Unified Source Routing Instruction using MPLS Label Stack
draft-xu-mpls-unified-source-routing-instruction-01
The information below is for an old version of the document.
| Document | Type |
This is an older version of an Internet-Draft whose latest revision state is "Replaced".
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|
|---|---|---|---|
| Authors | Xiaohu Xu , Stewart Bryant , Robert Raszuk , Uma Chunduri , Luis M. Contreras , Luay Jalil , Hamid Assarpour , Gunter Van de Velde , Jeff Tantsura , Shaowen Ma | ||
| Last updated | 2017-06-13 (Latest revision 2017-03-12) | ||
| Replaced by | draft-xu-mpls-sr-over-ip | ||
| RFC stream | (None) | ||
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draft-xu-mpls-unified-source-routing-instruction-01
Network Working Group X. Xu, Ed.
Internet-Draft S. Bryant, Ed.
Intended status: Standards Track Huawei
Expires: December 15, 2017 R. Raszuk
Bloomberg LP
U. Chunduri
Huawei
L. Contreras
Telefonica I+D
L. Jalil
Verizon
H. Assarpour
Broadcom
V. Gunter
Nokia
J. Tantsura
Individual
S. Ma
Juniper
June 13, 2017
Unified Source Routing Instruction using MPLS Label Stack
draft-xu-mpls-unified-source-routing-instruction-01
Abstract
MPLS-SPRING is an MPLS data plane-based source routing paradigm in
which a sender of a packet is allowed to partially or completely
specify the route the packet takes through the network by imposing
stacked MPLS labels to the packet. MPLS-SPRING could be leveraged to
realize a unified source routing mechanism across MPLS, IPv4 and IPv6
data planes by using a unified source routing instruction set while
preserving backward compatibility with MPLS-SPRING.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
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time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on December 15, 2017.
Copyright Notice
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
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Packet Forwarding Procedures . . . . . . . . . . . . . . . . 4
5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 7
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
7. Security Considerations . . . . . . . . . . . . . . . . . . . 7
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
8.1. Normative References . . . . . . . . . . . . . . . . . . 7
8.2. Informative References . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9
1. Introduction
MPLS-SPRING [I-D.ietf-spring-segment-routing-mpls] is an MPLS data
plane-based source routing paradigm in which a sender of a packet is
allowed to partially or completely specify the route the packet takes
through the network by imposing stacked MPLS labels to the packet.
MPLS-SPRING could be leveraged to realize a unified source routing
mechanism across MPLS, IPv4 and IPv6 data planes by using a unified
source routing instruction set while preserving backward
compatibility with MPLS-SPRING. More specifically, the source
routing instruction set information contained in a source routed
packet could be uniformly encoded as an MPLS label stack no matter
the underlay is IPv4, IPv6 or MPLS.
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The traditional IPv4 and IPv6 source routing mechanisms by use of
IPv4 Source Routing Options and IPv6 Route Header Type 0 Extension
respectively have been deprecated due to their obvious security
vulnerabilities. IPv6 SPRING (a.k.a., SRv6)
[I-D.ietf-6man-segment-routing-header] is a newly proposed IPv6
source routing mechanism in which the source route instruction
information is encoded as an ordered list of 128-bit long IPv6
addresses and contained in the Source Routing Header (SRH). Although
it has overcome the security vulnerability issues associated with the
traditional IPv6 source routing mechanism as claimed in
[I-D.ietf-6man-segment-routing-header], it still has the following
obvious drawbacks which need to be addressed: 1) the encapsulation
overhead is significant especially when the list of the explicit
routing hops is very long; 2) for those transit IPv6 routers that
don't support the flow label-based load-balancing mechanism yet, the
ECMP load-balancing effect may be impacted seriously if they could
not recognize the SRH and therefore could not obtain the five tuple
of the source routed IPv6 packet; 3) it requires a totally new
forwarding logic on basis of the SRH and the forwarding performance
associated with the IPv6 SRH may still be a big concern for some
hardware platforms.
