draft-ietf-taps-transports-01.txt   draft-ietf-taps-transports-02.txt 
Network Working Group G. Fairhurst, Ed. Network Working Group G. Fairhurst, Ed.
Internet-Draft University of Aberdeen Internet-Draft University of Aberdeen
Intended status: Informational B. Trammell, Ed. Intended status: Informational B. Trammell, Ed.
Expires: June 22, 2015 M. Kuehlewind, Ed. Expires: August 10, 2015 M. Kuehlewind, Ed.
ETH Zurich ETH Zurich
December 19, 2014 February 06, 2015
Services provided by IETF transport protocols and congestion control Services provided by IETF transport protocols and congestion control
mechanisms mechanisms
draft-ietf-taps-transports-01 draft-ietf-taps-transports-02
Abstract Abstract
This document describes services provided by existing IETF protocols This document describes services provided by existing IETF protocols
and congestion control mechanisms. It is designed to help and congestion control mechanisms. It is designed to help
application and network stack programmers and to inform the work of application and network stack programmers and to inform the work of
the IETF TAPS Working Group. the IETF TAPS Working Group.
Status of This Memo Status of This Memo
skipping to change at page 1, line 36 skipping to change at page 1, line 36
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on June 22, 2015. This Internet-Draft will expire on August 10, 2015.
Copyright Notice Copyright Notice
Copyright (c) 2014 IETF Trust and the persons identified as the Copyright (c) 2015 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
skipping to change at page 2, line 46 skipping to change at page 2, line 46
multiple stream, because it can accept blocks of data out of order, multiple stream, because it can accept blocks of data out of order,
UDP-Lite provides partial integrity protection, and LEDBAT can UDP-Lite provides partial integrity protection, and LEDBAT can
provide low-priority "scavenger" communication. provide low-priority "scavenger" communication.
2. Terminology 2. Terminology
The following terms are defined throughout this document, and in The following terms are defined throughout this document, and in
subsequent documents produced by TAPS describing the composition and subsequent documents produced by TAPS describing the composition and
decomposition of transport services. decomposition of transport services.
[Editor Note: The terminology below was presented at the TAPS WG [NOTE: The terminology below was presented at the TAPS WG meeting in
meeting in Honolulu. While the factoring of the terminology seems Honolulu. While the factoring of the terminology seems
uncontroversial, there may be some entities which still require names uncontroversial, there may be some entities which still require names
(e.g. information about the interface between the transport and lower (e.g. information about the interface between the transport and lower
layers which could lead to the availablity or unavailibility of layers which could lead to the availablity or unavailibility of
certain transport protocol features). Comments are welcome via the certain transport protocol features). Comments are welcome via the
TAPS mailing list.] TAPS mailing list.]
Transport Service Feature: a specific end-to-end feature that a Transport Service Feature: a specific end-to-end feature that a
transport service provides to its clients. Examples include transport service provides to its clients. Examples include
confidentiality, reliable delivery, ordered delivery, message- confidentiality, reliable delivery, ordered delivery, message-
versus-stream orientation, etc. versus-stream orientation, etc.
skipping to change at page 3, line 37 skipping to change at page 3, line 37
Application: an entity that uses the transport layer for end-to-end Application: an entity that uses the transport layer for end-to-end
delivery data across the network (this may also be an upper layer delivery data across the network (this may also be an upper layer
protocol or tunnel encpasulation). protocol or tunnel encpasulation).
3. Existing Transport Protocols 3. Existing Transport Protocols
This section provides a list of known IETF transport protocol and This section provides a list of known IETF transport protocol and
transport protocol frameworks. transport protocol frameworks.
[Editor Note: Contributions to the sections in the list below are [EDITOR'S NOTE: Contributions to the subsections below are welcome]
welcome]
3.1. Transport Control Protocol (TCP) 3.1. Transport Control Protocol (TCP)
TCP is an IETF standards track transport protocol. [RFC0793] TCP is an IETF standards track transport protocol. [RFC0793]
introduces TCP as follows: "The Transmission Control Protocol (TCP) introduces TCP as follows: "The Transmission Control Protocol (TCP)
is intended for use as a highly reliable host-to-host protocol is intended for use as a highly reliable host-to-host protocol
between hosts in packet-switched computer communication networks, and between hosts in packet-switched computer communication networks, and
in interconnected systems of such networks." Since its introduction, in interconnected systems of such networks." Since its introduction,
TCP has become the default connection-oriented, stream-based TCP has become the default connection-oriented, stream-based
transport protocol in the Internet. It is widely implemented by transport protocol in the Internet. It is widely implemented by
skipping to change at page 4, line 15 skipping to change at page 4, line 15
3.1.1. Protocol Description 3.1.1. Protocol Description
TCP is a connection-oriented protocol, providing a three way TCP is a connection-oriented protocol, providing a three way
handshake to allow a client and server to set up a connection, and handshake to allow a client and server to set up a connection, and
mechanisms for orderly completion and immediate teardown of a mechanisms for orderly completion and immediate teardown of a
connection. TCP is defined by a family of RFCs [RFC4614]. connection. TCP is defined by a family of RFCs [RFC4614].
TCP provides multiplexing to multiple sockets on each host using port TCP provides multiplexing to multiple sockets on each host using port
numbers. An active TCP session is identified by its four-tuple of numbers. An active TCP session is identified by its four-tuple of
local and remote IP addresses and local port and remote port numbers. local and remote IP addresses and local port and remote port numbers.
