Features of the User Datagram Protocol (UDP) and Lightweight UDP (UDP- Lite) Transport Protocols
draft-fairhurst-taps-transports-usage-udp-00
The information below is for an old version of the document.
| Document | Type |
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|---|---|---|---|
| Authors | Gorry Fairhurst , Tom Jones | ||
| Last updated | 2016-02-23 | ||
| Replaced by | draft-ietf-taps-transports-usage-udp, RFC 8304 | ||
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draft-fairhurst-taps-transports-usage-udp-00
Internet Engineering Task Force G. Fairhurst
Internet-Draft T. Jones
Intended status: Informational University of Aberdeen
Expires: August 26, 2016 February 23, 2016
Features of the User Datagram Protocol (UDP) and Lightweight UDP (UDP-
Lite) Transport Protocols
draft-fairhurst-taps-transports-usage-udp-00
Abstract
This document describes how the User Datagram Protocol (UDP) and the
Lightweight User Datagram Protocol (UDP-Lite) transport protocols
expose services to applications and how an application can configure
and use the features offered by the transport service. The document
is intended as a contribution to the TAPS working group to assist in
analysis of the UDP and UDP-Lite transport interface.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on August 26, 2016.
Copyright Notice
Copyright (c) 2016 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
3. Pass 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3.1. Primitives Provided by UDP . . . . . . . . . . . . . . . 4
3.1.1. Excluded Primitives . . . . . . . . . . . . . . . . . 8
3.2. Primitives Provided by UDP-Lite . . . . . . . . . . . . . 8
4. Pass 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
4.1. CONNECTION-Related Primitives . . . . . . . . . . . . . . 9
4.2. DATA Related Primitives . . . . . . . . . . . . . . . . . 12
5. Pass 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
5.1. CONNECTION-Related Transport Service Features . . . . . . 13
5.2. DATA Transfer Related Transport Service Features . . . . 14
5.2.1. Sending Data . . . . . . . . . . . . . . . . . . . . 14
5.2.2. Receiving Data . . . . . . . . . . . . . . . . . . . 15
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 15
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15
8. Security Considerations . . . . . . . . . . . . . . . . . . . 15
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 15
9.1. Normative References . . . . . . . . . . . . . . . . . . 15
9.2. Informative References . . . . . . . . . . . . . . . . . 17
Appendix A. Revision Notes . . . . . . . . . . . . . . . . . . . 18
Appendix B. Notes Based on Typical Usage . . . . . . . . . . . . 18
Appendix C. UDP Multicast . . . . . . . . . . . . . . . . . . . 19
C.1. Multicast Primitives . . . . . . . . . . . . . . . . . . 19
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 21
1. Terminology
This document uses common terminology defined in
[I-D.ietf-taps-transports-usage]. This document also refers to the
terminology of [RFC2119], but does not itself define new terms using
this terminology.
2. Introduction
This document presents defined interactions between transport
protocols and applications in the form of 'primitives' (function
calls). Primitives can be invoked by an application or a transport
protocol; the latter type is called an "event". The list of
transport service features and primitives in this document is
strictly based on the parts of protocol specifications that relate to
what the protocol provides to an application using it and how the
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application interacts with it. It does not cover parts of a protocol
that are explicitly stated as optional to implement.
This follows the methodology defined in
[I-D.ietf-taps-transports-usage], specifically:
"The document presents a three-pass process to arrive at a list of
transport service features.
In the first pass, the relevant RFC text is discussed for each
protocol.
In the second pass, this discussion is used to derive a list of
primitives that are uniformly categorized across protocols. Here,
an attempt is made to present or -- where text describing
primitives does not yet exist -- construct primitives in a
slightly generalized form to highlight similarities. This is, for
example, achieved by renaming primitives of protocols or by
avoiding a strict 1:1-mapping between the primitives in the
protocol specification and primitives in the list.
Finally, the third pass presents transport service features based
on pass 2, identifying which protocols implement them. In the
list resulting from the second pass, some transport service
features are missing because they are implicit in some protocols,
and they only become explicit when we consider the superset of all
features offered by all protocols. For example, TCP's reliability
includes integrity via a checksum, but we have to include a
protocol like UDP-Lite as specified in [RFC3828] (which has a
configurable checksum) in the list before we can consider an
always-on checksum as a transport service feature. Similar
arguments apply to other protocol functions (e.g., congestion
control).
The complete list of features across all protocols is therefore
only available after pass 3.
3. Pass 1
This first iteration summarizes the relevant text parts of the RFCs
describing the UDP and UDP-Lite protocols, focusing on what the
transport protocols provide to the application and how the transport
is used (based on abstract API descriptions, where they are
available).
