draft-ietf-mpls-sr-over-ip-07.txt   rfc8663.txt 
Network Working Group X. Xu Internet Engineering Task Force (IETF) X. Xu
Internet-Draft Alibaba, Inc Request for Comments: 8663 Alibaba, Inc
Intended status: Standards Track S. Bryant Category: Standards Track S. Bryant
Expires: December 18, 2019 Huawei ISSN: 2070-1721 Futurewei Technologies
A. Farrel A. Farrel
Old Dog Consulting Old Dog Consulting
S. Hassan S. Hassan
Cisco Cisco
W. Henderickx W. Henderickx
Nokia Nokia
Z. Li Z. Li
Huawei Huawei
June 16, 2019 December 2019
SR-MPLS over IP MPLS Segment Routing over IP
draft-ietf-mpls-sr-over-ip-07
Abstract Abstract
MPLS Segment Routing (SR-MPLS) is an MPLS data plane-based source MPLS Segment Routing (SR-MPLS) is a method of source routing a packet
routing paradigm in which the sender of a packet is allowed to through an MPLS data plane by imposing a stack of MPLS labels on the
partially or completely specify the route the packet takes through packet to specify the path together with any packet-specific
the network by imposing stacked MPLS labels on the packet. SR-MPLS instructions to be executed on it. SR-MPLS can be leveraged to
can be leveraged to realize a source routing mechanism across MPLS, realize a source-routing mechanism across MPLS, IPv4, and IPv6 data
IPv4, and IPv6 data planes by using an MPLS label stack as a source planes by using an MPLS label stack as a source-routing instruction
routing instruction set while making no changes to SR-MPLS set while making no changes to SR-MPLS specifications and
specifications and interworking with SR-MPLS implementations. interworking with SR-MPLS implementations.
This document describes how SR-MPLS capable routers and IP-only This document describes how SR-MPLS-capable routers and IP-only
routers can seamlessly co-exist and interoperate through the use of routers can seamlessly coexist and interoperate through the use of
SR-MPLS label stacks and IP encapsulation/tunneling such as MPLS-in- SR-MPLS label stacks and IP encapsulation/tunneling such as MPLS-
UDP as defined in RFC 7510. over-UDP as defined in RFC 7510.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This is an Internet Standards Track document.
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering This document is a product of the Internet Engineering Task Force
Task Force (IETF). Note that other groups may also distribute (IETF). It represents the consensus of the IETF community. It has
working documents as Internet-Drafts. The list of current Internet- received public review and has been approved for publication by the
Drafts is at https://datatracker.ietf.org/drafts/current/. Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 7841.
Internet-Drafts are draft documents valid for a maximum of six months Information about the current status of this document, any errata,
and may be updated, replaced, or obsoleted by other documents at any and how to provide feedback on it may be obtained at
time. It is inappropriate to use Internet-Drafts as reference https://www.rfc-editor.org/info/rfc8663.
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This Internet-Draft will expire on December 18, 2019.
Copyright Notice Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the Copyright (c) 2019 IETF Trust and the persons identified as the
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Terminology
2. Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Use Cases
3. Procedures of SR-MPLS over IP . . . . . . . . . . . . . . . . 5 3. Procedures of SR-MPLS-over-IP
3.1. Forwarding Entry Construction . . . . . . . . . . . . . . 5 3.1. Forwarding Entry Construction
3.1.1. FIB Construction Example . . . . . . . . . . . . . . 6 3.1.1. FIB Construction Example
3.2. Packet Forwarding Procedures . . . . . . . . . . . . . . 8 3.2. Packet-Forwarding Procedures
3.2.1. Packet Forwarding with Penultimate Hop Popping . . . 9 3.2.1. Packet Forwarding with Penultimate Hop Popping
3.2.2. Packet Forwarding without Penultimate Hop Popping . . 10 3.2.2. Packet Forwarding without Penultimate Hop Popping
3.2.3. Additional Forwarding Procedures . . . . . . . . . . 11 3.2.3. Additional Forwarding Procedures
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13 4. IANA Considerations
5. Security Considerations . . . . . . . . . . . . . . . . . . . 13 5. Security Considerations
6. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 13 6. References
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 15 6.1. Normative References
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 15 6.2. Informative References
8.1. Normative References . . . . . . . . . . . . . . . . . . 15 Acknowledgements
8.2. Informative References . . . . . . . . . . . . . . . . . 16 Contributors
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 18 Authors' Addresses
1. Introduction 1. Introduction
MPLS Segment Routing (SR-MPLS) [I-D.ietf-spring-segment-routing-mpls] MPLS Segment Routing (SR-MPLS) [RFC8660] is a method of source
is an MPLS data plane-based source routing paradigm in which the routing a packet through an MPLS data plane. This is achieved by the
sender of a packet is allowed to partially or completely specify the sender imposing a stack of MPLS labels that partially or completely
route the packet takes through the network by imposing stacked MPLS specify the path that the packet is to take and any instructions to
labels on the packet. SR-MPLS uses an MPLS label stack to encode a be executed on the packet as it passes through the network. SR-MPLS
source routing instruction set. This can be used to realize a source uses an MPLS label stack to encode a sequence of source-routing
routing mechanism that can operate across MPLS, IPv4, and IPv6 data instructions. This can be used to realize a source-routing mechanism
planes. This approach makes no changes to SR-MPLS specifications and that can operate across MPLS, IPv4, and IPv6 data planes. This
allows interworking with SR-MPLS implementations. More specifically, approach makes no changes to SR-MPLS specifications and allows
the source routing instruction set information contained in a source interworking with SR-MPLS implementations. More specifically, the
routed packet could be uniformly encoded as an MPLS label stack no source-routing instructions in a source-routed packet could be
matter whether the underlay is IPv4, IPv6 (including Segment Routing uniformly encoded as an MPLS label stack regardless of whether the
for IPv6 (SRv6) [RFC8354]), or MPLS. underlay is IPv4, IPv6 (including Segment Routing for IPv6 (SRv6)
[RFC8354]), or MPLS.
This document describes how SR-MPLS capable routers and IP-only This document describes how SR-MPLS-capable routers and IP-only
routers can seamlessly co-exist and interoperate through the use of routers can seamlessly coexist and interoperate through the use of
SR-MPLS label stacks and IP encapsulation/tunneling such as MPLS-in- SR-MPLS label stacks and IP encapsulation/tunneling such as MPLS-
UDP [RFC7510]. over-UDP [RFC7510].
Section 2 describes various use cases for the tunneling SR-MPLS over Section 2 describes various use cases for tunneling SR-MPLS over IP.
IP. Section 3 describes a typical application scenario and how the Section 3 describes a typical application scenario and how the packet
packet forwarding happens. forwarding happens.
1.1. Terminology 1.1. Terminology
This memo makes use of the terms defined in [RFC3031] and This memo makes use of the terms defined in [RFC3031] and [RFC8660].
[I-D.ietf-spring-segment-routing-mpls].
