A Unified Approach to IP Segment Routing
draft-bryant-mpls-unified-ip-sr-01
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| Authors | Stewart Bryant , Adrian Farrel , John Drake | ||
| Last updated | 2017-08-11 (Latest revision 2017-06-28) | ||
| Replaced by | draft-xu-mpls-sr-over-ip | ||
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draft-bryant-mpls-unified-ip-sr-01
MPLS Working Group S. Bryant, Ed.
Internet-Draft Huawei
Intended status: Standards Track A. Farrel, Ed.
Expires: February 12, 2018 J. Drake
Juniper Networks
August 11, 2017
A Unified Approach to IP Segment Routing
draft-bryant-mpls-unified-ip-sr-01
Abstract
Segment routing is a source routed forwarding method that allows
packets to be steered through a network on paths other than the
shortest path derived from the routing protocol. The approach uses
information encoded in the packet header to partially or completely
specify the route the packet takes through the network, and does not
make use of a signaling protocol to pre-install paths in the network.
Two different encapsulations have been defined to enable segment
routing in an MPLS network and in an IPv6 network. While
acknowledging that there is a strong need to support segment routing
in both environments, this document defines a converged, unified
approach to segment routing that enables a single mechanism to be
applied in both types of network. The resulting approach is also
applicable to IPv4 networks without the need for any changes to the
IPv4 specification.
This document makes no changes to the segment routing architecture
and builds on existing protocol mechanisms such as the encapsulation
of MPLS within UDP defined in RFC 7510.
No new procedures are introduced, but existing mechanisms are
combined to achieve the desired result.
Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on February 12, 2018.
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Copyright (c) 2017 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. The Unified Segment Routing Protocol Stack . . . . . . . . . 4
3. The Segment Routing Instruction Stack . . . . . . . . . . . . 6
3.1. TTL . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
4. UDP/IP Encapsulation. . . . . . . . . . . . . . . . . . . . . 7
5. Elements of Procedure . . . . . . . . . . . . . . . . . . . . 7
5.1. Domain Ingress . . . . . . . . . . . . . . . . . . . . . 8
5.2. Legacy Transit . . . . . . . . . . . . . . . . . . . . . 8
5.3. On-Path Pass-Through SR Nodes . . . . . . . . . . . . . . 9
5.4. SR Transit Nodes . . . . . . . . . . . . . . . . . . . . 9
5.5. Penultimate SR Transit . . . . . . . . . . . . . . . . . 10
5.6. Domain Egress . . . . . . . . . . . . . . . . . . . . . . 10
6. Modes of Deployment . . . . . . . . . . . . . . . . . . . . . 10
6.1. Interconnection of SR Domains . . . . . . . . . . . . . . 10
6.2. SR Within and IP Network . . . . . . . . . . . . . . . . 11
7. Control Plane . . . . . . . . . . . . . . . . . . . . . . . . 12
8. OAM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
9. Comparison with SRv6 . . . . . . . . . . . . . . . . . . . . 13
10. Security Considerations . . . . . . . . . . . . . . . . . . . 13
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11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14
12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 14
13. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 14
14. References . . . . . . . . . . . . . . . . . . . . . . . . . 14
14.1. Normative References . . . . . . . . . . . . . . . . . . 14
14.2. Informative References . . . . . . . . . . . . . . . . . 15
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 16
1. Introduction
Segment routing (SR) [I-D.ietf-spring-segment-routing] is a source
routed forwarding method that allows packets to be steered through a
network on paths other than the shortest path derived from the
routing protocol. SR also allows the packets to be steered through a
set of packet processing functions along that path. SR uses
information encoded in the packet header to partially or completely
specify the route the packet takes through the network and does not
make use of a signaling protocol to pre-install paths in the network.
MPLS-SPRING [I-D.ietf-spring-segment-routing-mpls] (also known as
MPLS Segment Routing or MPLS-SR) encodes the route the packet takes
through the network and the instructions to be applied to the packet
as it transits the network by imposing a stack of MPLS label entries
on the packet.
