service instances is the same, and the SFC will operate with
operate with flow stability and symmetry if the methods described flow stability and symmetry if the methods described above are
above are employed. employed.
4 Steering into SFCs Using a Classifier 4 Steering into SFCs Using a Classifier
In many applications of SFCs, a classifier will be used to direct In many applications of SFCs, a classifier will be used to direct
traffic into SFCs. The classifier inspects the first or first few traffic into SFCs. The classifier inspects the first or first few
packets in a flow to determine which SFC the flow should be sent packets in a flow to determine which SFC the flow should be sent
into. The decision criteria can be based on just the IP 5-tuple of into. The decision criteria can be based on just the IP 5-tuple of
the header (i.e filter-based forwarding), or could involve analysis the header (i.e filter-based forwarding), or could involve analysis
of the payload of packets using deep packet inspection. Integration of the payload of packets using deep packet inspection. Integration
with a subscriber management system such as PCRF or AAA may be with a subscriber management system such as PCRF or AAA may be
skipping to change at page 33, line 33 skipping to change at page 33, line 33
| +---+ +---+ | | +---+ +---+ |
| | | |
| +---+ +---+ +---+ | | +---+ +---+ +---+ |
+--+ X +---+ Y +---+ Z +-+ +--+ X +---+ Y +---+ Z +-+
+---+ +---+ +---+ +---+ +---+ +---+
Figure 9 - Subscriber/Application-Aware Steering with a Classifier Figure 9 - Subscriber/Application-Aware Steering with a Classifier
In the diagram, the classifier receives subscriber traffic and sends In the diagram, the classifier receives subscriber traffic and sends
the traffic out of one of two logical interfaces, depending on the traffic out of one of two logical interfaces, depending on
classification criteria. The logical interfaces of the classifier classification criteria. The logical interfaces of the classifier are
are connected to VRFs in a router that are entries to two SFCs connected to VRFs in a router that are entries to two SFCs (shown as
(shown as O in the diagram). O in the diagram).
In this scenario, the entry VRF for each chain does not advertise In this scenario, the entry VRF for each chain does not advertise the
the destination network prefixes and the modified method of setting destination network prefixes and the modified method of setting
prefixes, described in Section 2.8.2 can be employed. Also, the prefixes, described in Section 2.8.2 can be employed. Also, the exit
exit VRF for each SFC does not peer with a gateway or proxy node in VRF for each SFC does not peer with a gateway or proxy node in the
the destination network and packets are forwarded using IP lookup in destination network and packets are forwarded using IP lookup in the
the main routing table or in a VRF that the exit traffic from the main routing table or in a VRF that the exit traffic from the SFCs is
SFCs is directed into (shown as X in the diagram). A flow table may directed into (shown as X in the diagram). A flow table may be
be required to ensure that reverse traffic is sent into the correct required to ensure that reverse traffic is sent into the correct SFC.
SFC.
An alternative would be where the classifier is itself a An alternative would be where the classifier is itself a distributed,
distributed, virtualized service function, but with multiple egress virtualized service function, but with multiple egress interfaces. In
interfaces. In that case, each virtual classifier instance could be that case, each virtual classifier instance could be entry VRF would
attached to a set of VRFs that connect to different SFCs. Each chain load balance across the first SF instance set in its SFC. The reverse
entry VRF would load balance across the first SF instance set in its flow table mechanism described in Section 3.4.3 could be employed to
SFC. The reverse flow table mechanism described in Section 3.4.3 ensure that flows return to the originating classifier instance which
could be employed to ensure that flows return to the originating may maintain subscriber context and perform charging and accounting.
classifier instance which may maintain subscriber context and
perform charging and accounting.
5 External Domain Co-ordination 5 External Domain Co-ordination
It is likely that SFCs will be managed as a separate administrative It is likely that SFCs will be managed as a separate administrative
domain from the networks that they receive traffic from, and send domain from the networks that they receive traffic from, and send
traffic to. If the connected networks use BGP for route traffic to. If the connected networks use BGP for route distribution,
distribution, the controller in the SFC domain can join the network the controller in the SFC domain can join the network domains by
domains by creating BGP peering sessions with routing systems or creating BGP peering sessions with routing systems or route
route reflectors in those network domains to exchange VPN routes, or reflectors in those network domains to exchange VPN routes, or with
with local border routers that peer with the external domains. While local border routers that peer with the external domains. While a
a controller can modify route targets for the VRFs within its SFC controller can modify route targets for the VRFs within its SFC
domain, it is likely to not have any control over the external domain, it is likely to not have any control over the external
networks with which it is peering. Hence, the design does not assume networks with which it is peering. Hence, the design does not assume
that the RTs of external network domains can be modified by the that the RTs of external network domains can be modified by the
controller. It may however learn those RTs and use them in it's controller. It may however learn those RTs and use them in it's
modified route advertisements. modified route advertisements.
