MPLS Payload Protocol Identifier
draft-xu-mpls-payload-protocol-identifier-01
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| Author | Xiaohu Xu | ||
| Last updated | 2016-06-30 | ||
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draft-xu-mpls-payload-protocol-identifier-01
Network Working Group X. Xu
Internet-Draft Huawei
Intended status: Standards Track June 30, 2016
Expires: January 1, 2017
MPLS Payload Protocol Identifier
draft-xu-mpls-payload-protocol-identifier-01
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 is useful for any new encapsulation
header which may need to be encapsulated with an MPLS header.
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 January 1, 2017.
Copyright Notice
Copyright (c) 2016 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 . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Protocol Type Field . . . . . . . . . . . . . . . . . . . . . 3
4. Data Plane Processing of PIL . . . . . . . . . . . . . . . . 3
4.1. Egress LSRs . . . . . . . . . . . . . . . . . . . . . . . 4
4.2. Ingress LSRs . . . . . . . . . . . . . . . . . . . . . . 4
4.3. Transit LSRs . . . . . . . . . . . . . . . . . . . . . . 5
4.4. 4.4. Penultimate Hop LSRs . . . . . . . . . . . . . . . . 5
5. 5. Signaling for PIL Processing Capability . . . . . . . . . 5
5.1. LDP . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
5.2. RSVP-TE . . . . . . . . . . . . . . . . . . . . . . . . . 5
5.3. BGP . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
5.4. ISIS . . . . . . . . . . . . . . . . . . . . . . . . . . 5
5.5. OSPF . . . . . . . . . . . . . . . . . . . . . . . . . . 5
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
7. Security Considerations . . . . . . . . . . . . . . . . . . . 5
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
9.1. Normative References . . . . . . . . . . . . . . . . . . 6
9.2. Informative References . . . . . . . . . . . . . . . . . 6
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 6
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 is useful for any new encapsulation
header which may need to be encapsulated with an MPLS header. With
this explicit protocol identifier field, there is no need any more
for each new encapsulation header to deal with the notorious first
nibble issue associated with MPLS individually. More specifically,
there is no need to intentionally avoid the first nibble of each new
encapsulation header from being 0100 (IPv4) or 0110 (IPv6).
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].
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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 [RFC7274] 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: 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
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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.
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).
5. Determine the top label (TL) and push it on to the label stack.
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6. 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. 4.4. Penultimate Hop LSRs
No change is needed at penultimate hop LSRs.
5. 5. Signaling for PIL Processing Capability
5.1. LDP
TBD
5.2. RSVP-TE
TBD
5.3. BGP
TBD
5.4. ISIS
TBD
5.5. OSPF
TBD
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. Security Considerations
TBD
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8. Acknowledgements
TBD
9. References
9.1. Normative References
[ETYPES] The IEEE Registration Authority, "IEEE 802 Numbers", 2012.
[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>.
[RFC7274] Kompella, K., Andersson, L., and A. Farrel, "Allocating
and Retiring Special-Purpose MPLS Labels", RFC 7274,
DOI 10.17487/RFC7274, June 2014,
<http://www.rfc-editor.org/info/rfc7274>.
9.2. Informative References
[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>.
[RFC6790] Kompella, K., Drake, J., Amante, S., Henderickx, W., and
L. Yong, "The Use of Entropy Labels in MPLS Forwarding",
RFC 6790, DOI 10.17487/RFC6790, November 2012,
<http://www.rfc-editor.org/info/rfc6790>.
Author's Address
Xiaohu Xu
Huawei
Email: xuxiaohu@huawei.com
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