IPS C. Monia Internet Draft Nishan Systems Document: draft-monia-ips-enccrcex-00.txt September 2001 Category: Individual Submission Common Encapsulation CRC Format Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026 [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 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. Monia Expires March 2002 [Page 1] Common Encapsulation CRC Format September 2001 Status of this Memo.......................................................1 1. Abstract.............................................................3 2. Conventions used in this document....................................3 3. Proposed Change......................................................3 4. Security Considerations..............................................5 5. References...........................................................5 6. Author's Addresses...................................................5 Full Copyright Statement..................................................6 Monia Expires March 2001 [Page 2] Common Encapsulation CRC Format September 2001 1. Abstract This document proposes a change to the FC Common Encapsulation specification [ENCAP] to define how a Fibre Channel CRC is instantiated for transmission over an IP network. 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 [RFC2119]. 3. Proposed Change As specified in [ENCAP], the method for generating the fibre channel CRC is fully defined in [FC-FS]. Although the process for CRC computation is given, the encapsulation specification does not describe how the resulting value is instantiated and transmitted over the IP network. The following proposed changes define the required format by example. Add the text delimited by the left and right arrows to the last paragraph of section 2.1 on page 6: " ....When the CRCV Flag bit is one, the CRC field SHALL contain a CRC for words 0 to 5 of the FC Encapsulation Header computed using the polynomial, initial value, and bit order defined for Fibre Channel [3]. Modify figures 4 and 5 to show the fibre channel CRC as part of the FC frame. Add the following new section Start of new section ============== 3.2 CRC Format The CRC for the header or fibre channel frame is generated and formatted for transmission on the IP network as shown in the following example. Figure 1 shows a fibre channel ACK_1 frame as it appears in memory. Monia Expires March 2001 [Page 3] Common Encapsulation CRC Format September 2001 +--------+-------------+-------------+-------------+--------------+ | Word | Byte 0(msb) | Byte 1 | Byte 2 | Byte 3 (lsb) | +--------+-------------+-------------+-------------+--------------+ | 0 | C0 | 01 | 02 | 03 | +--------+-------------+-------------+-------------+--------------+ | 1 | 00 | 04 | 05 | 06 | +--------+-------------+-------------+-------------+--------------+ | 2 | 00 | C0 | 00 | 00 | +--------+-------------+-------------+-------------+--------------+ | 3 | 02 | 00 | 00 | 03 | +--------+-------------+-------------+-------------+--------------+ | 4 | FF | FF | FF | FF | +--------+-------------+-------------+-------------+--------------+ | 5 | 00 | 00 | 00 | 00 | +--------+-------------+-------------+-------------+--------------+ Figure 1 -- Memory Image of Data Block (ACK_1) in Big Endian Format In accordance with FC-FS [FC-FS], the CRC is generated from a bit stream in fibre channel format. As shown in Figure 2, the bit stream is obtained by transposing the contents of each byte and serializing the result starting with the least significant bit of word 0, byte 0. The resulting CRC is appended to the bit stream as shown. +--------+-------------+-------------+-------------+--------------+ | Word | Byte 0(msb) | Byte 1 | Byte 2 | Byte 3 (lsb) | +--------+-------------+-------------+-------------+--------------+ | 0 | 03 | 80 | 40 | C0 | +--------+-------------+-------------+-------------+--------------+ | 1 | 00 | 20 | A0 | 60 | +--------+-------------+-------------+-------------+--------------+ | 2 | 00 | 03 | 00 | 00 | +--------+-------------+-------------+-------------+--------------+ | 3 | 40 | 00 | 00 | C0 | +--------+-------------+-------------+-------------+--------------+ | 4 | FF | FF | FF | FF | +--------+-------------+-------------+-------------+--------------+ | 5 | 00 | 00 | 00 | 00 | +--------+-------------+-------------+-------------+--------------+ | CRC | 9B | 61 | F4 | 08 | +--------+-------------+-------------+-------------+--------------+ Figure 2 -- Data Block and CRC in FC Bit Stream Format Figure 3 shows the memory image of the corresponding data block and CRC before encapsulation and transmission on the IP network. The CRC is an extension of the payload and SHALL be transmitted with the payload in network byte order. Monia Expires March 2001 [Page 4] Common Encapsulation CRC Format September 2001 +--------+-------------+-------------+-------------+--------------+ | Word | Byte 0(msb) | Byte 1 | Byte 2 | Byte 3 (lsb) | +--------+-------------+-------------+-------------+--------------+ | 0 | C0 | 01 | 02 | 03 | +--------+-------------+-------------+-------------+--------------+ | 1 | 00 | 03 | 04 | 05 | +--------+-------------+-------------+-------------+--------------+ | 2 | 00 | C0 | 00 | 00 | +--------+-------------+-------------+-------------+--------------+ | 3 | 02 | 00 | 00 | 03 | +--------+-------------+-------------+-------------+--------------+ | 4 | FF | FF | FF | FF | +--------+-------------+-------------+-------------+--------------+ | 5 | 00 | 00 | 00 | 00 | +--------+-------------+-------------+-------------+--------------+ | CRC | D9 | 86 | 2F | 10 | +--------+-------------+-------------+-------------+--------------+ Figure 3 -- Memory Image of Data Block and CRC in Big Endian format ================= End of new section 4. Security Considerations No changes to the security considerations in [ENCAP] are required. 5. References [RFC2026] Bradner, S., "The Internet Standards Process -- Revision 3", BCP 9, RFC 2026, October 1996. [ENCAP] Rajagopal, M, et-al, " "FC Frame Encapsulation ", draft-ietf-ips- fcencapsulation-02.txt, August 2001 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997 [FC-FS] dpANS X3.XXX-200X, "Fibre Channel Framing and Signaling Interface", Revision 1.2, NCITS Project 1331-D, February 2001 6. Author's Addresses Charles Monia Nishan Systems 3850 North First Street San Jose, CA 95134 Monia Expires March 2001 [Page 5] Common Encapsulation CRC Format September 2001 Phone: (408) 519-3986 Email: cmonia@nishansystems.com 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 Monia Expires March 2001 [Page 6] Common Encapsulation CRC Format September 2001 Monia Expires March 2001 [Page 7]