Section 3 describes various use cases for the unified source routing
instruction mechanism and Section 4 describes a typical application
scenario and how the packet forwarding happens.
1.1. 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 RFC 2119 [RFC2119].
2. Terminology
This memo makes use of the terms defined in [RFC3031] and
[I-D.ietf-spring-segment-routing-mpls].
3. Use Cases
The unified source routing mechanism across IPv4, IPv6 and MPLS is
useful at least in the following use cases:
o Incremental deployment of the MPLS-SPRING technology. Since there
is no need to run any other label distribution protocol (e.g.,
LDP, see [I-D.ietf-spring-segment-routing-ldp-interop] for more
details.) on those non-MPLS-SPRING routers for incremental
deployment purposes, the network provisioning is greatly
simplified, which is one of the major claimed benefits of the
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MPLS-SPRING technology (i.e., running a single protocol). In
fact, this unified source routing mechanism is even useful in a
fully upgraded MPLS-SPRING network since the headache associated
with the MPLS-SPRING load-balancing as described in
[I-D.ietf-mpls-spring-entropy-label] can now be avoided by using
the source port of the UDP tunnel header as an entropy field
instead.
o A poor man's light-weight alternative to SRv6
[I-D.ietf-6man-segment-routing-header]. At least, it could be
deployed as an interim until full featured SRv6 is available on
more platforms. Since the Source Routing Header (SRH)
[I-D.ietf-6man-segment-routing-header] consisting of an ordered
list of 128-bit long IPv6 addresses is now replaced by an ordered
list of 32-bit long label entries (i.e., label stack), the
encapsulation overhead and forwarding performance issues
associated with SRv6 are eliminated.
o A new IPv4 source routing mechanism which has overcome the
security vulnerability issues associated with the traditional IPv4
source routing mechanism.
o Traffic Engineering scenarios where only a few routers (e.g., the
entry and exit nodes of each plane in the dual-plane network ) are
specified as segments of explicit paths. In this way, only a few
routers are required to support the MPLS-SPRING capability while
all the other routers just need to support IP forwarding
capability, which would significantly reduce the deployment cost
of this new technology.
o MPLS-based Service Function Chaining (SFC)
[I-D.xu-mpls-service-chaining]. Based on the unified source
routing mechanism as described in this document, only SFC-related
nodes including Service Function Forwarders (SFF), Service
Functions (SF) and classifiers are required to recognize the SFC
encapsulation header in the MPLS label stack form, while the
intermediate routers just need to support vanilla IP forwarding
(either IPv4 or IPv6). In other words, it undoubtedly complies
with the transport-independence requirement as listed in the SFC
architecture document [RFC7665].
4. Packet Forwarding Procedures
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+-----+ +-----+ +-----+ +-----+ +-----+
| A +-------+ B +-------+ C +--------+ D +--------+ H |
+-----+ +--+--+ +--+--+ +--+--+ +-----+
| | |
| | |
+--+--+ +--+--+ +--+--+
| E +-------+ F +--------+ G |
+-----+ +-----+ +-----+
+--------+
|IP(A->E)|
+--------+ +--------+
| L(G) | |IP(E->G)|
+--------+ +--------+ +--------+
| L(H) | | L(H) | |IP(G->H)|
+--------+ +--------+ +--------+
| Packet | ---> | Packet | ---> | Packet |
+--------+ +--------+ +--------+
Figure 1
As shown in Figure 1, Assume Router A, E, G and H are MPLS-SPRING-
capable routers while the remaining are only capable of forwarding IP
packets. Router A, E, G and H advertise their Segment Routing
related information via IS-IS or OSPF. Now assume router A wants to
send a given IP or MPLS packet via an explicit path of {E->G->H},
router A would impose an MPLS label stack corresponding to that
explicit path on the received IP packet. Since there is no Label
Switching Path (LSP) towards router E, router A would replace the top
label indicating router E with an IP-based tunnel for MPLS (e.g.,
MPLS-over-UDP [RFC7510] or MPLS-over-GRE [RFC4023]) towards router E
and then send it out. In other words, router A would pop the top
label and then encapsulate the MPLS packet with an IP-based tunnel
towards router E. When the IP-encapsulated MPLS packet arrives at
router E, router E would strip the IP-based tunnel header and then
process the decapsulated MPLS packet accordingly. Since there is no
LSP towards router G which is indicated by the current top label of
the decapsulated MPLS packet, router E would replace the current top
label with an IP-based tunnel towards router G and send it out. When
the packet arrives at router G, router G would strip the IP-based
tunnel header and then process the decapsulated MPLS packet. Since
there is no LSP towards router H, router G would replace the current
top label with an IP-based tunnel towards router H. Now the packet
encapsulated with the IP-based tunnel towards router H is exactly the
original packet that router A had intended to send towards router H.