The destination port during connection setup has a different role as
it is often used to indicate the requested service.
TCP partitions a continuous stream of bytes into segments, sized to TCP partitions a continuous stream of bytes into segments, sized to
fit in IP packets, constrained by the maximum size of lower layer fit in IP packets. ICMP-based PathMTU discovery [RFC1191][RFC1981]
frame. PathMTU discovery is supported. Each byte in the stream is as well as Packetization Layer Path MTU Discovery (PMTUD) [RFC4821]
identified by a sequence number. The sequence number is used to are supported.
order segments on receipt, to identify segments in acknowledgments,
and to detect unacknowledged segments for retransmission. This is Each byte in the stream is identified by a sequence number. The
the basis of TCP's reliable, ordered delivery of data in a stream. sequence number is used to order segments on receipt, to identify
TCP Selective Acknowledgment [RFC2018] extends this mechanism by segments in acknowledgments, and to detect unacknowledged segments
making it possible to identify missing segments more precisely, for retransmission. This is the basis of TCP's reliable, ordered
reducing spurious retransmission. delivery of data in a stream. TCP Selective Acknowledgment [RFC2018]
extends this mechanism by making it possible to identify missing
segments more precisely, reducing spurious retransmission.
Receiver flow control is provided by a sliding window: limiting the Receiver flow control is provided by a sliding window: limiting the
amount of unacknowledged data that can be outstanding at a given amount of unacknowledged data that can be outstanding at a given
time. The window scale option [RFC7323] allows a receiver to use time. The window scale option [RFC7323] allows a receiver to use
windows greater than 64KB. windows greater than 64KB.
All TCP senders provide Congestion Control: This uses a separate All TCP senders provide Congestion Control: This uses a separate
window, where each time congestion is detected, this congestion window, where each time congestion is detected, this congestion
window is reduced. A receiver detects congestion using one of three window is reduced. A receiver detects congestion using one of three
mechanisms: A retransmission timer, loss (interpreted as a congestion mechanisms: A retransmission timer, detection of loss (interpreted as
signal), and Explicit Congestion Notification (ECN) [RFC3168] to a congestion signal), or Explicit Congestion Notification (ECN)
provide early signaling (see [I-D.ietf-aqm-ecn-benefits]) [RFC3168] to provide early signaling (see
[I-D.ietf-aqm-ecn-benefits])
A TCP protocol instance can be extended [RFC4614] and tuned. Some A TCP protocol instance can be extended [RFC4614] and tuned. Some
features are sender-side only, requiring no negotiation with the features are sender-side only, requiring no negotiation with the
receiver; some are receiver-side only, some are explicitly negotiated receiver; some are receiver-side only, some are explicitly negotiated
during connection setup. during connection setup.
By default, TCP segment partitioning uses Nagle's algorithm [RFC0896] By default, TCP segment partitioning uses Nagle's algorithm [RFC0896]
to buffer data at the sender into large segments, potentially to buffer data at the sender into large segments, potentially
incurring sender-side buffering delay; this algorithm can be disabled incurring sender-side buffering delay; this algorithm can be disabled
by the sender to transmit more immediately, e.g. to enable smoother by the sender to transmit more immediately, e.g. to enable smoother
interactive sessions. interactive sessions.
[EDITOR'S NOTE: add URGENT and PUSH flag (note [RFC6093] says SHOULD
NOT use due to the range of TCP implementations that process TCP
urgent indications differently.) ]
A checksum provides an Integrity Check and is mandatory across the
entire packet. The TCP checksum does not support partial corruption
protection as in DCCP/UDP-Lite). This check protects from
misdelivery of data corrupted data, but is relatively weak, and
applications that require end to end integrity of data are
recommended to include a stronger integrity check of their payload
data.
A TCP service is unicast. A TCP service is unicast.
3.1.2. Interface description 3.1.2. Interface description
A TCP API is defined in [REF], but there is currently no API A User/TCP Interface is defined in [RFC0793] providing six user
specified in the RFC series. commands: Open, Send, Receive, Close, Status. This interface does
not describe configuration of TCP options or parameters beside use of
the PUSH and URGENT flags.
In API implementations derived from the BSD Sockets API, TCP sockets In API implementations derived from the BSD Sockets API, TCP sockets
are created using the "SOCK_STREAM" socket type. are created using the "SOCK_STREAM" socket type.
The features used by a protocol instance may be set and tuned via The features used by a protocol instance may be set and tuned via
this API. this API.
(more on the API goes here) (more on the API goes here)
3.1.3. Transport Protocol Components 3.1.3. Transport Protocol Components
The transport protocol components provided by TCP are: The transport protocol components provided by TCP are:
o unicast o unicast
o connection-oriented setup with feature negotiation o connection setup with feature negotiation and application-to-port
mapping
o port multiplexing o port multiplexing
o reliable delivery o reliable delivery
o ordered delivery o ordered delivery for each byte stream
o segmented, stream-oriented delivery in a single stream o error detection (checksum)
o segmentation
o stream-oriented delivery in a single stream
o data bundling (Nagle's algorithm)
o flow control
o congestion control o congestion control
(discussion of how to map this to features and TAPS: what does the [EDITOR'S NOTE: discussion of how to map this to features and TAPS:
higher layer need to decide? what can the transport layer decide what does the higher layer need to decide? what can the transport
based on global settings? what must the transport layer decide based layer decide based on global settings? what must the transport layer
on network characteristics?) decide based on network characteristics?]
