| Network Working Group | G. Fairhurst, Ed. |
| Internet-Draft | University of Aberdeen |
| Intended status: Informational | B. Trammell, Ed. |
| Expires: June 18, 2015 | ETH Zurich |
| December 15, 2014 |
Services provided by IETF transport protocols and congestion control mechanisms
draft-ietf-taps-transports-00
This document describes services provided by existing IETF protocols and congestion control mechanisms. It is designed to help application and network stack programmers and to inform the work of the IETF TAPS Working Group.
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Most Internet applications make use of the Transport Services provided by TCP (a reliable, in-order stream protocol) or UDP (an unreliable datagram protocol). We use the term “Transport Service” to mean an end-to-end facility provided by the transport layer. That service can only be provided correctly if information is supplied from the application. The application may determine the information to be supplied at design time, compile time, or run time and may include guidance on whether an aspect of the service is required, a preference by the application, or something in between. Examples of Transport service facilities are reliable delivery, ordered delivery, content privacy to in-path devices, integrity protection, and minimal latency.
Transport protocols such as SCTP, DCCP, MPTCP, UDP and UDP-Lite have been defined at the transport layer.
In addition, a transport service may be built on top of these transport protocols, using a fraemwork such as WebSockets, or RTP. Service built on top of UDP or UDP-Lite typically also need to specify a congestion control mechanism, such as TFRC or the LEDBAT congestion control mechanism. This extends the set of available Transport Services beyond those provided to applications by TCP and UDP.
Transport services can aslo be differentiated by the services they provide: for instance, SCTP offers a message-based service that does not suffer head-of-line blocking when used with multiple stream, because it can accept blocks of data out of order, UDP-Lite provides partial integrity protection when used over link-layer services that can support this, and LEDBAT can provide low-priority “scavenger” communication.
The following terms are defined throughout this document, and in subsequent documents produced by TAPS describing the composition and decomposition of transport services.
The terminology below is that as was presented at the TAPS WG meeting in Honolulu. While the factoring of the terminology seems uncontroversial, thre may be some entities which still require names (e.g. information about the interface between the transport and lower layers which could lead to the availablity or unavailibility of certain transport protocol features)
This section provides a list of known IETF transport protocol and transport protocol frameworks.
TCP [RFC0793] provides a bidirectional byte-oriented stream over a connection- oriented protocol. The protocol and API use the byte-stream model.
[EDITOR’S NOTE: Mirja Kuehlewind signed up as contributor for this section.]
SCTP [RFC4960] provides a bidirectional set of logical unicast streams over one a connection-oriented protocol. The protocol and API use messages, rather than a byte-stream. Each stream of messages is independently managed, therefore retransmission does not hold back data sent using other logical streams.
[EDITOR’S NOTE: Michael Tuexen and Karen Nielsen signed up as contributors for these sections.]
PR-SCTP [RFC3758] is a variant of SCTP that provides partial reliability.
The User Datagram Protocol (UDP) [RFC0768] provides a unidirectional minimal message-passing transport that has no inherent congestion control mechanisms. The service may be multicast and/or unicast.
[EDITOR’S NOTE: Kevin Fall signed up as contributor for this section.]
A special class of applications can derive benefit from having partially-damaged payloads delivered, rather than discarded, when using paths that include error-prone links. Such applications can tolerate payload corruption and may choose to use the Lightweight User Datagram Protocol [RFC3828]. The service may be multicast and/or unicast.
The Datagram Congestion Control Protocol (DCCP) [RFC4340] is a bidirectional transport protocol that provides unicast connections of congestion-controlled unreliable messages. DCCP is suitable for applications that transfer fairly large amounts of data and that can benefit from control over the tradeoff between timeliness and reliability.
RTP provides an end-to-end network transport service, suitable for applications transmitting real-time data, such as audio, video or data, over multicast or unicast network services, including TCP, UDP, UDP-Lite, DCCP.
[EDITOR’S NOTE: Varun Singh signed up as contributor for this section.]
Features as derived from the subsections above.
This section is blank for now.
This document has no considerations for IANA.
This document surveys existing transport protocols and protocols providing transport-like services. Confidentiality, integrity, and authenticity are among the features provided by those services. This document does not specify any new components or mechanisms for providing these features. Each RFC listed in this document discusses the security considerations of the specification it contains.
Non-editor contributors of text will be listed here, as in the authors section.
This work is partially supported by the European Commission under grant agreement FP7-ICT-318627 mPlane; support does not imply endorsement. Special thanks to Mirja Kuehlewind for the terminology section and for leading the terminology discussion in Honolulu.
| [RFC0791] | Postel, J., "Internet Protocol", STD 5, RFC 791, September 1981. |
| [RFC2460] | Deering, S. and R. Hinden, "Internet Protocol, Version 6 (IPv6) Specification", RFC 2460, December 1998. |