Internet DRAFT - draft-fairhurst-taps-transports
draft-fairhurst-taps-transports
Network Working Group G. Fairhurst
Internet-Draft University of Aberdeen
Intended status: Informational B. Trammell
Expires: April 30, 2015 ETH Zurich
October 27, 2014
Services provided by IETF transport protocols and congestion control
mechanisms
draft-fairhurst-taps-transports-00
Abstract
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.
Status of This Memo
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This Internet-Draft will expire on April 30, 2015.
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Copyright (c) 2014 IETF Trust and the persons identified as the
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
1. Introduction
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.
2. Terminology
This section presents the terminology used in this document.
[EDITOR'S NOTE: Terminology to be discussed in Honolulu. We need to
determine what a "service" as used by the IETF, as opposed to a
"service component", "property", an "aspect", "dimension", etc.]
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3. Transport Protocols
This section provides a list of known IETF transport protocol and
transport protocol frameworks.
[EDITOR'S NOTE: combine these tables into one? Also, reorder them to
match ths sections below.]
+---------+-------------------------------------+------+---------------------+
| Section | Benefit | Setup| Mode |
+---------+-------------------------------------+------+---------------------+
| 3.1 | Transmission Control Protocol (TCP) | CO | Unicast |
| 3.1.1 | Multipath-TCP (MPTCP) | CO | Unicast |
| 3.2 | SCTP | CO | Unicast |
| 3.2.1 | SCTP-PR | CO | Unicast |
| 3.3 | User Datagram Protocol (UDP) | DG | Unicast/Multicst |
| 3.4 | UDP-Lite | DG | Unicast/Multicst |
| 3.5 | DCCP | CO | Unicast |
| 3.X | More as needed | | |
+---------+-------------------------------------+------+---------------------+
Table 1: Key IETF Transport Protocol - by cmmunication mode
+---------+-------------------------------------+------+---------------------+
| Section | Benefit | Style| Reliability |
+---------+-------------------------------------+------+---------------------+
| 3.1 | Transmission Control Protocol (TCP) | Str | Ordered Byte Stream |
| 3.1.1 | Multipath-TCP (MPTCP) | Str | Ordered Byte Stream |
| 3.2 | SCTP | Mess | Message Streams |
| 3.2.1 | SCTP-PR | Mess | Partial M Streams |
| 3.3 | User Datagram Protocol (UDP) | Mess | Datagram Message |
| 3.4 | UDP-Lite | Mess | Error Tolerant DG |
| 3.5 | DCCP | Mess | Unrel Message Stream|
| 3.X | More as needed | | |
+---------+-------------------------------------+------+---------------------+
Table 2: Key IETF Transport Protocol - by reliability
"Setup" defines whether the protocol performs a connection-oriented
protocol handshake prior o communication or is datagram based. This
provides reliable negotiation of options, including negotiation of a
suitable congestion control mechanism.This property can impact the
ability of the protocol to traverse firewalls.
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+---------+-------------------------------------+----------------------------+
| Section | Benefit | Congestion Control |
+---------+-------------------------------------+----------------------------+
| 3.1 | Transmission Control Protocol (TCP) | Yes |
| 3.1.1 | Multipath-TCP (MPTCP) | Yes (Multipath) |
| 3.2 | SCTP | Yes |
| 3.2.1 | SCTP-PR | Yes |
| 3.3 | User Datagram Protocol (UDP) | At application layer |
| 3.4 | UDP-Lite | At application layer |
| 3.5 | DCCP | Yes, Various CCIDs defined |
| 3.X | More as needed | |
+---------+-------------------------------------+----------------------------+
Table 3: Key IETF Transport Protocol - by congestion control
Some other protocol frameworks that may potentially be considered for
inclusion in future versions of this document. Examples are:
o Multicast - RMT
o RTP-based methods
o HTTP-based methods
o TLS
o DTLS
The following subsections describes each of these transports.
3.1. Transport Control Protocol (TCP)
TCP provides a bidirectional byte-oriented stream over a connection-
oriented protocol. The protocol and API use the byte-stream model.
