draft-ietf-taps-transports-usage-udp-01.txt   draft-ietf-taps-transports-usage-udp-02.txt 
Internet Engineering Task Force G. Fairhurst Internet Engineering Task Force G. Fairhurst
Internet-Draft T. Jones Internet-Draft T. Jones
Intended status: Informational University of Aberdeen Intended status: Informational University of Aberdeen
Expires: November 12, 2017 May 11, 2017 Expires: November 15, 2017 May 16, 2017
Features of the User Datagram Protocol (UDP) and Lightweight UDP (UDP- Features of the User Datagram Protocol (UDP) and Lightweight UDP (UDP-
Lite) Transport Protocols Lite) Transport Protocols
draft-ietf-taps-transports-usage-udp-01 draft-ietf-taps-transports-usage-udp-02
Abstract Abstract
This is an informational document that describes the transport This is an informational document that describes the transport
protocol interface primitives provided by the User Datagram Protocol protocol interface primitives provided by the User Datagram Protocol
(UDP) and the Lightweight User Datagram Protocol (UDP-Lite) transport (UDP) and the Lightweight User Datagram Protocol (UDP-Lite) transport
protocols. It identifies the datagram services exposed to protocols. It identifies the datagram services exposed to
applications and how an application can configure and use the applications and how an application can configure and use the
features offered by the Internet datagram transport service. The features offered by the Internet datagram transport service. The
resulting road map to documentation may be of help to users of the resulting road map to documentation may be of help to users of the
UDP and UDP-Lite protocols. UDP and UDP-Lite protocols.
Status of This Memo Status of this Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
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 November 12, 2017. This Internet-Draft will expire on November 15, 2017.
Copyright Notice Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the Copyright (c) 2017 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
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described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. UDP and UDP-Lite Primitives . . . . . . . . . . . . . . . . . 3 3. UDP and UDP-Lite Primitives . . . . . . . . . . . . . . . . . 3
3.1. Primitives Provided by UDP . . . . . . . . . . . . . . . 4 3.1. Primitives Provided by UDP . . . . . . . . . . . . . . . . 3
3.1.1. Excluded Primitives . . . . . . . . . . . . . . . . . 10 3.1.1. Excluded Primitives . . . . . . . . . . . . . . . . . 10
3.2. Primitives Provided by UDP-Lite . . . . . . . . . . . . . 10 3.2. Primitives Provided by UDP-Lite . . . . . . . . . . . . . 10
4. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 11 4. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 11
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11
6. Security Considerations . . . . . . . . . . . . . . . . . . . 11 6. Security Considerations . . . . . . . . . . . . . . . . . . . 11
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 11 7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 11
7.1. Normative References . . . . . . . . . . . . . . . . . . 12 7.1. Normative References . . . . . . . . . . . . . . . . . . . 11
7.2. Informative References . . . . . . . . . . . . . . . . . 13 7.2. Informative References . . . . . . . . . . . . . . . . . . 13
Appendix A. Multicast Primitives . . . . . . . . . . . . . . . . 15 Appendix A. Multicast Primitives . . . . . . . . . . . . . . . . . 14
Appendix B. Revision Notes . . . . . . . . . . . . . . . . . . . 18 Appendix B. Revision Notes . . . . . . . . . . . . . . . . . . . . 17
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 19 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 19
1. Introduction 1. Introduction
This document presents defined interactions between transport This document presents defined interactions between transport
protocols and applications in the form of 'primitives' (function protocols and applications in the form of 'primitives' (function
calls) for the User Datagram Protocol (UDP) [RFC0768] and the calls) for the User Datagram Protocol (UDP) [RFC0768] and the
Lightweight User Datagram Protocol (UDP-Lite) [RFC3828]. In this Lightweight User Datagram Protocol (UDP-Lite) [RFC3828]. In this
usage, the word application refers to any program built on the usage, the word application refers to any program built on the
datagram interface, and including tunnels and other upper layer datagram interface, and including tunnels and other upper layer
protocols that use UDP and UDP-LIte. protocols that use UDP and UDP-LIte.
The de facto standard application programming interface (API) for The de facto standard application programming interface (API) for TCP
TCP/IP applications is the "socket" interface [POSIX]. An /IP applications is the "socket" interface [POSIX]. An application
application can use the recv() and send() POSIX functions as well as can use the recv() and send() POSIX functions as well as the
the recvfrom() and sendto() and recvmsg() and sendmsg() functions. recvfrom() and sendto() and recvmsg() and sendmsg() functions. The
The UDP and UDP-Lite sockets API differs from that for TCP in several UDP and UDP-Lite sockets API differs from that for TCP in several key
key ways. (Examples of usage of this API are provided in [STEVENS].) ways. (Examples of usage of this API are provided in [STEVENS].)