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3.1. Primitives Provided by UDP
The User Datagram Protocol (UDP) [RFC0768] States: "This User
Datagram Protocol (UDP) is defined to make available a datagram mode
of packet-switched computer communication in the environment of an
interconnected set of computer networks." It "provides a procedure
for application programs to send messages to other programs with a
minimum of protocol mechanism (..)".
The User Interface section of [RFC0768] specifies that the user
interface to an application should be able to create receive ports,
source and destination ports and addresses, and provide operations to
receive data based on ports with an indication of source port and
address. Operations should be provided that allows datagrams be sent
specifying the source and destination ports and addresses to be sent.
UDP for IPv6 is defined by [RFC2460], and API extensions to support
this in [RFC3493]. [RFC6935] and [RFC6936] defines an update to the
UDP transport specified in RFC 2460. This enables use of a zero UDP
checksum mode with a tunnel protocol, providing that the method
satisfies the requirements in [RFC6936].
UDP offers only a basic transport interface. UDP datagrams may be
directly sent and received, without any connection setup. Using the
sockets API, applications can receive packets from more than one IP
source address on a single UDP socket. It does not provide
congestion control, retransmission, nor support to optimise
fragmentation etc. This means that applications using UDP need to
provide additional functions on top of the UDP transport API. This
requires parameters to be passed through the API and complicates the
analysis of the API.
[I-D.ietf-tsvwg-rfc5405bis] also states "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. Binding a UDP socket does not establish a
connection - UDP does not notify the remote end when a local UDP
socket is bound. Binding a socket also allows configuring options
that affect the UDP or IP layers, for example, use of the UDP
checksum or the IP Timestamp option. On some stacks, a bound socket
also allows an application to be notified when ICMP error messages
are received for its transmissions [RFC1122]."
Guidance on the use of services provided by UDP is provided in
[I-D.ietf-tsvwg-rfc5405bis].
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The following primitives are specified:
CONNECT: The CONNECT primitive allows the association of source and
port sets to a socket to enable creation of a 'connection' for UDP
traffic. This UDP connection allows an application to be notified
of errors received from the network stack and provides a shorthand
access to the send and receive primitives. Since UDP is itself
connectionless, no datagrams are sent because this primitive is
executed. A further connect call can be used to change the
association to a source/port pair.
SEND: The SEND primitive hands over a provided number of bytes that
UDP should send to the other side of a UDP connection in a UDP
datagram. The primitive can be used by an application to directly
send datagrams to an endpoint defined by an address/port pair. If
a connection has been created, then the address/port pair is
inferred from the current connection for the socket. A connection
created on the socket will allow network errors to be returned to
the application as a notification on the send primitive. Messages
passed to the send primitive that cannot be sent atomically in a
datagram will not be sent by the network layer, generating an
error.
RECEIVE: The RECEIVE primitive allocates a receiving buffer to
accommodate a received datagram. The primitive returns the number
of bytes provided from a received UDP datagram. Section 4.1.3.5
of [RFC1122] states "When a UDP datagram is received, its
specific-destination address MUST be passed up to the application
layer."
DISABLE_CHECKSUM: The CHECKSUM function controls the optional usage
of UDP checksums for sending datagrams. [RFC0768] and IPv6
[RFC6935] [RFC6936] [I-D.ietf-tsvwg-rfc5405bis]. When set it
overrides the default UDP behaviour disabling the checksum on
sending. Section 4.1.3.4 of [RFC1122] states "An application MAY
optionally be able to control whether a UDP checksum will be
generated, but it MUST default to checksumming on."
SET_IP_OPTIONS: The SET_IP_OPTIONS function enables a datagram to be
sent with the specified IP options. Section 4.1.3.2 of[RFC1122]
states that an "application MUST be able to specify IP options to
be sent in its UDP datagrams, and UDP MUST pass these options to
the IP layer."
GET_IP_OPTIONS: The GET_IP_OPTIONS function enables a receiver to
read the IP options of a received datagram. Section 4.1.3.2
of[RFC1122] states that a UDP receiver "MUST pass any IP option
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that it receives from the IP layer transparently to the
application layer".
SET_DF: The SET_DF function sets the Don't Fragment (DF) flag to be
used in the field of an IP header of a packet that carries a UDP
datagram. A UDP application should implement a method that avoids
IP fragmentation ( section 4 of [I-D.ietf-tsvwg-rfc5405bis]). It
can use Packetization-Layer-Path MTU Discovery (PLPMTUD) [RFC4821]
or Path MTU Discovery [RFC1191].