3.2. Multipath TCP (MP-TCP) 3.2. Multipath TCP (MP-TCP)
[Editor Note: a few sentences describing Multipath TCP [RFC6824] go [EDITOR'S NOTE: a few sentences describing Multipath TCP [RFC6824] go
here. Note that this adds transport-layer multihoming to the here. Note that this adds transport-layer multihoming to the
components TCP provides] components TCP provides]
3.3. Stream Control Transmission Protocol (SCTP) 3.3. Stream Control Transmission Protocol (SCTP)
SCTP [RFC4960] is an IETF standards track transport protocol that SCTP [RFC4960] is an IETF standards track transport protocol that
provides a bidirectional s set of logical unicast meessage streams provides a bidirectional set of logical unicast meessage streams over
over a connection-oriented protocol. The protocol and API use a connection-oriented protocol.
messages, rather than a byte-stream. Each stream of messages is Compared to TCP, this protocol and API use messages, rather than a
independently managed, therefore retransmission does not hold back byte-stream. Each stream of messages is independently managed,
data sent using other logical streams. therefore retransmission does not hold back data sent using other
logical streams.
An SCTP Integrity Check is mandatory across the entire packet (it
does not support partial corruption protection as in DCCP/UD-Lite).
The SCTP Partial Reliability Extension (SCTP-PR) is defined in The SCTP Partial Reliability Extension (SCTP-PR) is defined in
[RFC3758]. [RFC3758].
SCTP supports PLPMTU discovery using padding chunks to construct path
probes.
[EDITOR'S NOTE: Michael Tuexen and Karen Nielsen signed up as [EDITOR'S NOTE: Michael Tuexen and Karen Nielsen signed up as
contributors for these sections.] contributors for these sections.]
3.3.1. Protocol Description 3.3.1. Protocol Description
An SCTP service is unicast. An SCTP service is unicast.
PLPMTUD is required for SCTP.
3.3.2. Interface Description 3.3.2. Interface Description
The SCTP API is described in the specifications published in the RFC The SCTP API is described in the specifications published in the RFC
series. series.
3.3.3. Transport Protocol Components 3.3.3. Transport Protocol Components
The transport protocol components provided by SCTP are: The transport protocol components provided by SCTP are:
o unicast o unicast
o connection-oriented setup with feature negotiation o connection setup with feature negotiation and application-to-port
mapping
o port multiplexing o port multiplexing
o reliable or partially reliable delivery o reliable or partially reliable delivery
o ordered delivery within a stream o ordered delivery within a stream
o support for multiple prioritised streams o support for multiple prioritised streams
o flow control (slow receiver function)
o message-oriented delivery o message-oriented delivery
o congestion control o congestion control
[EDITOR'S NOTE: Please update list.] o application PDU bundling
o integrity check
[EDITOR'S NOTE: update this list.]
3.4. User Datagram Protocol (UDP) 3.4. User Datagram Protocol (UDP)
The User Datagram Protocol (UDP) [RFC0768] [RFC2460] is an IETF The User Datagram Protocol (UDP) [RFC0768] [RFC2460] is an IETF
standards track transport protocol. It provides a uni-directional standards track transport protocol. It provides a uni-directional
minimal message-passing transport that has no inherent congestion minimal message-passing transport that has no inherent congestion
control mechanisms or other transport functions. IETF guidance on control mechanisms or other transport functions. IETF guidance on
the use of UDP is provided in [RFC5405]. UDP is widely implemented the use of UDP is provided in [RFC5405]. UDP is widely implemented
by endpoints and widely used by common applications. by endpoints and widely used by common applications.
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UDP is a connection-less datagram protocol, with no connection setup UDP is a connection-less datagram protocol, with no connection setup
or feature negotiation. The protocol and API use messages, rather or feature negotiation. The protocol and API use messages, rather
than a byte-stream. Each stream of messages is independently than a byte-stream. Each stream of messages is independently
managed, therefore retransmission does not hold back data sent using managed, therefore retransmission does not hold back data sent using
other logical streams. other logical streams.
It provides multiplexing to multiple sockets on each host using port It provides multiplexing to multiple sockets on each host using port
numbers. An active UDP session is identified by its four-tuple of numbers. An active UDP session is identified by its four-tuple of
local and remote IP addresses and local port and remote port numbers. local and remote IP addresses and local port and remote port numbers.
UDP fragments packets into IP packets, constrained by the maximum UDP maps each data segement into an IP packet, or a sequence of IP
size of lower layer frame. fragemnts.
Mechanisms for receiver flow control, congestion control, PathMTU UDP is connectionless. However, applications send a sequence of
discovery, support for ECN, etc need to be provided by upper layer messages that constitute a UDP flow. Therefore mechanisms for
protocols [RFC5405]. receiver flow control, congestion control, PathMTU discovery/PLPMTUD,
support for ECN, etc need to be provided by upper layer protocols
[RFC5405].
PMTU discovery and PLPMTU discovery may be used by upper layer
protocols built on top of UDP [RFC5405].
