PPP in a Real-time Oriented HDLC-like Framing (RFC2687)
Original Publication Date: 1999-Sep-01
Included in the Prior Art Database: 2019-Feb-11
Internet Society Requests For Comment (RFCs)
This document proposes the suspend/resume-oriented solution for the real-time encapsulation format part of the architecture. [STANDARDS-TRACK]
Network Working Group C. Bormann Request for Comments: 2687 Universitaet Bremen TZI Category: Standards Track September 1999
PPP in a Real-time Oriented HDLC-like Framing
Status of this Memo
This document specifies an Internet standards track protocol for the Internet community, and requests discussion and suggestions for improvements. Please refer to the current edition of the "Internet Official Protocol Standards" (STD 1) for the standardization state and status of this protocol. Distribution of this memo is unlimited.
Copyright (C) The Internet Society (1999). All Rights Reserved.
A companion document describes an architecture for providing integrated services over low-bitrate links, such as modem lines, ISDN B-channels, and sub-T1 links . The main components of the architecture are: a real-time encapsulation format for asynchronous and synchronous low-bitrate links, a header compression architecture optimized for real-time flows, elements of negotiation protocols used between routers (or between hosts and routers), and announcement protocols used by applications to allow this negotiation to take place.
This document proposes the suspend/resume-oriented solution for the real-time encapsulation format part of the architecture. The general approach is to start from the PPP Multilink fragmentation protocol  and its multi-class extension  and add suspend/resume in a way that is as compatible to existing hard- and firmware as possible.
As an extension to the "best-effort" services the Internet is well- known for, additional types of services ("integrated services") that support the transport of real-time multimedia information are being developed for, and deployed in the Internet.
The present document defines the suspend/resume-oriented solution for the real-time encapsulation format part of the architecture. As described in more detail in the architecture document, a real-time encapsulation format is required as, e.g., a 1500 byte packet on a
Bormann Standards Track [Page 1]
RFC 2687 PPP in Real-time Oriented HDLC-like Framing September 1999
28.8 kbit/s modem link makes this link unavailable for the transmission of real-time information for about 400 ms. This adds a worst-case delay that causes real-time applications to operate with round-trip delays on the order of at least a second -- unacceptable for real-time conversation.
A true suspend/resume-oriented approach can only be implemented on a type-1 sender , but provides the best possible delay performance to this type of senders. The format defined in this document may also be of interest to certain type-2-senders that want to exploit the better bit-efficiency of this format as compared to . The format was designed so that it can be implemented by both type-1 and type-2 receivers.
1.1. Specification Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL"...