GET_INTERFACE_MTU: The GET_INTERFACE_MTU function indicates the
largest unfragmented IP packet that may be sent. A UDP endpoint
can subtract the size of all network and transport headers to
determine the maximum size of unfragmented UDP payload. UDP
applications should use this value as part of a method to avoid
sending UDP datagrams that would result in IP packets that exceed
the effective path maximum transmission unit (PMTU) allowed on the
network path. The effective PMTU specified in Section 1 of
[RFC1191] is equivalent to the "effective MTU for sending"
specified in [RFC1122]. [RFC4821] states: "If PLPMTUD updates the
MTU for a particular path, all Packetization Layer sessions that
share the path representation (as described in Section 5.2) SHOULD
be notified to make use of the new MTU and make the required
congestion control adjustments."
SET_TTL: The SET_TTL function sets the hop limit (TTL field) to be
used in the field of an IPv4 header of a packet that carries an
UDP datagram. This is used to limit the scope of unicast
datagrams. Section 3.2.2.4 of [RFC1122] states an "incoming Time
Exceeded message MUST be passed to the transport layer".
GET_TTL: The GET_TTL function reads the value of the TTL field from
the IPv4 header of a received UDP datagram. Section 3.2.2.4 of
[RFC1122] states that a UDP receiver "MAY pass the received TOS up
to the application layer" When used for applications such as the
Generalized TTL Security Mechanism (GTSM) [RFC5082], this needs
the UDP receiver API to pass the received value of this field to
the application.
SET_IPV6_UNICAST_HOPS: The SET_IPV6_UNICAST_HOPS function sets the
hop limit field to be used in the field of an IPv4 header of a
packet that carries an UDP datagram. For IPv6 unicast datagrams,
this is functionally equivalent to the SET_TTL IPv4 function.
GET_IPV6_UNICAST_HOPS: The GET_IPV6_UNICAST_HOPS function reads the
value from the hop count field in the IPv6 header of a received
UDP datagram. For IPv6 unicast datagrams, this is functionally
equivalent to GET_TTL IPv4 function.
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SET_DSCP: The SET_DSCP function sets the DSCP (or legacy TOS) value
to be used in the field of an IP header of a packet that carries a
UDP Datagram. Section 2.4 of [RFC1123] states that "Applications
MUST select appropriate TOS values when they invoke transport
layer services, and these values MUST be configurable.". The
application should be able to change the TOS during the connection
lifetime, and the TOS value should be passed to the IP layer
unchanged. Section 4.1.4 of [RFC1122] also states that on
reception the "UDP MAY pass the received TOS value up to the
application layer". [RFC2475] [RFC3260] replaces this field in
the IP Header assigning the six most significant bits to carry the
Differentiated Services Code Point (DSCP) field. Preserving the
intention of [RFC1122] to allow the application to specify the
"Type of Service", this should be interpreted to mean that an API
should allow the application to set the DSCP. Section 3.1.6 of
[I-D.ietf-tsvwg-rfc5405bis] describes the way UDP applications
should use this field. Normally a UDP socket will assign a single
DSCP value to all Datagrams in a flow, but it is allowed to use
different DSCP values for datagrams within the same flow in some
cases, as described in [I-D.ietf-tsvwg-rfc5405bis].
SET_ECN: The SET_ECN function sets the ECN field in the IP Header of
a UDP Datagram. When use of the TOS field was redefined
[RFC3260], 2 bits of the field were assigned to support Explicit
Congestion Notification (ECN) [RFC3168]. Section 3.1.5
[I-D.ietf-tsvwg-rfc5405bis] describes the way UDP applications
should use this field.
GET_ECN: The GET_ECN function returns the value of the ECN field in
the IP Header of a received UDP Datagram. Section 3.1.5
[I-D.ietf-tsvwg-rfc5405bis] states that a UDP receiver "MUST check
the ECN field at the receiver for each UDP datagram that it
receives on this port", requiring the UDP receiver API to pass to
pass the received ECN field up to the application layer to enable
appropriate congestion feedback.
ERROR_REPORT The ERROR_REPORT event informs an application of "soft
errors", including the arrival of an ICMP or ICMPv6 error message.
Section 4.1.4 of [RFC1122] states "UDP MUST pass to the
application layer all ICMP error messages that it receives from
the IP layer." For example, this event is required to implement
ICMP-based Path MTU Discovery [RFC1191] [RFC1981].
CLOSE: The close primitive closes a connection. No further
datagrams may be sent/received. Since UDP is itself
connectionless, no datagrams are sent because this command is
executed.
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3.1.1. Excluded Primitives
Section 3.4 of [RFC1122] also describes "GET_MAXSIZES: - replaced,
GET_SRCADDR (Section 3.3.4.3) and ADVISE_DELIVPROB:". These
mechanisms are no longer used. It also specifies use of the Source
Quench ICMP message, which has since been deprecated [RFC6633]. The
IPV6_V6ONLY function defined in Section 5.3 of [RFC3493] restricts
the use of information from the name resolver to only allow
communication of AF_INET6 sockets to use IPv6 only. This is not
considered part of the transport service.