The approach to IPv6 segment routing (SR) described in
[I-D.ietf-6man-segment-routing-header] proposes that the segment
routing instruction list is encoded as an ordered list of 128-bit
IPv6 addresses that is carried in a new IPv6 extension header: the
Source Routing Header (SRH). This approach can be challenging to
implement in some types of forwarder, particularly where a large
number of instructions/segments are needed to specify the required
behaviour. Furthermore, the approach does not allow the use of SR
techniques in legacy IPv4 networks. In this document we describe a
method for running SR in IP networks that has a lower overhead and
that uses an MPLS label stack carried in UDP as a method of encoding
the segment routing instructions to be executed as the packet
traverses the network. We call this Unified Segment Routing (USR)
because the same instruction encoding method can be applied to MPLS,
IPv4, and IPv6.
The format defined in this document uses 32 bits per additional
instruction compared to the 128 bits for the method described in
[I-D.ietf-6man-segment-routing-header]. The methods are further
compared in Section 9.
The sequence of 32 bit units, one for each instruction, is called the
Segment Routing Instruction Stack (SRIS). Each basic unit is encoded
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as an MPLS label stack entry and the segment routing instructions
(i.e., the Segment Identifiers, SIDs) are encoded in the 20 bit MPLS
Label fields. This is a hardware convenience rather than an
indication of the use of MPLS as a forwarding protocol and the MPLS
protocol stack, and in particular the MPLS control protocols, do not
need to be deployed. It is a hardware convenience because many
hardware components are already able to perform lookups based on MPLS
labels.
In summary, the processing described in this document is a
combination of normal MPLS-over-UDP behavior as described in
[RFC7510], MPLS-SR lookup and label-pop behavior as described in
[I-D.ietf-spring-segment-routing-mpls], and normal IP forwarding. No
new procedures are introduced, but existing mechanisms are combined
to achieve the desired result.
The method defined is a complementary way of running SR in an IP
network that can be used alongside or interchangeably with that
defined in [I-D.ietf-6man-segment-routing-header]. Implementers and
deployers should consider the benefits and drawbacks of each method
and select the approach most suited to their needs.
2. The Unified Segment Routing Protocol Stack
The USR protocol stack is shown in Figure 1.
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+---------------------+
| |
| IP Header |
| |
+---------------------+
| |
| UDP Header |
| |
+---------------------+
| |
| Segment Routing |
| Instruction Stack |
~ ~
~ ~
| |
+---------------------+
| |
| Payload |
~ ~
~ ~
| |
+---------------------+
Figure 1: Packet Encapsulation
The payload may be of any type that, with an appropriate convergence
layer, can be carried over a packet network. It is anticipated that
the most common packet types will be IPv4, IPv6, native MPLS, and
pseudowires [RFC3985].
Preceding the Payload is the Segment Routing Instruction Stack (SRIS)
that carries the sequence of instructions to be executed on the
packet as it traverses the network. This is the Segment Identifier
(SID) stack that is the ordered list of segments described in
[I-D.ietf-spring-segment-routing].
Preceding the SRIS is a UDP header. The UDP header is included to:
o Introduce entropy to allow equal-cost multi-path load balancing
(ECMP) [RFC2992] in the IP layer [RFC7510].
o Provide a protocol multiplexing layer as an alternative to using a
new IP type/next header.
o Allow transit through firewalls and other middleboxes.
o Provide disagregation.
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Preceding the UDP header is the IP header which may be IPv4 or IPv6.
3. The Segment Routing Instruction Stack
The SRIS consists of a sequence of Segment Identifiers as described
in [I-D.ietf-spring-segment-routing] encoded as an MPLS label stack
as described in [I-D.ietf-spring-segment-routing-mpls].
The top SRIS entry is the next instruction to be executed. When the
node to which this instruction is directed has processed the
instruction it is removed (popped) from the SRIS, and the next
instruction processed.
Each instruction is encoded in a single Label Stack Entry (LSE) as
shown in Figure 2. The structure of the LSE is unchanged from
[RFC3032].
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Instruction | TC |S| TTL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Instruction: Label Value, 20 bits
TC: Traffic Class, 3 bits
S: Bottom of Stack, 1 bit
TTL: Time to Live, 8 bits
Figure 2: SRIS Label Stack Entry
As with [I-D.ietf-spring-segment-routing-mpls] a 32 bit LSE is used
to carry each SR instruction. The instruction itself is carried in
the 20 bit Label Value field. The TC field has the normal meaning as
defined in [RFC3032] and modified in [RFC5462]. The S bit has bottom
of stack semantics defined in [RFC3032]. TTL is discussed in
Section 3.1.
