INTERNET-DRAFT EXPIRES: OCTOBER 1997 INTERNET-DRAFT Network Working Group K. Dobbins INTERNET-DRAFT T. Grant Category: Informational D. Ruffen Cabletron Systems Incorporated April 1997 SBCD Protocol Specification Status of this Memo This document is an Internet-Draft. 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". To learn the current status of any Internet-Draft, please check the "1id-abstract.txt" listing contained in the Internet-Drafts Shadow Directories on ftp.is.co.za (Africa), nic.nordu.net (Europe), munnari.oz.au (Pacific Rim), ds.internic.net (US East Coast), or ftp.isi.edu (US West Coast). Abstract The Switch Broadcast Control and Delivery (SBCD) protocol is part of the InterSwitch Message Protocol (ISMP). ISMP was designed to facilitate interswitch communication within distributed connection-oriented switching networks. The SBCD protocol is used to reduce the amount of broadcast traffic across the switch fabric by restricting unresolved broadcast packets to only those ports that belong to the same VLAN as the source. Table of Contents Status of this Memo........................................1 Abstract...................................................1 1. Introduction...........................................1 1.1 Data Conventions..................................1 2. ISMP Overview..........................................2 3. General ISMP Packet Format.............................3 3.1 Frame Header......................................3 3.2 ISMP Packet Header................................4 3.3 ISMP Message Body.................................5 4. SBCD Protocol Operational Overview.....................5 5. Tag-Based Flood Message................................6 References.................................................8 Security Considerations....................................8 Author's Addresses.........................................8 1. Introduction This Internet-Draft is being distributed to members of the Internet community in order to solicit reactions to the proposals contained herein. While the specification discussed here may not be directly relevant to the research problems of the Internet, it may be of interest to researchers and implementers. 1.1 Data Conventions The methods used in this memo to describe and picture data adhere to the standards of Internet Protocol documentation K. Dobbins, et. al. [Page 1] INTERNET-DRAFT SBCD Protocol Specification April 1997 [RFC1700], in particular: The convention in the documentation of Internet Protocols is to express numbers in decimal and to picture data in "big-endian" order. That is, fields are described left to right, with the most significant octet on the left and the least significant octet on the right. The order of transmission of the header and data described in this document is resolved to the octet level. Whenever a diagram shows a group of octets, the order of transmission of those octets is the normal order in which they are read in English. Whenever an octet represents a numeric quantity the left most bit in the diagram is the high order or most significant bit. That is, the bit labeled 0 is the most significant bit. Similarly, whenever a multi-octet field represents a numeric quantity the left most bit of the whole field is the most significant bit. When a multi-octet quantity is transmitted the most significant octet is transmitted first. 2. ISMP Overview The InterSwitch Message Protocol (ISMP) is used for interswitch communication within distributed connection-oriented switching networks. ISMP provides the following services: - Topology services. Each switch maintains a distributed topology of the switch fabric by exchanging the following interswitch messages with other switches: - Interswitch Keepalive messages (SNDM protocol) are sent by each switch to announce its existence to its neighboring switches and to establish the topology of the switch fabric. - Interswitch Spanning Tree BPDU messages and Interswitch Remote Blocking messages (LSMP protocol) are used to determine and maintain a loop-free flood path between all network switches in the fabric. This flood path is used for all undirected interswitch messages -- that is, messages of the ARLD, SBCD and SFCT protocols. - Interswitch Link State messages (VLS Protocol) are used to determine and maintain a fully connected mesh topology graph of the switch fabric. Call-originating switches use the topology graph to determine the path over which to route a call connection. K. Dobbins, et. al. [Page 2] INTERNET-DRAFT SBCD Protocol Specification April 1997 - Address resolution services. Interswitch Resolve messages (ARLD protocol) are used to resolve a packet destination address when the packet source and destination pair does not match a known connection. Interswitch New User messages (also part of the ARLD protocol) are used to provide end-station address mobility between switches. - Tag-based flooding. A tag-based broadcast method (SBCD protocol) is used to restrict the broadcast of unresolved packets to only those ports within the fabric that belong to the same VLAN as the source. - Call tapping services. Interswitch Tap messages (SFCT protocol) are used to monitor traffic moving between two end stations. Traffic can be monitored in one or both directions along the connection path. NOTE This document describes the SBCD protocol. Other ISMP protocols are described in other RFCs. See the References section for a list of these related RFCs. 3. General ISMP Packet Format ISMP packets are of variable length and have the following general structure: - Frame header - ISMP packet header - ISMP message body 3.1 Frame Header ISMP packets are encapsulated within an IEEE 802-compliant frame using a standard header as shown 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 00 | | + Destination address +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 04 | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Source address + 08 | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 12 | Type | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + 16 | | + + : : K. Dobbins, et. al. [Page 3] INTERNET-DRAFT SBCD Protocol Specification April 1997 Destination address This 6-octet field contains the Media Access Control (MAC) address of the multicast channel over which all switches in the fabric receive ISMP packets. The destination address of all ISMP packets contain a value of 01-00-1D-00-00-00. Source address This 6-octet field contains the physical (MAC) address of the switch originating the ISMP packet. Type This 2-octet field identifies the type of data carried within the frame. The type field of ISMP packets contains