draft-ietf-mpls-sfc-encapsulation-01.txt   draft-ietf-mpls-sfc-encapsulation-02.txt 
MPLS Working Group A. Malis MPLS Working Group A. Malis
Internet-Draft S. Bryant Internet-Draft S. Bryant
Intended status: Informational Huawei Technologies Intended status: Informational Huawei Technologies
Expires: June 7, 2019 J. Halpern Expires: June 14, 2019 J. Halpern
Ericsson Ericsson
W. Henderickx W. Henderickx
Nokia Nokia
December 04, 2018 December 11, 2018
MPLS Encapsulation for SFC NSH MPLS Encapsulation For The SFC NSH
draft-ietf-mpls-sfc-encapsulation-01 draft-ietf-mpls-sfc-encapsulation-02
Abstract Abstract
This document describes how to use a Service Function Forwarder (SFF) This document describes how to use a Service Function Forwarder (SFF)
Label (similar to a pseudowire label or VPN label) to indicate the Label (similar to a pseudowire label or VPN label) to indicate the
presence of a Service Function Chaining (SFC) Network Service Header presence of a Service Function Chaining (SFC) Network Service Header
(NSH) between an MPLS label stack and the packet payload. This (NSH) between an MPLS label stack and the packet payload. This
allows SFC packets using the NSH to be forwarded between SFFs over an allows SFC packets using the NSH to be forwarded between SFFs over an
MPLS network, and the selection between multiple SFFs in the MPLS network, and to select one of multiple SFFs in the destination
destination MPLS node. MPLS node.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/. Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on June 7, 2019. This Internet-Draft will expire on June 14, 2019.
Copyright Notice Copyright Notice
Copyright (c) 2018 IETF Trust and the persons identified as the Copyright (c) 2018 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of (https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. MPLS Encapsulation Using an SFF Label . . . . . . . . . . . . 3 2. MPLS Encapsulation Using an SFF Label . . . . . . . . . . . . 3
2.1. MPLS Label Stack Construction at the Sending Node . . . . 3 2.1. MPLS Label Stack Construction at the Sending Node . . . . 3
2.2. SFF Label Processing at the Destination Node . . . . . . 4 2.2. SFF Label Processing at the Destination Node . . . . . . 4
3. Equal Cost Multipath (ECMP) Considerations . . . . . . . . . 4 3. Equal Cost Multipath (ECMP) Considerations . . . . . . . . . 4
4. Operations, Administration, and Maintenance (OAM) 4. Operations, Administration, and Maintenance (OAM)
Considerations . . . . . . . . . . . . . . . . . . . . . . . 4 Considerations . . . . . . . . . . . . . . . . . . . . . . . 5
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
6. Security Considerations . . . . . . . . . . . . . . . . . . . 5 6. Security Considerations . . . . . . . . . . . . . . . . . . . 5
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 6 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
8.1. Normative References . . . . . . . . . . . . . . . . . . 6 8.1. Normative References . . . . . . . . . . . . . . . . . . 6
8.2. Informative References . . . . . . . . . . . . . . . . . 6 8.2. Informative References . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
1. Introduction 1. Introduction
As discussed in [RFC8300], a number of transport encapsulations for As discussed in [RFC8300], a number of transport encapsulations for
the Service Function Chaining (SFC) Network Service Header (NSH) the Service Function Chaining (SFC) Network Service Header (NSH)
already exist, such as Ethernet, UDP, GRE, and others. already exist, such as Ethernet, UDP, GRE, and others.
This document describes an MPLS transport encapsulation for the NSH, This document describes an MPLS transport encapsulation for the NSH
and also describes how to use a Service Function Forwarder (SFF) and how to use a Service Function Forwarder (SFF) [RFC7665] Label to
[RFC7665] Label to indicate the presence of the NSH in the MPLS indicate the presence of the NSH in the MPLS packet payload. This
packet payload. This allows SFC packets using the NSH to be allows SFC packets using the NSH to be forwarded between SFFs in an
forwarded between SFFs in an MPLS transport network, where MPLS is MPLS transport network, where MPLS is used to interconnect the
used to interconnect the network nodes that contain one or more SFFs. network nodes that contain one or more SFFs. The label is also used
The label is also used to select between multiple SFFs in the to select between multiple SFFs in the destination MPLS node.
destination MPLS node.
