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 or an extended special purpose label [SPL] with value of 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: . 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 or an extended special purpose label with value of 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, . [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]