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP "OPTIONAL" in this document are to be interpreted as described in
14 [RFC2119] [RFC8174] when, and only when, they appear in all BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
2. Use Cases 2. Use Cases
Tunneling SR-MPLS using IPv4 and/or IPv6 (including SRv6) tunnels is Tunneling SR-MPLS using IPv4 and/or IPv6 (including SRv6) tunnels is
useful at least in the use cases listed below. In all cases, this useful at least in the use cases listed below. In all cases, this
can be enabled using an IP tunneling mechanism such as MPLS-in-UDP as can be enabled using an IP tunneling mechanism such as MPLS-over-UDP
described in [RFC7510]. The tunnel selected MUST have its remote end as described in [RFC7510]. The tunnel selected MUST have its remote
point (destination) address equal to the address of the next SR-MPLS endpoint (destination) address equal to the address of the next node
capable node identified as being on the SR path (i.e., the egress of capable of SR-MPLS identified as being on the SR path (i.e., the
the active segment). The local end point (source) address is set to egress of the active segment). The local endpoint (source) address
an address of the encapsulating node. [RFC7510] gives further advice is set to an address of the encapsulating node. [RFC7510] gives
on how to set the source address if the UDP zero-checksum mode is further advice on how to set the source address if the UDP zero-
used with MPLS-in-UDP. Using UDP as the encapsulation may be checksum mode is used with MPLS-over-UDP. Using UDP as the
particularly beneficial because it is agnostic of the underlying encapsulation may be particularly beneficial because it is agnostic
transport. of the underlying transport.
o Incremental deployment of the SR-MPLS technology may be * Incremental deployment of the SR-MPLS technology may be
facilitated by tunneling SR-MPLS packets across parts of a network facilitated by tunneling SR-MPLS packets across parts of a network
that are not SR-MPLS as shown in Figure 1. This demonstrates how that are not SR-MPLS as shown in Figure 1. This demonstrates how
islands of SR-MPLS may be connected across a legacy network. It islands of SR-MPLS may be connected across a legacy network. It
may be particularly useful for joining sites (such as data may be particularly useful for joining sites (such as data
centers). centers).
________________________ ________________________
_______ ( ) _______ _______ ( ) _______
( ) ( IP Network ) ( ) ( ) ( IP Network ) ( )
( SR-MPLS ) ( ) ( SR-MPLS ) ( SR-MPLS ) ( ) ( SR-MPLS )
( Network ) ( ) ( Network ) ( Network ) ( ) ( Network )
( -------- -------- ) ( -------- -------- )
( | Border | SR-in-UDP Tunnel | Border | ) ( | Border | SR-in-UDP Tunnel | Border | )
( | Router |========================| Router | ) ( | Router |========================| Router | )
( | R1 | | R2 | ) ( | R1 | | R2 | )
( -------- -------- ) ( -------- -------- )
( ) ( ) ( ) ( ) ( ) ( )
( ) ( ) ( ) ( ) ( ) ( )
(_______) ( ) (_______) (_______) ( ) (_______)
(________________________) (________________________)
Figure 1: SR-MPLS in UDP to Tunnel Between SR-MPLS Sites Figure 1: SR-MPLS-over-UDP to Tunnel between SR-MPLS Sites
o If encoding of entropy ([RFC6790] is desired, IP tunneling * If the encoding of entropy [RFC6790] is desired, IP-tunneling
mechanisms that allow encoding of entropy, such as MPLS-in-UDP mechanisms that allow the encoding of entropy, such as MPLS-over-
encapsulation [RFC7510] where the source port of the UDP header is UDP encapsulation [RFC7510] where the source port of the UDP
used as an entropy field, may be used to maximize the utilization header is used as an entropy field, may be used to maximize the
of ECMP and/or LAG, especially when it is difficult to make use of utilization of Equal-Cost Multipath (ECMP) and/or Link Aggregation
the entropy label mechanism. This is to be contrasted with Groups (LAGs), especially when it is difficult to make use of the
[RFC4023] where MPLS-in-IP does not provide for an entropy entropy-label mechanism. This is to be contrasted with [RFC4023]
mechanism. Refer to [I-D.ietf-mpls-spring-entropy-label]) for where MPLS-over-IP does not provide for an entropy mechanism.
more discussion about using entropy labels in SR-MPLS. Refer to [RFC8662]) for more discussion about using entropy labels
in SR-MPLS.
o Tunneling MPLS over IP provides a technology that enables SR in an * Tunneling MPLS over IP provides a technology that enables Segment
IPv4 and/or IPv6 network where the routers do not support SRv6 Routing (SR) in an IPv4 and/or IPv6 network where the routers do
capabilities [I-D.ietf-6man-segment-routing-header] and where MPLS not support SRv6 capabilities [IPv6-SRH] and where MPLS forwarding
forwarding is not an option. This is shown in Figure 2. is not an option. This is shown in Figure 2.
__________________________________ __________________________________
__( IP Network )__ __( IP Network )__
__( )__ __( )__
( -- -- -- ) ( -- -- -- )
-------- -- -- |SR| -- |SR| -- |SR| -- -------- -------- -- -- |SR| -- |SR| -- |SR| -- --------
| Ingress| |IR| |IR| | | |IR| | | |IR| | | |IR| | Egress | | Ingress| |IR| |IR| | | |IR| | | |IR| | | |IR| | Egress|
--->| Router |===========| |======| |======| |======| Router |---> -->| Router |===========| |======| |======| |======| Router|-->
| SR | | | | | | | | | | | | | | | | | | SR | | SR | | | | | | | | | | | | | | | | | | SR |
-------- -- -- | | -- | | -- | | -- -------- -------- -- -- | | -- | | -- | | -- --------
(__ -- -- -- __) (__ -- -- -- __)
(__ __) (__ __)
(__________________________________) (__________________________________)
Key: Key:
IR : IP-only Router IR : IP-only Router
SR : SR-MPLS-capable Router SR : SR-MPLS-capable Router
== : SR-MPLS in UDP Tunnel == : SR-MPLS-over-UDP Tunnel
Figure 2: SR-MPLS Enabled Within an IP Network Figure 2: SR-MPLS Enabled within an IP Network
3. Procedures of SR-MPLS over IP 3. Procedures of SR-MPLS-over-IP
This section describes the construction of forwarding information This section describes the construction of forwarding information
base (FIB) entries and the forwarding behavior that allow the base (FIB) entries and the forwarding behavior that allow the
deployment of SR-MPLS when some routers in the network are IP only deployment of SR-MPLS when some routers in the network are IP only
(i.e., do not support SR-MPLS). Note that the examples in (i.e., do not support SR-MPLS). Note that the examples in Sections
Section 3.1.1 and Section 3.2 assume that OSPF or ISIS is enabled: in 3.1.1 and 3.2 assume that OSPF or IS-IS is enabled; in fact, other
fact, other mechanisms of discovery and advertisement could be used mechanisms of discovery and advertisement could be used including
including other routing protocols (such as BGP) or a central other routing protocols (such as BGP) or a central controller.
controller.
3.1. Forwarding Entry Construction 3.1. Forwarding Entry Construction
This sub-section describes the how to construct the forwarding This subsection describes how to construct the forwarding information
information base (FIB) entry on an SR-MPLS-capable router when some base (FIB) entry on an SR-MPLS-capable router when some or all of the
or all of the next-hops along the shortest path towards a prefix next hops along the shortest path towards a prefix Segment Identifier
Segment Identifier (prefix-SID) are IP-only routers. Section 3.1.1 (Prefix-SID) are IP-only routers. Section 3.1.1 provides a concrete
provides a concrete example of how the process applies when using example of how the process applies when using OSPF or IS-IS.