SFF Labels are similar to other service labels at the bottom of an SFF Labels are similar to other service labels at the bottom of an
MPLS label stack that denote the contents of the MPLS payload being MPLS label stack that denote the contents of the MPLS payload being
other than IP, such as a layer 2 pseudowire, an IP packet that is other than IP, such as a layer 2 pseudowire, an IP packet that is
routed in a VPN context with a private address, or an Ethernet routed in a VPN context with a private address, or an Ethernet
virtual private wire service. virtual private wire service.
This informational document follows well-established MPLS procedures This informational document follows well-established MPLS procedures
and does not require any actions by IANA or any new protocol and does not require any actions by IANA or any new protocol
extensions. extensions.
Note that using the MPLS label stack as a replacement for the SFC
NSH, covering use cases that do not require per-packet metadata, is
described elsewhere [I-D.ietf-mpls-sfc].
2. MPLS Encapsulation Using an SFF Label 2. MPLS Encapsulation Using an SFF Label
The encapsulation is a standard MPLS label stack [RFC3032] with an The encapsulation is a standard MPLS label stack [RFC3032] with an
SFF Label at the bottom of the stack, followed by a NSH as defined by SFF Label at the bottom of the stack, followed by a NSH as defined by
[RFC8300] and the NSH payload. [RFC8300] and the NSH payload.
Much like a pseudowire label, an SFF Label is allocated by the Much like a pseudowire label, an SFF Label is allocated by the
downstream receiver of the NSH from its per-platform label space. downstream receiver of the NSH from its per-platform label space.
If a receiving node supports more than one SFF (i.e, more than one If a receiving node supports more than one SFF (i.e, more than one
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That said, a number of methods are possible, such as via a protocol That said, a number of methods are possible, such as via a protocol
exchange, or via a controller that manages both the sender and the exchange, or via a controller that manages both the sender and the
receiver using NETCONF/YANG, BGP, PCEP, etc. These are meant as receiver using NETCONF/YANG, BGP, PCEP, etc. These are meant as
possible examples and not to constrain the future definition of such possible examples and not to constrain the future definition of such
advertisement methods. advertisement methods.
While the SFF label will usually be at the bottom of the label stack, While the SFF label will usually be at the bottom of the label stack,
there may be cases where there are additional label stack entries there may be cases where there are additional label stack entries
beneath it. For example, when an ACH is carried that applies to the beneath it. For example, when an ACH is carried that applies to the
SFF, a GAL [RFC5586] will be in the label stack below the SFF. SFF, a GAL [RFC5586] will be in the label stack below the SFF.
Similarly, an ELI/EL [RFC6790] may be carried below the SFF in the Similarly, an Entropy Label Indicator/Entropy Label (ELI/EL)
label stack. This is identical to the situation with VPN labels. [RFC6790] may be carried below the SFF in the label stack. This is
identical to the situation with VPN labels.
2.1. MPLS Label Stack Construction at the Sending Node 2.1. MPLS Label Stack Construction at the Sending Node
When one SFF wishes to send an SFC packet with the NSH to another SFF When one SFF wishes to send an SFC packet with a NSH to another SFF
over an MPLS transport network, a label stack needs to be constructed over an MPLS transport network, a label stack needs to be constructed
by the MPLS node that contains the sending SFF in order to transport by the MPLS node that contains the sending SFF in order to transport
the packet to the destination MPLS node that contains the receiving the packet to the destination MPLS node that contains the receiving
SFF. The label can be constructed as follows: SFF. The label stack is constructed as follows:
1. Push on zero or more labels that are interpreted by the 1. Push zero or more labels that are interpreted by the destination
destination MPLS node, such as the Generic Associated Channel MPLS node on to the packet, such as the Generic Associated
[RFC5586] label (see OAM Considerations below). Channel [RFC5586] label (see Section 4).
