SFC Working Group A. Malis
Internet-Draft S. Bryant
Intended status: Informational Huawei Technologies
Expires: December 21, 2018 J. Halpern
Ericsson
June 19, 2018
MPLS Encapsulation for SFC NSH
draft-malis-mpls-sfc-encapsulation-00
Abstract
This document describes how to use a Service Function Forwarder (SFF)
Label (similar to a pseudowire label or VPN label) to indicate the
presence of a Service Function Chaining (SFC) Network Service Header
(NSH) between an MPLS label stack and the packet payload. This
allows SFC packets using the NSH to be forwarded between SFFs over an
MPLS network, and the selection between multiple SFFs in the
destination node.
Status of This Memo
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. MPLS Encapsulation . . . . . . . . . . . . . . . . . . . . . 2
3. SFF Label . . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 3
5. Security considerations . . . . . . . . . . . . . . . . . . . 3
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 4
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 4
7.1. Normative References . . . . . . . . . . . . . . . . . . 4
7.2. Informative References . . . . . . . . . . . . . . . . . 4
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 5
1. Introduction
As discussed in [RFC8300], a number of encapsulations for the Service
Function Chaining (SFC) Network Service Header (NSH) already exist,
such as in Ethernet, GRE [RFC2784], and VXLAN-GPE
[I-D.ietf-nvo3-vxlan-gpe]. This document describes an MPLS
encapsulation for the NSH, and also describes how to use an Service
Function Forwarder (SFF) [RFC7665] Label to indicate the presence of
the NSH header in the MPLS packet payload. This allows SFC packets
using the NSH to be forwarded between SFFs over an MPLS network, and
the selection between multiple SFFs in the destination node.
SFF Labels are similar to other labels at the bottom of an MPLS label
stack that denote the contents of the MPLS payload being other than
globally routed IP, such as a layer 2 pseudowire, an IP packet that
is routed in a VPN context with a private address, or an Ethernet
virtual private wire service.
This informational document follows well-established MPLS procedures
and does not require any actions by IANA or any new protocol
elements.
2. MPLS Encapsulation
The encapsulation is simply a standard MPLS label stack [RFC3032]
with the SFF Label at the bottom of the stack, followed by a NSH as
defined by [RFC8300] and the NSH payload.
As discussed by [RFC4928] and [RFC7325], there are Equal Cost
Multipath (ECMP) considerations for payloads carried by MPLS. Many
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existing routers use deep packet inspection to examine the payload of
an MPLS packet, and if the first nibble of the payload is equal to
0x4 or 0x6, these routers assume that the payload is IPv4 or IPv6
respectively, and perform ECMP load balancing on the MPLS packets.
For SFC, this is undesirable for several reasons. First of all, NSH
is not IPv4 and IPv6, and the presumed contents of the TCP/IP five-
tuple used for load balancing would be incorrect. Also, as discussed
in [RFC8300], ECMP in general is undesirable for SFC and should be
avoided. For this reason, the NSH Base Header was carefully
constructed so that the NSH could not look like IPv4 or IPv6 based on
its first nibble. See Section 2.2 of [RFC8300] for further details.
3. SFF Label
Much like a pseudowire label, an SFF Label is allocated by the
downstream receiver of the NSH header from its per-platform label
space.
If a receiving node supports more than one SFF (i.e, more than one
SFC forwarding instance), then the SFF Label can be used select the
proper SFF, by having the receiving advertise more than one SFF Label
to its upstream sending nodes as appropriate.
The method used by the downstream receiving node to advertise SFF
Labels to the upstream sending node is currently out of scope of this
document. That said, a number of methods are possible, such as via a
protocol exchange, or via a centralized controller that manages both
the sender and the receiver via NETCONF/YANG, BGP, PCEP, etc. These
are meant as possible examples and not to constrain the future
definition of such advertisement methods.
4. IANA Considerations
This document does not request any actions from IANA.
Editorial note to RFC Editor: This section may be removed at your
discretion.
5. Security considerations
This document describes a method for transporting SFC packets using
the NSH over MPLS. It follows well-established MPLS procedures and
does not define any new protocol elements or allocate any new code
points. It is operationally equivalent to other existing NSH
encapsulations as defined in [RFC8300]. As such, it should have no
effect on SFC security as already discussed in Section 8 of
[RFC8300].
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6. Acknowledgements
Thanks to Jim Guichard for his review and comments.
7. References
7.1. Normative References
[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,
<https://www.rfc-editor.org/info/rfc3032>.
[RFC8300] Quinn, P., Ed., Elzur, U., Ed., and C. Pignataro, Ed.,
"Network Service Header (NSH)", RFC 8300,
DOI 10.17487/RFC8300, January 2018,
<https://www.rfc-editor.org/info/rfc8300>.
7.2. Informative References
[I-D.ietf-nvo3-vxlan-gpe]
Maino, F., Kreeger, L., and U. Elzur, "Generic Protocol
Extension for VXLAN", draft-ietf-nvo3-vxlan-gpe-06 (work
in progress), April 2018.
[RFC2784] Farinacci, D., Li, T., Hanks, S., Meyer, D., and P.
Traina, "Generic Routing Encapsulation (GRE)", RFC 2784,
DOI 10.17487/RFC2784, March 2000,
<https://www.rfc-editor.org/info/rfc2784>.
[RFC4928] Swallow, G., Bryant, S., and L. Andersson, "Avoiding Equal
Cost Multipath Treatment in MPLS Networks", BCP 128,
RFC 4928, DOI 10.17487/RFC4928, June 2007,
<https://www.rfc-editor.org/info/rfc4928>.
[RFC7325] Villamizar, C., Ed., Kompella, K., Amante, S., Malis, A.,
and C. Pignataro, "MPLS Forwarding Compliance and
Performance Requirements", RFC 7325, DOI 10.17487/RFC7325,
August 2014, <https://www.rfc-editor.org/info/rfc7325>.
[RFC7665] Halpern, J., Ed. and C. Pignataro, Ed., "Service Function
Chaining (SFC) Architecture", RFC 7665,
DOI 10.17487/RFC7665, October 2015,
<https://www.rfc-editor.org/info/rfc7665>.
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Authors' Addresses
Andrew G. Malis
Huawei Technologies
Email: agmalis@gmail.com
Stewart Bryant
Huawei Technologies
Email: stewart.bryant@gmail.com
Joel M. Halpern
Ericsson
Email: joel.halpern@ericsson.com
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