3.2. Primitives Provided by UDP-Lite
The Lightweight User Datagram Protocol (UDP-Lite) [RFC3828] provides
similar services to UDP. It changed the semantics of the UDP
"payload length" field to that of a "checksum coverage length" field.
UDP-Lite requires the pseudo-header checksum to be computed at the
sender and checked at a receiver. Otherwise, UDP-Lite is
semantically identical to UDP.
The sending interface of UDP-Lite differs from that of UDP by the
addition of a single (socket) option that communicates the checksum
coverage length. This specifies the intended checksum coverage, with
the remaining unprotected part of the payload called the "error-
insensitive part".
The receiving interface of UDP-Lite differs from that of UDP by the
addition of a single (socket) option that specifies the minimum
acceptable checksum coverage.
The UDP-Lite MIB further defines the checksum coverage method
[RFC5097]. Guidance on the use of services provided by UDP-Lite is
provided in [I-D.ietf-tsvwg-rfc5405bis].
UDP-Lite requires use of the UDP or UDP-Lite checksum, and hence
"Checksum Enable" function is not permitted. All other primitives
and functions for UDP are permitted, in addition the following are
defined:
SET_CHECKSUM_COVERAGE: The SET_CHECKSUM_COVERAGE function sets the
coverage area for a sent datagram. UDP-Lite traffic uses this
primitive to set the coverage length provided by the UDP checksum.
Section 3.3 of [RFC5097] states that "Applications that wish to
define the payload as partially insensitive to bit errors ...
should do this by an explicit system call on the sender side."
The default is to provide the same coverage as for UDP.
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SET_MIN_COVERAGE The SET_MIN_COVERAGE function sets the minimum
acceptable coverage protection for received datagrams. UDP-Lite
traffic uses this primitive to set the coverage length that is
checked on receive (section 1.1 of [RFC5097] describes the
corresponding MIB entry as udpliteEndpointMinCoverage).
Section 3.3 of [RFC3828] states that "applications that wish to
receive payloads that were only partially covered by a checksum
should inform the receiving system by an explicit system call".
The default is to require only minimal coverage of the datagram
payload.
4. Pass 2
Here we categorize the services from pass 1 based on whether they
relate to a connection or to data transmission. Services are
presented following the nomenclature
"CATEGORY.[SUBCATEGORY].SERVICENAME.PROTOCOL". We present
"connection" as a general protocol-independent concept and use it to
refer to UDP and UDP-Lite connections (identifiable by a unique
socket pair, where a socket is defined as an IP address and port).
We define the "transport address" as "the combination of an IP
address, transport protocol and the port number used by the transport
protocol". The "application" is the user of the protocol
[I-D.ietf-tsvwg-rfc5405bis].
4.1. CONNECTION-Related Primitives
ESTABLISHMENT: Active creation of a connection from one transport
address to one or more transport addresses.
Interfaces to UDP and UDP-Lite allow both connection-oriented and
connection-less usage of the API [I-D.ietf-tsvwg-rfc5405bis].
o CONNECT.UDP:
Pass 1 primitive event: 'connect' followed by 'send'.
Parameters: 1 local IP address (optional); 1 destination transport
address.
Comments: Associates a transport address creating a UDP socket
connection. This can be called again with a new transport address
to create a new connection. The CONNECT function allows an
application to receive errors from messages sent to a transport
address.
o CONNECT.UDP-Lite:
Pass 1 primitive event: 'connect' followed by 'send'.
Parameters: 1 local IP address (optional); 1 destination transport
address.
Comments: Associates the transport address creating a UDP-Lite
socket connection. This can be called again with a new transport
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address to create a new connection. The CONNECT function allows
an application to receive errors from messages sent to a transport
address.
AVAILABILITY
o LISTEN.UDP:
Pass 1 primitive: 'receive'.
Parameters: 1 local IP address (optional); 1 destination transport
address.
Comments: The receive function registers the application to listen
for in-coming UDP datagrams at an endpoint.
o LISTEN.UDP-Lite:
Pass 1 primitive: 'receive'
Parameters: 1 local IP address (optional); 1 destination transport
address.
Comments: The receive function registers the application to listen
for in-coming UDP-Lite datagrams at an endpoint.
MAINTENANCE
o CHECKSUM.UDP:
pass 1 primitive event: 'send' or 'connect' followed by 'send'.
Parameter: 0 when no checksum is used, 1 for checksum (default).