OSPF or ISIS.
Consider router A that receives a labeled packet with top label L(E) Consider router A that receives a labeled packet with top label L(E)
that corresponds to the prefix-SID SID(E) of prefix P(E) advertised that corresponds to the Prefix-SID SID(E) of prefix P(E) advertised
by router E. Suppose the i-th next-hop router (termed NHi) along the by router E. Suppose the i-th next-hop router (termed NHi) along the
shortest path from router A toward SID(E) is not SR-MPLS capable shortest path from router A toward SID(E) is not SR-MPLS capable
while both routers A and E are SR-MPLS capable. The following while both routers A and E are SR-MPLS capable. The following
processing steps apply: processing steps apply:
o Router E is SR-MPLS capable, so it advertises a Segment Routing * Router E is SR-MPLS capable, so it advertises a Segment Routing
Global Block (SRGB). The SRGB is defined in [RFC8402]. There are Global Block (SRGB). The SRGB is defined in [RFC8402]. There are
a number of ways that the advertisement can be achieved including a number of ways that the advertisement can be achieved including
IGPs, BGP, configuration/management protocols. For example, see IGPs, BGP, and configuration/management protocols. For example,
[I-D.ietf-bess-datacenter-gateway]. see [DC-GATEWAY].
o When Router E advertises the prefix-SID SID(E) of prefix P(E) it * When Router E advertises the Prefix-SID SID(E) of prefix P(E), it
MUST also advertise the encapsulation endpoint and the tunnel type MUST also advertise the egress endpoint address and the
of any tunnel used to reach E. This information is flooded domain encapsulation type of any tunnel used to reach E. This
wide. information is flooded domain wide.
o If A and E are in different routing domains then the information * If A and E are in different routing domains, then the information
MUST be flooded into both domains. How this is achieved depends MUST be flooded into both domains. How this is achieved depends
on the advertisement mechanism being used. The objective is that on the advertisement mechanism being used. The objective is that
router A knows the characteristics of router E that originated the router A knows the characteristics of router E that originated the
advertisement of SID(E). advertisement of SID(E).
o Router A programs the FIB entry for prefix P(E) corresponding to * Router A programs the FIB entry for prefix P(E) corresponding to
the SID(E) according to whether a pop or swap action is advertised the SID(E) according to whether a pop or swap action is advertised
for the prefix. The resulting action may be: for the prefix. The resulting action may be:
* pop the top label - pop the top label
* swap the top label to a value equal to SID(E) plus the lower - swap the top label to a value equal to SID(E) plus the lower
bound of the SRGB of E bound of the SRGB of E
Once constructed, the FIB can be used by a router to tell it how to Once constructed, the FIB can be used by a router to tell it how to
process packets. It encapsulates the packets according to the process packets. It encapsulates the packets according to the
appropriate encapsulation advertised for the segment and then it appropriate encapsulation advertised for the segment and then sends
sends the packets towards the next hop NHi. the packets towards the next hop NHi.
3.1.1. FIB Construction Example 3.1.1. FIB Construction Example
This section is non-normative and provides a worked example of how a This section is non-normative and provides a worked example of how a
FIB might be constructed using OSPF and ISIS extensions. It is based FIB might be constructed using OSPF and IS-IS extensions. It is
on the process described in Section 3.1. based on the process described in Section 3.1.
o Router E is SR-MPLS capable, so it advertises a Segment Routing * Router E is SR-MPLS capable, so it advertises a Segment Routing
Global Block (SRGB) using Global Block (SRGB) using [RFC8665] or [RFC8667].
[I-D.ietf-ospf-segment-routing-extensions] or
[I-D.ietf-isis-segment-routing-extensions].
o When Router E advertises the prefix-SID SID(E) of prefix P(E) it * When Router E advertises the Prefix-SID SID(E) of prefix P(E), it
also advertises the encapsulation endpoint and the tunnel type of also advertises the encapsulation endpoint address and the tunnel
any tunnel used to reach E using [I-D.ietf-isis-encapsulation-cap] type of any tunnel used to reach E using [ISIS-ENCAP] or
or [I-D.ietf-ospf-encapsulation-cap]. [OSPF-ENCAP].
o If A and E are in different domains then the information is * If A and E are in different domains, then the information is
flooded into both domains and any intervening domains. flooded into both domains and any intervening domains.
* The OSPF Tunnel Encapsulation TLV - The OSPF Tunnel Encapsulations TLV [OSPF-ENCAP] or the IS-IS
[I-D.ietf-ospf-encapsulation-cap] or the ISIS Tunnel Tunnel Encapsulation Type sub-TLV [ISIS-ENCAP] is flooded
Encapsulation sub-TLV [I-D.ietf-isis-encapsulation-cap] is domain wide.
flooded domain-wide.
* The OSPF SID/label range TLV - The OSPF SID/Label Range TLV [RFC8665] or the IS-IS SR-
[I-D.ietf-ospf-segment-routing-extensions] or the ISIS SR- Capabilities sub-TLV [RFC8667] is advertised domain wide so
Capabilities Sub-TLV [I-D.ietf-isis-segment-routing-extensions] that router A knows the characteristics of router E.
is advertised domain-wide so that router A knows the
characteristics of router E.
* When router E advertises the prefix P(E): - When router E advertises the prefix P(E):
+ If router E is running ISIS it uses the extended o If router E is running IS-IS, it uses the extended
reachability TLV (TLVs 135, 235, 236, 237) and associates reachability TLV (TLVs 135, 235, 236, 237) and associates
the IPv4/IPv6 or IPv4/IPv6 source router ID sub-TLV(s) the IPv4/IPv6 or IPv4/IPv6 Source Router ID sub-TLV(s)
[RFC7794]. [RFC7794].
+ If router E is running OSPF it uses the OSPFv2 Extended o If router E is running OSPF, it uses the OSPFv2 Extended
Prefix Opaque LSA [RFC7684] and sets the flooding scope to Prefix Opaque Link-State Advertisement (LSA) [RFC7684] and
AS-wide. sets the flooding scope to Autonomous System (AS) wide.
* If router E is running ISIS and advertises the ISIS capability - If router E is running IS-IS and advertises the IS-IS Router
TLV (TLV 242) [RFC7981], it sets the "router-ID" field to a CAPABILITY TLV (TLV 242) [RFC7981], it sets the "Router ID"
valid value or includes an IPV6 TE router-ID sub-TLV (TLV 12), field to a valid value or includes an IPv6 TE Router ID sub-TLV
or does both. The "S" bit (flooding scope) of the ISIS (TLV 12), or it does both. The "S" bit (flooding scope) of the
capability TLV (TLV 242) is set to "1" . IS-IS Router CAPABILITY TLV (TLV 242) is set to "1".
o Router A programs the FIB entry for prefix P(E) corresponding to * Router A programs the FIB entry for prefix P(E) corresponding to
the SID(E) according to whether a pop or swap action is advertised the SID(E) according to whether a pop or swap action is advertised
for the prefix as follows: for the prefix as follows:
* If the NP flag in OSPF or the P flag in ISIS is clear: - If the No-PHP (NP) Flag in OSPF or the Persistent (P) Flag in
IS-IS is clear:
pop the top label pop the top label
* If the NP flag in OSPF or the P flag in ISIS is set: - If the No-PHP (NP) Flag in OSPF or the Persistent (P) Flag in
IS-IS is set:
swap the top label to a value equal to SID(E) plus the lower swap the top label to a value equal to SID(E) plus the lower
bound of the SRGB of E bound of the SRGB of E
When forwarding the packet according to the constructed FIB entry the When forwarding the packet according to the constructed FIB entry,
router encapsulates the packet according to the encapsulation as the router encapsulates the packet according to the encapsulation as
advertised using the mechanisms described in advertised using the mechanisms described in [ISIS-ENCAP] or
[I-D.ietf-isis-encapsulation-cap] or [OSPF-ENCAP]. It then sends the packets towards the next hop NHi.