For IPv4 the UDP checksum is optional, but recommended for use in the For IPv4 the UDP checksum is optional, but recommended for use in the
general Internet [RFC5405]. [RFC2460] requires the use of this general Internet [RFC5405]. [RFC2460] requires the use of this
checksum for IPv6, but [RFC6935] permits this to be relaxed for checksum for IPv6, but [RFC6935] permits this to be relaxed for
specific types of application. The checksum support considerations specific types of application. The checksum support considerations
for omitting the checksum are defined in [RFC6936]. for omitting the checksum are defined in [RFC6936].
This check protects from misdelivery of data corrupted data, but is
relatively weak, and applications that require end to end integrity
of data are recommended to include a stronger integrity check of
their payload data.
A UDP service may support IPv4 broadcast, multicast, anycast and A UDP service may support IPv4 broadcast, multicast, anycast and
unicast. unicast, determined by the IP destination address.
3.4.2. Interface Description 3.4.2. Interface Description
There is no current API specified in the RFC Series, but guidance on [RFC0768] describes basic requirements for an API for UDP. Guidance
use of common APIs is provided in [RFC5405]. on use of common APIs is provided in [RFC5405].
Many operating systems also allow a UDP socket to be connected, i.e.,
to bind a UDP socket to a specific pair of addresses and ports. This
is similar to the corresponding TCP sockets API functionality.
However, for UDP, this is only a local operation that serves to
simplify the local send/receive functions and to filter the traffic
for the specified addresses and ports [RFC5405].
3.4.3. Transport Protocol Components 3.4.3. Transport Protocol Components
The transport protocol components provided by UDP are: The transport protocol components provided by UDP are:
o unicast o unicast
o port multiplexing
o IPv4 broadcast, multicast and anycast o IPv4 broadcast, multicast and anycast
o non-reliable, non-ordered delivery o non-reliable delivery
o flow control (slow receiver function)
o non-ordered delivery
o message-oriented delivery o message-oriented delivery
o optional checksum protection. o optional checksum protection.
3.5. Lightweight User Datagram Protocol (UDP-Lite) 3.5. Lightweight User Datagram Protocol (UDP-Lite)
The Lightweight User Datagram Protocol (UDP-Lite) [RFC3828] is an The Lightweight User Datagram Protocol (UDP-Lite) [RFC3828] is an
IETF standards track transport protocol. UDP-Lite provides a IETF standards track transport protocol. UDP-Lite provides a
bidirectional set of logical unicast or multicast message streams bidirectional set of logical unicast or multicast message streams
over a datagram protocol. IETF guidance on the use of UDP-Lite is over a datagram protocol. IETF guidance on the use of UDP-Lite is
provided in [RFC5405]. provided in [RFC5405].
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bidirectional set of logical unicast or multicast message streams bidirectional set of logical unicast or multicast message streams
over a datagram protocol. IETF guidance on the use of UDP-Lite is over a datagram protocol. IETF guidance on the use of UDP-Lite is
provided in [RFC5405]. provided in [RFC5405].
[EDITOR'S NOTE: Gorry Fairhurst signed up as a contributor for this [EDITOR'S NOTE: Gorry Fairhurst signed up as a contributor for this
section.] section.]
3.5.1. Protocol Description 3.5.1. Protocol Description
UDP-Lite is a connection-less datagram protocol, with no connection UDP-Lite is a connection-less datagram protocol, with no connection
setup or feature negotiation. The protocol and API use messages, setup or feature negotiation. The protocol use messages, rather than
rather than a byte-stream. Each stream of messages is independently a byte-stream. Each stream of messages is independently managed,
managed, therefore retransmission does not hold back data sent using therefore retransmission does not hold back data sent using other
other logical streams. logical streams.
It provides multiplexing to multiple sockets on each host using port It provides multiplexing to multiple sockets on each host using port
numbers. An active UDP-Lite session is identified by its four-tuple numbers. An active UDP-Lite session is identified by its four-tuple
of local and remote IP addresses and local port and remote port of local and remote IP addresses and local port and remote port
numbers. numbers.
UDP-Lite fragments packets into IP packets, constrained by the UDP-Lite fragments packets into IP packets, constrained by the
maximum size of lower layer frame. maximum size of IP packet.
UDP-Lite changes the semantics of the UDP "payload length" field to UDP-Lite changes the semantics of the UDP "payload length" field to
that of a "checksum coverage length" field. Otherwise, UDP-Lite is that of a "checksum coverage length" field. Otherwise, UDP-Lite is
semantically identical to UDP. Applications using UDP-Lite therefore semantically identical to UDP. Applications using UDP-Lite therefore
can not make assumptions regarding the correctness of the data can not make assumptions regarding the correctness of the data
received in the insensitive part of the UDP-Lite payload. received in the insensitive part of the UDP-Lite payload.
As for UDP, mechanisms for receiver flow control, congestion control, As for UDP, mechanisms for receiver flow control, congestion control,
PathMTU discovery, support for ECN, etc need to be provided by upper PMTU or PLPMTU discovery, support for ECN, etc need to be provided by
layer protocols [RFC5405]. upper layer protocols [RFC5405].
Examples of use include a class of applications that can derive Examples of use include a class of applications that can derive
benefit from having partially-damaged payloads delivered, rather than benefit from having partially-damaged payloads delivered, rather than
discarded. One use is to support are tolerate payload corruption and discarded. One use is to support error tolerate payload corruption
over paths that include error-prone links, another application is when used over paths that include error-prone links, another
when header integrity checks are required but payload integrity is application is when header integrity checks are required, but payload
provided by some other mechanism (e.g. [RFC6936]. integrity is provided by some other mechanism (e.g. [RFC6936].