Comments: Only possible for UDP.
o SET_CHECKSUM_COVERAGE.UDP-Lite:
Parameters: Coverage length at sender (default maximum coverage)
Comments: Only possible for UDP-Lite.
o SET_MIN_CHECKSUM_COVERAGE.UDP-Lite:
Parameter: Coverage length at receiver (default minimum coverage)
Comments: Only possible for UDP-Lite.
o SET_DF.UDP:
Pass 1 primitive event: 'send' or 'open' followed by 'send'.
Parameter: 0 when DF is not set (default), 1 when DF is set.
o SET_DF.UDP-Lite:
Pass 1 primitive event: 'send' or 'open' followed by 'send'.
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Parameter: 0 when DF is not set (default), 1 when DF is set.
o GET_INTERFACE_MTU
Pass 1 primitive / event: GET_INTERFACE_MTU
Parameters: MTU value set at sending interface.
Comments: This allows an application to determine the local MTU
for sending.
o SET_TTL.UDP (IPV6_UNICAST_HOPS):
Pass 1 primitive / event: SET_TTL/IPV6_UNICAST_HOPS
Parameter: IPv4 TTL value or IPv6 Hop Count value
Comments: This allows an application to change the IPv4 TTL of
IPv6 Hop count value for outgoing UDP datagrams.
o SET_TTL.UDP-Lite (IPV6_UNICAST_HOPS):
Pass 1 primitive / event: TTL/IPV6_UNICAST_HOPS
Parameter: IPv4 TTL value or IPv6 Hop Count value
Comments: This allows an application to change the IPv4 TTL of
IPv6 Hop count value for outgoing UDP datagrams.
o SET_DSCP.UDP:
Parameter: DSCP value
Comments: This allows a UDP application to change the DSCP value
for outgoing UDP datagrams.
o SET_DSCP.UDP-Lite:
Parameter: DSCP value
Comments: This allows a UDP-Lite application to change the DSCP
value.
o ERROR.UDP:
Pass 1 primitive event: 'ERROR_REPORT'.
Parameters: Error report
Comments: This returns soft errors that may be ignored without
harm by many applications; An application must connect to be able
receive these notifications.
o ERROR.UDP-Lite:
Pass 1 primitive event: 'ERROR_REPORT'.
Parameters: Error report
Comments: This returns soft errors that may be ignored without
harm by many applications; An application must connect to be able
receive these notifications.
TERMINATION
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o CLOSE.UDP:
Pass 1 primitive event: Close
Comments: No further UDP datagrams are sent/received.
o CLOSE.UDP-Lite:
Pass 1 primitive event: Close
Comments: No further UDP-Lite datagrams are sent/received.
4.2. DATA Related Primitives
All functions in this section refer to an existing connection, i.e.
a connection that was either established or made available for
receiving data. In addition to the listed parameters, all sending
commands contain a reference to a data block and all receiving
commands contain a reference to available buffer space for the data.
o SEND.UDP:
Pass 1 primitive / event: 'send'
Parameters: IP Address and Port Number of the destination endpoint
(optional if connected).
Comments: This provides a message for unreliable transmission
using UDP to the specified transport address. IP address and Port
may be omitted for connected UDP sockets.
o SEND.UDP-Lite:
Pass 1 primitive / event: 'send'
Parameters: IP Address and Port Number of the destination endpoint
(optional if connected).
Comments: This provides a message for unreliable transmission
using UDP-Lite to the specified transport address. IP address and
Port may be omitted for connected UDP sockets.
o RECEIVE.UDP:
Pass 1 primitive / event: 'receive'
Parameters: Buffer for received datagram.
Comments: The datagram received TTL/Hop count field, received ECN
field, and IP options can be read per message on receive.
o RECEIVE.UDP-Lite:
Pass 1 primitive / event: 'receive'
Parameters: Buffer for received datagram.
Comments: The datagram received TTL/Hop count field, received ECN
field, and IP options can be read per message on receive.
o SEND_FAILURE.UDP:
Pass 1 primitive / event: 'send'
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Comment: This may be used to probe effective PMTU when using in
combination with the 'set-DF' function.
o SEND_FAILURE.UDP-Lite:
Pass 1 primitive / event: 'send'
Comment: This may be used to probe effective PMTU when using in
combination with the 'set-DF' function.
5. Pass 3
This section presents the superset of all transport service features
in all protocols that were discussed in the preceding sections, based
on the list of primitives in pass 2, but also on text in pass 1 to
include features that can be configured in one protocol and are
static properties in another. Some minor details are omitted for the
sake of generalization.
[AUTHOR'S NOTE: the list here looks pretty similar to the list in
pass 2 for now. This will change as more protocols are integrated.