If the packet is an MPLS packet, router G could use any IP-based
tunnel for MPLS (e.g., MPLS-over-UDP [RFC7510] or MPLS-over-GRE
[RFC4023]). If the packet is an IP packet, router G could use any IP
tunnel for IP (e.g., IP-in-UDP [I-D.xu-intarea-ip-in-udp] or GRE
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[RFC2784]). That original IP or MPLS packet would be forwarded
towards router H via an IP-based tunnel. When the encapsulated
packet arrives at router H, router H would decapsulate it into the
original packet and then process it accordingly.
Note that in the above description, it's assumed that the label
associated with each prefix-SID advertised by the owner of the
prefix-SID is a Penultimate Hop Popping (PHP) label (e.g., the NP-
flag [I-D.ietf-ospf-segment-routing-extensions] associated with the
corresponding prefix SID is not set). Figure 2 demostrates the
packet walk in the case where the label associated with each prefix-
SID advertised by the owner of the prefix-SID is not a Penultimate
Hop Popping (PHP) label (e.g., the NP-flag
[I-D.ietf-ospf-segment-routing-extensions] associated with the
corresponding prefix SID is set). Although the above description is
based on the use of prefix-SIDs, the unified source routing
instruction approach is actually applicable to the use of adj-SIDs as
well. For instance, when the top label of a received MPLS packet
indicates an given adj-SID and the corresponding adjacent node to
that adj-SID is not MPLS-capable, the top label would be replaced by
an IP-based tunnel towards that adjacent node and then forwarded over
the correponding link indicated by that adj-SID.
+-----+ +-----+ +-----+ +-----+ +-----+
| A +-------+ B +-------+ C +--------+ D +--------+ H |
+-----+ +--+--+ +--+--+ +--+--+ +-----+
| | |
| | |
+--+--+ +--+--+ +--+--+
| E +-------+ F +--------+ G |
+-----+ +-----+ +-----+
+--------+
|IP(A->E)|
+--------+ +--------+
| L(E) | |IP(E->G)|
+--------+ +--------+ +--------+
| L(G) | | L(G) | |IP(G->H)|
+--------+ +--------+ +--------+
| L(H) | | L(H) | | L(H) |
+--------+ +--------+ +--------+
| Packet | ---> | Packet | ---> | Packet |
+--------+ +--------+ +--------+
Figure 2
Note that as for which tunnel encapsulation type should be used, it
could be manually specified on tunnel ingress routers or be learnt
from the tunnel egress routers' advertisements of its tunnel
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encapsulation capability. How to advertise the tunnel encapsulation
capability using IS-IS or OSPF are specified in
[I-D.ietf-isis-encapsulation-cap] and
[I-D.ietf-ospf-encapsulation-cap] respectively.
5. Acknowledgements
Thanks Joel Halpern, Bruno Decraene and Loa Andersson for their
insightful comments on this draft.
6. IANA Considerations
No IANA action is required.
7. Security Considerations
TBD.