In order to steer traffic from external network domains into an SFC, In order to steer traffic from external network domains into an SFC,
the controller will advertise a destination network's prefixes into the controller will advertise a destination network's prefixes into
the peering source network domain with a BGP next-hop and label the peering source network domain with a BGP next-hop and label
associated with the SFC entry point that may be on a routing system associated with the SFC entry point that may be on a routing system
attached to the first SF instance. This advertisement may be over attached to the first SF instance. This advertisement may be over
regular MP-BGP/VPN peering which assumes existing standard VPN regular MP-BGP/VPN peering which assumes existing standard VPN
routing/forwarding behavior on the network domain's routers routing/forwarding behavior on the network domain's routers
(PEs/ASBRs). The controller can learn routes to networks in external (PEs/ASBRs). The controller can learn routes to networks in external
domains at the egress of an SFC and advertise routes to those domains at the egress of an SFC and advertise routes to those network
network into other external domains using the first ingress routing into other external domains using the first ingress routing instance
instance as the next hop thus allowing dynamic steering through re- as the next hop thus allowing dynamic steering through re-
origination of routes. origination of routes.
An operational benefit of this approach is that the SFC topology An operational benefit of this approach is that the SFC topology
within a domain need not be exposed to other domains. Additionally, within a domain need not be exposed to other domains. Additionally,
using non-specific routes inside an SFC, as described in Section using non-specific routes inside an SFC, as described in Section
2.8.1, means that new networks can be attached to a SFC without 2.8.1, means that new networks can be attached to a SFC without
needing to configure prefixes inside the chain. needing to configure prefixes inside the chain.
The controller will typically remove the destination network's RTs The controller will typically remove the destination network's RTs
and replace them with the RTs of the source network while and replace them with the RTs of the source network while advertising
advertising the modified routes. Alternatively, an external domain the modified routes. Alternatively, an external domain may be
may be provisioned with an additional export-only RT and an import- provisioned with an additional export-only RT and an import- only RT
only RT that the controller can use. that the controller can use.
6 Fine-grained steering using BGP Flow-Spec 6 Fine-grained steering using BGP Flow-Spec
When steering traffic from an external network domain into an SFC When steering traffic from an external network domain into an SFC
based on attributes of the packet flow, BGP Flow-spec can be used as based on attributes of the packet flow, BGP Flow-spec can be used as
a signaling option. a signaling option.
In this case, the controller can advertise one or more flow-spec In this case, the controller can advertise one or more flow-spec
routes into the entry VRF with the appropriate Service-topology-RT routes into the entry VRF with the appropriate Service-topology-RT
for the SFC. Alternatively, it can use the procedures described in for the SFC. Alternatively, it can use the procedures described in
RFC5575 or [flowspec-redirect-ip] on the gateway router to redirect RFC5575 or [flowspec-redirect-ip] on the gateway router to redirect
traffic towards the first SF. traffic towards the first SF.
skipping to change at page 35, line 39 skipping to change at page 35, line 34
domains there may be a requirement to exchange information between domains there may be a requirement to exchange information between
controllers. Again, a BGP session between controllers can be used to controllers. Again, a BGP session between controllers can be used to
exchange route information as described in the previous sections and exchange route information as described in the previous sections and
allow such domain spanning SFCs to be created. allow such domain spanning SFCs to be created.
8 Coordination Between SF Instances and Controller using BGP 8 Coordination Between SF Instances and Controller using BGP
In many cases, the configuration of SF instance determines its In many cases, the configuration of SF instance determines its
network behavior. E.g. when NAT pools are set up, or when an SSL network behavior. E.g. when NAT pools are set up, or when an SSL
gateway is configured with a set of enterprise IP addresses to use. gateway is configured with a set of enterprise IP addresses to use.
In these cases, the addresses that will be used by the SFs need to In these cases, the addresses that will be used by the SFs need to be
be known in the networks connecting to them in order that traffic known in the networks connecting to them in order that traffic can be
can be properly routed. When SFCs are involved, this means that the properly routed. When SFCs are involved, this means that the
controller has to be notified when such configuration changes are controller has to be notified when such configuration changes are
made in SF instances. Sometimes, the changes will be made by end- made in SF instances. Sometimes, the changes will be made by end-
customers and it is desirable the controller adjust the SFC routing
configuration automatically when the change is made, and without configuration automatically when the change is made, and without
customers needing to notify the service provider via a portal, for customers needing to notify the service provider via a portal, for
instance, or requiring development of integration modules linking instance, or requiring development of integration modules linking the
the SF instances and the controller. SF instances and the controller.
