SPRING J. Guichard, Ed.
Internet-Draft Futurewei Technologies
Intended status: Standards Track J. Tantsura, Ed.
Expires: March 28, 2021 Apstra inc.
September 24, 2020
Integration of Network Service Header (NSH) and Segment Routing for
Service Function Chaining (SFC)
draft-ietf-spring-nsh-sr-03
Abstract
This document describes two application scenarios where Network
Service Header (NSH) and Segment Routing (SR) can be deployed
together to support Service Function Chaining (SFC) in an efficient
manner while maintaining separation of the service and transport
planes as originally intended by the SFC architecture.
In both scenarios, SR is responsible for steering packets between
SFFs along a given Service Function Path (SFP) while NSH is
responsible for maintaining the integrity of the service plane, the
SFC instance context, and any associated metadata.
These application scenarios demonstrate that NSH and SR can work
jointly and complement each other leaving the network operator with
the flexibility to use whichever transport technology makes sense in
specific areas of their network infrastructure, and still maintain an
end-to-end service plane using NSH.
Status of This Memo
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provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on March 28, 2021.
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Copyright Notice
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. SFC Overview and Rationale . . . . . . . . . . . . . . . 2
1.2. Requirements Language . . . . . . . . . . . . . . . . . . 3
2. SFC within Segment Routing Networks . . . . . . . . . . . . . 4
3. NSH-based SFC with SR-based Transport Tunnel . . . . . . . . 5
4. SR-based SFC with Integrated NSH Service Plane . . . . . . . 9
5. Encapsulation Details . . . . . . . . . . . . . . . . . . . . 11
5.1. NSH using SR-MPLS Transport . . . . . . . . . . . . . . . 11
5.2. NSH using SRv6 Transport . . . . . . . . . . . . . . . . 12
6. Security Considerations . . . . . . . . . . . . . . . . . . . 13
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13
7.1. UDP Port Number for NSH . . . . . . . . . . . . . . . . . 13
7.2. Protocol Number for NSH . . . . . . . . . . . . . . . . . 14
8. Contributing Authors . . . . . . . . . . . . . . . . . . . . 14
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 15
9.1. Normative References . . . . . . . . . . . . . . . . . . 15
9.2. Informative References . . . . . . . . . . . . . . . . . 16
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 17
1. Introduction
1.1. SFC Overview and Rationale
The dynamic enforcement of a service-derived, adequate forwarding
policy for packets entering a network that supports advanced Service
Functions (SFs) has become a key challenge for network operators.
Particularly, cascading SFs at the so-called Third Generation
Partnership Project (3GPP) Gi interface in the context of mobile
network infrastructure, have shown their limitations, such as the
same redundant classification features must be supported by many SFs
to execute their function, some SFs are receiving traffic that they
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are not supposed to process (e.g., TCP proxies receiving UDP
traffic), which inevitably affects their dimensioning and
performance, an increased design complexity related to the properly
ordered invocation of several SFs, etc.
In order to solve those problems and to decouple the services
topology from the underlying physical network while allowing for
simplified service delivery, Service Function Chaining (SFC)
techniques have been introduced [RFC7665].
SFC techniques are meant to rationalize the service delivery logic
and master the companion complexity while optimizing service
activation time cycles for operators that need more agile service
delivery procedures to better accommodate ever-demanding customer
requirements. Indeed, SFC allows to dynamically create service
planes that can be used by specific traffic flows. Each service
plane is realized by invoking and chaining the relevant service
functions in the right sequence. [RFC7498] provides an overview of
the overall SFC problem space and [RFC7665] specifies an SFC data
plane architecture. The SFC architecture has the merit to not make
assumptions on how advanced features (e.g., load-balancing, loose or
strict service paths) could be enabled within a domain. Various
deployment options are made available to operators with the SFC
architecture and this approach is fundamental to accommodate various
and heterogeneous deployment contexts.
Many approaches can be considered for encoding the information
required for SFC purposes (e.g., communicate a service chain pointer,
encode a list of loose/explicit paths, or disseminate a service chain
identifier together with a set of context information). Likewise,
many approaches can also be considered for the channel to be used to
carry SFC-specific information (e.g., define a new header, re-use
existing packet header fields, or define an IPv6 extension header).