[I-D.ietf-ospf-encapsulation-cap]). It then sends the packets
towards the next hop NHi.
Note that [RFC7510] specifies the use of port number 6635 to indicate Note that [RFC7510] specifies the use of port number 6635 to indicate
that the payload of a UDP packet is MPLS, and port number 6636 for that the payload of a UDP packet is MPLS, and port number 6636 for
MPLS-in-UDP utilizing DTLS. However, MPLS-over-UDP utilizing DTLS. However, [ISIS-ENCAP] and [OSPF-ENCAP]
[I-D.ietf-isis-encapsulation-cap] and provide dynamic protocol mechanisms to configure the use of any
[I-D.ietf-ospf-encapsulation-cap] provide dynamic protocol mechanisms Dynamic Port for a tunnel that uses UDP encapsulation. Nothing in
to configure the use any Dynamic Port for a tunnel that uses UDP this document prevents the use of an IGP or any other mechanism to
encapsulation. Nothing in this document prevents the use of an IGP negotiate the use of a Dynamic Port when UDP encapsulation is used
or any other mechanism to negotiate the use of a Dynamic Port when for SR-MPLS, but if no such mechanism is used, then the port numbers
UDP encapsulation is used for SR-MPLS, but if no such mechanism is specified in [RFC7510] are used.
used then the port numbers specified in [RFC7510] are used.
3.2. Packet Forwarding Procedures 3.2. Packet-Forwarding Procedures
[RFC7510] specifies an IP-based encapsulation for MPLS, i.e., MPLS- [RFC7510] specifies an IP-based encapsulation for MPLS, i.e., MPLS-
in-UDP. This approach is applicable where IP-based encapsulation for over-UDP. This approach is applicable where IP-based encapsulation
MPLS is required and further fine-grained load balancing of MPLS for MPLS is required and further fine-grained load balancing of MPLS
packets over IP networks over Equal-Cost Multipath (ECMP) and/or Link packets over IP networks over ECMP and/or LAGs is also required.
Aggregation Groups (LAGs) is also required. This section provides This section provides details about the forwarding procedure when UDP
details about the forwarding procedure when UDP encapsulation is encapsulation is adopted for SR-MPLS-over-IP. Other encapsulation
adopted for SR-MPLS over IP. Other encapsulation and tunnelling and tunneling mechanisms can be applied using similar techniques, but
mechanisms can be applied using similar techniques, but for clarity for clarity, this section uses UDP encapsulation as the exemplar.
this section uses UDP encapsulation as the exemplar.
Nodes that are SR-MPLS capable can process SR-MPLS packets. Not all Nodes that are SR-MPLS capable can process SR-MPLS packets. Not all
of the nodes in an SR-MPLS domain are SR-MPLS capable. Some nodes of the nodes in an SR-MPLS domain are SR-MPLS capable. Some nodes
may be "legacy routers" that cannot handle SR-MPLS packets but can may be "legacy routers" that cannot handle SR-MPLS packets but can
forward IP packets. An SR-MPLS-capable node MAY advertise its forward IP packets. A node capable of SR-MPLS MAY advertise its
capabilities using the IGP as described in Section 3. There are six capabilities using the IGP as described in Section 3. There are six
types of node in an SR-MPLS domain: types of nodes in an SR-MPLS domain:
o Domain ingress nodes that receive packets and encapsulate them for * Domain ingress nodes that receive packets and encapsulate them for
transmission across the domain. Those packets may be any payload transmission across the domain. Those packets may be any payload
protocol including native IP packets or packets that are already protocol including native IP packets or packets that are already
MPLS encapsulated. MPLS encapsulated.
o Legacy transit nodes that are IP routers but that are not SR-MPLS * Legacy transit nodes that are IP routers but that are not SR-MPLS
capable (i.e., are not able to perform segment routing). capable (i.e., are not able to perform Segment Routing).
o Transit nodes that are SR-MPLS capable but that are not identified * Transit nodes that are SR-MPLS capable but that are not identified
by a SID in the SID stack. by a SID in the SID stack.
o Transit nodes that are SR-MPLS capable and need to perform SR-MPLS * Transit nodes that are SR-MPLS capable and need to perform SR-MPLS
routing because they are identified by a SID in the SID stack. routing because they are identified by a SID in the SID stack.
o The penultimate SR-MPLS capable node on the path that processes * The penultimate node capable of SR-MPLS on the path that processes
the last SID on the stack on behalf of the domain egress node. the last SID on the stack on behalf of the domain egress node.
o The domain egress node that forwards the payload packet for * The domain egress node that forwards the payload packet for
ultimate delivery. ultimate delivery.
3.2.1. Packet Forwarding with Penultimate Hop Popping 3.2.1. Packet Forwarding with Penultimate Hop Popping
The description in this section assumes that the label associated The description in this section assumes that the label associated
with each prefix-SID is advertised by the owner of the prefix-SID as with each Prefix-SID is advertised by the owner of the Prefix-SID as
a Penultimate Hop Popping (PHP) label. That is, if one of the IGP a Penultimate Hop-Popping (PHP) label. That is, if one of the IGP
flooding mechanisms is used, the NP flag in OSPF or the P flag in flooding mechanisms is used, the NP-Flag in OSPF or the P-Flag in IS-
ISIS associated with the prefix-SID is not set. IS associated with the Prefix-SID is not set.
+-----+ +-----+ +-----+ +-----+ +-----+ +-----+ +-----+ +-----+ +-----+ +-----+
| A +-------+ B +-------+ C +-------+ D +-------+ H | | A +-------+ B +-------+ C +-------+ D +-------+ H |
+-----+ +--+--+ +--+--+ +--+--+ +-----+ +-----+ +--+--+ +--+--+ +--+--+ +-----+
| | | | | |
| | | | | |
+--+--+ +--+--+ +--+--+ +--+--+ +--+--+ +--+--+
| E +-------+ F +-------+ G | | E +-------+ F +-------+ G |
+-----+ +-----+ +-----+ +-----+ +-----+ +-----+
skipping to change at page 9, line 40 skipping to change at line 390
+--------+ +--------+ +--------+ +--------+ +--------+ +--------+
| UDP | |IP(E->G)| |IP(G->H)| | UDP | |IP(E->G)| |IP(G->H)|
+--------+ +--------+ +--------+ +--------+ +--------+ +--------+
| L(G) | | UDP | | UDP | | L(G) | | UDP | | UDP |
+--------+ +--------+ +--------+ +--------+ +--------+ +--------+
| L(H) | | L(H) | |Exp Null| | L(H) | | L(H) | |Exp Null|
+--------+ +--------+ +--------+ +--------+ +--------+ +--------+
| Packet | ---> | Packet | ---> | Packet | | Packet | ---> | Packet | ---> | Packet |
+--------+ +--------+ +--------+ +--------+ +--------+ +--------+
Figure 3: Packet Forwarding Example with PHP Figure 3: Packet-Forwarding Example with PHP
In the example shown in Figure 3, assume that routers A, E, G and H In the example shown in Figure 3, assume that routers A, E, G, and H
are SR-MPLS-capable while the remaining routers (B, C, D and F) are are capable of SR-MPLS while the remaining routers (B, C, D, and F)
only capable of forwarding IP packets. Routers A, E, G, and H are only capable of forwarding IP packets. Routers A, E, G, and H
advertise their Segment Routing related information, such as via IS- advertise their Segment Routing related information, such as via IS-
IS or OSPF. IS or OSPF.