the value 0x81FD. 3.2 ISMP Packet Header The ISMP packet header consists of 6 octets, as shown 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 00 |///////////////////////////////////////////////////////////////| ://////// Frame header /////////////////////////////////////////: +//////// (14 octets) /////////+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 12 |///////////////////////////////| Version | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 16 | ISMP message type | Sequence number | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 20 | | + + : : Frame header This 14-octet field contains the frame header. Version This 2-octet field contains the version number of the InterSwitch Message Protocol to which this ISMP packet adheres. This document describes ISMP Version 2.0. ISMP message type This 2-octet field contains a value indicating which type of ISMP message is contained within the message body. Valid values are as follows: K. Dobbins, et. al. [Page 4] INTERNET-DRAFT SBCD Protocol Specification April 1997 1 (reserved) 2 Interswitch Keepalive messages (SNDM protocol) 3 Interswitch Link State messages (VLS protocol) 4 Interswitch Spanning Tree BPDU messages and Remote Blocking messages (LSMP protocol) 5 Interswitch Resolve and New User messages (ARLD protocol) 6 (reserved) 7 Tag-Based Flood messages (SBCD protocol) 8 Interswitch Tap messages (SFCT protocol) SBCD protocol messages have a message type of 7. Sequence number This 2-octet field contains an internally generated sequence number used by the various protocol handlers for internal synchronization of messages. 3.3 ISMP Message Body The ISMP message body is a variable-length field containing the actual data of the ISMP message. The length and content of this field are determined by the value found in the message type field. 4. SBCD Protocol Operational Overview The SBCD protocol is used to reduce the amount of broadcast traffic across the switch fabric by restricting the broadcast of unresolved packets to only those ports that belong to the same VLAN as the source. When a switch is unable to resolve the destination address of a packet, it encapsulates the original packet with a tag-based flooding header. This header contains a list of identifiers of the VLANs to which the packet source belongs. The encapsulated packet is then sent over the switch flood path. The switch flood path is formed using a spanning tree algorithm that provides a single path through the switch fabric and guarantees loop-free delivery to every switch in the fabric. When a switch receives a tag-based flood packet, it examines the encapsulated header to determine the VLAN(s) to which the packet should be sent. If any of the switch's local access ports belong to one or more of the specified VLANs, the switch strips off the tag-based header and forwards the original packet out the appropriate access port(s). The switch also forwards the entire encapsulated packet along the flood path to its downstream neighboring switches, if any. K. Dobbins, et. al. [Page 5] INTERNET-DRAFT SBCD Protocol Specification April 1997 5. Tag-Based Flood Message The SBCD tag-based flood message consists of a variable number of octets, as shown 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 00 | | + Frame header / + : ISMP packet header : | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 20 | SBCD version | Opcode | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 24 | Status | Call Tag | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 28 | | + Source MAC of packet +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 32 | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Originating switch MAC + 36 | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 40 | Count | | +-+-+-+-+-+-+-+-+ + 44 | VLAN list | : : | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ n | | + + : Original packet : + + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ n = 41 + length of VLAN list Frame header/ISMP packet header This 20-octet field contains the frame header and the ISMP packet header. SBCD version This 2-octet field contains the version number of the SBCD protocol to which this message adheres. This document describes SBCD Version 1. Opcode This 2-octet field contains the operation code of the message. K. Dobbins, et. al. [Page 6] INTERNET-DRAFT SBCD Protocol Specification April 1997 The value here should be 1, indicating the message is a flood request. Status This 2-octet field is currently unused. It is reserved for future use. Call tag This 2-octet field contains the call tag of the end station packet encapsulated within this tag-based flood message. The call tag is a 16-bit value (generated by the originating switch) that uniquely identifies the packet. Source MAC of packet This 6-octet field contains the physical (MAC) address of the end station that originated the packet identified by the call tag. Originating switch MAC This 6-octet field contains the physical (MAC) address of the switch that issued the original tag-based flooded message. Count This 1-octet field contains the number of VLAN identifiers included in the VLAN list. VLAN list This variable-length field contains a list of the VLAN identifiers of all VLANs to which the source end station belongs. Each entry in this list has the following format: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Value length | | +-+-+-+-+-+-+-+-+ + | VLAN identifier value | : : | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The 1-octet value length field contains the length of the VLAN identifier. VLAN identifiers can be from 1 to 16 characters long. K. Dobbins, et. al. [Page 7] INTERNET-DRAFT SBCD Protocol Specification April 1997 Original packet This variable-length field contains the original packet as sent by the source end station. References [RFC1700] Reynolds, S.J., Postel, J. Assigned Numbers. October 1994. Dobbins, K., et. al. ARLD Protocol Specification Work in Progress. Dobbins, K., et. al. ISM Protocol Specification Work in Progress Dobbins, K., et. al. LSMP Protocol Specification Work in Progress. Dobbins, K., et. al. SFCT Protocol Specification Work in Progress. Dobbins, K., et. al. SNDM Protocol Specification Work in Progress. Dobbins, K., et. al. VLS Protocol Specification Work in Progress. Security Considerations Security issues are not discussed in this document. Authors' Addresses Cabletron Systems, Inc., is located at: Post Office Box 5005 Rochester, NH 03866-5005 (603) 332-9400 Kurt Dobbins Email: dobbins@ctron.com Tom Grant Email: tgrant@ctron.com Dave Ruffen Email: ruffen@ctron.com INTERNET-DRAFT EXPIRES: OCTOBER 1997 INTERNET-DRAFT