One option for automatic notification for SFs that support BGP is One option for automatic notification for SFs that support BGP is for
for the connected forwarding system (physical or virtual SFF) to the connected forwarding system (physical or virtual SFF) to also
also support BGP, and for SF instances to be configured to peer with support BGP, and for SF instances to be configured to peer with the
the SFF. When changes are made to the configuration of a SF SFF. When changes are made to the configuration of a SF instance,
instance, that for example, the SF will accept packets from a that for example, the SF will accept packets from a particular
particular network prefix on one of its interfaces, the SF instance network prefix on one of its interfaces, the SF instance will send a
will send a BGP route update to the SFF it is connected to and which BGP route update to the SFF it is connected to and which it has a BGP
it has a BGP session with. The controller can then adjust the routes session with. The controller can then adjust the routes along SFCs to
along SFCs to ensure that packets with destinations in the new ensure that packets with destinations in the new prefix reach the
prefix reach the reconfigured SF instance. reconfigured SF instance.
BGP could also be used to signal from the controller to a SF BGP could also be used to signal from the controller to a SF instance
instance that certain traffic should be sent out from a particular that certain traffic should be sent out from a particular interface.
interface. This could be used to direct suspect traffic to a This could be used to direct suspect traffic to a security scrubbing
security scrubbing center,for example. center,for example.
Note that the SFF need not support a BGP stack itself; it can proxy Note that the SFF need not support a BGP stack itself; it can proxy
BGP messages to the controller which will support such a stack. BGP messages to the controller which will support such a stack.
9 BGP Extended Communities 9 BGP Extended Communities
9.1 Route-Target_RECORD 9.1 Route-Target Record
Route-Target Record (RT-Record) is an optional, transitive BGP Route-Target Record (RT Record) is defined as a transitive BGP
attribute of Type code TBD. It contains an RT value representing one Extended Community, that contains a Route-Target value representing
of the RTs that the route has been attached with previously, and one of the RTs that the route has been attached with previously, and
which may no longer be attached to the route on subsequent re- which may no longer be attached to the route on subsequent re-
advertisements (see Section 2.8.5). It is encoded as follows: advertisements (see Section 2.8.5).
0 1 2 3 A Sub-Type code 0x13 is assigned in the three BGP Extended Community
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 types - Two-Octet AS-Specific 0x00, IPv4-Address-Specific 0x01 and
Four-Octet AS-Specific 0x02. A Sub-Type code 0x0013 is also assigned
in the BGP Transitive IPv6 Address-Specific Extended Community.
The Extended Community is encoded as follows:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Attr Type Code | | | 0x00,0x01,0x02| Sub-Type=0x13 | Route-Target Value |
+-+-+-+-+-+-+-+-+ Route-Target Extended Community Value + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| (8B or 20B) | | Route-Target Value contd. |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Attr Type Code : The BGP Attribute Type Code for the Route-Target
It can be 16 for RFC 4360 Extended Community, or
25 for IPv6 Address Specific Extended Community
Value : It contains a Route-Target Extended Community of The Type field of the BGP Route-Target Extended Community is
one of the types specified in RFC 4360 or RFC copied into the Type field of the RT Record Extended Community.
5701
The Value field (Global Administrator and Local Administrator) of
the Route-Target Extended Community is copied into the Route-
Target Value field of the RT Record Extended Community.
When comparing a RT-Record to a Route-Target, only the Type and
the Route-Target value fields are used in the comparison. The sub-
type field is masked out.
When a speaker re-originates a route that contains one or more When a speaker re-originates a route that contains one or more
RTs, it must add each of these RTs as RT-Record extended communities RTs, it must add each of these RTs as RT Record extended communities
of the re-originated route. in the re-originated route.
A speaker must not re-originate a route to an RT, if this RT is A speaker must not re-originate a route with an RT, if this RT is
present as an RT-Record extended community. already present as an RT Record extended community.
9.2 CONSISTENT_HASH_SORT_ORDER 9.2 CONSISTENT_HASH_SORT_ORDER
Consistent Hash Sort Order is an optional transitive Opaque BGP Consistent Hash Sort Order is an optional transitive Opaque BGP
Extended Community of type TBD, defined as follows: Extended Community of sub-type 0x14, defined as follows:
Type Field : The value of the high-order octet is determined by Type Field : The value of the high-order octet is determined by
provisioning as per [RFC4360]. The value of the low- provisioning as per [RFC4360]. The value of the low-
order octet is to be assigned by IANA from the order octet is assigned as 0x14 by IANA from the
Transitive Opaque Extended Community Sub-Types Transitive Opaque Extended Community Sub-Types registry.
registry.