3.1. TTL
The setting of the TTL is application specific, but the following
operational consideration should be born in mind. In SR the size of
the label stack may be increased within a single routing domain by
various operations such as the pushing of a binding SID. Furthermore
in SR packets are not necessarily constrained to travel on the
shortest path with that routing domain. Consideration therefore has
to be given to possibility of a forwarding loop. To mitigate against
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this it is RECOMMENDED that the TTL is continuously decremented as
the packet passes through the SR network regardless of any other
changes to the network layer encapsulation.
4. UDP/IP Encapsulation.
The procedures defined in [RFC7510] are followed. RFC7510 specifies
the values to be used in the UDP Source Port, Destination Port, and
Checksum fields.
An administrative domain, or set of administrative domains that are
sufficiently well managed and monitored to be able to safely use IP
segment routing is likely to comply with the requirements called out
in [RFC7510] to permit operation with a zero checksum over IPv6.
However each operator needs to validate the decision on whether or
not to use a UDP checksum for themselves.
The [RFC7510] UDP header may be carried over IPv4 or over IPv6.
The IP source address is the address of the encapsulating device.
The IP destination address is implied by the instruction at the top
of the instruction stack.
If IPv4 is in use, fragmentation is not permitted.
5. Elements of Procedure
There are six type of node in an SR domain:
o Domain ingress nodes that receive packets and encapsulate them for
transmission across the domain. These packets may be native IP
packets or may already be SR packets.
o Legacy transit nodes that are IP routers but are not able to
perform segment routing.
o Transit nodes that are SR capable but that are not identified by a
SID in the SID stack.
o Transit nodes that are SR capable and need to perform SR routing.
o The penultimate SR capable node on the path that processes the
last SID on the stack.
o The domain egress node that forwards the payload packet for
ultimate delivery.
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The following sub-sections describe the processing behavior in each
case.
In summary, the processing is a combination of normal MPLS-over-UDP
behavior as described in [RFC7510], MPLS-SR lookup and label-pop
behavior as described in [I-D.ietf-spring-segment-routing-mpls], and
normal IP forwarding. No new procedures are introduced, but existing
mechanisms ae combined to achieve the desired result.
The descriptions in the following sections represent the functional
behavior. Optimizations on this behavior may be possible in
implementations.
5.1. Domain Ingress
Domain ingress nodes receive packets from outside the domain and
encapsulate them to be forwarded across the domain. Received packets
may already be MPLS-SR packets (in the case of connecting two MPLS-SR
networks across a native IP network), or may be IP or MPLS packets.
In the latter case, the packet is classified by the domain ingress
node and an MPLS-SR stack is imposed. In the former case the MPLS-SR
stack is already in the packet. The top entry in the stack is popped
from the stack and retained for use below.
The packet is then encapsulated in UDP with the destination port set
to 6635 to indicate "MPLS-UDP" as described in [RFC7510]. The source
UDP port is set randomly or to provide entropy as described in
[RFC7510].
The packet is then encapsulated in IP for transmission across the
network. The IP source address is set to the domain ingress node,
and the destination address is set to the address corresponding to
the label that was previously popped from the stack.
This corresponds to sending the packet out of a virtual interface
that corresponds to a virtual link between the ingress node and the
next hop SR node realized by a UDP tunnel.
The packet is then sent into the IP network and is routed according
to the local FIB and applying hashing to resolve any ECMP choices.
5.2. Legacy Transit
A legacy transit node is an IP router that has no SR capabilities.
When such a router receives an MPLS-SR-in-UDP packet it will carry
out normal TTL processing and if the packet is still live it will
forward it as it would any other UDP-in-IP packet. The packet will
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be routed toward the destination indicated in the packet header using
the local FIB and applying hashing to resolve any ECMP choices.
If the packet is mistakenly addressed to the legacy router, the UDP
tunnel will be terminated and the packet will be discarded either
because the MPLS-in-UDP port is not supported or because the
uncovered top label has not been allocated. This is, however, a
misconnection and should not occur unless there is a routing error.
5.3. On-Path Pass-Through SR Nodes
Just because a node is SR capable and receives an MPLS-SR-in-UDP
packet does not mean that it performs SR processing on the packet.
Only routers identified by SIDs in the SR stack need to do such
processing.