Among all these approaches, the IETF endorsed a transport-independent
SFC encapsulation scheme: NSH [RFC8300]; which is the most mature SFC
encapsulation solution. This design is pragmatic as it does not
require replicating the same specification effort as a function of
underlying transport encapsulation. Moreover, this design approach
encourages consistent SFC-based service delivery in networks enabling
distinct transport protocols in various network segments or even
between SFFs vs SF-SFF hops.
1.2. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
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RFC2119 [RFC2119] when, and only when, they appear in all capitals,
as shown here.
2. SFC within Segment Routing Networks
As described in [RFC8402], Segment Routing (SR) leverages the source
routing technique. Concretely, a node steers a packet through an SR
policy instantiated as an ordered list of instructions called
segments. While initially designed for policy-based source routing,
SR also finds its application in supporting SFC
[I-D.ietf-spring-sr-service-programming].
The two SR flavors, namely SR-MPLS [RFC8660] and SRv6 [RFC8754], can
both encode an SF as a segment so that an SFC can be specified as a
segment list. Nevertheless, and as discussed in [RFC7498], traffic
steering is only a subset of the issues that motivated the design of
the SFC architecture. Further considerations such as simplifying
classification at intermediate SFs and allowing for coordinated
behaviors among SFs by means of supplying context information
(a.k.a., metadata) should be considered when designing an SFC data
plane solution.
While each scheme (i.e., NSH-based SFC and SR-based SFC) can work
independently, this document describes how the two can be used
together in concert and complement each other through two
representative application scenarios. Both application scenarios may
be supported using either SR-MPLS or SRv6:
o NSH-based SFC with SR-based transport plane: in this scenario SR
provides the transport encapsulation between SFFs while NSH is
used to convey and trigger SFC policies.
o SR-based SFC with integrated NSH service plane: in this scenario
each service hop of the SFC is represented as a segment of the SR
segment-list. SR is thus responsible for steering traffic through
the necessary SFFs as part of the segment routing path while NSH
is responsible for maintaining the service plane and holding the
SFC instance context (including associated metadata).
It is of course possible to combine both of these two scenarios to
support specific deployment requirements and use cases.
A classifier SHOULD assign an NSH Service Path Identifier (SPI) per
SR policy so that different traffic flows that use the same NSH
Service Function Path (SFP) but different SR policy can coexist on
the same SFP without conflict during SFF processing.
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3. NSH-based SFC with SR-based Transport Tunnel
Because of the transport-independent nature of NSH-based service
function chains, it is expected that the NSH has broad applicability
across different network domains (e.g., access, core). By way of
illustration the various SFs involved in a service chain are
available in a single data center, or spread throughout multiple
locations (e.g., data centers, different POPs), depending upon the
operator preference (e.g., hierarchical SFC [RFC8459]) and/or
availability of service resources. Regardless of where the service
resources are deployed it is necessary to provide traffic steering
through a set of SFFs and NSH-based service chains provide the
flexibility for the network operator to choose which particular
transport encapsulation to use between SFFs, which may be different
depending upon which area of the network the SFFs/SFs are currently
deployed. Therefore from an SFC architecture perspective, segment
routing is simply one of multiple available transport encapsulations
that can be used for traffic steering between SFFs. Concretely, NSH
does not require to use a unique transport encapsulation when
traversing a service chain. NSH-based service forwarding relies upon
underlying service node capabilities.
The following three figures provide an example of an SFC established
flow F that has SF instances located in different data centers, DC1
and DC2. For the purpose of illustration, let the SFC's SPI be 100
and the initial Service Index (SI) be 255.
Referring to Figure 1, packets of flow F in DC1 are classified into
an NSH-based SFC and encapsulated after classification as <Inner
Pkt><NSH: SPI 100, SI 255><Outer-transport> and forwarded to SFF1
(which is the first SFF hop for this service chain).
After removing the outer transport encapsulation, that may or may not
be SR-MPLS or SRv6, SFF1 uses the SPI and SI carried within the NSH
encapsulation to determine that it should forward the packet to SF1.
