Point-to-Point Protocol extensions for bridging (RFC1220)
Original Publication Date: 1991-Apr-01
Included in the Prior Art Database: 2019-Feb-11
Internet Society Requests For Comment (RFCs)
This document defines an extension of the Internet Point-to-Point Protocol (PPP) described in RFC 1171, targeting the use of Point-to- Point lines for Remote Bridging. [STANDARDS-TRACK]
Network Working Group F. Baker, Editor Request for Comments: 1220 ACC April 1991
Point-to-Point Protocol Extensions for Bridging
1. Status of this Memo
This document defines an extension of the Internet Point-to-Point Protocol (PPP) described in RFC 1171, targeting the use of Point-to- Point lines for Remote Bridging. It is a product of the Point-to- Point Protocol Extensions Working Group of the Internet Engineering Task Force (IETF).
This RFC specifies an IAB standards track protocol for the Internet community, and requests discussion and suggestions for improvements. Please refer to the current edition of the "IAB Official Protocol Standards" for the standardization state and status of this protocol. Distribution of this memo is unlimited.
2. Historical Perspective
Two basic algorithms are ambient in the industry for Bridging of Local Area Networks. The more common algorithm is called "Transparent Bridging" and has been standardized for Extended LAN configurations by IEEE 802.1. IEEE 802.5 has proposed an alternative approach, called "Source Routing", and is in the process of standardizing that approach for IEEE 802.5 extended networks.
Although there is a subcommittee of IEEE 802.1 addressing remote bridging, neither standard directly defines Remote Bridging per se, as that would technically be beyond the IEEE 802 committee’s charter. Both allow for it, however, modeling the line as an unspecified interface between half-bridges.
This document assumes that the devices at either end of a serial link
- have agreed to utilize the RFC 1171 line discipline in some form.
- may have agreed, by some other means, to exchange other protocols on the line interspersed with each other and with any bridged PDUs.
- may be willing to use the link as a vehicle for Remote Bridging.
- may have multiple point-to-point links that are configured in parallel to simulate a single line of higher speed or
Point-to-Point Protocol Extensions Working Group [Page 1]
RFC 1220 Bridging Point-to-Point Protocol April 1991
reliability, but message sequence issues are solved by the transmitting end.
3. General Considerations
3.1. Link Quality Monitoring
It is strongly recommended that Point-to-Point Bridge Protocol implementations utilize Magic Number Loopback Detection and Link- Quality-Monitoring. This is because the 802.1 Spanning Tree protocol, which is integral to both Transparent Bridging and Source Routing (as standardized), is unidirectional during normal operation, with HELLO PDUs emanating from the Root System in the general direction of the leaves, without any reverse traffic except in response to network events.
3.2. Message Sequence
The multiple link case requires consideration of message sequentiality. The transmitting station must determine either that the protocol being bridged requires transmissions to arrive in the order of their original transmission, and enqueue all transmissions on a given conversation onto the same link to force order preservation, or t...