Network Working Group Eswaran Srinivasan (Editor) Internet Draft Juniper Networks Expiration Date: June 30, 2007 December 27, 2006 Compressing Protocol Identifiers for Frame Relay draft-srinivasan-fr-pid-comp-00.txt Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. 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." The list of current Internet-Drafts can be accessed at http://www.ietf.org/1id-abstracts.html. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. Abstract This document describes a method for compressing the network protocol identifiers for Frame Relay. This will reduce the payload overhead bytes and can improve the packet processing. 1. Specification of Requirements 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. 2. Introduction At a higher level, Frame Relay uses a virtual circuit to connect the two service endpoints. It can either be a permanent virtual circuit (PVC) or switched virtual circuit (SVC). Also, each virtual circuit is uniquely identified by a Data Link Connection Identifier (DLCI). Each virtual circuit can carry different types of network interconnect traffic. Frame Relay uses NLPID and SNAP headers to encapsulate the different types of frames that can be carried over a virtual circuit. In other words, the NLPID and SNAP headers are used to identify the type of the payload carried by a frame. The NLPID and SNAP headers are collectively referred as "Protocol Identifiers" in this document. However, if a virtual circuit is used for carrying only a specific payload type, truly there is no need for using NLPID and/or SNAP header(s) to identify the payload type. These headers can be viewed as extra overhead bytes in these cases. This memo discusses a method to compress the protocol identifiers used in a Frame Relay frame when a virtual circuit can be bonded to a specific payload type. 3. Virtual circuits for control and data traffic A Frame Relay virtual circuit can be used for carrying either the control traffic (Example: LMI traffic) or data traffic. Some of the DLCIs are reserved and can't be used for carrying data traffic. This memo is addressing only the virtual circuits used for carrying the data traffic. Hence, the virtual circuits used for the control traffic are not affected and there won't be any changes to the payload carried by these circuits. 4. Compressing protocol identifiers The data traffic carried by a virtual circuit can be either a routed frame or bridged frame. The sub-sections below discussses the frame format for the different payload types. 4.1. Routed Frames Usually, Frame Relay uses NLPID as the protocol identifier for carrying the routed frames over a virtual circuit. However, due to the NLPID space limitation, not all the routed protocols have assigned NLPID values. For such packets, NLPID and SNAP are used as the protocol identifiers. However, when a virtual circuit has a bonding to a particular protocol type, all the routed frames can be carried over without the NLPID and SNAP protocol identifiers. The figure below shows the packet format for a routed frame without any protocol identifiers: Format of Routed Frame +-------------------------------+ | Q.922 Address | +-------------------------------+ | Routed Frame Payload | +-------------------------------+ | FCS | +-------------------------------+ 4.2. Bridged Frames In general, Frame Relay uses NLPID and SNAP as the protocol identifiers for carrying the bridged frames over a virtual circuit. Hence, a frame bridged over Frame Relay can have one of the following frame formats: Format of Bridged Ethernet/802.3 Frame +-------------------------------+ | Q.922 Address | +-------------------------------+ | MAC Destination Address | +-------------------------------+ | (Remainder of MAC frame) | +-------------------------------+ | LAN FCS (VC dependent option) + +-------------------------------+ | FCS | +-------------------------------+ Format of Bridged 802.4 Frame +-------------------------------+ | Q.922 Address | +-------------------------------+ | Frame Control | +-------------------------------+ | MAC Destination Address | +-------------------------------+ | (Remainder of MAC frame) | +-------------------------------+ | LAN FCS (VC dependent option) + +-------------------------------+ | FCS | +-------------------------------+ Format of Bridged 802.5 Frame +-------------------------------+ | Q.922 Address | +-------------------------------+ | Frame Control | +-------------------------------+ | MAC Destination Address | +-------------------------------+ | (Remainder of MAC frame) | +-------------------------------+ | LAN FCS (VC dependent option) + +-------------------------------+ | FCS | +-------------------------------+ Format of Bridged FDDI Frame +-------------------------------+ | Q.922 Address | +-------------------------------+ | Frame Control | +-------------------------------+ | MAC Destination Address | +-------------------------------+ | (Remainder of MAC frame) | +-------------------------------+ | LAN FCS (VC dependent option) + +-------------------------------+ | FCS | +-------------------------------+ Format of Bridged 802.6 Frame +-------------------------------+ | Q.922 Address | +-------------------------------+ ------- | Reserved | +-------------------------------+ Common | BEtag | PDU +-------------------------------+ Header | BAsize | +-------------------------------+ ------- | MAC Destination Address | +-------------------------------+ | (Remainder of MAC frame) | +-------------------------------+ | Common PDU Trailer + +-------------------------------+ | FCS | +-------------------------------+ Format of BPDU Frame +-------------------------------+ | Q.922 Address | +-------------------------------+ | BPDU as defined by | | 802.1(d) or 802.1(g)[12] | +-------------------------------+ | FCS | +-------------------------------+ Format of Source Routing BPDU Frame +-------------------------------+ | Q.922 Address | +-------------------------------+ | Source Routing BPDU | +-------------------------------+ | FCS | +-------------------------------+ 5. Acronyms BPDU Bridge Protocol Data Unit DLCI Data Link Connection Identifier FCS Frame Check Sum MAC Media Access Control LAN Local Area Network LMI Local Management Interface NLPID Network Level Protocol ID PDU Protocol Data Unit PVC Permanent Virtual Circuit SNAP Subnetwork Access Protocol SVC Switched Virtual Circuit VC Virtual Circuit 6. Security Considerations This document specifies only encapsulations, and not the protocols used to carry the encapsulated packets across the network. Each such protocol may have its own set of security issues, but those issues are not affected by the encapsulations specified herein. 7. IANA Considerations This document has no IANA actions. 8. Full Copyright Statement Copyright (C) The IETF Trust (2006). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 9. Intellectual Property Statement The IETF takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; nor does it represent that it has made any independent effort to identify any such rights. Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. Copies of IPR disclosures made to the IETF Secretariat and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementers or users of this specification can be obtained from the IETF on-line IPR repository at http://www.ietf.org/ipr. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf-ipr@ietf.org. 10. Normative References [RFC2427] "Multiprotocol Interconnect over Frame Relay", RFC2427, September 1998. 11. Informative References [RFC2684] "Multiprotocol Encapsulation over ATM Adapdation Layer 5", RFC2684, September 1999. 12. Author Information Eswaran Srinivasan Juniper Networks, 1194 N. Mathilda Ave, Sunnyvale, CA 94089 E-mail: esriniva@juniper.net