IPS C. Monia Internet Draft Nishan Systems Document: draft-monia-ips-ifcpenc-00.txt February 2001 [Expires August, 2001 iFCP Encapsulation Goals and Requirements Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026 [1]. 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/ietf/1id-abstracts.txt The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. 1. Abstract This document specifies iFCP requirements and design goals applicable to a common FCIP/iFCP format for the encapsulation of Fibre Channel frames. 2. 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 [2]. 3. Common Goals and Requirements This section describes encapsulation requirements and guidelines that are common to both iFCP and FCIP. Requirements: The encapsulation must: iFCP Encapsulation Requirements February, 2001 a) Contain the information needed to recreate the fibre channel frame at the receiving end, including the class-specific FC frame delimiters. b) Backstop the TCP/IP checksum by embedding additional error detection information in the TCP/IP payload. c) Provide some means for the detection and discard of stale frames. That is, frames whose lifetime in the IP network has exceeded that portion of the E_D_TOV or R_A_TOV time limits budgeted to the IP network. d) Provide some means to recover frame synchronization in the event that a check of the payload-embedded error information indicates the presence of data corruption. The following information should be included in the encapsulation: a) The version number of the common encapsulation specification b) A number identifying the client protocol (e.g., iFCP or FCIP) 3.1 Guidelines: 3.1.1 Use of CRCs by the Encapsulation and De-encapsulation processes The use of CRCs for supplemental error detection should be avoided. Although iFCP implementations must have some way to generate them, it is assumed that an FCIP implementation, which transports FC frame images, does not require such a capability. The additional error detection information should therefore be computationally simple to implement, such as checksums or repeated data patterns. Simple approaches can be justified on the basis that they need only protect the small amount of information added by encapsulation. The FC payload will still be protected by its embedded CRC, which will be checked when the frame is received by the FC fabric interface or N_PORT. 4. iFCP Requirements The following sections discuss iFCP requirements. As discussed below, such requirements no longer include the need for an extensible header. 4.1 Augmented Data In iFCP, Fibre Channel Extended Link Service Messages containing N_PORT addresses in the payload are supplemented with augmented data so the destination gateway can map the payload addresses appropriately. In order to simplify the encapsulation, use of an extensible header to contain this data will no longer be required by iFCP. Such information will either be included in the standard encapsulation envelope or transported using multi-frame sequences. iFCP Encapsulation Requirements February, 2001 Special flags in the encapsulation header MUST be allocated to allow the receiving hardware to easily detect and direct such frames for processing within the iFCP layer. 4.2 Common Encapsulation Functional Template To illustrate the desired properties of an encapsulation, the figure below outlines a functional template. +----------------------+ | Framing Preamble | +----------------------+ | Encapsulation | | Header | +----------------------+ | Header Checksum | +----------------------+ | | | FC Frame Image | | | | | | | +----------------------+ Encapsulation Template The template contains the following fields: Framing Preamble _ Information marking the start of the encapsulated frame. Formatted to facilitate the recovery of frame synchronization in the event that data corruption is detected during de-encapsulation. Encapsulation Header _ Containing: a) Client protocol and encapsulation identifiers b) Frame length in 32-bit words c) Flags fields d) Frame time stamp e) Fibre channel SOF/EOF encoding Header Checksum FC Frame Image, including the FC CRC. This template has the following characteristics: a) All the information needed for header validation is in or adjacent to the header itself. b) The encapsulation information, including the SOF/EOF is in the header and is protected by the checksum. iFCP Encapsulation Requirements February, 2001 c) The FC frame image is protected by its embedded CRC, which is checked by the FC hardware. The de-encapsulation process need not validate this CRC. The SOF/EOF fields should contain additional check data for verification and consistency checking, such as the ones-complement of the SOF/EOF encoding. When appropriate, similar data integrity information should be included in other header fields. If a header error is detected, the de-encapsulation process may attempt to re-acquire frame synchronization. It is assumed that the process will minimally involve a scan for a series of preamble patterns. For that reason, some form of word stuffing is often used to break up preambles embedded in the payload. The encapsulation SHOULD avoid this method if possible. A preferred alternative is to supplement preamble detection with additional header consistency checks. 5. Security Considerations The security considerations are those defined in the client protocol specifications (FCIP or iFCP). 9. References 1 Bradner, S., "The Internet Standards Process -- Revision 3", BCP 9, RFC 2026, October 1996. 2 Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997 10. Acknowledgments 11. Author's Addresses Charles Monia Nishan Systems 3850 North First Street San Jose, CA 95134 Phone: +1 (408) 519-3986 Email: cmonia@nishansystems.com iFCP Encapsulation Requirements February, 2001 Full Copyright Statement "Copyright (C) The Internet Society (date). All Rights Reserved. This document and translations of it may be copied and furnished to others, and derivative works that comment on or otherwise explain it or assist in its implmentation may be prepared, copied, published and distributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works. However, this document itself may not be modified in any way, such as by removing the copyright notice or references to the Internet Society or other Internet organizations, except as needed for the purpose of developing Internet standards in which case the procedures for copyrights defined in the Internet Standards process must be followed, or as required to translate it into iFCP Encapsulation Requirements February, 2001