A UDP-Lite service may support IPv4 broadcast, multicast, anycast and A UDP-Lite service may support IPv4 broadcast, multicast, anycast and
unicast. unicast.
3.5.2. Interface Description 3.5.2. Interface Description
There is no current API specified in the RFC Series, but guidance on There is no current API specified in the RFC Series, but guidance on
use of common APIs is provided in [RFC5405]. use of common APIs is provided in [RFC5405].
The interface of UDP-Lite differs from that of UDP by the addition of The interface of UDP-Lite differs from that of UDP by the addition of
skipping to change at page 9, line 25 skipping to change at page 10, line 48
the application via the UDP-Lite MIB module [RFC5097]. the application via the UDP-Lite MIB module [RFC5097].
3.5.3. Transport Protocol Components 3.5.3. Transport Protocol Components
The transport protocol components provided by UDP-Lite are: The transport protocol components provided by UDP-Lite are:
o unicast o unicast
o IPv4 broadcast, multicast and anycast o IPv4 broadcast, multicast and anycast
o port multiplexing
o non-reliable, non-ordered delivery o non-reliable, non-ordered delivery
o message-oriented delivery o message-oriented delivery
o partial integrity protection o partial integrity protection
3.6. Datagram Congestion Control Protocol (DCCP) 3.6. Datagram Congestion Control Protocol (DCCP)
Datagram Congestion Control Protocol (DCCP) [RFC4340] is an IETF Datagram Congestion Control Protocol (DCCP) [RFC4340] is an IETF
standards track bidirectional transport protocol that provides standards track bidirectional transport protocol that provides
unicast connections of congestion-controlled unreliable messages. 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 trade off between
timeliness and reliability [RFC4336].
[EDITOR'S NOTE: Gorry Fairhurst signed up as a contributor for this [EDITOR'S NOTE: Gorry Fairhurst signed up as a contributor for this
section.] section.]
The DCCP Problem Statement describes the goals that DCCP sought to
address [RFC4336]. It is suitable for applications that transfer
fairly large amounts of data and that can benefit from control over
the trade off between timeliness and reliability [RFC4336].
It offers low overhead, and many characteristics common to UDP, but
can avoid "Re-inventing the wheel" each time a new multimedia
application emerges. Specifically it includes core functions
(feature negotiation, path state management, RTT calculation, PMTUD,
etc): This allows applications to use a compatible method defining
how they send packets and where suitable to choose common algorithms
to manage their functions. Examples of suitable applications include
interactive applications, streaming media or on-line games [RFC4336].
3.6.1. Protocol Description 3.6.1. Protocol Description
DCCP is a connection-oriented datagram protocol, providing a three DCCP is a connection-oriented datagram protocol, providing a three
way handshake to allow a client and server to set up a connection, way handshake to allow a client and server to set up a connection,
and mechanisms for orderly completion and immediate teardown of a and mechanisms for orderly completion and immediate teardown of a
connection. The protocol is defined by a family of RFCs. connection. The protocol is defined by a family of RFCs.
It provides multiplexing to multiple sockets on each host using port It provides multiplexing to multiple sockets on each host using port
numbers. An active DCCP session is identified by its four-tuple of numbers. An active DCCP session is identified by its four-tuple of
local and remote IP addresses and local port and remote port numbers. local and remote IP addresses and local port and remote port numbers.
skipping to change at page 10, line 4 skipping to change at page 11, line 39
3.6.1. Protocol Description 3.6.1. Protocol Description
DCCP is a connection-oriented datagram protocol, providing a three DCCP is a connection-oriented datagram protocol, providing a three
way handshake to allow a client and server to set up a connection, way handshake to allow a client and server to set up a connection,
and mechanisms for orderly completion and immediate teardown of a and mechanisms for orderly completion and immediate teardown of a
connection. The protocol is defined by a family of RFCs. connection. The protocol is defined by a family of RFCs.
It provides multiplexing to multiple sockets on each host using port It provides multiplexing to multiple sockets on each host using port
numbers. An active DCCP session is identified by its four-tuple of numbers. An active DCCP session is identified by its four-tuple of
local and remote IP addresses and local port and remote port numbers. local and remote IP addresses and local port and remote port numbers.
At connection setup, DCCP also exchanges the the service code At connection setup, DCCP also exchanges the the service code
[RFC5595] mechanism to allow transport instantiations to indicate the [RFC5595] mechanism to allow transport instantiations to indicate the
service treatment that is expected from the network. service treatment that is expected from the network.
The protocol segments data into messages, sized to fit in IP packets, The protocol segments data into messages, typically sized to fit in
constrained by the maximum size of lower layer frame. Each message IP packets, but which may be fragemented providing they are less than
is identified by a sequence number. The sequence number is used to the A DCCP interface MAY allow applications to request fragmentation
identify segments in acknowledgments, to detect unacknowledged for packets larger than PMTU, but not larger than the maximum packet
segments, to measure RTT, etc. The protocol may support ordered or size allowed by the current congestion control mechanism (CCMPS)
unordered delivery of data, and does not itself provide [RFC4340].
retransmission.