SF1 applies its service, decrements the SI by 1, and returns the
packet to SFF1. SFF1 therefore has <SPI 100, SI 254> when the packet
comes back from SF1. SFF1 does a lookup on <SPI 100, SI 254> which
results in <next-hop: DC1-GW1> and forwards the packet to DC1-GW1.
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+--------------------------- DC1 ----------------------------+
| +-----+ |
| | SF1 | |
| +--+--+ |
| | |
| | |
| +------------+ | +------------+ |
| | N(100,255) | | | F:Inner Pkt| |
| +------------+ | +------------+ |
| | F:Inner Pkt| | | N(100,254) | |
| +------------+ ^ | | +------------+ |
| (2) | | | (3) |
| | | v |
| (1) | (4) |
|+------------+ ----> +--+---+ ----> +---------+ |
|| | NSH | | NSH | | |
|| Classifier +------------+ SFF1 +--------------+ DC1-GW1 + |
|| | | | | | |
|+------------+ +------+ +---------+ |
| |
| +------------+ +------------+ |
| | N(100,255) | | N(100,254) | |
| +------------+ +------------+ |
| | F:Inner Pkt| | F:Inner Pkt| |
| +------------+ +------------+ |
| |
+------------------------------------------------------------+
Figure 1: SR for inter-DC SFC - Part 1
Referring now to Figure 2, DC1-GW1 performs a lookup using the
information conveyed in the NSH which results in <next-hop: DC2-GW1,
encapsulation: SR>. The SR encapsulation has the SR segment-list to
forward the packet across the inter-DC network to DC2.
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+----------- Inter DC ----------------+
| (5) |
+------+ ----> | +---------+ ----> +---------+ |
| | NSH | | | SR | | |
+ SFF1 +----------|-+ DC1-GW1 +-------------+ DC2-GW1 + |
| | | | | | | |
+------+ | +---------+ +---------+ |
| |
| +------------+ |
| | S(DC2-GW1) | |
| +------------+ |
| | N(100,254) | |
| +------------+ |
| | F:Inner Pkt| |
| +------------+ |
+-------------------------------------+
Figure 2: SR for inter-DC SFC - Part 2
When the packet arrives at DC2, as shown in Figure 3, the SR
encapsulation is removed and DC2-GW1 performs a lookup on the NSH
which results in next hop: SFF2. The outer transport encapsulation
may be any transport that is able to identify NSH as the next
protocol.
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+------------------------ DC2 ----------------------+
| +-----+ |
| | SF2 | |
| +--+--+ |
| | |
| | |
| +------------+ | +------------+ |
| | N(100,254) | | | F:Inner Pkt| |
| +------------+ | +------------+ |
| | F:Inner Pkt| | | N(100,253) | |
| +------------+ ^ | | +------------+ |
| (7) | | | (8) |
| | | v |
| (6) | (9) |
|+----------+ ----> +--+---+ ----> |
|| | NSH | | IP |
|| DC2-GW1 +------------+ SFF2 | |
|| | | | |
|+----------+ +------+ |
| |
| +------------+ +------------+ |
| | N(100,254) | | F:Inner Pkt| |
| +------------+ +------------+ |
| | F:Inner Pkt| |
| +------------+ |
+---------------------------------------------------+
Figure 3: SR for inter-DC SFC - Part 3
The benefits of this scheme are listed hereafter:
o The network operator is able to take advantage of the transport-
independent nature of the NSH encapsulation.
o The network operator is able to take advantage of the traffic
steering capability of SR where appropriate.
o Clear responsibility division and scope between NSH and SR.
Note that this scenario is applicable to any case where multiple
segments of a service chain are distributed into multiple domains or
where traffic-engineered paths are necessary between SFFs (strict
forwarding paths for example). Further note that the above example
can also be implemented using end to end segment routing between SFF1
and SFF2. (As such DC-GW1 and DC-GW2 are forwarding the packets
based on segment routing instructions and are not looking at the NSH
header for forwarding).
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4. SR-based SFC with Integrated NSH Service Plane
In this scenario we assume that the SFs are NSH-aware and therefore
it should not be necessary to implement an SFC proxy to achieve SFC.