Now assume that router A (the Domain ingress) wants to send a packet Now assume that router A (the Domain ingress) wants to send a packet
to router H (the Domain egress) via the explicit path {E->G->H}. to router H (the Domain egress) via the explicit path {E->G->H}.
Router A will impose an MPLS label stack on the packet that Router A will impose an MPLS label stack on the packet that
corresponds to that explicit path. Since the next hop toward router corresponds to that explicit path. Since the next hop toward router
E is only IP-capable (B is a legacy transit node), router A replaces E is only IP capable (B is a legacy transit node), router A replaces
the top label (that indicated router E) with a UDP-based tunnel for the top label (that indicated router E) with a UDP-based tunnel for
MPLS (i.e., MPLS-over-UDP [RFC7510]) to router E and then sends the MPLS (i.e., MPLS-over-UDP [RFC7510]) to router E and then sends the
packet. In other words, router A pops the top label and then packet. In other words, router A pops the top label and then
encapsulates the MPLS packet in a UDP tunnel to router E. encapsulates the MPLS packet in a UDP tunnel to router E.
When the IP-encapsulated MPLS packet arrives at router E (which is an When the IP-encapsulated MPLS packet arrives at router E (which is a
SR-MPLS-capable transit node), router E strips the IP-based tunnel transit node capable of SR-MPLS), router E strips the IP-based tunnel
header and then processes the decapsulated MPLS packet. The top header and then processes the decapsulated MPLS packet. The top
label indicates that the packet must be forwarded toward router G. label indicates that the packet must be forwarded toward router G.
Since the next hop toward router G is only IP-capable, router E Since the next hop toward router G is only IP capable, router E
replaces the current top label with an MPLS-over-UDP tunnel toward replaces the current top label with an MPLS-over-UDP tunnel toward
router G and sends it out. That is, router E pops the top label and router G and sends it out. That is, router E pops the top label and
then encapsulates the MPLS packet in a UDP tunnel to router G. then encapsulates the MPLS packet in a UDP tunnel to router G.
When the packet arrives at router G, router G will strip the IP-based When the packet arrives at router G, router G will strip the IP-based
tunnel header and then process the decapsulated MPLS packet. The top tunnel header and then process the decapsulated MPLS packet. The top
label indicates that the packet must be forwarded toward router H. label indicates that the packet must be forwarded toward router H.
Since the next hop toward router H is only IP-capable (D is a legacy Since the next hop toward router H is only IP capable (D is a legacy
transit router), router G would replace the current top label with an transit router), router G would replace the current top label with an
MPLS-over-UDP tunnel toward router H and send it out. However, since MPLS-over-UDP tunnel toward router H and send it out. However, since
router G reaches the bottom of the label stack (G is the penultimate router G reaches the bottom of the label stack (G is the penultimate
SR-MPLS capable node on the path) this would leave the original node capable of SR-MPLS on the path), this would leave the original
packet that router A wanted to send to router H encapsulated in UDP packet that router A wanted to send to router H encapsulated in UDP
as if it was MPLS (i.e., with a UDP header and destination port as if it was MPLS (i.e., with a UDP header and destination port
indicating MPLS) even though the original packet could have been any indicating MPLS) even though the original packet could have been any
protocol. That is, the final SR-MPLS has been popped exposing the protocol. That is, the final SR-MPLS has been popped exposing the
payload packet. payload packet.
To handle this, when a router (here it is router G) pops the final To handle this, when a router (here it is router G) pops the final
SR-MPLS label, it inserts an explicit null label [RFC3032] before SR-MPLS label, it inserts an explicit NULL label [RFC3032] before
encapsulating the packet in an MPLS-over-UDP tunnel toward router H encapsulating the packet in an MPLS-over-UDP tunnel toward router H
and sending it out. That is, router G pops the top label, discovers and sending it out. That is, router G pops the top label, discovers
it has reached the bottom of stack, pushes an explicit null label, it has reached the bottom of stack, pushes an explicit NULL label,
and then encapsulates the MPLS packet in a UDP tunnel to router H. and then encapsulates the MPLS packet in a UDP tunnel to router H.
3.2.2. Packet Forwarding without Penultimate Hop Popping 3.2.2. Packet Forwarding without Penultimate Hop Popping
Figure 4 demonstrates the packet walk in the case where the label Figure 4 demonstrates the packet walk in the case where the label
associated with each prefix-SID advertised by the owner of the associated with each Prefix-SID advertised by the owner of the
prefix-SID is not a Penultimate Hop Popping (PHP) label (e.g., the Prefix-SID is not a Penultimate Hop-Popping (PHP) label (e.g., the
the NP flag in OSPF or the P flag in ISIS associated with the prefix- NP-Flag in OSPF or the P-Flag in IS-IS associated with the Prefix-SID
SID is set). Apart from the PHP function the roles of the routers is is set). Apart from the PHP function, the roles of the routers are
unchanged from Section 3.2.1. unchanged from Section 3.2.1.
+-----+ +-----+ +-----+ +-----+ +-----+ +-----+ +-----+ +-----+ +-----+ +-----+
| A +-------+ B +-------+ C +--------+ D +--------+ H | | A +-------+ B +-------+ C +--------+ D +--------+ H |
+-----+ +--+--+ +--+--+ +--+--+ +-----+ +-----+ +--+--+ +--+--+ +--+--+ +-----+
| | | | | |
| | | | | |
+--+--+ +--+--+ +--+--+ +--+--+ +--+--+ +--+--+
| E +-------+ F +--------+ G | | E +-------+ F +--------+ G |
+-----+ +-----+ +-----+ +-----+ +-----+ +-----+
skipping to change at page 11, line 28 skipping to change at line 470
+--------+ +--------+ +--------+ +--------+ +--------+ +--------+
| L(E) | | UDP | |IP(G->H)| | L(E) | | UDP | |IP(G->H)|
+--------+ +--------+ +--------+ +--------+ +--------+ +--------+
| L(G) | | L(G) | | UDP | | L(G) | | L(G) | | UDP |
+--------+ +--------+ +--------+ +--------+ +--------+ +--------+
| L(H) | | L(H) | | L(H) | | L(H) | | L(H) | | L(H) |
+--------+ +--------+ +--------+ +--------+ +--------+ +--------+
| Packet | ---> | Packet | ---> | Packet | | Packet | ---> | Packet | ---> | Packet |
+--------+ +--------+ +--------+ +--------+ +--------+ +--------+
Figure 4: Packet Forwarding Example without PHP Figure 4: Packet-Forwarding Example without PHP
As can be seen from the figure, the SR-MPLS label for each segment is As can be seen from the figure, the SR-MPLS label for each segment is
left in place until the end of the segment where it is popped and the left in place until the end of the segment where it is popped and the
next instruction is processed. next instruction is processed.