Additional functions in the sockets API are provided by socket Additional functions in the sockets API are provided by socket
options, examples include: options, examples include:
o SO_REUSEADDR specifies the rules for validating addresses supplied o SO_REUSEADDR specifies the rules for validating addresses supplied
to bind() should allow reuse of local addresses to bind() should allow reuse of local addresses
o SO_REUSEPORT specifies that the rules for validating ports o SO_REUSEPORT specifies that the rules for validating ports
supplied to bind() should allow reuse of a local port supplied to bind() should allow reuse of a local port
o IP_RECVTTL returns the IP Time To Live (TTL) field from IP header o IP_RECVTTL returns the IP Time To Live (TTL) field from IP header
of a received datagram. of a received datagram.
Some platforms also offer applications the ability to directly Some platforms also offer applications the ability to directly
assemble and transmit IP packets through "raw sockets" or similar assemble and transmit IP packets through "raw sockets" or similar
facilities. The raw socket API is a second, more cumbersome method facilities. The raw socket API is a second, more cumbersome method
of using UDP. The use of this API is discussed in the RFC series in of using UDP. The use of this API is discussed in the RFC series in
the UDP Guidelines [RFC8085]. the UDP Guidelines [RFC8085].
The list of transport service features and primitives in this The list of transport service features and primitives in this
document is strictly based on the parts of protocol specifications in document is strictly based on the parts of protocol specifications in
RFC-series that relate to what the transport protocol provides to an RFC-series that relate to what the transport protocol provides to an
application that uses it and how the application interacts with the application that uses it and how the application interacts with the
transport protocol. Primitives can be invoked by an application or a transport protocol. Primitives can be invoked by an application or a
transport protocol; the latter type is called an "event". transport protocol; the latter type is called an "event".
The description in the next section follows the methodology defined The description in the next section follows the methodology defined
skipping to change at page 3, line 35 skipping to change at page 3, line 32
protocol. protocol.
The presented road map to documentation of the transport interface The presented road map to documentation of the transport interface
may also help developers working with UDP and UDP-Lite. may also help developers working with UDP and UDP-Lite.
2. Terminology 2. Terminology
This document is intended as a contribution to the Transport Services This document is intended as a contribution to the Transport Services
(TAPS) working group to assist in analysis of the UDP and UDP-Lite (TAPS) working group to assist in analysis of the UDP and UDP-Lite
transport interface. It uses common terminology defined in "Usage of transport interface. It uses common terminology defined in "Usage of
Transport Features Provided by IETF Transport Protocols" Transport Features Provided by IETF Transport Protocols" [I-D.ietf-
[I-D.ietf-taps-transports-usage]. This document also refers to the taps-transports-usage]. This document also refers to the terminology
terminology of RFC 2119 [RFC2119], but does not itself define new of RFC 2119 [RFC2119], but does not itself define new terms using
terms using this terminology. this terminology.
3. UDP and UDP-Lite Primitives 3. UDP and UDP-Lite Primitives
This section summarizes the relevant text parts of the RFCs This section summarizes the relevant text parts of the RFCs
describing the UDP and UDP-Lite protocols, focusing on what the describing the UDP and UDP-Lite protocols, focusing on what the
transport protocols provide to the application (in and how the transport protocols provide to the application (in and how the
transport is used (based on abstract API descriptions, where they are transport is used (based on abstract API descriptions, where they are
available). available).
This section describes unicast usage, but UDP and UDP-Lite also This section describes unicast usage, but UDP and UDP-Lite also
support IPv4 broadcast and IPv4/IPv6 multicast [RFC8085]. Many support IPv4 broadcast and IPv4/IPv6 multicast [RFC8085]. Many
primitives also apply when the transports are used with IP broadcast primitives also apply when the transports are used with IP broadcast
and multicast. Appendix Appendix A describes where to find and multicast. Appendix Appendix Appendix A describes where to find
documentation for network-layer primitives required to use UDP or documentation for network-layer primitives required to use UDP or
UDP-Lite with IP multicast. UDP-Lite with IP multicast.
3.1. Primitives Provided by UDP 3.1. Primitives Provided by UDP
The User Datagram Protocol (UDP) [RFC0768] States: "This User The User Datagram Protocol (UDP) [RFC0768] States: "This User
Datagram Protocol (UDP) is defined to make available a datagram mode Datagram Protocol (UDP) is defined to make available a datagram mode
of packet-switched computer communication in the environment of an of packet-switched computer communication in the environment of an
interconnected set of computer networks." It "provides a procedure interconnected set of computer networks." It "provides a procedure
for application programs to send messages to other programs with a for application programs to send messages to other programs with a
minimum of protocol mechanism (..)". minimum of protocol mechanism (..)".
The User Interface section of RFC768 states that the user interface The User Interface section of RFC768 states that the user interface
to an application should be able to create receive, source and to an application should be able to create receive, source and
destination ports and addresses, and provide operations to receive destination ports and addresses, and provide operations to receive
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The User Interface section of RFC768 states that the user interface The User Interface section of RFC768 states that the user interface
to an application should be able to create receive, source and to an application should be able to create receive, source and
destination ports and addresses, and provide operations to receive destination ports and addresses, and provide operations to receive
data based on ports with an indication of source port and address. data based on ports with an indication of source port and address.