The operation relies upon SR to perform SFF-SFF transport and NSH to
provide the service plane between SFs thereby maintaining SFC context
(e.g., the service plane path referenced by the SPI) and any
associated metadata.
When a service chain is established, a packet associated with that
chain will first carry an NSH that will be used to maintain the end-
to-end service plane through use of the SFC context. The SFC context
is used by an SFF to determine the SR segment list for forwarding the
packet to the next-hop SFFs. The packet is then encapsulated using
the (transport-specific) SR header and forwarded in the SR domain
following normal SR operations.
When a packet has to be forwarded to an SF attached to an SFF, the
SFF performs a lookup on the prefix SID associated with the SF to
retrieve the next hop context between the SFF and SF (e.g., to
retrieve the destination MAC address in case native Ethernet
encapsulation is used between SFF and SF). How the next hop context
is populated is out of the scope of this document. The SFF strips
the SR information of the packet, updates the SR information, and
saves it to a cache indexed by the NSH SPI. This saved SR
information is used to encapsulate and forward the packet(s) coming
back from the SF.
When the SF receives the packet, it processes it as usual and sends
it back to the SFF. Once the SFF receives this packet, it extracts
the SR information using the NSH SPI as the index into the cache.
The SFF then pushes the SR header on top of the NSH header, and
forwards the packet to the next segment in the segment list.
Figure 4 illustrates an example of this scenario.
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+-----+ +-----+
| SF1 | | SF2 |
+--+--+ +--+--+
| |
| |
+-----------+ | +-----------+ +-----------+ | +-----------+
|N(100,255) | | |F:Inner Pkt| |N(100,254) | | |F:Inner Pkt|
+-----------+ | +-----------+ +-----------+ | +-----------+
|F:Inner Pkt| | |N(100,254) | |F:Inner Pkt| | |N(100,253) |
+-----------+ | +-----------+ +-----------+ | +-----------+
(2) ^ | (3) | (5) ^ | (6) |
| | | | | |
| | v | | v
+------------+ (1)--> +-+----+ (4)--> +---+--+ (7)-->IP
| | NSHoSR | | NSHoSR | |
| Classifier +--------+ SFF1 +---------------------+ SFF2 |
| | | | | |
+------------+ +------+ +------+
+------------+ +------------+
| S(SF1) | | S(SF2) |
+------------+ +------------+
| S(SFF2) | | N(100,254) |
+------------+ +------------+
| S(SF2) | | F:Inner Pkt|
+------------+ +------------+
| N(100,255) |
+------------+
| F:Inner Pkt|
+------------+
Figure 4: NSH over SR for SFC
The benefits of this scheme include:
o It is economically sound for SF vendors to only support one
unified SFC solution. The SF is unaware of the SR.
o It simplifies the SFF (i.e., the SR router) by nullifying the
needs for re-classification and SR proxy.
o It provides a unique and standard way to pass metadata to SFs.
Note that currently there is no solution for SR-MPLS to carry
metadata and there is no solution to pass metadata to SR-unaware
SFs.
o SR is also used for forwarding purposes including between SFFs.
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o It takes advantage of SR to eliminate the NSH forwarding state in
SFFs. This applies each time strict or loose SFPs are in use.
o It requires no interworking as would be the case if SR-MPLS based
SFC and NSH-based SFC were deployed as independent mechanisms in
different parts of the network.
5. Encapsulation Details
5.1. NSH using SR-MPLS Transport
SR-MPLS instantiates Segment IDs (SIDs) as MPLS labels and therefore
the segment routing header is a stack of MPLS labels.
When carrying NSH within an SR-MPLS transport, the full encapsulation
headers are as illustrated in Figure 5.
+------------------+
~ MPLS-SR Labels ~
+------------------+
| NSH Base Hdr |
+------------------+
| Service Path Hdr |
+------------------+
~ Metadata ~
+------------------+
Figure 5: NSH using SR-MPLS Transport
As described in [RFC8402], the IGP signaling extension for IGP-Prefix
segment includes a flag to indicate whether directly connected
neighbors of the node on which the prefix is attached should perform
the NEXT operation or the CONTINUE operation when processing the SID.