Routers that are not addressed by the destination address in the IP
header simply treat the packet as a normal UDP-in-IP packet carrying
out normal TTL processing and if the packet is still live routing the
packet according to the local FIB and applying hashing to resolve any
ECMP choices.
This is important because it means that the SR stack can be kept
relatively small and the packet can be steered through the network
using shortest path first routing between selected SR nodes.
5.4. SR Transit Nodes
When a router receives an MPLS-SR-in-UDP packet that is addressed to
it, it acts as follows:
o Perform TTL processing as normal for an IP packet.
o Determine that the packet is addressed to the local node.
o Find that the payload is UDP and that the destination port
indicates MPLS-in-UDP.
o Strip the IP and UDP headers.
o Pop the top label from the SID stack and retain it for use below.
o Encapsulate the packet in UDP with the destination port set to
6635 and the source port set for entropy. The entropy value may
be retained from the received UDP header or may be freshly
generated.
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o Encapsulate the packet in IP with the IP source address set to
this transit router, and the destination address set to the
address corresponding to the label that was previously popped from
the stack.
o Send the packet into the IP network routing the packet according
to the local FIB and applying hashing to resolve any ECMP choices.
5.5. Penultimate SR Transit
NOTE: This section needs a correction to the PHP behaviour since in
SR this depends on a flag in the SID advertisement. This will be
corrected in a future revision of this text.
The penultimate SR transit node is only different from the SR transit
node described in Section 5.4 because it pops the final MPLS-SR SID
from the stack. In order to avoid confusion at the egress, the
router replaces the popped SR label with an explicit null label
(label value 0 [RFC3032]). The packet is then encapsulated and sent
as described in Section 5.4.
5.6. Domain Egress
NOTE: This section may also need changing depending on any correction
to the text in the previous section. This will also be addressed in
a future revision of this document.
The domain egress strips the IP and UDP headers, pops the explicit
null label, and forwards the payload packet according to its type and
the local routing/forwarding mechanisms.
6. Modes of Deployment
As previously noted, the procedures described in this document may be
used to connect islands of SR functionality across an IP backbone, or
can provide SR function within a native IP network. This section
briefly expounds upon those two deployment modes.
6.1. Interconnection of SR Domains
Figure 3 shows two SR domains interconnected by an IP network. The
procedures described in this document are deployed at border routers
R1 and R2 and packets are carried across the backbone network in a
UDP tunnel.
R1 acts as the domain ingress as described in Section 5.1. It takes
the MPLS-SR packet from the SR domain, pops the top label and uses it
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to identify its peer border router R2. R1 then encapsulates the
packet in UDP in IP and sends it toward R2.
Routers within the IP network simply forward the packet using normal
IP routing.
R2 acts as a domain egress router as described in Section 5.6. It
receives a packet that is addressed to it, strips the IP and UDP
headers, and acts on the payload SR label stack to continue to route
the packet.
________________________
______ ( ) ______
( ) ( IP Network ) ( )
( ) ( ) ( )
( -------- -------- )
( | Border | SR-in-UDP Tunnel | Border | )
( SR | Router |========================| Router | SR )
( | R1 | | R2 | )
( -------- -------- )
( ) ( ) ( )
(______) ( ) (______)
(________________________)
Figure 3: SR in UDP to Tunnel Between SR Sites
6.2. SR Within and IP Network
Figure 4 shows the procedures defined in this document to provide SR
function across an IP network.
R1 receives a native packet and classifies it, determining that it
should be sent on the SR path R2-R3-R4-R5. It imposes a label stack
accordingly and then acts as a domain ingress as described in
Section 5.1. It pops the label for R2, and encapsulates the packet
in UDP in IP, sets the IP source to R1 and the IP destination to R2,
and sends the packet into the IP network.
Routers Ra and Rb are transit routers that simply forward the packets
using normal IP forwarding. They may be legacy transit routers (see
Section 5.2) or on-path pass-through SR nodes (see Section 5.3).
R2 is an SR transit nodes as described in Section 5.4. It receives a
packet addressed to it, strips the IP and UDP headers, and processes
the SR label stack. It pops the top label and uses it to identify
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the next SR hop which is R3. R2 then encapsulates the packet in UDP
in IP setting the IP source to R2 and the IP destination to R3.