Operations should be provided that allows datagrams be sent Operations should be provided that allows datagrams be sent
specifying the source and destination ports and addresses to be sent. specifying the source and destination ports and addresses to be sent.
UDP has been defined for IPv6 [RFC2460], together with API extensions UDP has been defined for IPv6 [RFC2460], together with API extensions
for a Basic Socket Interface Extensions for IPv6 [RFC3493]. for a Basic Socket Interface Extensions for IPv6 [RFC3493].
[RFC6935] and [RFC6936] defines an update to the UDP transport [RFC6935] and [RFC6936] defines an update to the UDP transport
specified in RFC 2460. This enables use of a zero UDP checksum mode specified in RFC 2460. This enables use of a zero UDP checksum mode
with a tunnel protocol, providing that the method satisfies the with a tunnel protocol, providing that the method satisfies the
requirements in the corresponding applicability statement [RFC6936]. requirements in the corresponding applicability statement [RFC6936].
UDP offers only a basic transport interface. UDP datagrams may be UDP offers only a basic transport interface. UDP datagrams may be
directly sent and received, without exchanging messages between the directly sent and received, without exchanging messages between the
endpoints to setup a connection (i.e., no handshake is performed by endpoints to setup a connection (i.e., no handshake is performed by
the transport protocol prior to communication). Using the sockets the transport protocol prior to communication). Using the sockets
API, applications can receive packets from more than one IP source API, applications can receive packets from more than one IP source
address on a single UDP socket. Common support allows specification address on a single UDP socket. Common support allows specification
of the local IP address, destination IP address, local port and of the local IP address, destination IP address, local port and
destination port values. Any or all of these can be indicated, with destination port values. Any or all of these can be indicated, with
defaults supplied by the local system when these are not specified. defaults supplied by the local system when these are not specified.
The local endpoint is set using the BIND call and set on the remote The local endpoint is set using the BIND call and set on the remote
endpoint using the CONNECT call. The CLOSE function has local endpoint using the CONNECT call. The CLOSE function has local
significance only. It does not impact the status of the remote significance only. It does not impact the status of the remote
endpoint. endpoint.
Neither UDP nor UDP-Lite provide congestion control, retransmission, Neither UDP nor UDP-Lite provide congestion control, retransmission,
nor do they have support to optimise fragmentation and other nor do they have support to optimise fragmentation and other
transport functions. This means that applications using UDP need to transport functions. This means that applications using UDP need to
provide additional functions on top of the UDP transport API provide additional functions on top of the UDP transport API
[RFC8085]. Some transport functions require parameters to be passed [RFC8085]. Some transport functions require parameters to be passed
through the API to control the network layer (IPv4 or IPv6). These through the API to control the network layer (IPv4 or IPv6). These
additional primitives could be considered a part of the network layer additional primitives could be considered a part of the network layer
(e.g., control of the setting of the Don't Fragment (DF) flag on a (e.g., control of the setting of the Don't Fragment (DF) flag on a
transmitted IPv4 datagram), but are nonetheless essential to allow a transmitted IPv4 datagram), but are nonetheless essential to allow a
user of the UDP API to implement functions that are normally user of the UDP API to implement functions that are normally
associated with the transport layer (such as probing for the path associated with the transport layer (such as probing for the path
maximum transmission size). This document includes such primitives. maximum transmission size). This document includes such primitives.
Guidance on the use of the services provided by UDP is provided in Guidance on the use of the services provided by UDP is provided in
the UDP Guidelines [RFC8085]. This also states "many operating the UDP Guidelines [RFC8085]. This also states "many operating
systems also allow a UDP socket to be connected, i.e., to bind a UDP 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 socket to a specific pair of addresses and ports. This is similar to
the corresponding TCP sockets API functionality. However, for UDP, the corresponding TCP sockets API functionality. However, for UDP,
this is only a local operation that serves to simplify the local this is only a local operation that serves to simplify the local send
send/receive functions and to filter the traffic for the specified /receive functions and to filter the traffic for the specified
addresses and ports. Binding a UDP socket does not establish a addresses and ports. Binding a UDP socket does not establish a
connection - UDP does not notify the remote endpoint when a local UDP connection - UDP does not notify the remote endpoint when a local UDP
socket is bound. Binding a socket also allows configuring options socket is bound. Binding a socket also allows configuring options
that affect the UDP or IP layers, for example, use of the UDP 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 checksum or the IP Timestamp Option. On some stacks, a bound socket
also allows an application to be notified when Internet Control also allows an application to be notified when Internet Control
Message (ICMP) error messages are received for its transmissions Message (ICMP) error messages are received for its transmissions
[RFC1122]." [RFC1122]."
The POSIX Base Specifications [POSIX] define an API that offers The POSIX Base Specifications [POSIX] define an API that offers
mechanisms for an application to receive asynchronous data events at mechanisms for an application to receive asynchronous data events at
the socket layer. Calls such as "poll", "select" or "queue" allow an the socket layer. Calls such as "poll", "select" or "queue" allow an
application to be notified when data has arrived at a socket or when application to be notified when data has arrived at a socket or when
a socket has flushed its buffers. a socket has flushed its buffers.