When NSH is carried beneath SR-MPLS it is necessary to terminate the
NSH-based SFC at the tail-end node of the SR-MPLS label stack. This
is the equivalent of MPLS Ultimate Hop Popping (UHP) and therefore
the prefix-SID associated with the tail-end of the SFC MUST be
advertised with the CONTINUE operation so that the penultimate hop
node does not pop the top label of the SR-MPLS label stack and
thereby expose NSH to the wrong SFF. It is RECOMMENDED that a
specific prefix-SID be allocated at each node for use by the SFC
application for this purpose.
At the end of the SR-MPLS path it is necessary to provide an
indication to the tail-end that NSH follows the SR-MPLS label stack.
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There are several ways to achieve this but its specification is
outside the scope of this document.
5.2. NSH using SRv6 Transport
When carrying NSH within an SRv6 transport the full encapsulation is
as illustrated in Figure 6.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Next Header | Hdr Ext Len | Routing Type | Segments Left |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Last Entry | Flags | Tag | S
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ e
| | g
| Segment List[0] (128 bits IPv6 address) | m
| | e
| | n
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ t
| |
| | R
~ ... ~ o
| | u
| | t
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ i
| | n
| Segment List[n] (128 bits IPv6 address) | g
| |
| | S
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ R
// // H
// Optional Type Length Value objects (variable) //
// //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Ver|O|U| TTL | Length |U|U|U|U|MD Type| Next Protocol |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ N
| Service Path Identifier | Service Index | S
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ H
| |
~ Variable-Length Context Headers (opt.) ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 6: NSH using SRv6 Transport
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Encapsulation of NSH following SRv6 may be indicated either by
encapsulating NSH in UDP (UDP port TBA1) and indicating UDP in the
Next Header field of the SRH, or by indicating an IP protocol number
for NSH in the Next Header of the SRH. The behavior for
encapsulating NSH over UDP, including the selection of the source
port number in particular, adheres to similar considerations as those
discussed in [RFC8086].
6. Security Considerations
Generic SFC-related security considerations are discussed in
[RFC7665].
NSH-specific security considerations are discussed in [RFC8300].
NSH-in-UDP with DTLS [RFC6347] should follow the considerations
discussed in Section 5 of [RFC8086], with a destination port number
set to TBA2.
Generic segment routing related security considerations are discussed
in section 7 of [RFC8754] and section 5 of [RFC8663].
7. IANA Considerations
7.1. UDP Port Number for NSH
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IANA is requested to assign the UDP port numbers TBA1 and TBA2 to the NSH from the "Service Name and Transport Protocol Port Number Registry" available at
https://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.xhtml:
Service Name: NSH-in-UDP
Transport Protocol(s): UDP
Assignee: IESG iesg@ietf.org
Contact: IETF Chair chair@ietf.org
Description: NSH-in-UDP Encapsulation
Reference: [ThisDocument]
Port Number: TBA1
Service Code: N/A
Known Unauthorized Uses: N/A
Assignment Notes: N/A
Service Name: NSH-UDP-DTLS
Transport Protocol(s): UDP
Assignee: IESG iesg@ietf.org
Contact: IETF Chair chair@ietf.org
Description: NSH-in-UDP with DTLS Encapsulation
Reference: [ThisDocument]
Port Number: TBA2
Service Code: N/A
Known Unauthorized Uses: N/A
Assignment Notes: N/A
7.2. Protocol Number for NSH
IANA is requested to assign a protocol number TBA3 for the NSH from the "Assigned Internet Protocol Numbers" registry available at
https://www.iana.org/assignments/protocol-numbers/protocol-numbers.xhtml.
+---------+---------+--------------+---------------+----------------+
| Decimal | Keyword | Protocol | IPv6 | Reference |
| | | | Extension | |
| | | | Header | |
+---------+---------+--------------+---------------+----------------+
| TBA3 | NSH | Network | N | [ThisDocument] |
| | | Service | | |
| | | Header | | |
+---------+---------+--------------+---------------+----------------+
8. Contributing Authors
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The following coauthors, along with their respective affiliations at
the time of WG adoption, provided valuable inputs and text contributions
to this document.