Rc, Rd, and Re are transit routers and perform as Ra and Rb.
R3 is an SR transit node and performs as R2.
R4 is a penultimate SR transit node as described in Section 5.5. It
receives a packet addressed to it, strips the IP and UDP headers, and
processes the SR label stack. It pops the top label and uses it to
identify the next SR hop which is R5. This was the last label in the
stack so R4 includes an explicit null label before encapsulating the
packet in UDP in IP setting the IP source to R4 and the IP
destination to R5.
NOTE may also need adjustment to line up with the PHP text.
R5 is the domain egress as described in Section 5.6. It receives a
packet addressed to it, strips the IP and UDP headers, and pops the
explicit null label before forwarding the payload packet.
__________________________________
__( IP Network )__
__( )__
( -- -- -- )
-------- -- -- |R2| -- |R3| -- |R4| -- --------
| Ingress| |Ra| |Rb| | | |Rc| | | |Rd| | | |Re| | Egress |
--->| Router |===========| |======| |======| |======| Router |--->
| R1 | | | | | | | | | | | | | | | | | | R5 |
-------- -- -- | | -- | | -- | | -- --------
(__ -- -- -- __)
(__ __)
(__________________________________)
Figure 4: SR Within an IP Network
7. Control Plane
The method of advertising the tunnel encapsulation capability of a
router using IS-IS or OSPF are specified in
[I-D.ietf-isis-encapsulation-cap] and
[I-D.ietf-ospf-encapsulation-cap] respectively. No changes to those
procedures are needed in support of this work.
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8. OAM
OAM at the payload layer follows the normal OAM procedures for the
payload. To the payload the whole SR network looks like a tunnel.
OAM in the IP domain follows the normal IP procedures. This can only
be carried out between on the IP hops between pairs of SR nodes.
OAM between instruction processing entities i.e. at the SR layer uses
the procedures documented for MPLS.
9. Comparison with SRv6
The format described in [I-D.ietf-6man-segment-routing-header]
(referred to here as SRv6) requires an initial 36 octet IPv6 header:
no encoding is provided for operation in an IPv4 network. USR
requires either an initial 36 octet IPv6 header or an initial 20
octet IPv4 header.
o SRv6 requires an 8 octet SR header, USR requires a UDP header
which is also 8 octets.
o SRv6 requires 16 octets per SID, whereas USR requires only 4
octets per SID.
o The SRv6 SIDs can be a global identifiers, but the USR SIDs cannot
be.
o Both SRv6 SIDs and USR SIDs can be domain unique SIDs.
o SRv6 retains the intended path in the packet. This information
might be of value for diagnostic purposes although it provides no
evidence of what path the packet actually took. If such
information proves valuable, it could be conveyed in USR using
metadata.
As previously noted, the method defined is a complementary way of
running SR in an IPv6 network that can be used alongside or
interchangeably with SRv6. Implementers and deployers should
consider the benefits and drawbacks of each method and select the
approach most suited to their needs.
10. Security Considerations
The security consideration of [I-D.ietf-spring-ipv6-use-cases] and
[RFC7510] apply.
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It is difficult for an attacker to pass a raw MPLS encoded packet
into a network and operators have considerable experience at
excluding such packets at the network boundaries.
It is easy for an ingress node to detect any attempt to smuggle IP
packet into the network since it would see that the UDP destination
port was set to MPLS. SR packets not having a destination address
terminating in the network would be transparently carried and would
pose no security risk to the network under consideration.
11. IANA Considerations
This document makes no IANA requests.
12. Acknowledgements
This draft was partly inspired by
[I-D.xu-mpls-unified-source-routing-instruction], and we acknowledge
the following authors of version -02 of that draft: Robert Raszuk,
Uma Chunduri, Luis M. Contreras, Luay Jalil, Hamid Assarpour, Gunter
Van De Velde, Jeff Tantsura, and Shaowen Ma.
Thanks to Joel Halpern, Bruno Decraene, Loa Andersson, Ron Bonica,
and Eric Rosen for their insightful comments on this draft.
13. Contributors
o Xiaohu Xu, Huawei Technologies, xuxiaohu@huawei.com
o Mach Chen, Huawei Technologies, mach.chen@huawei.com
14. References
14.1. Normative References
[I-D.ietf-spring-segment-routing]
Filsfils, C., Previdi, S., Decraene, B., Litkowski, S.,
and R. Shakir, "Segment Routing Architecture", draft-ietf-
spring-segment-routing-12 (work in progress), June 2017.