A callback-driven API to the network interface can be structured on A callback-driven API to the network interface can be structured on
top of these calls. Implicit connection setup allows an application top of these calls. Implicit connection setup allows an application
to delegate connection life management to the transport API. The to delegate connection life management to the transport API. The
transport API uses protocol primitives to offer the automated service transport API uses protocol primitives to offer the automated service
to the application via the sockets API. By combining UDP primitives to the application via the sockets API. By combining UDP primitives
(CONNECT.UDP, SEND.UDP), a higher level API could offer a similar (CONNECT.UDP, SEND.UDP), a higher level API could offer a similar
service. service.
The following datagram primitives are specified: The following datagram primitives are specified:
CONNECT: The CONNECT primitive allows the association of source and CONNECT: The CONNECT primitive allows the association of source and
destination port sets to a socket to enable creation of a destination port sets to a socket to enable creation of a
'connection' for UDP traffic. This UDP connection allows an 'connection' for UDP traffic. This UDP connection allows an
application to be notified of errors received from the network application to be notified of errors received from the network
stack and provides a shorthand access to the send and receive stack and provides a shorthand access to the send and receive
primitives. Since UDP is itself connectionless, no datagrams are primitives. Since UDP is itself connectionless, no datagrams are
sent because this primitive is executed. A further connect call sent because this primitive is executed. A further connect call
can be used to change the association. can be used to change the association.
Two forms of usage may be identified for the CONNECT primitive: Two forms of usage may be identified for the CONNECT primitive:
skipping to change at page 6, line 21 skipping to change at page 6, line 16
CONNECT primitive. The bind operation establishes the use of CONNECT primitive. The bind operation establishes the use of
a known local port for datagrams, rather than using an a known local port for datagrams, rather than using an
ephemeral port. The connect operation specifies a known ephemeral port. The connect operation specifies a known
address port combination to be used by default for future address port combination to be used by default for future
datagrams. This form is used either after receiving a datagrams. This form is used either after receiving a
datagram from an endpoint that causes the creation of a datagram from an endpoint that causes the creation of a
connection, or can be triggered by third party configuration connection, or can be triggered by third party configuration
or a protocol trigger (such as reception of a UDP Service or a protocol trigger (such as reception of a UDP Service
Description Protocol, SDP [RFC4566], record). Description Protocol, SDP [RFC4566], record).
LISTEN: The roles of a client and a server are often not appropriate LISTEN: The roles of a client and a server are often not appropriate
for UDP, where connections can be peer-to-peer. The listening for UDP, where connections can be peer-to-peer. The listening
functions are performed using one of the forms of the CONNECT functions are performed using one of the forms of the CONNECT
primitive described above. primitive described above.
SEND: The SEND primitive hands over a provided number of bytes that 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 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 datagram. The primitive can be used by an application to directly
send datagrams to an endpoint defined by an address/port pair. If send datagrams to an endpoint defined by an address/port pair. If
a connection has been created, then the address/port pair is a connection has been created, then the address/port pair is
inferred from the current connection for the socket. Connecting a inferred from the current connection for the socket. Connecting a
socket allows network errors to be returned to the application as socket allows network errors to be returned to the application as
a notification on the send primitive. Messages passed to the send a notification on the send primitive. Messages passed to the send
primitive that cannot be sent atomically in a datagram will not be primitive that cannot be sent atomically in a datagram will not be
sent by the network layer, generating an error. sent by the network layer, generating an error.
RECEIVE: The RECEIVE primitive allocates a receiving buffer to RECEIVE: The RECEIVE primitive allocates a receiving buffer to
accommodate a received datagram. The primitive returns the number accommodate a received datagram. The primitive returns the number
of bytes provided from a received UDP datagram. Section 4.1.3.5 of bytes provided from a received UDP datagram. Section 4.1.3.5
of the requirements of Internet hosts [RFC1122] states "When a UDP of the requirements of Internet hosts [RFC1122] states "When a UDP
datagram is received, its specific-destination address MUST be datagram is received, its specific-destination address MUST be
passed up to the application layer." passed up to the application layer."
CHECKSUM_ENABLED: The optional CHECKSUM primitive controls whether a CHECKSUM_ENABLED: The optional CHECKSUM primitive controls whether a
sender enables the UDP checksum when sending datagrams ( [RFC0768] sender enables the UDP checksum when sending datagrams ( [RFC0768]
and [RFC6935] [RFC6936] [RFC8085]). When unset, this overrides and [RFC6935] [RFC6936] [RFC8085]). When unset, this overrides the
the default UDP behaviour, disabling the checksum on sending. default UDP behaviour, disabling the checksum on sending. Section
Section 4.1.3.4 of the requirements for Internet hosts [RFC1122] 4.1.3.4 of the requirements for Internet hosts [RFC1122] states
states "An application MAY optionally be able to control whether a "An application MAY optionally be able to control whether a UDP
UDP checksum will be generated, but it MUST default to checksum will be generated, but it MUST default to checksumming
checksumming on." on."
