Network Working Group R. Stewart Internet Draft Cisco Systems Category: Internet Draft March 27, 2002 SCTP DDP Adaptation draft-stewart-sctp-roi-00.txt Status of this Memo This document is an internet-draft and is in full conformance with all provisions of Section 10 of [RFC2026]. 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 The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. Abstract This document describes a method to adapt DDP to SCTP using a generic DDP description found in [DDP-DRAFT]. This adaption provides a method for two peers to know that each side is performing direct placement thus enabling hardware acceleration if available. Table of Content 1 Introduction.................................................1 1.1 Conventions ...............................................2 1.1 Terms .....................................................2 2 Adaptation Layer Formats.....................................2 2.1 Adaptation Layer Indicator ................................2 3 Procedures...................................................2 3.1 Association Initialization ................................2 3.2 DDP Placement behavior with SCTP...........................3 4 IANA considerations..........................................3 5 Security Considerations......................................3 6 Acknowledgments..............................................3 7 Authors' Addresses...........................................3 8 References...................................................4 1 Introduction This document describes a method to adapt DDP to SCTP using a generic DDP description found in [DDP-DRAFT]. This adaption provides a method for two peers to know that each side is performing direct placement thus enabling hardware acceleration if available. Some implementations may include this adaptation layer within their SCTP implementations to obtain maximum performance but the behavior of SCTP will be unaffected. In order to accomplish this we specify Stewart [Page 1] Internet Draft SCTP DDP Adaption March 2002 the use of the new adaptation layer indication as defined in [STEWa]. 1.1 Conventions The keywords MUST, MUST NOT, REQUIRED, SHALL, SHALL NOT, SHOULD, SHOULD NOT, RECOMMENDED, NOT RECOMMENDED, MAY, and OPTIONAL, when they appear in this document, are to be interpreted as described in [RFC2119]. 1.2 Terms DDP - is an acronym meaning Direct Data Placement. 2 Adaptation Layer Formats 2.1 Adaptation Layer Indicator We define a adaption indication which MUST appear in the INIT or INIT-ACK with the following format as defined in [STEWa]. 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type =0xC006 | Length = Variable | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Adaptation Indication | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Adaptation Indication: The following value is defined for DDP in this document: DDP - 0x00000001 3 Procedures 3.1 Association Initialization At the startup of an association, an endpoint wishing to perform DDP placement MUST include an adaptation layer indication in its INIT or INIT-ACK (as defined in 2.1). After the exchange of the first two messages (INIT and INIT-ACK), an endpoint MUST verify that the peer supports the mode by confirmation that the peer included the DDP adaptation indication. If both peer DID specify a DDP adaptation then: - Each endpoint MUST enable their DDP engine formating each message as defined in [DDP-DRAFT]. - Each endpoint MUST enable the SCTP_DISABLE_FRAGMENTS option as defined in [STEWb]. Stewart [Page 2] Internet Draft SCTP DDP Adaption March 2002 If the peer endpoint did NOT specify a DDP placement adaptation then the local endpoint MUST disable DDP adaptation and it MUST NOT send DATA chunks with the format described in [DDP-DRAFT]. 3.2 DDP Placement behavior with SCTP When DDP is used in combination with SCTP no further procedures are needed other than both endpoints knowing that DDP is occurring. SCTP, once the SCTP_DISABLE_FRAGMENTS option is set, will always assure that EACH send message fits in one complete SCTP chunk. The receiver will NOT need to be concerned with message boundaries and loss events since each SCTP DATA chunk will always have the BE bits set. The placement algorithm will only need to look into the bytes described in [DDP-DRAFT] and place the data into the user buffers. [Editors note: Instead of disabling fragments we may want to consider setting the fragment size to a known value. This would then make it predictable as to where to place fragments. Not sure though what one would do if the FIRST piece of a message is missing. It may be better to have the DDP info on each inbound chunk... we need to consider both alternatives though]. If the sender specifies Unordered delivery (by setting the U bit) the receiver, after placement, MAY notify the receiving application that the data has arrived. In cases where Unordered delivery is NOT specified then the receiving SCTP MUST follow all normal reordering procedures as specified in [RFC2960]. 4 IANA considerations This document defines one new Adaptation Layer Indications as specified within section 2.1. 5 Security Considerations Any direct placement of memory poses a significant security risk, these threats should be addressed in [DDP-Draft]. This document does not add any additional security risks over those found in [RFC2960]. 6 Acknowledgments The author would like to thank the following people that have provided comments and input Stephen Bailey, Douglas Otis, and Allyn Romanow. 7 Authors' Addresses Randall R. Stewart 24 Burning Bush Trail. Crystal Lake, IL 60012 USA Stewart [Page 3] Internet Draft SCTP DDP Adaption March 2002 EMail: rrs@cisco.com 8 References [RFC1982] Elz, R. and R. Bush, "Serial Number Arithmetic", RFC 1982, August 1996. [RFC2026] Bradner, S., "The Internet Standards Process -- Revision 3", BCP 9, RFC 2026, October 1996. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC2960] R. R. Stewart, Q. Xie, K. Morneault, C. Sharp, H. J. Schwarzbauer, T. Taylor, I. Rytina, M. Kalla, L. Zhang, and, V. Paxson, "Stream Control Transmission Protocol," RFC 2960, October 2000. [STEWa] - Stewart, Ramalho, Xie, Tuexen, Rytina, Conrad, "SCTP Extensions for Dynamic Reconfiguration of IP Addresses", November 2001, draft-ietf-tsvwg-addip-sctp-03.txt, work-in-progress. [STEWb] - Stewart, Xie, Yarroll, Wood, Poon, Fujita, "Sockets API Extensions for SCTP", January 2002, draft-ietf-tsvwg-sctpsocket-03.txt, work-in-progress. [DDP-DRAFT] - The universal DDP placement format draft? Full Copyright Statement Copyright (C) The Internet Society (2002). All Rights Reserved. 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