2. Push on the SFF Label to identify the desired SFF in the 2. Push the SFF Label to identify the desired SFF in the receiving
receiving MPLS node. MPLS node.
3. Push on zero or more additional labels such that (a) the 3. Push zero or more additional labels such that (a) the resulting
resulting label stack will cause the packet to be transported to label stack will cause the packet to be transported to the
the destination MPLS node, and (b) when the packet arrives at the destination MPLS node, and (b) when the packet arrives at the
destination node, either: destination node, either:
* the SFF Label will be at the top of the label stack, or * the SFF Label will be at the top of the label stack (this is
typically the case when penultimate hop popping is used at the
penultimate node, or the source and destination nodes are
direct neighbors), or
* the SFF Label will rise to the top of the label stack before * as a part of normal MPLS processing, the SFF Label becomes the
the packet is forwarded to another node and before the packet top label in the stack before the packet is forwarded to
is dispatched to a higher layer. another node and before the packet is dispatched to a higher
layer.
2.2. SFF Label Processing at the Destination Node 2.2. SFF Label Processing at the Destination Node
The destination MPLS node performs a lookup on the SFF label to The destination MPLS node performs a lookup on the SFF label to
retrieve the next-hop context between the SFF and SF, e.g. to retrieve the next-hop context between the SFF and SF, e.g. to
retrieve the destination MAC address in the case where native retrieve the destination MAC address in the case where native
Ethernet encapsulation is used between SFF and SF. How the next-hop Ethernet encapsulation is used between SFF and SF. How the next-hop
context is populated is out of the scope of this document. context is populated is out of the scope of this document.
The receiving MPLS node then pops the SFF Label (and any labels The receiving MPLS node then pops the SFF Label (and any labels
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Many existing routers use deep packet inspection to examine the Many existing routers use deep packet inspection to examine the
payload of an MPLS packet, and if the first nibble of the payload is payload of an MPLS packet, and if the first nibble of the payload is
equal to 0x4 or 0x6, these routers (sometimes incorrectly, as equal to 0x4 or 0x6, these routers (sometimes incorrectly, as
discussed in [RFC4928]) assume that the payload is IPv4 or IPv6 discussed in [RFC4928]) assume that the payload is IPv4 or IPv6
respectively, and as a result, perform ECMP load balancing based on respectively, and as a result, perform ECMP load balancing based on
(presumed) information present in IP/TCP/UDP payload headers or in a (presumed) information present in IP/TCP/UDP payload headers or in a
combination of MPLS label stack and (presumed) IP/TCP/UDP payload combination of MPLS label stack and (presumed) IP/TCP/UDP payload
headers in the packet. headers in the packet.
For SFC, ECMP may or may not be desirable. To prevent unintended For SFC, ECMP may or may not be desirable. To prevent ECMP when it
ECMP when it is not desired, the NSH Base Header was carefully is not desired, the NSH Base Header was carefully constructed so that
constructed so that the NSH could not look like IPv4 or IPv6 based on the NSH could not look like IPv4 or IPv6 based on its first nibble.
its first nibble. See Section 2.2 of [RFC8300] for further details. See Section 2.2 of [RFC8300] for further details.
If ECMP is desired when SFC is used with an MPLS transport network, If ECMP is desired when SFC is used with an MPLS transport network,
there are two possible options, Entropy [RFC6790] and Flow-Aware there are two possible options, Entropy [RFC6790] and Flow-Aware
Transport [RFC6391] labels. A recommendation between these options, Transport [RFC6391] labels. A recommendation between these options,
and their proper placement in the label stack, is for future study. and their proper placement in the label stack, is for future study.