REQUIRE_CHECKSUM: The optional REQUIRE_CHECKSUM primitive determines REQUIRE_CHECKSUM: The optional REQUIRE_CHECKSUM primitive determines
whether UDP datagrams received with a zero checksum are permitted whether UDP datagrams received with a zero checksum are permitted
or discarded, UDP defaults to requiring checksums. or discarded, UDP defaults to requiring checksums. Section
Section 4.1.3.4 of the requirements for Internet hosts [RFC1122] 4.1.3.4 of the requirements for Internet hosts [RFC1122] states
states "An application MAY optionally be able to control whether "An application MAY optionally be able to control whether UDP
UDP datagrams without checksums should be discarded or passed to datagrams without checksums should be discarded or passed to the
the application." Section 3.1 of the specification for UDP-Lite application." Section 3.1 of the specification for UDP-Lite
[RFC3828] requires that the checksum field is non-zero, and hence [RFC3828] requires that the checksum field is non-zero, and hence
the UDP-Lite API must discard all datagrams received with a zero the UDP-Lite API must discard all datagrams received with a zero
checksum. checksum.
SET_IP_OPTIONS: The SET_IP_OPTIONS primitive request the network- SET_IP_OPTIONS: The SET_IP_OPTIONS primitive request the network-
layer to send a datagram with the specified IP options. layer to send a datagram with the specified IP options. Section
Section 4.1.3.2 of the requirements for Internet hosts[RFC1122] 4.1.3.2 of the requirements for Internet hosts[RFC1122] states
states that an "application MUST be able to specify IP options to that an "application MUST be able to specify IP options to be sent
be sent in its UDP datagrams, and UDP MUST pass these options to in its UDP datagrams, and UDP MUST pass these options to the IP
the IP layer." layer."
GET_IP_OPTIONS: The GET_IP_OPTIONS primitive retrieves the IP GET_IP_OPTIONS: The GET_IP_OPTIONS primitive retrieves the IP options
options of a datagram recieved at the network-layer. of a datagram received at the network-layer. Section 4.1.3.2 of
Section 4.1.3.2 of the requirements for Internet hosts[RFC1122] the requirements for Internet hosts[RFC1122] states that a UDP
states that a UDP receiver "MUST pass any IP option that it receiver "MUST pass any IP option that it receives from the IP
receives from the IP layer transparently to the application layer transparently to the application layer".
layer".
SET_DF: The SET_DF primitive allows the network-layer to fragment SET_DF: The SET_DF primitive allows the network-layer to fragment
packets using the Fragment Offset in IPv4 [RFC6864] and a host to packets using the Fragment Offset in IPv4 [RFC6864] and a host to
use Fragment Headers in IPv6 [RFC2460], IPv4 allows routers to use Fragment Headers in IPv6 [RFC2460]. The SET_DF primitive sets
fragments packets. The SET_DF primitive sets the Don't Fragment the Don't Fragment (DF) flag in the IPv4 packet header that
(DF) flag in the IPv4 packet header that carries a UDP datagram. carries a UDP datagram, which allows routers to fragment IPv4
Although some specific applications rely on fragmentation support, packets. Although some specific applications rely on
in general, a UDP application should implement a method that fragmentation support, in general, a UDP application should
avoids IP fragmentation (section 4 of [RFC8085]). NOTE: In many implement a method that avoids IP fragmentation (section 4 of
other IETF transports (e.g., TCP) the transport provides the [RFC8085]). NOTE: In many other IETF transports (e.g., TCP, SCTP)
support needed to use DF. However, when using UDP, the the transport provides the support needed to use DF. However, when
application is responsible for the techniques needed to discover using UDP, the application is responsible for the techniques
the effective path maximum transmission unit (PMTU) allowed on the needed to discover the effective path maximum transmission unit
network path, coordinating with the network layer. The acceptable (PMTU) allowed on the network path, coordinating with the network
maximum packet size can be determined using Packetization-Layer- layer. The acceptable maximum packet size can be determined using
Path MTU Discovery (PLPMTUD) [RFC4821] or Path MTU Discovery Packetization-Layer-Path MTU Discovery (PLPMTUD) [RFC4821] or Path
[RFC1191] [RFC1981]. MTU Discovery [RFC1191] [I-D.ietf-6man-rfc1981bis].