8. References
8.1. 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,
<http://www.rfc-editor.org/info/rfc2119>.
8.2. 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-06 (work in progress), March 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-mpls-spring-entropy-label]
Kini, S., Kompella, K., Sivabalan, S., Litkowski, S.,
Shakir, R., and j. jefftant@gmail.com, "Entropy label for
SPRING tunnels", draft-ietf-mpls-spring-entropy-label-06
(work in progress), May 2017.
Xu, et al. Expires December 15, 2017 [Page 7]
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[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-03 (work in progress), May
2017.
[I-D.ietf-ospf-segment-routing-extensions]
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-16 (work in progress), May 2017.
[I-D.ietf-spring-segment-routing-ldp-interop]
Filsfils, C., Previdi, S., Bashandy, A., Decraene, B., and
S. Litkowski, "Segment Routing interworking with LDP",
draft-ietf-spring-segment-routing-ldp-interop-07 (work in
progress), May 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-08
(work in progress), March 2017.
[I-D.xu-intarea-ip-in-udp]
Xu, X., Lee, Y., and F. Yongbing, "Encapsulating IP in
UDP", draft-xu-intarea-ip-in-udp-04 (work in progress),
December 2016.
[I-D.xu-mpls-service-chaining]
Xu, X., Bryant, S., Assarpour, H., Shah, H., Contreras,
L., daniel.bernier@bell.ca, d., jefftant@gmail.com, j.,
and S. Ma, "Service Chaining using an Unified Source
Routing Instruction", draft-xu-mpls-service-chaining-02
(work in progress), May 2017.
[RFC2784] Farinacci, D., Li, T., Hanks, S., Meyer, D., and P.
Traina, "Generic Routing Encapsulation (GRE)", RFC 2784,
DOI 10.17487/RFC2784, March 2000,
<http://www.rfc-editor.org/info/rfc2784>.
[RFC3031] Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol
Label Switching Architecture", RFC 3031,
DOI 10.17487/RFC3031, January 2001,
<http://www.rfc-editor.org/info/rfc3031>.
Xu, et al. Expires December 15, 2017 [Page 8]
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[RFC4023] Worster, T., Rekhter, Y., and E. Rosen, Ed.,
"Encapsulating MPLS in IP or Generic Routing Encapsulation
(GRE)", RFC 4023, DOI 10.17487/RFC4023, March 2005,
<http://www.rfc-editor.org/info/rfc4023>.
[RFC4817] Townsley, M., Pignataro, C., Wainner, S., Seely, T., and
J. Young, "Encapsulation of MPLS over Layer 2 Tunneling
Protocol Version 3", RFC 4817, DOI 10.17487/RFC4817, March
2007, <http://www.rfc-editor.org/info/rfc4817>.
[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>.
[RFC7665] Halpern, J., Ed. and C. Pignataro, Ed., "Service Function
Chaining (SFC) Architecture", RFC 7665,
DOI 10.17487/RFC7665, October 2015,
<http://www.rfc-editor.org/info/rfc7665>.
Authors' Addresses
Xiaohu Xu (editor)
Huawei
Email: xuxiaohu@huawei.com
Stewart Bryant (editor)
Huawei
Email: stewart.bryant@gmail.com
Robert Raszuk
Bloomberg LP
Email: robert@raszuk.net
Uma Chunduri
Huawei
Email: uma.chunduri@gmail.com
Xu, et al. Expires December 15, 2017 [Page 9]
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Luis M. Contreras
Telefonica I+D
Email: luismiguel.contrerasmurillo@telefonica.com
Luay Jalil
Verizon
Email: luay.jalil@verizon.com
Hamid Assarpour
Broadcom
Email: hamid.assarpour@broadcom.com
Van De Velde, Gunter
Nokia
Email: gunter.van_de_velde@nokia.com
Jeff Tantsura
Individual
Email: jefftant.ietf@gmail.com
Shaowen Ma
Juniper
Email: mashao@juniper.net
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