For example, when we merge with TCP and SCTP. In pass 3, we can
derive "no congestion control" as a transport service feature of UDP;
however, since it would be strange to call the lack of congestion
control a feature, the natural outcome is then to list "congestion
control" as a feature of TCP and SCTP.]
5.1. CONNECTION-Related Transport Service Features
ESTABLISHMENT:
Active creation of a connection from one transport endpoint to one or
more transport endpoints.
AVAILABILITY:
Prepare to receive incoming requests
o Listen, 1 specified interface
Protocols: UDP, UDP-Lite
o Listen, N specified interfaces
Protocols: UDP, UDP-Lite
o Listen, All local interfaces (unspecified)
Protocols: UDP, UDP-Lite
MAINTENANCE:
Make adjustments to an open connection or notifications from the
connection.
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o Specify IP options
Protocols: UDP, UDP-Lite
o Specify Checksum enabled
Protocols: UDP
o Specify Checksum_Coverage
Protocols: UDP-Lite
o Specify Checksum_Coverage
Protocols: UDP-Lite
o Specify DF field
Protocols: UDP, UDP-Lite
o Specify TTL/Hop count field
Protocols: UDP, UDP-Lite
o Specify DSCP Field
Protocols: UDP, UDP-Lite
o Specify ECN field
Protocols: UDP, UDP-Lite
5.2. DATA Transfer Related Transport Service Features
All features in the this section relate to DATA.SEND and DATA.RECEIVE
in Pass 2.
5.2.1. Sending Data
All features in this section are provided by DATA.SEND from pass 2.
DATA.SEND is given a data block from the application, which we here
call a "message".
o Send data
Protocols: UDP, UDP-Lite
o Send data on a connection
Protocols: UDP, UDP-Lite
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5.2.2. Receiving Data
All features in this section are provided by DATA.RECEIVE from pass
2. DATA.RECEIVE is given a data block from the application, which we
here call a "message".
o Receive data
Protocols: UDP, UDP-Lite
o Receive data on a connection
Protocols: UDP, UDP-Lite
6. Acknowledgements
This work was partially funded by the European Union's Horizon 2020
research and innovation programme under grant agreement No. 644334
(NEAT). The views expressed are solely those of the author(s).
7. IANA Considerations
This memo includes no request to IANA.
If there are no requirements for IANA, the section will be removed
during conversion into an RFC by the RFC Editor.
8. Security Considerations
Security considerations for the use of UDP and UDP-Lire are provided
in the referenced RFCs. Security guidance for application usage is
provide in the UDP-Guidelines [I-D.ietf-tsvwg-rfc5405bis].
9. References
9.1. Normative References
[I-D.ietf-taps-transports-usage]
Welzl, M., Tuexen, M., and N. Khademi, "On the Usage of
Transport Service Features Provided by IETF Transport
Protocols", draft-ietf-taps-transports-usage-00 (work in
progress), January 2016.
[RFC0768] Postel, J., "User Datagram Protocol", STD 6, RFC 768,
DOI 10.17487/RFC0768, August 1980,
<http://www.rfc-editor.org/info/rfc768>.
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[RFC1122] Braden, R., Ed., "Requirements for Internet Hosts -
Communication Layers", STD 3, RFC 1122,
DOI 10.17487/RFC1122, October 1989,
<http://www.rfc-editor.org/info/rfc1122>.
[RFC1123] Braden, R., Ed., "Requirements for Internet Hosts -
Application and Support", STD 3, RFC 1123,
DOI 10.17487/RFC1123, October 1989,
<http://www.rfc-editor.org/info/rfc1123>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", RFC 2460, DOI 10.17487/RFC2460,
December 1998, <http://www.rfc-editor.org/info/rfc2460>.
[RFC2553] Gilligan, R., Thomson, S., Bound, J., and W. Stevens,
"Basic Socket Interface Extensions for IPv6", RFC 2553,
DOI 10.17487/RFC2553, March 1999,
<http://www.rfc-editor.org/info/rfc2553>.
[RFC3168] Ramakrishnan, K., Floyd, S., and D. Black, "The Addition
of Explicit Congestion Notification (ECN) to IP",
RFC 3168, DOI 10.17487/RFC3168, September 2001,
<http://www.rfc-editor.org/info/rfc3168>.
[RFC3493] Gilligan, R., Thomson, S., Bound, J., McCann, J., and W.
Stevens, "Basic Socket Interface Extensions for IPv6",
RFC 3493, DOI 10.17487/RFC3493, February 2003,
<http://www.rfc-editor.org/info/rfc3493>.