GET_INTERFACE_MTU: The GET_INTERFACE_MTU primitive retrieves a GET_MMS_S: The GET_MMS_S primitive retrieves a network-layer value
network-layer value that indicates the largest non-fragmented IP that indicates the maximum send transport-message size that may be
packet that may be sent from the configured interface. A UDP sent using a non-fragmented IP packet from the configured
endpoint can subtract the size of all network and transport interface. This value is specified in section 6.1 of [RFC1191]
headers to determine the maximum size of non-fragmented UDP and section 5.1 of [I-D.ietf-6man-rfc1981bis]. It is calculated
payload. UDP applications should use this value as part of a from Effective Maximum Transmit Unit for Sending (EMTU_S), and the
method to avoid sending UDP datagrams that would result in IP link MTU for the given source IP address. This takes into account
packets that exceed the effective path maximum transmission unit of the size of the IP header plus space reserved by the IP layer
(PMTU) allowed on the network path. The effective PATH (specified for additional headers (if any). UDP applications should use this
in Section 1 of [RFC1191]) is equivalent to the "effective MT for value as part of a method to avoid sending UDP datagrams that
sending" (specified in [RFC1122]). The specification of PLPMTUD would result in IP packets that exceed the effective PMTU allowed
[RFC4821] states: "If PLPMTUD updates the MT for a particular across the network path. The effective PMTU (specified in Section
path, all Packetization Layer sessions that share the path 1 of [RFC1191]) is equivalent to the EMTU_S (specified in
representation (as described in Section 5.2) SHOULD be notified to [RFC1122]). The specification of PLPMTUD [RFC4821] states: "If
make use of the new MT and make the required congestion control PLPMTUD updates the MTU for a particular path, all Packetization
adjustments." To determine an appropriate UDP payload size, Layer sessions that share the path representation (as described in
applications MUST subtract the size of the IP header (which Section 5.2) SHOULD be notified to make use of the new MTU and
includes any IPv4 optional headers or IPv6 extension headers) as make the required congestion control adjustments".
well as the length of the UDP header (8 bytes) from the PMTU size.
SET_TTL: The SET_TTL primitive sets the hop limit (TTL field) in the GET_MMS_R: The GET_MMS_R primitive retrieves a network-layer value
that indicates the largest receive transport-message size that may
be received from the configured interface. This value is
specified in section 3.1 of [RFC1191]. It is calculated from
Effective Maximum Transmit Unit for Receiving (EMTU_R), and the
link MTU for the given source IP address, and takes into account
the size of the IP header plus space reserved by the IP layer for
additional headers (if any).
SET_TTL: The SET_TTL primitive sets the hop limit (TTL field) in the
network-layer that is used in the IPv4 header of a packet that network-layer that is used in the IPv4 header of a packet that
carries an UDP datagram. This is used to limit the scope of carries an UDP datagram. This is used to limit the scope of
unicast datagrams. Section 3.2.2.4 of the requirements for unicast datagrams. Section 3.2.2.4 of the requirements for
Internet hosts [RFC1122] states an "incoming Time Exceeded message Internet hosts [RFC1122] states an "incoming Time Exceeded message
MUST be passed to the transport layer". MUST be passed to the transport layer".
GET_TTL: The GET_TTL primitive retrieves the value of the TTL field GET_TTL: The GET_TTL primitive retrieves the value of the TTL field
in a network packet received at the network-layer. in a network packet received at the network-layer. Section
Section 3.2.2.4 of the requirements for Internet hosts [RFC1122] 3.2.2.4 of the requirements for Internet hosts [RFC1122] states
states that a UDP receiver "MAY pass the received ToS up to the that a UDP receiver "MAY pass the received ToS up to the
application layer" When used for applications such as the application layer" When used for applications such as the
Generalized TTL Security Mechanism (GTSM) [RFC5082], this needs Generalized TTL Security Mechanism (GTSM) [RFC5082], this needs
the UDP receiver API to pass the received value of this field to the UDP receiver API to pass the received value of this field to
the application. the application.
SET_IPV6_UNICAST_HOPS: The SET_IPV6_UNICAST_HOPS primitive sets the SET_IPV6_UNICAST_HOPS: The SET_IPV6_UNICAST_HOPS primitive sets the
network-layer hop limit field in an IPv6 packet header [RFC2460] network-layer hop limit field in an IPv6 packet header [RFC2460]
carrying a UDP datagram. For IPv6 unicast datagrams, this is carrying a UDP datagram. For IPv6 unicast datagrams, this is
functionally equivalent to the SET_TTL IPv4 function. functionally equivalent to the SET_TTL IPv4 function.
GET_IPV6_UNICAST_HOPS: The GET_IPV6_UNICAST_HOPS primitive is a GET_IPV6_UNICAST_HOPS: The GET_IPV6_UNICAST_HOPS primitive is a
network-layer function that reads the hop count in the IPv6 header network-layer function that reads the hop count in the IPv6 header
[RFC2460] information of a received UDP datagram. For IPv6 [RFC2460] information of a received UDP datagram. For IPv6
unicast datagrams, this is functionally equivalent to the GET_TTL unicast datagrams, this is functionally equivalent to the GET_TTL
IPv4 function. IPv4 function.
SET_DSCP: The SET_DSCP primitive is a network-layer function that SET_DSCP: The SET_DSCP primitive is a network-layer function that
sets the Differentiated Services (diffserv) Code Point, DSCP, (or sets the Differentiated Services (diffserv) Code Point, DSCP, (or
the legacy Type of Service, ToS) value [RFC2474] to be used in the the legacy Type of Service, ToS) value [RFC2474] to be used in the
field of an IP header of a packet that carries a UDP datagram. field of an IP header of a packet that carries a UDP datagram.