Each message is identified by a sequence number. The sequence number
is used to identify segments in acknowledgments, to detect
unacknowledged segments, to measure RTT, etc. The protocol may
support ordered or unordered delivery of data, and does not itself
provide retransmission. There is a Data Checksum option, which
contains a strong CRC, lets endpoints detect application data
corruption. It also supports reduced checksum coverage, a partial
integrity mechanisms similar to UDP-lIte.
Receiver flow control is supported: limiting the amount of Receiver flow control is supported: limiting the amount of
unacknowledged data that can be outstanding at a given time. unacknowledged data that can be outstanding at a given time.
A DCCP protocol instance can be extended [RFC4340] and tuned. Some A DCCP protocol instance can be extended [RFC4340] and tuned. Some
features are sender-side only, requiring no negotiation with the features are sender-side only, requiring no negotiation with the
receiver; some are receiver-side only, some are explicitly negotiated receiver; some are receiver-side only, some are explicitly negotiated
during connection setup. during connection setup.
DCCP supports negotiation of the congestion control profile, examples DCCP supports negotiation of the congestion control profile, to
of specified profiles include [RFC4341] [RFC4342] [RFC5662]. All provide Plug and Play congestion control mechanisms. examples of
IETF-defined methods provide Congestion Control. specified profiles include [RFC4341] [RFC4342] [RFC5662]. All IETF-
defined methods provide Congestion Control.
Examples of suitable applications include interactive applications, DCCP use a Connect packet to start a session, and permits half-
streaming media or on-line games [RFC4336]. connections that allow each client to choose features it wishes to
support. Simultaneous open [RFC5596], as in TCP, can enable
interoperability in the presence of middleboxes. The Connect packet
includes a Service Code field [RFC5595] designed to allow middle
boxes and endpoints to identify the characteristics required by a
session. A lightweight UDP-based encapsulation (DCCP-UDP) has been
defined [RFC6773] that permits DCCP to be used over paths where it is
not natively supported. Support in NAPT/NATs is defined in [RFC4340]
and [RFC5595].
Upper layer protocols specified on top of DCCP include: DTLS
[RFC5595], RTP [RFC5672], ICE/SDP [RFC6773].
A DCCP service is unicast. A DCCP service is unicast.
A common packet format has allowed tools to evolve that can read and
interpret DCCP packets (e.g. Wireshark).
3.6.2. Interface Description 3.6.2. Interface Description
API charactersitics include: - Datagram transmission. - Notification
of the current maximum packet size. - Send and reception of zero-
length payloads. - Set the Slow Receiver flow control at areceiver.
- Detct a Slow receiver at the sender.
There is no current API specified in the RFC Series. There is no current API specified in the RFC Series.
3.6.3. Transport Protocol Components 3.6.3. Transport Protocol Components
The transport protocol components provided by DCCP are: The transport protocol components provided by DCCP are:
o unicast o unicast
o connection-oriented setup o connection setup with feature negotiation and application-to-port
mapping
o feature negotiation o Service Codes
o port multiplexing
o non-reliable, ordered delivery o non-reliable, ordered delivery
o flow control (slow receiver function)
o drop notification
o timestamps
o message-oriented delivery o message-oriented delivery
o partial integrity protection o partial integrity protection
3.7. Realtime Transport Protocol (RTP) 3.7. Realtime Transport Protocol (RTP)
RTP provides an end-to-end network transport service, suitable for RTP provides an end-to-end network transport service, suitable for
applications transmitting real-time data, such as audio, video or applications transmitting real-time data, such as audio, video or
data, over multicast or unicast network services, including TCP, UDP, data, over multicast or unicast network services, including TCP, UDP,
UDP-Lite, DCCP. UDP-Lite, DCCP.
[EDITOR'S NOTE: Varun Singh signed up as contributor for this [EDITOR'S NOTE: Varun Singh signed up as contributor for this
section.] section.]
3.8. Transport Layer Security (TLS) and Datagram TLS (DTLS) as a 3.8. Transport Layer Security (TLS) and Datagram TLS (DTLS) as a
pseudotransport pseudo transport
(A few words on TLS [RFC5246] and DTLS [RFC6347] here, and how they [NOTE: A few words on TLS [RFC5246] and DTLS [RFC6347] here, and how
get used by other protocols to meet security goals as an add-on they get used by other protocols to meet security goals as an add-on
interlayer above transport.) interlayer above transport.]
3.8.1. Protocol Description 3.8.1. Protocol Description
3.8.2. Interface Description 3.8.2. Interface Description
3.8.3. Transport Protocol Components 3.8.3. Transport Protocol Components
3.9. Hypertext Transport Protocol (HTTP) as a pseudotransport 3.9. Hypertext Transport Protocol (HTTP) as a pseudotransport
[RFC3205] [RFC3205]
[EDITOR'S NOTE: No identified contributor for this section yet.]
3.9.1. Protocol Description 3.9.1. Protocol Description
3.9.2. Interface Description 3.9.2. Interface Description
3.9.3. Transport Protocol Components 3.9.3. Transport Protocol Components
3.10. WebSockets 3.10. WebSockets
[RFC6455] [RFC6455]
[EDITOR'S NOTE: No identified contributor for this section yet.]