Value Field : The value field contains a Sort Order sub-field that Value Field : The value field contains a Sort Order sub-field that
indicates the relative order of this route among the indicates the relative order of this route among the
ECMP set for the prefix, to be sorted in increasing ECMP set for the prefix, to be sorted in increasing
order. It is a 32-bit unsigned integer. The field is order. It is a 32-bit unsigned integer. The field is
encoded as shown below: encoded as shown below:
+------------------------------+ +------------------------------+
| Sort Order (4 octets) | | Sort Order (4 octets) |
+------------------------------+ +------------------------------+
| Reserved (2 octets) | | Reserved (2 octets) |
+------------------------------+ +------------------------------+
10 Summary and Conclusion 10 Summary and Conclusion
The architecture for service function chains described in this The architecture for service function chains described in this
document uses virtual networks implemented as overlays in order to document uses virtual networks implemented as overlays in order to
create service function chains. The virtual networks use standards- create service function chains. The virtual networks use standards-
based encapsulation tunneling, such as MPLS over GRE/UDP or VXLAN, based encapsulation tunneling, such as MPLS over GRE/UDP or VXLAN, to
to transport packets into an SFC and between service function transport packets into an SFC and between service function instances
instances without routing in the user address space. Two methods of without routing in the user address space. Two methods of installing
installing routes to form service chains are described. routes to form service chains are described.
In environments with physical routers, a controller may operate in In environments with physical routers, a controller may operate in
tandem with existing BGP route reflectors, and would contain the SFC tandem with existing BGP route reflectors, and would contain the SFC
topology model, and the ability to install the local static toology model, and the ability to install the local static interface
interface routes to SF instances. In a virtualized environment, the routes to SF instances. In a virtualized environment, the controller
controller can emulate route refection internally and simply install can emulate route refection internally and simply install required
required routes directly without advertisements occurring. routes directly without advertisements occurring.
11 Security Considerations 11 Security Considerations
The security considerations for SFCs are broadly similar to those The security considerations for SFCs are broadly similar to those
concerning the data, control and management planes of any device concerning the data, control and management planes of any device
placed in a network. Details are out of scope for this document. placed in a network. Details are out of scope for this document.
12 IANA Considerations 12 IANA Considerations
The new BGP Extended Communities in Section 9 require a type The new BGP Extended Communities in Section 9 are assigned types as
allocation in the IANA registry for extended communities. defined above in the IANA registry for extended communities.
13 Acknowledgments
This document was prepared using 2-Word-v2.0.template.dot.
This document is based on earlier drafts [draft-rfernando-bess-
service-chaining] and [draft-mackie-sfc-using-virtual-networking].
The authors would like to thank D. Daino, D.R. Lopez, D. Bernier, W.
Haeffner, A. Farrel, L. Fang, and N. So, for their contributions to
the earlier drafts. The authors would also like to thank the
following individuals for their review and feedback on the original
proposals: E. Rosen, J. Guchard, P. Quinn, P. Bosch, D. Ward, A.
Ganesan, N. Seth, G. Pildush and N. Bitar. The authors also thank
Wim Henderickx for his useful suggestions on several aspects of the
draft.
14 Informative References 13 Informative References
[NFVE2E] "Network Functions Virtualisation: End to End [NFVE2E] "Network Functions Virtualisation: End to End Architecture,
Architecture, http://docbox.etsi.org/ISG/NFV/70- http://docbox.etsi.org/ISG/NFV/70-
DRAFT/0010/NFV-0010v016.zip". DRAFT/0010/NFV-0010v016.zip".
[RFC2328] J. Moy, "OSPF Version 2", RFC 2328, April, 1998. [RFC2328] J. Moy, "OSPF Version 2", RFC 2328, April, 1998.
[sfc-arch] Halpern, J. and Pignataro, C., "Service Function Chaining [sfc-arch] Halpern, J. and Pignataro, C., "Service Function Chaining
(SFC) Architecture", RFC 7665, October 2015. (SFC) Architecture", RFC 7665, October 2015.
[RFC4364] Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private [RFC4364] Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private
Networks (VPNs)", RFC 4364, February 2006. Networks (VPNs)", RFC 4364, February 2006.
skipping to change at page 39, line 5 skipping to change at page 39, line 38
[draft-ietf-bess-evpn-overlay-02] [draft-ietf-bess-evpn-overlay-02]
A. Sajassi, et al, "A Network Virtualization Overlay A. Sajassi, et al, "A Network Virtualization Overlay
Solution using EVPN", draft-ietf-bess-evpn-overlay, Solution using EVPN", draft-ietf-bess-evpn-overlay,
February 2015. February 2015.