Section 2.4 of the requirements for Internet hosts[RFC1123] states Section 2.4 of the requirements for Internet hosts[RFC1123] states
that "Applications MUST select appropriate ToS values when they that "Applications MUST select appropriate ToS values when they
invoke transport layer services, and these values MUST be invoke transport layer services, and these values MUST be
configurable.". The application should be able to change the ToS configurable.". The application should be able to change the ToS
during the connection lifetime, and the ToS value should be passed during the connection lifetime, and the ToS value should be passed
to the IP layer unchanged. Section 4.1.4 of [RFC1122] also states 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 that on reception the "UDP MAY pass the received ToS value up to
the application layer". The Differentiated Services (diffuser) the application layer". The Differentiated Services (diffuser)
model [RFC2475] [RFC3260] replaces this field in the IP Header model [RFC2475] [RFC3260] replaces this field in the IP Header
assigning the six most significant bits to carry the assigning the six most significant bits to carry the
Differentiated Services Code Point (DSCP) field [RFC2474]. Differentiated Services Code Point (DSCP) field [RFC2474].
Preserving the intention of the hist requirements [RFC1122] to Preserving the intention of the hist requirements [RFC1122] to
allow the application to specify the "Type of Service", this allow the application to specify the "Type of Service", this
should be interpreted to mean that an API should allow the should be interpreted to mean that an API should allow the
application to set the DSCP. Section 3.1.6 of the UDP Guidelines application to set the DSCP. Section 3.1.6 of the UDP Guidelines
[RFC8085] describes the way UDP applications should use this [RFC8085] describes the way UDP applications should use this
field. Normally a UDP socket will assign a single DSCP value to field. Normally a UDP socket will assign a single DSCP value to
all datagrams in a flow, but a sender is allowed to use different all datagrams in a flow, but a sender is allowed to use different
DSCP values for datagrams within the same flow in certain DSCP values for datagrams within the same flow in certain
cases[RFC8085]. There are guidelines for WebRTC that illustrate cases[RFC8085]. There are guidelines for WebRTC that illustrate
this use [RFC7657]. this use [RFC7657].
SET_ECN: The SET_ECN primitive is a network-layer function that sets SET_ECN: The SET_ECN primitive is a network-layer function that sets
the ECN field in the IP Header of a UDP datagram. The ECN field the ECN field in the IP Header of a UDP datagram. The ECN field
defaults to a value of 00. When the use of the ToS field was defaults to a value of 00. When the use of the ToS field was
redefined by diffserv [RFC3260], 2 bits of the field were assigned redefined by diffserv [RFC3260], 2 bits of the field were assigned
to support Explicit Congestion Notification (ECN) [RFC3168]. to support Explicit Congestion Notification (ECN) [RFC3168].
Section 3.1.5 of the UDP Guidelines [RFC8085] describes the way Section 3.1.5 of the UDP Guidelines [RFC8085] describes the way
UDP applications should use this field. NOTE: In many other IETF UDP applications should use this field. NOTE: In many other IETF
transports (e.g., TCP) the transport provides the support needed transports (e.g., TCP) the transport provides the support needed
to use ECN, when using UDP, the application or higher layer to use ECN, when using UDP, the application or higher layer
protocol is itself responsible for the techniques needed to use protocol is itself responsible for the techniques needed to use
ECN. ECN.
GET_ECN: The GET_ECN primitive is a network-layer function that GET_ECN: The GET_ECN primitive is a network-layer function that
returns the value of the ECN field in the IP Header of a received returns the value of the ECN field in the IP Header of a received
UDP datagram. Section 3.1.5 of the UDP Guidelines [RFC8085] UDP datagram. Section 3.1.5 of the UDP Guidelines [RFC8085]
states that a UDP receiver "MUST check the ECN field at the states that a UDP receiver "MUST check the ECN field at the
receiver for each UDP datagram that it receives on this port", receiver for each UDP datagram that it receives on this port",
requiring the UDP receiver API to pass to pass the received ECN requiring the UDP receiver API to pass to pass the received ECN
field up to the application layer to enable appropriate congestion field up to the application layer to enable appropriate congestion
feedback. feedback.
ERROR_REPORT The ERROR_REPORT event informs an application of "soft ERROR_REPORT The ERROR_REPORT event informs an application of "soft
errors", including the arrival of an ICMP or ICMPv6 error message. errors", including the arrival of an ICMP or ICMPv6 error message.
Section 4.1.4 of the host requirements [RFC1122] states "UDP MUST Section 4.1.4 of the host requirements [RFC1122] states "UDP MUST
pass to the application layer all ICMP error messages that it pass to the application layer all ICMP error messages that it
receives from the IP layer." For example, this event is required receives from the IP layer." For example, this event is required
to implement ICMP-based Path MT Discovery [RFC1191] [RFC1981]. to implement ICMP-based Path MTU Discovery [RFC1191] [I-D.ietf-
UDP applications must perform a CONNECT to receive ICMP errors. 6man-rfc1981bis]. UDP applications must perform a CONNECT to
receive ICMP errors.