3.10.1. Protocol Description 3.10.1. Protocol Description
3.10.2. Interface Description 3.10.2. Interface Description
3.10.3. Transport Protocol Components 3.10.3. Transport Protocol Components
4. Transport Service Features 4. Transport Service Features
(drawn from the candidate features provided by protocol components in [EDITOR'S NOTE: this section will drawn from the candidate features
the previous section - please discussion on list) provided by protocol components in the previous section - please
discuss on taps@ietf.org list]
4.1. Complete Protocol Feature Matrix 4.1. Complete Protocol Feature Matrix
(a comprehensive matrix table goes here; Volunteer: Dave Thaler) [EDITOR'S NOTE: Dave Thaler has signed up as a contributor for this
section. Michael Welzl also has a beginning of a matrix which could
be useful here.]
[EDITOR'S NOTE: The below is a strawman proposal below by Gorry
Fairhurst for initial discussion]
The table below summarises protocol mechanisms that have been
standardised. It does not make an assessment on whether specific
implementations are fully compliant to these specifications.
+-----------------+---------+---------+---------+---------+---------+
| Mechanism | UDP | UDP-L | DCCP | SCTP | TCP |
+-----------------+---------+---------+---------+---------+---------+
| Unicast | Yes | Yes | Yes | Yes | Yes |
| | | | | | |
| Mcast/IPv4Bcast | Yes(2) | Yes | No | No | No |
| | | | | | |
| Port Mux | Yes | Yes | Yes | Yes | Yes |
| | | | | | |
| Mode | Dgram | Dgram | Dgram | Stream | Stream |
| | | | | | |
| Connected | No | No | Yes | Yes | Yes |
| | | | | | |
| Data bundling | No | No | No | No | Yes |
| | | | | | |
| Feature Nego | No | No | Yes | Yes | Yes |
| | | | | | |
| Options | No | No | Support | Support | Support |
| | | | | | |
| Data priority | * | * | * | Yes | No |
| | | | | | |
| Data bundling | No | No | No | No | Yes |
| | | | | | |
| Reliability | None | None | None | Select | Full |
| | | | | | |
| Ordered deliv | No | No | No | Stream | Yes |
| | | | | | |
| Corruption Tol. | No | Support | Support | No | No |
| | | | | | |
| Flow Control | No | No | Support | Yes | Yes |
| | | | | | |
| PMTU/PLPMTU | (1) | (1) | Yes | Yes | Yes |
| | | | | | |
| Cong Control | (1) | (1) | Yes | Yes | Yes |
| | | | | | |
| ECN Support | (1) | (1) | Yes | No | Yes |
| | | | | | |
| NAT support | Limited | Limited | Support | TBD | Support |
| | | | | | |
| Security | DTLS | DTLS | DTLS | DTLS | TLS, AO |
| | | | | | |
| UDP encaps | N/A | None | Yes | Yes | None |
| | | | | | |
| RTP support | Support | Support | Support | ? | Support |
+-----------------+---------+---------+---------+---------+---------+
Note (1): this feature requires support in an upper layer protocol.
Note (2): this feature requires support in an upper layer protocol
when used with IPv6.
5. IANA Considerations 5. IANA Considerations
This document has no considerations for IANA. This document has no considerations for IANA.
6. Security Considerations 6. Security Considerations
This document surveys existing transport protocols and protocols This document surveys existing transport protocols and protocols
providing transport-like services. Confidentiality, integrity, and providing transport-like services. Confidentiality, integrity, and
authenticity are among the features provided by those services. This authenticity are among the features provided by those services. This
document does not specify any new components or mechanisms for document does not specify any new components or mechanisms for
providing these features. Each RFC listed in this document discusses providing these features. Each RFC listed in this document discusses
the security considerations of the specification it contains. the security considerations of the specification it contains.
7. Contributors 7. Contributors
Non-editor contributors of text will be listed here, as in the [EDITOR'S NOTE: Non-editor contributors of text will be listed here,
authors section. as noted in the authors section.]
8. Acknowledgments 8. Acknowledgments
This work is partially supported by the European Commission under This work is partially supported by the European Commission under
grant agreement FP7-ICT-318627 mPlane; support does not imply grant agreement FP7-ICT-318627 mPlane; support does not imply
endorsement. endorsement.
9. References 9. References
9.1. Normative References 9.1. Normative References
skipping to change at page 13, line 11 skipping to change at page 17, line 5
[RFC0793] Postel, J., "Transmission Control Protocol", STD 7, RFC [RFC0793] Postel, J., "Transmission Control Protocol", STD 7, RFC
793, September 1981. 793, September 1981.
[RFC0896] Nagle, J., "Congestion control in IP/TCP internetworks", [RFC0896] Nagle, J., "Congestion control in IP/TCP internetworks",
RFC 896, January 1984. RFC 896, January 1984.
[RFC1122] Braden, R., "Requirements for Internet Hosts - [RFC1122] Braden, R., "Requirements for Internet Hosts -
Communication Layers", STD 3, RFC 1122, October 1989. Communication Layers", STD 3, RFC 1122, October 1989.
[RFC1191] Mogul, J. and S. Deering, "Path MTU discovery", RFC 1191,
November 1990.
[RFC1981] McCann, J., Deering, S., and J. Mogul, "Path MTU Discovery
for IP version 6", RFC 1981, August 1996.
