Network working group X. Xu
Internet Draft M. Chen
Category: Standard Track Huawei
Expires: March 2014 September 26, 2013
MPLS Payload Protocol Identifier
draft-xu-mpls-payload-protocol-identifier-00
Abstract
The MPLS label stack has no explicit protocol identifier field to
indicate the protocol type of the MPLS payload. This document
proposes a mechanism for containing a protocol identifier field
within the MPLS packet, which may be useful in some emerging use
cases (e.g., network service chain and MPLS payload inspection).
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
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 March 26, 2014.
Copyright Notice
Copyright (c) 2013 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
Xu, et al. Expires March 26, 2014 [Page 1]
Internet-Draft MPLS Payload Protocol Identifier September 2013
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Conventions used in this document
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].
Table of Contents
1. Introduction ................................................ 3
2. Terminology ................................................. 3
3. Protocol Type Field ......................................... 3
4. Data Plane Processing of PIL ................................ 4
4.1. Egress LSRs ............................................ 4
4.2. Ingress LSRs ........................................... 5
4.3. Transit LSRs ........................................... 5
4.4. Penultimate Hop LSR .................................... 5
5. Signaling for PIL Processing Capability ..................... 6
5.1. LDP .................................................... 6
5.2. RSVP-TE ................................................ 6
5.3. BGP .................................................... 6
5.4. OSPF ................................................... 6
5.5. ISIS ................................................... 6
6. IANA Considerations ......................................... 6
7. Acknowledgements ............................................ 6
8. References .................................................. 6
8.1. Normative References ................................... 6
8.2. Informative References ................................. 6
Authors' Addresses ............................................. 7
Xu, et al. Expires March 26, 2014 [Page 2]
Internet-Draft MPLS Payload Protocol Identifier September 2013
1. Introduction
The MPLS label stack has no explicit protocol identifier field to
indicate the protocol type of the MPLS payload. This document
proposes a mechanism for containing a protocol identifier field
within the MPLS packet, which may be useful in some emerging use
cases (e.g., network service chain and MPLS payload inspection).
2. Terminology
This memo makes use of the terms defined in [RFC3032].
3. Protocol Type Field
The encapsulation format for Protocol Type field is depicted as below:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PIL | EXP |1| TTL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 0| Reserved | Protocol Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Payload |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Protocol Identifier Label (PIL)
This field contains a special purpose label with value of
<TBD> or an extended special purpose label [SPL] with
value of <TBD> which indicates that a Protocol Type field
appears immediately after the bottom of the label stack.
EXP
The usage of this field is in accordance with the
current MPLS specification [RFC3032].
S
The Bottom of Stack (BoS) field is set since the PIL MUST
always appear at the bottom of the label stack.
TTL
Xu, et al. Expires March 26, 2014 [Page 3]
Internet-Draft MPLS Payload Protocol Identifier September 2013
The usage of this field is in accordance with the
current MPLS specification [RFC3032].
Reserved
MUST be set to 0 and ignored on reception.
Protocol Type
This field indicates the protocol type of the MPLS
payload as per [ETYPES].
Payload
This field contains the MPLS payload which can be an IP
packet, an Ethernet frame, or any other type of payload
(e.g., network service header).
4. Data Plane Processing of PIL
4.1. Egress LSRs
Suppose egress LSR Y is capable of processing the Protocol Type field
contained in MPLS packets. LSR Y indicates this to all ingress LSRs
via signaling (see Section 5). LSR Y MUST be prepared to deal with
both packets with an imposed Protocol Type field and those without;
the PIL will distinguish these cases. If a particular ingress LSR
chooses not to impose a Protocol Type field, LSR Y's processing of
the received label stack (which might be empty) is as if LSR Y chose
not to accept Protocol Type field.
If an ingress LSR X chooses to impose the Protocol Type field, then
LSR Y will receive an MPLS packet constructed as follows: <Top Label
(TL), Application Label (AL), PIL> <Protocol Type field> <remaining
MPLS payload>. Note that here the TL could be replaced with an IP-
based tunnel [RFC4023] and the AL is optional.
LSR Y recognizes TL as the label it distributed to its upstream LSR
and pops the TL (note that the TL may be an implicit null label, in
which case it doesn't appear in the label stack and LSR Y MUST
process the packet starting with the AL label (if present) and/or the
PIL.) LSR Y recognizes the PIL with S bit set. LSR Y then processes
the Protocol Type field, which will determine how LSR Y processes the
MPLS payload.