[RFC3828] Larzon, L-A., Degermark, M., Pink, S., Jonsson, L-E., Ed.,
and G. Fairhurst, Ed., "The Lightweight User Datagram
Protocol (UDP-Lite)", RFC 3828, DOI 10.17487/RFC3828, July
2004, <http://www.rfc-editor.org/info/rfc3828>.
[RFC6935] Eubanks, M., Chimento, P., and M. Westerlund, "IPv6 and
UDP Checksums for Tunneled Packets", RFC 6935,
DOI 10.17487/RFC6935, April 2013,
<http://www.rfc-editor.org/info/rfc6935>.
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9.2. Informative References
[I-D.ietf-tsvwg-rfc5405bis]
Eggert, L., Fairhurst, G., and G. Shepherd, "UDP Usage
Guidelines", draft-ietf-tsvwg-rfc5405bis-07 (work in
progress), November 2015.
[POSIX] "IEEE Std. 1003.1-2001, , "Standard for Information
Technology - Portable Operating System Interface (POSIX)",
Open Group Technical Standard: Base Specifications Issue
6, ISO/IEC 9945:2002", December 2001.
[RFC1191] Mogul, J. and S. Deering, "Path MTU discovery", RFC 1191,
DOI 10.17487/RFC1191, November 1990,
<http://www.rfc-editor.org/info/rfc1191>.
[RFC1981] McCann, J., Deering, S., and J. Mogul, "Path MTU Discovery
for IP version 6", RFC 1981, DOI 10.17487/RFC1981, August
1996, <http://www.rfc-editor.org/info/rfc1981>.
[RFC2475] Blake, S., Black, D., Carlson, M., Davies, E., Wang, Z.,
and W. Weiss, "An Architecture for Differentiated
Services", RFC 2475, DOI 10.17487/RFC2475, December 1998,
<http://www.rfc-editor.org/info/rfc2475>.
[RFC3260] Grossman, D., "New Terminology and Clarifications for
Diffserv", RFC 3260, DOI 10.17487/RFC3260, April 2002,
<http://www.rfc-editor.org/info/rfc3260>.
[RFC3678] Thaler, D., Fenner, B., and B. Quinn, "Socket Interface
Extensions for Multicast Source Filters", RFC 3678,
DOI 10.17487/RFC3678, January 2004,
<http://www.rfc-editor.org/info/rfc3678>.
[RFC4821] Mathis, M. and J. Heffner, "Packetization Layer Path MTU
Discovery", RFC 4821, DOI 10.17487/RFC4821, March 2007,
<http://www.rfc-editor.org/info/rfc4821>.
[RFC5082] Gill, V., Heasley, J., Meyer, D., Savola, P., Ed., and C.
Pignataro, "The Generalized TTL Security Mechanism
(GTSM)", RFC 5082, DOI 10.17487/RFC5082, October 2007,
<http://www.rfc-editor.org/info/rfc5082>.
[RFC5097] Renker, G. and G. Fairhurst, "MIB for the UDP-Lite
protocol", RFC 5097, DOI 10.17487/RFC5097, January 2008,
<http://www.rfc-editor.org/info/rfc5097>.
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[RFC6633] Gont, F., "Deprecation of ICMP Source Quench Messages",
RFC 6633, DOI 10.17487/RFC6633, May 2012,
<http://www.rfc-editor.org/info/rfc6633>.
[RFC6936] Fairhurst, G. and M. Westerlund, "Applicability Statement
for the Use of IPv6 UDP Datagrams with Zero Checksums",
RFC 6936, DOI 10.17487/RFC6936, April 2013,
<http://www.rfc-editor.org/info/rfc6936>.
[STEVENS] "Stevens, W., Fenner, B., and A. Rudoff, "UNIX Network
Programming, The sockets Networking API", Addison-
Wesley.", 2004.
Appendix A. Revision Notes
Note to RFC-Editor: please remove this entire section prior to
publication.
Individual draft -00:
o This is the first version. Comments and corrections are welcome
directly to the authors or via the IETF TAPS working group mailing
list.
Appendix B. Notes Based on Typical Usage
This appendix contains notes to assist in a later revision.
The de facto standard application programming interface (API) for
TCP/IP applications is the "sockets" interface[POSIX]. Some
platforms also offer applications the ability to directly assemble
and transmit IP packets through "raw sockets" or similar facilities.
This is a second, more cumbersome method of using UDP. The use of
this API is discussed in the RFC series in
[I-D.ietf-tsvwg-rfc5405bis].
The UDP sockets API differs from that for TCP in several key ways.
Because application programmers are typically more familiar with the
TCP sockets API, this section discusses these differences. [STEVENS]
provides usage examples of the UDP sockets API.
This section provides notes on some topics relating to implemented
UDP APIs.
A UDP application can use the recv() and send() POSIX functions as
well as the recvfrom() and sendto() and recvmsg and sendmsg()
functions.