[RFC2018] Mathis, M., Mahdavi, J., Floyd, S., and A. Romanow, "TCP [RFC2018] Mathis, M., Mahdavi, J., Floyd, S., and A. Romanow, "TCP
Selective Acknowledgment Options", RFC 2018, October 1996. Selective Acknowledgment Options", RFC 2018, October 1996.
[RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6 [RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", RFC 2460, December 1998. (IPv6) Specification", RFC 2460, December 1998.
[RFC3168] Ramakrishnan, K., Floyd, S., and D. Black, "The Addition [RFC3168] Ramakrishnan, K., Floyd, S., and D. Black, "The Addition
of Explicit Congestion Notification (ECN) to IP", RFC of Explicit Congestion Notification (ECN) to IP", RFC
3168, September 2001. 3168, September 2001.
skipping to change at page 14, line 9 skipping to change at page 18, line 9
[RFC4342] Floyd, S., Kohler, E., and J. Padhye, "Profile for [RFC4342] Floyd, S., Kohler, E., and J. Padhye, "Profile for
Datagram Congestion Control Protocol (DCCP) Congestion Datagram Congestion Control Protocol (DCCP) Congestion
Control ID 3: TCP-Friendly Rate Control (TFRC)", RFC 4342, Control ID 3: TCP-Friendly Rate Control (TFRC)", RFC 4342,
March 2006. March 2006.
[RFC4614] Duke, M., Braden, R., Eddy, W., and E. Blanton, "A Roadmap [RFC4614] Duke, M., Braden, R., Eddy, W., and E. Blanton, "A Roadmap
for Transmission Control Protocol (TCP) Specification for Transmission Control Protocol (TCP) Specification
Documents", RFC 4614, September 2006. Documents", RFC 4614, September 2006.
[RFC4821] Mathis, M. and J. Heffner, "Packetization Layer Path MTU
Discovery", RFC 4821, March 2007.
[RFC4960] Stewart, R., "Stream Control Transmission Protocol", RFC [RFC4960] Stewart, R., "Stream Control Transmission Protocol", RFC
4960, September 2007. 4960, September 2007.
[RFC5097] Renker, G. and G. Fairhurst, "MIB for the UDP-Lite [RFC5097] Renker, G. and G. Fairhurst, "MIB for the UDP-Lite
protocol", RFC 5097, January 2008. protocol", RFC 5097, January 2008.
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246, August 2008. (TLS) Protocol Version 1.2", RFC 5246, August 2008.
[RFC5348] Floyd, S., Handley, M., Padhye, J., and J. Widmer, "TCP [RFC5348] Floyd, S., Handley, M., Padhye, J., and J. Widmer, "TCP
Friendly Rate Control (TFRC): Protocol Specification", RFC Friendly Rate Control (TFRC): Protocol Specification", RFC
5348, September 2008. 5348, September 2008.
[RFC5405] Eggert, L. and G. Fairhurst, "Unicast UDP Usage Guidelines [RFC5405] Eggert, L. and G. Fairhurst, "Unicast UDP Usage Guidelines
for Application Designers", BCP 145, RFC 5405, November for Application Designers", BCP 145, RFC 5405, November
2008. 2008.
[RFC5595] Fairhurst, G., "The Datagram Congestion Control Protocol [RFC5595] Fairhurst, G., "The Datagram Congestion Control Protocol
(DCCP) Service Codes", RFC 5595, September 2009. (DCCP) Service Codes", RFC 5595, September 2009.
[RFC5596] Fairhurst, G., "Datagram Congestion Control Protocol
(DCCP) Simultaneous-Open Technique to Facilitate NAT/
Middlebox Traversal", RFC 5596, September 2009.
[RFC5662] Shepler, S., Eisler, M., and D. Noveck, "Network File [RFC5662] Shepler, S., Eisler, M., and D. Noveck, "Network File
System (NFS) Version 4 Minor Version 1 External Data System (NFS) Version 4 Minor Version 1 External Data
Representation Standard (XDR) Description", RFC 5662, Representation Standard (XDR) Description", RFC 5662,
January 2010. January 2010.
[RFC5672] Crocker, D., "RFC 4871 DomainKeys Identified Mail (DKIM)
Signatures -- Update", RFC 5672, August 2009.
[RFC6773] Phelan, T., Fairhurst, G., and C. Perkins, "DCCP-UDP: A
Datagram Congestion Control Protocol UDP Encapsulation for
NAT Traversal", RFC 6773, November 2012.
[RFC5925] Touch, J., Mankin, A., and R. Bonica, "The TCP [RFC5925] Touch, J., Mankin, A., and R. Bonica, "The TCP
Authentication Option", RFC 5925, June 2010. Authentication Option", RFC 5925, June 2010.
[RFC5681] Allman, M., Paxson, V., and E. Blanton, "TCP Congestion [RFC5681] Allman, M., Paxson, V., and E. Blanton, "TCP Congestion
Control", RFC 5681, September 2009. Control", RFC 5681, September 2009.
[RFC6093] Gont, F. and A. Yourtchenko, "On the Implementation of the [RFC6093] Gont, F. and A. Yourtchenko, "On the Implementation of the
TCP Urgent Mechanism", RFC 6093, January 2011. TCP Urgent Mechanism", RFC 6093, January 2011.
[RFC6298] Paxson, V., Allman, M., Chu, J., and M. Sargent, [RFC6298] Paxson, V., Allman, M., Chu, J., and M. Sargent,
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