[EDITOR'S NOTE: Describe the aspects(?) of TCP: reliable, connection-
oriented, congestion-controlled, single-stream-oriented, non-
boundary-preserving... Note that we want to describe the
characteristics of the SOCK_STREAM API as well as just the wire
protocol.]
3.1.1. Multipath TCP (MPTCP)
[EDITOR'S NOTE: aspects of MPTCP beyond TCP.]
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3.2. Stream Control Transmission Protocol (SCTP)
This section will describe SCTP.
SCTP 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
3.2.1. Partial Reliability SCTP (PR-CTP)
SCTP-PR [RFC3758] is a variant of SCTP that provides partial
reliability.
3.3. User Datagram Protocol (UDP)
The User Datagram Protocol (UDP) 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: Describe the aspects(?) of UDP: unreliable,
congestion control to be applied above the transport, datagram-
oriented, connectionless, boundary-preserving... Note that we want to
describe the characteristics of the SOCK_DGRAM API as well as just
the wire protocol.]
Using UDP robustly requires each application to implement a raft of
functions (mostly re-inventing or adaptng mechansism already found in
TCP, SCTP and DCCP). [EDITOR'S NOTE: reference RFC 5405/bis ]
3.4. UDP-Lite
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 (UDP-Lite) The service may be multicast and/or
unicast
[EDITOR'S NOTE: compare to UDP]
[RFC3828] and [RFC 5405/bis]
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3.5. Datagram Congestion Control Protocl (DCCP)
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.
[EDITOR'S NOTE: Describe the aspects(?) of DCCP...]
[FC4340 et al]
3.6. Realtime Transport Protocol (RTP)
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: Describe the aspects(?) of RTP...]
3.7. Hypertext Transport Protocol (HTTP) as a pseudotransport
HTTP provides end-to-end network unicast transport service.
[EDITOR'S NOTE: Reference BCP 56, note that this implies TCP but also
brings with it object semantics you may not want.]
3.7.1. WebSockets
[EDITOR'S NOTE: point out how websockets kind of fixes this.]
4. Transport service components
Aspects as derived from the subsections above.
This section is blank for now.
5. Acknowledgements
The authors were part-funded by the European Community under its
Seventh Framework Programme. The views expressed are solely those of
the authors.
Comments are welcome to the authors or via the IETF TAPS mailing
lists.
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6. IANA Considerations
XXX RFC ED - PLEASE REMOVE THIS SECTION XXX
This memo includes no request to IANA.
7. Security Considerations
This document introduces no new security considerations. Each RFC
listed in this document discusses the security considerations of the
specification it contains.
8. References
8.1. Normative References
[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.
8.2. Informative References
[RFC0768] Postel, J., "User Datagram Protocol", STD 6, RFC 768,
August 1980.
[RFC0793] Postel, J., "Transmission Control Protocol", STD 7, RFC
793, September 1981.
[RFC0896] Nagle, J., "Congestion control in IP/TCP internetworks",
RFC 896, January 1984.
[RFC4340] Kohler, E., Handley, M., and S. Floyd, "Datagram
Congestion Control Protocol (DCCP)", RFC 4340, March 2006.
[RFC4960] Stewart, R., "Stream Control Transmission Protocol", RFC
4960, September 2007.
[RFC5348] Floyd, S., Handley, M., Padhye, J., and J. Widmer, "TCP
Friendly Rate Control (TFRC): Protocol Specification", RFC
5348, September 2008.
[RFC5405] Eggert, L. and G. Fairhurst, "Unicast UDP Usage Guidelines
for Application Designers", BCP 145, RFC 5405, November
2008.
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Authors' Addresses
Godred Fairhurst
University of Aberdeen
School of Engineering, Fraser Noble Building
Aberdeen AB24 3UE
UK
Email: gorry@erg.abdn.ac.uk
Brian Trammell
ETH Zurich
Gloriastrasse 35
Zurich 8092
CH
Email: ietf@trammell.ch
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