[draft-ietf-sfc-nsh] [draft-ietf-sfc-nsh]
Quinn, P., et al, "Network Service Header", draft-ietf- Quinn, P., et al, "Network Service Header", draft-ietf-
sfc-nsh-00, March 2015. sfc-nsh-00, March 2015.
[draft-niu-sfc-mechanism] [draft-niu-sfc-mechanism]
Niu, L., Li, H., and Jiang, Y., "A Service Function Niu, L., Li, H., and Jiang, Y., "A Service Function
Chaining Header and its Mechanism", draft-niu-sfc- Chaining Header and its Mechanism", draft-niu-sfc-
mechanism-00, January 2014. mechanism-00, January 2014.
[draft-rijsman-sfc-metadata-considerations] [draft-rijsman-sfc-metadata-considerations]
B. Rijsman, et al. "Metadata Considerations", draft- B. Rijsman, et al. "Metadata Considerations", draft-
rijsman-sfc-metadata-considerations-00, February 12, 2014 rijsman-sfc-metadata-considerations-00, February 12, 2014
[RFC6241] Enns, R., Bjorklund, M., Schoenwaelder, J., and A. [RFC6241] Enns, R., Bjorklund, M., Schoenwaelder, J., and A. Bierman,
Bierman, "Network Configuration Protocol (NETCONF)", RFC "Network Configuration Protocol (NETCONF)", RFC 6241, June
6241, June 2011. 2011.
[RFC4023] Worster, T., Rekhter, Y., and E. Rosen, "Encapsulating [RFC4023] Worster, T., Rekhter, Y., and E. Rosen, "Encapsulating MPLS
MPLS in IP or Generic Routing Encapsulation (GRE)", RFC in IP or Generic Routing Encapsulation (GRE)", RFC 4023,
4023, March 2005. March 2005.
[RFC7510] Xu, X., Sheth, N. et al, "Encapsulating MPLS in UDP", RFC [RFC7510] Xu, X., Sheth, N. et al, "Encapsulating MPLS in UDP", RFC
7510, April 2015. 7510, April 2015.
[draft-ietf-i2rs-architecture] [draft-ietf-i2rs-architecture]
Atlas, A., Halpern, J., Hares, S., Ward, D., and T Nadeau, Atlas, A., Halpern, J., Hares, S., Ward, D., and T Nadeau,
"An Architecture for the Interface to the Routing System", "An Architecture for the Interface to the Routing System",
draft-ietf-i2rs-architecture, work in progress, March draft-ietf-i2rs-architecture, work in progress, March
2015. 2015.
skipping to change at page 41, line ? skipping to change at page 40, line 34
[draft-ietf-idr-link-bandwidth] [draft-ietf-idr-link-bandwidth]
P. Mohapatra, R. Fernando, "BGP Link Bandwidth Extended P. Mohapatra, R. Fernando, "BGP Link Bandwidth Extended
Community", draft-ietf-idr-link-bandwidth, work in Community", draft-ietf-idr-link-bandwidth, work in
progress. progress.
[flowspec-redirect-ip] [flowspec-redirect-ip]
Uttaro, J. et al. "BGP Flow-Spec Redirect to IP Action", Uttaro, J. et al. "BGP Flow-Spec Redirect to IP Action",
draft-ietf-idr-flowspec-redirect-ip-02, February 2015. draft-ietf-idr-flowspec-redirect-ip-02, February 2015.
14 Acknowledgments
This document was prepared using 2-Word-v2.0.template.dot.
This document is based on earlier drafts [draft-rfernando-bess-
service-chaining] and [draft-mackie-sfc-using-virtual-networking].
The authors would like to thank D. Daino, D.R. Lopez, D. Bernier, W.
Haeffner, A. Farrel, L. Fang, and N. So, for their contributions to
the earlier drafts. The authors would also like to thank the
following individuals for their review and feedback on the original
proposals: E. Rosen, J. Guchard, P. Quinn, P. Bosch, D. Ward, A.
Ganesan, N. Seth, G. Pildush and N. Bitar. The authors also thank Wim
Henderickx for his useful suggestions on several aspects of the
Authors' Addresses Authors' Addresses
Rex Fernando Rex Fernando
Cisco Cisco
170 W Tasman Drive 170 W Tasman Drive
San Jose, CA 95134 San Jose, CA 95134
USA USA
Email: rex@cisco.com Email: rex@cisco.com
Stuart Mackie Stuart Mackie
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