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SO_REUSEADDR specifies that the rules used in validating addresses
supplied to bind() should allow reuse of local addresses.
SO_REUSEPORT specifies that the rules used in validating ports
supplied to bind() should allow reuse of a local port
Accessing TTL From applications: If the IP_RECVTTL option is enabled
on a SOCK_DGRAM socket, the recvmsg(2) call will return the IP TTL
(time to live) field for a UDP datagram. The msg_control field in
the msghdr structure points to a buffer that contains a cmsghdr
structure followed by the TTL.
Appendix C. UDP Multicast
UDP and UDP-Lite Multicast may be considered in later versions of
this document. This appendix contains notes to assist in this later
revision.
A host must request the ability to broadcast before it can send/
receive ipv4 broadcast traffic. A host must become a member of a
multicast group before it can receive datagrams sent to the group.
C.1. Multicast Primitives
UDP and UDP-Lite support IPv4 broadcast and IPv4/IPv6 Multicast. Use
of multicast requires additional functions at the transport API that
must be called to coordinate operation of the IPv4 and IPv6 network
layer protocols.
Guidance on the use of UDP and UDP-Lite for multicast services is
provided in [I-D.ietf-tsvwg-rfc5405bis].
The following are defined:
JoinLocalGroup: 1 of [RFC3493] provides a function that allows
joining of a local IPv4 multicast group.
IPV6_MULTICAST_IF: Section 5.2 of [RFC2553] states that this sets
the interface to use for outgoing multicast packets.
IP_MULTICAST_TTL: This sets the hop limit to use for outgoing
multicast packets. This is used to limit scope of multicast
datagrams. When used for applications such as GSTM, this needs
the UDP receiver API to pass the received value of this field to
the application. (This is equivalent to IPV6_MULTICAST_HOPS for
IPv6 multicast and TTL/IPV6_UNICAST_HOPS for unicast datagrams).
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IPV6_MULTICAST_HOPS: Section 5.2 of [RFC2553] states that this sets
the hop limit to use for outgoing multicast packets. When used
for applications such as GSTM, this needs the UDP receiver API to
pass the received value of this field to the application. (This
is equivalent to IP_MULTICAST_TTL for IPv4 multicast and TTL/
IPV6_UNICAST_HOPS for unicast datagrams).
IPV6_MULTICAST_LOOP: Section 5.2 of [RFC2553] states that this sets
whether a copy of a datagram is looped back by the IP layer for
local delivery when the datagram is sent to a group to which the
sending host itself belongs).
IPV6_JOIN_GROUP: Section 5.2 of [RFC2553] provides a function that
allows joining of an IPv6 multicast group.
SIOCGIPMSFILTER: Section 8.1 of [RFC0768] provides a function that
allows reading the multicast source filters.
SIOCSIPMSFILTER: Section 8.1 of [RFC0768] provides a function that
allows setting/modifying the multicast source filters.
IPV6_LEAVE_GROUP: Section 5.2 of [RFC2553] provides a function that
allows leaving of a multicast group.
LeaveHostGroup: Section 7.1 of [RFC3493] provides a function that
allows joining of an IPv4 multicast group.
LeaveLocalGroup: Section 7.1 of [RFC3493] provides a function that
allows joining of a local IPv4 multicast group.
Section 4.1.1 of [RFC3678] updates the interface to add support for
IGMPv3 with Any Source Multicast (ASM) using IPv4:
P_ADD_MEMBERSHIP: This is used to join an ASM group.
IP_BLOCK_SOURCE: This is used to leave an ASM group.
IP_UNBLOCK_SOURCE: This can be used to block data from a given
source to a given group.
IP_DROP_MEMBERSHIP: This can be used to undo a previous call to
IP_UNBLOCK_SOURCE.
Section 4.1.2 of [RFC3678] updates the interface to add support for
IGMPv3 with Any Source Multicast (ASM) using IPv4:
IP_ADD_SOURCE_MEMBERSHIP: This is used to join an SSM group.
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IP_DROP_SOURCE_MEMBERSHIP: This is used to leave an SSM group.
IP_DROP_MEMBERSHIP: This is supported, as a convenience, to drop all
sources which have been joined for a particular group and
interface. The operations are the same as if the socket had been
closed.
Authors' Addresses
Godred Fairhurst
University of Aberdeen
School of Engineering
Fraser Noble Building
Fraser Noble Building Aberdeen AB24 3UE
UK
Email: gorry@erg.abdn.ac.uk
Tom Jones
University of Aberdeen
School of Engineering
Fraser Noble Building
Aberdeen AB24 3UE
UK
Email: tom@erg.abdn.ac.uk
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