Mohamed Boucadair
Orange
mohamed.boucadair@orange.com
Joel Halpern
Ericsson
joel.halpern@ericsson.com
Syed Hassan
Cisco System, inc.
shassan@cisco.com
Wim Henderickx
Nokia
wim.henderickx@nokia.com
Haoyu Song
Futurewei Technologies
haoyu.song@futurewei.com
9. References
9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC6347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer
Security Version 1.2", RFC 6347, DOI 10.17487/RFC6347,
January 2012, <https://www.rfc-editor.org/info/rfc6347>.
[RFC7665] Halpern, J., Ed. and C. Pignataro, Ed., "Service Function
Chaining (SFC) Architecture", RFC 7665,
DOI 10.17487/RFC7665, October 2015,
<https://www.rfc-editor.org/info/rfc7665>.
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[RFC8086] Yong, L., Ed., Crabbe, E., Xu, X., and T. Herbert, "GRE-
in-UDP Encapsulation", RFC 8086, DOI 10.17487/RFC8086,
March 2017, <https://www.rfc-editor.org/info/rfc8086>.
[RFC8300] Quinn, P., Ed., Elzur, U., Ed., and C. Pignataro, Ed.,
"Network Service Header (NSH)", RFC 8300,
DOI 10.17487/RFC8300, January 2018,
<https://www.rfc-editor.org/info/rfc8300>.
[RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L.,
Decraene, B., Litkowski, S., and R. Shakir, "Segment
Routing Architecture", RFC 8402, DOI 10.17487/RFC8402,
July 2018, <https://www.rfc-editor.org/info/rfc8402>.
[RFC8660] Bashandy, A., Ed., Filsfils, C., Ed., Previdi, S.,
Decraene, B., Litkowski, S., and R. Shakir, "Segment
Routing with the MPLS Data Plane", RFC 8660,
DOI 10.17487/RFC8660, December 2019,
<https://www.rfc-editor.org/info/rfc8660>.
[RFC8663] Xu, X., Bryant, S., Farrel, A., Hassan, S., Henderickx,
W., and Z. Li, "MPLS Segment Routing over IP", RFC 8663,
DOI 10.17487/RFC8663, December 2019,
<https://www.rfc-editor.org/info/rfc8663>.
[RFC8754] Filsfils, C., Ed., Dukes, D., Ed., Previdi, S., Leddy, J.,
Matsushima, S., and D. Voyer, "IPv6 Segment Routing Header
(SRH)", RFC 8754, DOI 10.17487/RFC8754, March 2020,
<https://www.rfc-editor.org/info/rfc8754>.
9.2. Informative References
[I-D.ietf-spring-sr-service-programming]
Clad, F., Xu, X., Filsfils, C., daniel.bernier@bell.ca,
d., Li, C., Decraene, B., Ma, S., Yadlapalli, C.,
Henderickx, W., and S. Salsano, "Service Programming with
Segment Routing", draft-ietf-spring-sr-service-
programming-03 (work in progress), September 2020.
[RFC7498] Quinn, P., Ed. and T. Nadeau, Ed., "Problem Statement for
Service Function Chaining", RFC 7498,
DOI 10.17487/RFC7498, April 2015,
<https://www.rfc-editor.org/info/rfc7498>.
[RFC8459] Dolson, D., Homma, S., Lopez, D., and M. Boucadair,
"Hierarchical Service Function Chaining (hSFC)", RFC 8459,
DOI 10.17487/RFC8459, September 2018,
<https://www.rfc-editor.org/info/rfc8459>.
Guichard & Tantsura Expires March 28, 2021 [Page 16]
Internet-Draft NSH-SR SFC September 2020
Authors' Addresses
James N Guichard (editor)
Futurewei Technologies
2330 Central Express Way
Santa Clara
USA
Email: james.n.guichard@futurewei.com
Jeff Tantsura (editor)
Apstra inc.
USA
Email: jefftant.ietf@gmail.com
Guichard & Tantsura Expires March 28, 2021 [Page 17]