[I-D.ietf-spring-segment-routing-mpls]
Filsfils, C., Previdi, S., Bashandy, A., Decraene, B.,
Litkowski, S., and R. Shakir, "Segment Routing with MPLS
data plane", draft-ietf-spring-segment-routing-mpls-10
(work in progress), June 2017.
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[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC3032] Rosen, E., Tappan, D., Fedorkow, G., Rekhter, Y.,
Farinacci, D., Li, T., and A. Conta, "MPLS Label Stack
Encoding", RFC 3032, DOI 10.17487/RFC3032, January 2001,
<http://www.rfc-editor.org/info/rfc3032>.
[RFC5462] Andersson, L. and R. Asati, "Multiprotocol Label Switching
(MPLS) Label Stack Entry: "EXP" Field Renamed to "Traffic
Class" Field", RFC 5462, DOI 10.17487/RFC5462, February
2009, <http://www.rfc-editor.org/info/rfc5462>.
[RFC7510] Xu, X., Sheth, N., Yong, L., Callon, R., and D. Black,
"Encapsulating MPLS in UDP", RFC 7510,
DOI 10.17487/RFC7510, April 2015,
<http://www.rfc-editor.org/info/rfc7510>.
14.2. Informative References
[I-D.ietf-6man-segment-routing-header]
Previdi, S., Filsfils, C., Raza, K., Leddy, J., Field, B.,
daniel.voyer@bell.ca, d., daniel.bernier@bell.ca, d.,
Matsushima, S., Leung, I., Linkova, J., Aries, E., Kosugi,
T., Vyncke, E., Lebrun, D., Steinberg, D., and R. Raszuk,
"IPv6 Segment Routing Header (SRH)", draft-ietf-6man-
segment-routing-header-07 (work in progress), July 2017.
[I-D.ietf-isis-encapsulation-cap]
Xu, X., Decraene, B., Raszuk, R., Chunduri, U., Contreras,
L., and L. Jalil, "Advertising Tunnelling Capability in
IS-IS", draft-ietf-isis-encapsulation-cap-01 (work in
progress), April 2017.
[I-D.ietf-ospf-encapsulation-cap]
Xu, X., Decraene, B., Raszuk, R., Contreras, L., and L.
Jalil, "Advertising Tunneling Capability in OSPF", draft-
ietf-ospf-encapsulation-cap-06 (work in progress), July
2017.
[I-D.ietf-spring-ipv6-use-cases]
Brzozowski, J., Leddy, J., Filsfils, C., Maglione, R., and
M. Townsley, "IPv6 SPRING Use Cases", draft-ietf-spring-
ipv6-use-cases-11 (work in progress), June 2017.
Bryant, et al. Expires February 12, 2018 [Page 15]
Internet-Draft Unified SR using MPLS August 2017
[I-D.xu-mpls-unified-source-routing-instruction]
Xu, X., Filsfils, C., Bashandy, A., Raszuk, R., Chunduri,
U., Contreras, L., Jalil, L., Assarpour, H., Velde, G.,
Tantsura, J., Ma, S., and T. Mizrahi, "Unified Source
Routing Instructions using MPLS Label Stack", draft-xu-
mpls-unified-source-routing-instruction-03 (work in
progress), August 2017.
[RFC2992] Hopps, C., "Analysis of an Equal-Cost Multi-Path
Algorithm", RFC 2992, DOI 10.17487/RFC2992, November 2000,
<http://www.rfc-editor.org/info/rfc2992>.
[RFC3985] Bryant, S., Ed. and P. Pate, Ed., "Pseudo Wire Emulation
Edge-to-Edge (PWE3) Architecture", RFC 3985,
DOI 10.17487/RFC3985, March 2005,
<http://www.rfc-editor.org/info/rfc3985>.
Authors' Addresses
Stewart Bryant (editor)
Huawei
Email: stewart.bryant@gmail.com
Adrian Farrel (editor)
Juniper Networks
Email: afarrel@juniper.net
John Drake
Juniper Networks
Email: jdrake@juniper.net
Bryant, et al. Expires February 12, 2018 [Page 16]