Network Working Group M. MacDonald Internet Draft Nortel Networks Expiration Date: February 2000 August 1999 Virtual Bridge Tunneling Ethernet Encapsulation in IP 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 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. Abstract This document specifies an approach to provide extended LAN and VLAN services across IP routed networks. This is done by adding a virtual bridge identifier to packets destined to the remote location and then encapsulating this new packet in IP. This packet is then source routed across the IP network to a Virtual Bridge Tunnel terminating router where the header is stripped off and the virtual bridge identifier is used to forward the original packet out the corresponding tunnel interface. Within the IP network the packets are treated like any other IP packets and as such identical mechanisms such as security and quality of service can be applied. MacDonald [Page 1] Internet Draft Virtual Bridge Tunneling August 1999 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Bridge Tunnel Interface . . . . . . . . . . . . . . . . . . 2 Figure 1: A Virtual Bridge Tunnel . . . . . . . . . . . . 2 3. Bridge Tunnels . . . . . . . . . . . . . . . . . . . . . . . 3 Figure 2: Bridge Tunnel Packet . . . . . . . . . . . . . 3 Figure 3: Multiple VBTs . . . . . . . . . . . . . . . . . 3 4. Ethernet Encapsulation in IP . . . . . . . . . . . . . . . . 3 Figure 4: BTP Encapsulated in IP . . . . . . . . . . . . 3 5. Learning . . . . . . . . . . . . . . . . . . . . . . . . . . 4 6. Establishing a Tunnel . . . . . . . . . . . . . . . . . . . 4 7. BTP Processing . . . . . . . . . . . . . . . . . . . . . . . 4 8. Acronyms . . . . . . . . . . . . . . . . . . . . . . . . . . 5 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 6 10. Author's Address . . . . . . . . . . . . . . . . . . . . . . 7 1. Introduction It may be necessary to provide extended LAN and VLAN services between two or more remote locations that are connected via an IP routed network. Current implementations exist for Ethernet encapsulated in ATM and frame-relay however no mechanism is available to provide a similar service for IP routed networks. This document proposes an approach to providing Ethernet encapsulated in IP, essentially making the IP network transparent to the remote locations. This will allow the IP network to function as a virtual bridge by providing Ethernet encapsulation at the edge routers with tunneling between. 2. Bridge Tunnel Interface The local interface on the two edge routers is designated as the Bridge Tunnel Interface, BTI. Figure 1: A Virtual Bridge Tunnel Local LAN +-----------------------------+ Remote LAN Segment | IP Network | Segment 1.1.1.0/24 | | 1.1.1.0/24 | | +-----+ +-----+ | | +--+--+----| A |=======================| B |----+--+--+ | /+-----+ Virtual Bridge Tunnel +-----+\ | BTI | | BTI | A,B Edge Routers | +-----------------------------+ MacDonald [Page 2] Internet Draft Virtual Bridge Tunneling August 1999 3. Bridge Tunnels Because the potential exists for more than two remote locations requiring this service it is necessary to introduce a Bridge Tunnel ID, BTID in the form of a two byte header to the original Ethernet frame. This ID is a number from 1 to 65535. Figure 2: Bridge Tunnel Packet +----+---------------+---------+----- |BTID|Ethernet Header|IP Header|Data +----+---------------+---------+----- Figure 3: Multiple VBTs | | +-----------------------------+ | | +--+--+--- | IP Network | ---+--+--+ | \ | | / | 1.1.1.0/24 +-----+ A,B,C Edge Routers +-----+ 1.1.1.0/24 BTID 100 | A | | B | BTID 100 +-----+ +-----+ | | / | | \ | | +--+--+--- | | ---+--+--+ | | +-----+ | | 2.2.2.0/24 +-----------| C |-----------+ 3.3.3.0/24 BTID 200 +-----+ BTID 300 | | / \ | | +--+--+--- ---+--+--+ | | 2.2.2.0/24 3.3.3.0/24 BTID 200 BTID 300 4. Ethernet Encapsulation in IP The remote interface on the local router will perform the encapsulation of the Bridge Tunnel Packet BTP in IP. Figure 4: BTP Encapsulated in IP +---------+----+---------------+---------+----- |IP Header|BTID|Ethernet Header|IP Header|Data +---------+----+---------------+---------+----- MacDonald [Page 3] Internet Draft Virtual Bridge Tunneling August 1999 The IP Protocol Type is set to recognize that the data carried is a BTP. Any receiving router interface configured for VBT will examine the BTID to determine of the tunnel terminates on one of its local interfaces. If so it reassembles the original IP packet and forwards it out on the Bridge Tunnel Interface corresponding to that VBT configuration. 5. Learning Initially any packets received by the router on a BTI are forwarded to the remote router via the tunnel. Both routers examine the original MAC source addresses of the exchanged packets to create a MAC forwarding table. This table is then used to limit the traffic traversing the tunnel to that destined to devices at the remote location. In this sense the BTIs on the edge routers are performing a bridging function. 6. Establishing the Tunnel To configure a BTI on a router it is necessary to know the series of next hop routers between the two edge routers. This information is used to source-route the BTPs through the IP network. 7. BTP Processing Each router must keep a list of tunnels for which it is configured. Any packet arriving with a Protocol Type of BTP will be examined to determine the BTID. If the BTID corresponds to any of the tunnels configured on that router then the outer IP Header and BTID are stripped off and the remaining data is reassembled and forwarded out on the correct interface as raw data since it already has the required header information. MacDonald [Page 4] Internet Draft Virtual Bridge Tunneling August 1999 8. Acronyms BTI - Bridge Tunnel Interface BTID - Bridge Tunnel ID BTP - Bridge Tunnel Packet IP - Internet Protocol LAN - Local Area Network VBT - Virtual Bridge Tunnel VLAN - Virtual Local Area Network MacDonald [Page 5] Internet Draft Virtual Bridge Tunneling August 1999 9. References RFC 1701 Hanks, S., Li, T., Farinacci, D., and P. Traina, "Generic Routing Encapsulation", RFC 1701, NetSmiths, Ltd., Cisco Systems, October 1994. RFC 1702 Hanks, S., Li, T., Farinacci, D., and P. Traina, "Generic Routing Encapsulation over Ipv4 networks", RFC 1701, NetSmiths, Ltd., Cisco Systems, October 1994. RFC 1932 Cole, R., Shur, D., and D. Villamizer, "IP over ATM: A Framework Document", RFC 1932, AT&T Bell Laboratories, ANS, April 1996. STD 0041/RFC 894 Hornig, Charles, "A Standard for the Transmission of IP Datagrams Over Ethernet Networks", Symbolics Cambridge Research Center, April 1984. STD 0055/RFC 2427 Brown, C., and A. Malis, "Multiprotocol Interconnect over Frame Relay", STD 0055/RFC 2427, Consultant, Ascend Communications, Inc., September 1998. MacDonald [Page 6] Internet Draft Virtual Bridge Tunneling August 1999 10. Author's Address Mike MacDonald Nortel Networks 3500 Carling Ave Nepean, ON, Can. K2H 8E9 Phone: +1 613-765-7899 Fax: +1 613-765-4824 EMail: mikemac@nortelnetworks.com MacDonald [Page 7]