4. Operations, Administration, and Maintenance (OAM) Considerations 4. Operations, Administration, and Maintenance (OAM) Considerations
OAM at the SFC Layer is handled by SFC-defined mechanisms [RFC8300]. OAM at the SFC Layer is handled by SFC-defined mechanisms [RFC8300].
However, OAM may be required at the MPLS transport layer. If so, However, OAM may be required at the MPLS transport layer. If so,
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MPLS-encapsulated NSH packets would require insider knowledge of the MPLS-encapsulated NSH packets would require insider knowledge of the
network's control and management planes and a way to inject packets network's control and management planes and a way to inject packets
into internal interfaces. This is compared to, for example, NSH over into internal interfaces. This is compared to, for example, NSH over
UDP over IP, which could be injected into any external interface in a UDP over IP, which could be injected into any external interface in a
network that was not properly configured to filter out such packets network that was not properly configured to filter out such packets
at the ingress. at the ingress.
7. Acknowledgements 7. Acknowledgements
The authors would like to thank Jim Guichard, Eric Rosen, Med The authors would like to thank Jim Guichard, Eric Rosen, Med
Boucadair, Sasha Vainshtein, and Jeff Tantsura for their reviews and Boucadair, Sasha Vainshtein, Jeff Tantsura, Anoop Ghanwani, John
comments. Drake, and Loa Andersson for their reviews and comments.
8. References 8. References
8.1. Normative References 8.1. Normative References
[RFC3032] Rosen, E., Tappan, D., Fedorkow, G., Rekhter, Y., [RFC3032] Rosen, E., Tappan, D., Fedorkow, G., Rekhter, Y.,
Farinacci, D., Li, T., and A. Conta, "MPLS Label Stack Farinacci, D., Li, T., and A. Conta, "MPLS Label Stack
Encoding", RFC 3032, DOI 10.17487/RFC3032, January 2001, Encoding", RFC 3032, DOI 10.17487/RFC3032, January 2001,
<https://www.rfc-editor.org/info/rfc3032>. <https://www.rfc-editor.org/info/rfc3032>.
[RFC8300] Quinn, P., Ed., Elzur, U., Ed., and C. Pignataro, Ed., [RFC8300] Quinn, P., Ed., Elzur, U., Ed., and C. Pignataro, Ed.,
"Network Service Header (NSH)", RFC 8300, "Network Service Header (NSH)", RFC 8300,
DOI 10.17487/RFC8300, January 2018, DOI 10.17487/RFC8300, January 2018,
<https://www.rfc-editor.org/info/rfc8300>. <https://www.rfc-editor.org/info/rfc8300>.
8.2. Informative References 8.2. Informative References
[I-D.ietf-mpls-sfc]
Farrel, A., Bryant, S., and J. Drake, "An MPLS-Based
Forwarding Plane for Service Function Chaining", draft-
ietf-mpls-sfc-04 (work in progress), November 2018.
[RFC4928] Swallow, G., Bryant, S., and L. Andersson, "Avoiding Equal [RFC4928] Swallow, G., Bryant, S., and L. Andersson, "Avoiding Equal
Cost Multipath Treatment in MPLS Networks", BCP 128, Cost Multipath Treatment in MPLS Networks", BCP 128,
RFC 4928, DOI 10.17487/RFC4928, June 2007, RFC 4928, DOI 10.17487/RFC4928, June 2007,
<https://www.rfc-editor.org/info/rfc4928>. <https://www.rfc-editor.org/info/rfc4928>.
[RFC5586] Bocci, M., Ed., Vigoureux, M., Ed., and S. Bryant, Ed., [RFC5586] Bocci, M., Ed., Vigoureux, M., Ed., and S. Bryant, Ed.,
"MPLS Generic Associated Channel", RFC 5586, "MPLS Generic Associated Channel", RFC 5586,
DOI 10.17487/RFC5586, June 2009, DOI 10.17487/RFC5586, June 2009,
<https://www.rfc-editor.org/info/rfc5586>. <https://www.rfc-editor.org/info/rfc5586>.
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