3.2.3. Additional Forwarding Procedures 3.2.3. Additional Forwarding Procedures
Non-MPLS Interfaces: Although the description in the previous two Non-MPLS Interfaces: Although the description in the previous two
sections is based on the use of prefix-SIDs, tunneling SR-MPLS sections is based on the use of Prefix-SIDs, tunneling SR-MPLS
packets is useful when the top label of a received SR-MPLS packet packets is useful when the top label of a received SR-MPLS packet
indicates an adjacency-SID and the corresponding adjacent node to indicates an Adjacency SID and the corresponding adjacent node to
that adjacency-SID is not capable of MPLS forwarding but can still that Adjacency SID is not capable of MPLS forwarding but can still
process SR-MPLS packets. In this scenario the top label would be process SR-MPLS packets. In this scenario, the top label would be
replaced by an IP tunnel toward that adjacent node and then replaced by an IP tunnel toward that adjacent node and then
forwarded over the corresponding link indicated by the adjacency- forwarded over the corresponding link indicated by the Adjacency
SID. SID.
When to use IP-based Tunnels: The description in the previous two When to Use IP-Based Tunnels: The description in the previous two
sections is based on the assumption that MPLS-over-UDP tunnel is sections is based on the assumption that an MPLS-over-UDP tunnel
used when the nexthop towards the next segment is not MPLS- is used when the next hop towards the next segment is not MPLS
enabled. However, even in the case where the nexthop towards the enabled. However, even in the case where the next hop towards the
next segment is MPLS-capable, an MPLS-over-UDP tunnel towards the next segment is MPLS capable, an MPLS-over-UDP tunnel towards the
next segment could still be used instead due to local policies. next segment could still be used instead due to local policies.
For instance, in the example as described in Figure 4, assume F is For instance, in the example as described in Figure 4, assume F is
now an SR-MPLS-capable transit node while all the other now a transit node capable of SR-MPLS while all the other
assumptions remain unchanged: since F is not identified by a SID assumptions remain unchanged; since F is not identified by a SID
in the stack and an MPLS-over-UDP tunnel is preferred to an MPLS in the stack and an MPLS-over-UDP tunnel is preferred to an MPLS
LSP according to local policies, router E replaces the current top LSP according to local policies, router E replaces the current top
label with an MPLS-over-UDP tunnel toward router G and send it label with an MPLS-over-UDP tunnel toward router G and sends it
out. (Note that if an MPLS LSP was preferred, the packet would be out. (Note that if an MPLS LSP was preferred, the packet would be
forwarded as native SR-MPLS.) forwarded as native SR-MPLS.)
IP Header Fields: When encapsulating an MPLS packet in UDP, the IP Header Fields: When encapsulating an MPLS packet in UDP, the
resulting packet is further encapsulated in IP for transmission. resulting packet is further encapsulated in IP for transmission.
IPv4 or IPv6 may be used according to the capabilities of the IPv4 or IPv6 may be used according to the capabilities of the
network. The address fields are set as described in Section 2. network. The address fields are set as described in Section 2.
The other IP header fields (such as the ECN field [RFC6040], the The other IP header fields (such as the ECN field [RFC6040], the
DSCP code point [RFC2983], or IPv6 Flow Label) on each UDP- Differentiated Services Code Point (DSCP) [RFC2983], or IPv6 Flow
encapsulated segment SHOULD be configurable according to the Label) on each UDP-encapsulated segment SHOULD be configurable
operator's policy: they may be copied from the header of the according to the operator's policy; they may be copied from the
incoming packet; they may be promoted from the header of the header of the incoming packet; they may be promoted from the
payload packet; they may be set according to instructions header of the payload packet; they may be set according to
programmed to be associated with the SID; or they may be instructions programmed to be associated with the SID; or they may
configured dependent on the outgoing interface and payload. The be configured dependent on the outgoing interface and payload.
TTL field setting in the encapsulating packet header is handled as The TTL field setting in the encapsulating packet header is
described in [RFC7510] which refers to [RFC4023]. handled as described in [RFC7510], which refers to [RFC4023].
Entropy and ECMP: When encapsulating an MPLS packet with an IP Entropy and ECMP: When encapsulating an MPLS packet with an IP
tunnel header that is capable of encoding entropy (such as tunnel header that is capable of encoding entropy (such as
[RFC7510]), the corresponding entropy field (the source port in [RFC7510]), the corresponding entropy field (the source port in
the case of a UDP tunnel) MAY be filled with an entropy value that the case of a UDP tunnel) MAY be filled with an entropy value that
is generated by the encapsulator to uniquely identify a flow. is generated by the encapsulator to uniquely identify a flow.
However, what constitutes a flow is locally determined by the However, what constitutes a flow is locally determined by the
encapsulator. For instance, if the MPLS label stack contains at encapsulator. For instance, if the MPLS label stack contains at
least one entropy label and the encapsulator is capable of reading least one entropy label and the encapsulator is capable of reading
that entropy label, the entropy label value could be directly that entropy label, the entropy label value could be directly
copied to the source port of the UDP header. Otherwise, the copied to the source port of the UDP header. Otherwise, the
encapsulator may have to perform a hash on the whole label stack encapsulator may have to perform a hash on the whole label stack
or the five-tuple of the SR-MPLS payload if the payload is or the five-tuple of the SR-MPLS payload if the payload is
determined as an IP packet. To avoid re-performing the hash or determined as an IP packet. To avoid recalculating the hash or
hunting for the entropy label each time the packet is encapsulated hunting for the entropy label each time the packet is encapsulated
in a UDP tunnel it MAY be desirable that the entropy value in a UDP tunnel, it MAY be desirable that the entropy value
contained in the incoming packet (i.e., the UDP source port value) contained in the incoming packet (i.e., the UDP source port value)
is retained when stripping the UDP header and is re-used as the is retained when stripping the UDP header and is reused as the
entropy value of the outgoing packet. entropy value of the outgoing packet.
Congestion Considerations: Section 5 of [RFC7510] provides a Congestion Considerations: Section 5 of [RFC7510] provides a
detailed analysis of the implications of congestion in MPLS-over- detailed analysis of the implications of congestion in MPLS-over-
UDP systems and builds on section 3.1.3 of [RFC8085] that UDP systems and builds on Section 3.1.3 of [RFC8085], which
describes the congestion implications of UDP tunnels. All of describes the congestion implications of UDP tunnels. All of
those considerations apply to SR-MPLS-over-UDP tunnels as those considerations apply to SR-MPLS-over-UDP tunnels as
described in this document. In particular, it should be noted described in this document. In particular, it should be noted
that the traffic carried in SR-MPLS flows is likely to be IP that the traffic carried in SR-MPLS flows is likely to be IP
traffic. traffic.
4. IANA Considerations 4. IANA Considerations
This document makes no requests for IANA action. This document has no IANA actions.