Xu, et al. Expires March 26, 2014 [Page 4]
Internet-Draft MPLS Payload Protocol Identifier September 2013
4.2. Ingress LSRs
If an egress LSR Y indicates via signaling that it can process the
Protocol Type field, an ingress LSR X can choose whether or not to
insert it into the MPLS packet destined for LSR Y. The ingress LSR X
MUST NOT insert the Protocol Type field into that MPLS packet unless
the egress LSR X has explicitly announced that it could process it.
The steps that ingress LSR X performs to insert the Protocol Type
field are as follows:
1. On an incoming packet, identify the application to which the
packet belongs and determine whether the Protocol Type field needs to
be added to the incoming packet.
2. For packets requiring the insertion of the Protocol Type field,
prepend the Protocol Type field to the existing MPLS payload; then,
push the PIL on to the label stack with the S bit set.
3. Push the application label (AL) label (if required) on to the
label stack.
4. Push the EL and the ELI labels [RFC6790] on to the label stack
(if required).
6. Determine the top label (TL) and push it on to the label stack.
7. Determine the output interface and send the packet out.
4.3. Transit LSRs
Transit LSRs MAY operate with no change in forwarding behavior. If a
transit LSR recognizes the PIL and the subsequent Protocol Type field,
it MAY be allowed to do some additional value-added processing, such
as MPLS payload inspection, on the received MPLS packet containing
the PIL and the Protocol Type field.
4.4. Penultimate Hop LSR
No change is needed at penultimate hop LSRs.
Xu, et al. Expires March 26, 2014 [Page 5]
Internet-Draft MPLS Payload Protocol Identifier September 2013
5. Signaling for PIL Processing Capability
5.1. LDP
5.2. RSVP-TE
5.3. BGP
5.4. OSPF
5.5. ISIS
6. IANA Considerations
A special purpose label with value of <TBD> or an extended special
purpose label with value of <TBD> for the PIL needs to be assigned by
the IANA.
7. Acknowledgements
TBD.
8. References
8.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3032] Rosen, E., Rekhter, Y., Tappan, D., Fedorkow, G.,
Farinacci, D. and A. Conta, "MPLS Label Stack
Encoding", RFC 3032, January 2001.
8.2. Informative References
[RFC4023] Worster, T., Rekhter, Y., and E. Rosen, "Encapsulating MPLS
in IP or GRE", RFC4023, March 2005.
[ETYPES] The IEEE Registration Authority, "IEEE 802 Numbers", 2012,
<http://www.iana.org/assignments/ieee-802-numbers/
ieee-802-numbers.xml>.
[RFC5036] Andersson, L., Minei, I., and B. Thomas, "LDP
Specification", RFC 5036, October 2007.
Xu, et al. Expires March 26, 2014 [Page 6]
Internet-Draft MPLS Payload Protocol Identifier September 2013
[RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
Tunnels", RFC 3209, December 2001.
[RFC3107] Rekhter, Y. and E. Rosen, "Carrying Label Information in
BGP-4", RFC 3107, May 2001.
[RFC4970] Lindem, A., Ed., Shen, N., Vasseur, JP., Aggarwal, R., and
S. Shaffer, "Extensions to OSPF for Advertising Optional
Router Capabilities", RFC 4970, July 2007.
[RFC4971] Vasseur, JP., Shen, N., and R. Aggarwal, "Intermediate
System to Intermediate System (IS-IS) Extensions for
Advertising Router Information", RFC 4971, July 2007.
[RFC6790] Kompella, K., Drake, J., Amante, S., Henderickx, W., and
L. Yong, "The Use of Entropy Labels in MPLS Forwarding",
RFC 6790, November 2012.
[RFC5586] Bocci, M., Vigoureux, M., and S. Bryant, "MPLS Generic
Associated Channel", RFC 5586, June 2009.
[RFC4385] Bryant, S., Swallow, G., Martini, L., and D. McPherson,
"Pseudowire Emulation Edge-to-Edge (PWE3) Control Word for
Use over an MPLS PSN", RFC 4385, February 2006.
[RFC4928] Swallow, G., Bryant, S., and L. Andersson, "Avoiding Equal
Cost Multipath Treatment in MPLS Networks", BCP 128,
RFC 4928, June 2007.
[SPL] Kompella, K., Andersson, L., and A. Farrel, "Allocating and
Retiring Special Purpose MPLS Labels", draft-ietf-mpls-
special-purpose-labels-03 (work in progress), July 2013.
Authors' Addresses
Xiaohu Xu
Huawei Technologies
Beijing, China
Phone: +86-10-60610041
Email: xuxiaohu@huawei.com
Mach(Guoyi) Chen
Huawei Technologies
Beijing, China
Email: mach.chen@huawei.com
Xu, et al. Expires March 26, 2014 [Page 7]