5. Security Considerations 5. Security Considerations
The security consideration of [RFC8354] (which redirects the reader The security consideration of [RFC8354] (which redirects the reader
to [RFC5095]) and [RFC7510] apply. DTLS [RFC6347] SHOULD be used to [RFC5095]) and [RFC7510] apply. DTLS [RFC6347] SHOULD be used
where security is needed on an MPLS-SR-over-UDP segment including where security is needed on an SR-MPLS-over-UDP segment including
when the IP segment crosses the public Internet or some other when the IP segment crosses the public Internet or some other
untrusted environment. [RFC8402] provides security considerations untrusted environment. [RFC8402] provides security considerations
for Segment Routing, and Section 8.1 of that document is particularly for Segment Routing, and Section 8.1 of [RFC8402] is particularly
applicable to SR-MPLS. applicable to SR-MPLS.
It is difficult for an attacker to pass a raw MPLS encoded packet It is difficult for an attacker to pass a raw MPLS-encoded packet
into a network and operators have considerable experience at into a network, and operators have considerable experience in
excluding such packets at the network boundaries, for example by excluding such packets at the network boundaries, for example, by
excluding all packets that are revealed to be carrying an MPLS packet excluding all packets that are revealed to be carrying an MPLS packet
as the payload of IP tunnels. Further discussion of MPLS security is as the payload of IP tunnels. Further discussion of MPLS security is
found in [RFC5920]. found in [RFC5920].
It is easy for a network ingress node to detect any attempt to It is easy for a network ingress node to detect any attempt to
smuggle an IP packet into the network since it would see that the UDP smuggle an IP packet into the network since it would see that the UDP
destination port was set to MPLS, and such filtering SHOULD be destination port was set to MPLS, and such filtering SHOULD be
applied. If, however, the mechanisms described in applied. If, however, the mechanisms described in [RFC8665] or
[I-D.ietf-ospf-segment-routing-extensions] or [RFC8667] are applied, a wider variety of UDP port numbers might be
[I-D.ietf-isis-segment-routing-extensions] are applied, a wider in use making port filtering harder.
variety of UDP port numbers might be in use making port filtering
harder.
SR packets not having a destination address terminating in the SR packets not having a destination address terminating in the
network would be transparently carried and would pose no different network would be transparently carried and would pose no different
security risk to the network under consideration than any other security risk to the network under consideration than any other
traffic. traffic.
Where control plane techniques are used (as described in Section 3), Where control-plane techniques are used (as described in Section 3),
it is important that these protocols are adequately secured for the it is important that these protocols are adequately secured for the
environment in which they are run as discussed in [RFC6862] and environment in which they are run as discussed in [RFC6862] and
[RFC5920]. [RFC5920].
6. Contributors 6. References
Ahmed Bashandy
Individual
Email: abashandy.ietf@gmail.com
Clarence Filsfils
Cisco
Email: cfilsfil@cisco.com
John Drake
Juniper
Email: jdrake@juniper.net
Shaowen Ma
Mellanox Technologies
Email: mashaowen@gmail.com
Mach Chen
Huawei
Email: mach.chen@huawei.com
Hamid Assarpour
Broadcom
Email:hamid.assarpour@broadcom.com
Robert Raszuk
Bloomberg LP
Email: robert@raszuk.net
Uma Chunduri
Huawei
Email: uma.chunduri@gmail.com
Luis M. Contreras
Telefonica I+D
Email: luismiguel.contrerasmurillo@telefonica.com
Luay Jalil
Verizon
Email: luay.jalil@verizon.com
Gunter Van De Velde
Nokia
Email: gunter.van_de_velde@nokia.com
Tal Mizrahi
Marvell
Email: talmi@marvell.com
Jeff Tantsura
Individual
Email: jefftant@gmail.com
7. Acknowledgements
Thanks to Joel Halpern, Bruno Decraene, Loa Andersson, Ron Bonica,
Eric Rosen, Jim Guichard, Gunter Van De Velde, Andy Malis, Robert
Sparks, and Al Morton for their insightful comments on this draft.
Additional thanks to Mirja Kuehlewind, Alvaro Retana, Spencer
Dawkins, Benjamin Kaduk, Martin Vigoureux, Suresh Krishnan, and Eric
Vyncke for careful reviews and resulting comments.
8. References
8.1. Normative References
[I-D.ietf-spring-segment-routing-mpls] 6.1. Normative References
Bashandy, A., Filsfils, C., Previdi, S., Decraene, B.,
Litkowski, S., and R. Shakir, "Segment Routing with MPLS
data plane", draft-ietf-spring-segment-routing-mpls-22
(work in progress), May 2019.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC3031] Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol [RFC3031] Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol
Label Switching Architecture", RFC 3031, Label Switching Architecture", RFC 3031,
DOI 10.17487/RFC3031, January 2001, DOI 10.17487/RFC3031, January 2001,
<https://www.rfc-editor.org/info/rfc3031>. <https://www.rfc-editor.org/info/rfc3031>.
skipping to change at page 16, line 38 skipping to change at line 650
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>. May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L., [RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L.,
Decraene, B., Litkowski, S., and R. Shakir, "Segment Decraene, B., Litkowski, S., and R. Shakir, "Segment
Routing Architecture", RFC 8402, DOI 10.17487/RFC8402, Routing Architecture", RFC 8402, DOI 10.17487/RFC8402,
July 2018, <https://www.rfc-editor.org/info/rfc8402>. July 2018, <https://www.rfc-editor.org/info/rfc8402>.
8.2. Informative References [RFC8660] Bashandy, A., Filsfils, C., 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>.
[I-D.ietf-6man-segment-routing-header] 6.2. Informative References
Filsfils, C., Dukes, D., Previdi, S., Leddy, J.,
Matsushima, S., and d. daniel.voyer@bell.ca, "IPv6 Segment
Routing Header (SRH)", draft-ietf-6man-segment-routing-
header-21 (work in progress), June 2019.
[I-D.ietf-bess-datacenter-gateway] [DC-GATEWAY]
Farrel, A., Drake, J., Rosen, E., Patel, K., and L. Jalil, Farrel, A., Drake, J., Rosen, E., Patel, K., and L. Jalil,
"Gateway Auto-Discovery and Route Advertisement for "Gateway Auto-Discovery and Route Advertisement for
Segment Routing Enabled Domain Interconnection", draft- Segment Routing Enabled Domain Interconnection", Work in
ietf-bess-datacenter-gateway-02 (work in progress), Progress, Internet-Draft, draft-ietf-bess-datacenter-
February 2019. gateway-04, 21 August 2019, <https://tools.ietf.org/html/
draft-ietf-bess-datacenter-gateway-04>.
[I-D.ietf-isis-encapsulation-cap] [IPv6-SRH] Filsfils, C., Dukes, D., Previdi, S., Leddy, J.,
Matsushima, S., and D. Voyer, "IPv6 Segment Routing Header
(SRH)", Work in Progress, Internet-Draft, draft-ietf-6man-
segment-routing-header-26, 22 October 2019,
<https://tools.ietf.org/html/draft-ietf-6man-segment-
routing-header-26>.
[ISIS-ENCAP]
Xu, X., Decraene, B., Raszuk, R., Chunduri, U., Contreras, Xu, X., Decraene, B., Raszuk, R., Chunduri, U., Contreras,
L., and L. Jalil, "Advertising Tunnelling Capability in L., and L. Jalil, "Advertising Tunnelling Capability in
IS-IS", draft-ietf-isis-encapsulation-cap-01 (work in IS-IS", Work in Progress, Internet-Draft, draft-ietf-isis-
progress), April 2017. encapsulation-cap-01, 24 April 2017,
<https://tools.ietf.org/html/draft-ietf-isis-
[I-D.ietf-isis-segment-routing-extensions] encapsulation-cap-01>.
Previdi, S., Ginsberg, L., Filsfils, C., Bashandy, A.,
Gredler, H., and B. Decraene, "IS-IS Extensions for
Segment Routing", draft-ietf-isis-segment-routing-
extensions-25 (work in progress), May 2019.
[I-D.ietf-mpls-spring-entropy-label]
Kini, S., Kompella, K., Sivabalan, S., Litkowski, S.,
Shakir, R., and J. Tantsura, "Entropy label for SPRING
tunnels", draft-ietf-mpls-spring-entropy-label-12 (work in
progress), July 2018.
[I-D.ietf-ospf-encapsulation-cap] [OSPF-ENCAP]
Xu, X., Decraene, B., Raszuk, R., Contreras, L., and L. Xu, X., Decraene, B., Raszuk, R., Contreras, L., and L.
Jalil, "The Tunnel Encapsulations OSPF Router Jalil, "The Tunnel Encapsulations OSPF Router
Information", draft-ietf-ospf-encapsulation-cap-09 (work Information", Work in Progress, Internet-Draft, draft-
in progress), October 2017. ietf-ospf-encapsulation-cap-09, 10 October 2017,
<https://tools.ietf.org/html/draft-ietf-ospf-
[I-D.ietf-ospf-segment-routing-extensions] encapsulation-cap-09>.
Psenak, P., Previdi, S., Filsfils, C., Gredler, H.,
Shakir, R., Henderickx, W., and J. Tantsura, "OSPF
Extensions for Segment Routing", draft-ietf-ospf-segment-
routing-extensions-27 (work in progress), December 2018.
[RFC2983] Black, D., "Differentiated Services and Tunnels", [RFC2983] Black, D., "Differentiated Services and Tunnels",
RFC 2983, DOI 10.17487/RFC2983, October 2000, RFC 2983, DOI 10.17487/RFC2983, October 2000,
<https://www.rfc-editor.org/info/rfc2983>. <https://www.rfc-editor.org/info/rfc2983>.
[RFC5920] Fang, L., Ed., "Security Framework for MPLS and GMPLS [RFC5920] Fang, L., Ed., "Security Framework for MPLS and GMPLS
Networks", RFC 5920, DOI 10.17487/RFC5920, July 2010, Networks", RFC 5920, DOI 10.17487/RFC5920, July 2010,
<https://www.rfc-editor.org/info/rfc5920>. <https://www.rfc-editor.org/info/rfc5920>.
[RFC6790] Kompella, K., Drake, J., Amante, S., Henderickx, W., and [RFC6790] Kompella, K., Drake, J., Amante, S., Henderickx, W., and
skipping to change at page 18, line 15 skipping to change at line 717
[RFC8085] Eggert, L., Fairhurst, G., and G. Shepherd, "UDP Usage [RFC8085] Eggert, L., Fairhurst, G., and G. Shepherd, "UDP Usage
Guidelines", BCP 145, RFC 8085, DOI 10.17487/RFC8085, Guidelines", BCP 145, RFC 8085, DOI 10.17487/RFC8085,
March 2017, <https://www.rfc-editor.org/info/rfc8085>. March 2017, <https://www.rfc-editor.org/info/rfc8085>.
[RFC8354] Brzozowski, J., Leddy, J., Filsfils, C., Maglione, R., [RFC8354] Brzozowski, J., Leddy, J., Filsfils, C., Maglione, R.,
Ed., and M. Townsley, "Use Cases for IPv6 Source Packet Ed., and M. Townsley, "Use Cases for IPv6 Source Packet
Routing in Networking (SPRING)", RFC 8354, Routing in Networking (SPRING)", RFC 8354,
DOI 10.17487/RFC8354, March 2018, DOI 10.17487/RFC8354, March 2018,
<https://www.rfc-editor.org/info/rfc8354>. <https://www.rfc-editor.org/info/rfc8354>.
[RFC8662] Kini, S., Kompella, K., Sivabalan, S., Litkowski, S.,
Shakir, R., and J. Tantsura, "Entropy Label for Source
Packet Routing in Networking (SPRING) Tunnels", RFC 8662,
DOI 10.17487/RFC8662, December 2019,
<https://www.rfc-editor.org/info/rfc8662>.
[RFC8665] Psenak, P., Ed., Previdi, S., Ed., Filsfils, C., Gredler,
H., Shakir, R., Henderickx, W., and J. Tantsura, "OSPF
Extensions for Segment Routing", RFC 8665,
DOI 10.17487/RFC8665, December 2019,
<https://www.rfc-editor.org/info/rfc8665>.
[RFC8667] Previdi, S., Ed., Ginsberg, L., Ed., Filsfils, C.,
Bashandy, A., Gredler, H., and B. Decraene, "IS-IS
Extensions for Segment Routing", RFC 8667,
DOI 10.17487/RFC8667, December 2019,
<https://www.rfc-editor.org/info/rfc8667>.
Acknowledgements
Thanks to Joel Halpern, Bruno Decraene, Loa Andersson, Ron Bonica,
Eric Rosen, Jim Guichard, Gunter Van De Velde, Andy Malis, Robert
Sparks, and Al Morton for their insightful comments on this document.
Additional thanks to Mirja Kuehlewind, Alvaro Retana, Spencer
Dawkins, Benjamin Kaduk, Martin Vigoureux, Suresh Krishnan, and Eric
Vyncke for careful reviews and resulting comments.
Contributors
Ahmed Bashandy
Individual
Email: abashandy.ietf@gmail.com
Clarence Filsfils
Cisco
Email: cfilsfil@cisco.com
John Drake
Juniper
Email: jdrake@juniper.net
Shaowen Ma
Mellanox Technologies
Email: mashaowen@gmail.com
Mach Chen
Huawei
Email: mach.chen@huawei.com
Hamid Assarpour
Broadcom
Email:hamid.assarpour@broadcom.com
Robert Raszuk
Bloomberg LP
Email: robert@raszuk.net
Uma Chunduri
Huawei
Email: uma.chunduri@gmail.com
Luis M. Contreras
Telefonica I+D
Email: luismiguel.contrerasmurillo@telefonica.com
Luay Jalil
Verizon
Email: luay.jalil@verizon.com
Gunter Van De Velde
Nokia
Email: gunter.van_de_velde@nokia.com
Tal Mizrahi
Marvell
Email: talmi@marvell.com
Jeff Tantsura
Apstra, Inc.
Email: jefftant.ietf@gmail.com
Authors' Addresses Authors' Addresses
Xiaohu Xu Xiaohu Xu
Alibaba, Inc Alibaba, Inc
Email: xiaohu.xxh@alibaba-inc.com Email: xiaohu.xxh@alibaba-inc.com
Stewart Bryant Stewart Bryant
Huawei Futurewei Technologies
Email: stewart.bryant@gmail.com Email: stewart.bryant@gmail.com
Adrian Farrel Adrian Farrel
Old Dog Consulting Old Dog Consulting
Email: adrian@olddog.co.uk Email: adrian@olddog.co.uk
Syed Hassan Syed Hassan
Cisco Cisco
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