CLOSE: The close primitive closes a connection. No further CLOSE: The close primitive closes a connection. No further datagrams
datagrams can be sent or received. Since UDP is itself can be sent or received. Since UDP is itself connectionless, no
connectionless, no datagrams are sent when this primitive is datagrams are sent when this primitive is executed.
executed.
3.1.1. Excluded Primitives 3.1.1. Excluded Primitives
Section 3.4 of the host requirements [RFC1122] also describes Section 3.4 of the host requirements [RFC1122] also describes
"GET_MAXSIZES, GET_SRCADDR (Section 3.3.4.3) and ADVISE_DELIVPROB:". "GET_MAXSIZES, GET_SRCADDR (Section 3.3.4.3) and ADVISE_DELIVPROB:".
These mechanisms are no longer used. It also specifies use of the These mechanisms are no longer used. It also specifies use of the
Source Quench ICMP message, which has since been deprecated Source Quench ICMP message, which has since been deprecated
[RFC6633]. [RFC6633].
The IPV6_V6ONLY function defined in Section 5.3 of the basic socket The IPV6_V6ONLY function defined in Section 5.3 of the basic socket
interface for IPv6 [RFC3493] restricts the use of information from interface for IPv6 [RFC3493] restricts the use of information from
the name resolver to only allow communication of AF_INET6 sockets to the name resolver to only allow communication of AF_INET6 sockets to
use IPv6 only. This is not considered part of the transport service. use IPv6 only. This is not considered part of the transport service.
3.2. Primitives Provided by UDP-Lite 3.2. Primitives Provided by UDP-Lite
The Lightweight User Datagram Protocol (UDP-Lite) [RFC3828] provides The Lightweight User Datagram Protocol (UDP-Lite) [RFC3828] provides
similar services to UDP. It changed the semantics of the UDP similar services to UDP. It changed the semantics of the UDP "payload
"payload length" field to that of a "checksum coverage length" field. length" field to that of a "checksum coverage length" field. UDP-
UDP-Lite requires the pseudo-header checksum to be computed at the Lite requires the pseudo-header checksum to be computed at the sender
sender and checked at a receiver. Apart from the length and coverage and checked at a receiver. Apart from the length and coverage
changes, UDP-Lite is semantically identical to UDP. changes, UDP-Lite is semantically identical to UDP.
The sending interface of UDP-Lite differs from that of UDP by the The sending interface of UDP-Lite differs from that of UDP by the
addition of a single (socket) option that communicates the checksum addition of a single (socket) option that communicates the checksum
coverage length. This specifies the intended checksum coverage, with coverage length. This specifies the intended checksum coverage, with
the remaining unprotected part of the payload called the "error- the remaining unprotected part of the payload called the "error-
insensitive part". insensitive part".
The receiving interface of UDP-Lite differs from that of UDP by the The receiving interface of UDP-Lite differs from that of UDP by the
addition of a single (socket) option that specifies the minimum addition of a single (socket) option that specifies the minimum
skipping to change at page 11, line 5 skipping to change at page 11, line 8
the UDP Guidelines [RFC8085]. the UDP Guidelines [RFC8085].
UDP-Lite requires use of the UDP or UDP-Lite checksum, and hence it UDP-Lite requires use of the UDP or UDP-Lite checksum, and hence it
is not permitted to use the "DISABLE_CHECKSUM:" function to disable is not permitted to use the "DISABLE_CHECKSUM:" function to disable
use of a checksum, nor is it possible to disable receiver checksum use of a checksum, nor is it possible to disable receiver checksum
processing using the "REQUIRE_CHECKSUM:" function . All other processing using the "REQUIRE_CHECKSUM:" function . All other
primitives and functions for UDP are permitted. primitives and functions for UDP are permitted.
In addition, the following are defined: In addition, the following are defined:
SET_CHECKSUM_COVERAGE: The SET_CHECKSUM_COVERAGE primitive sets the SET_CHECKSUM_COVERAGE: The SET_CHECKSUM_COVERAGE primitive sets the
coverage area for a sent datagram. UDP-Lite traffic uses this coverage area for a sent datagram. UDP-Lite traffic uses this
primitive to set the coverage length provided by the UDP checksum. primitive to set the coverage length provided by the UDP checksum.
Section 3.3 of the UDP-Lite MIB [RFC5097] states that Section 3.3 of the UDP-Lite MIB [RFC5097] states that
"Applications that wish to define the payload as partially "Applications that wish to define the payload as partially
insensitive to bit errors ... Should do this by an explicit insensitive to bit errors ... Should do this by an explicit
system call on the sender side." The default is to provide the system call on the sender side." The default is to provide the
same coverage as for UDP. same coverage as for UDP.
SET_MIN_COVERAGE The SET_MIN_COVERAGE primitive sets the minimum SET_MIN_COVERAGE The SET_MIN_COVERAGE primitive sets the minimum
acceptable coverage protection for received datagrams. UDP-Lite acceptable coverage protection for received datagrams. UDP-Lite
traffic uses this primitive to set the coverage length that is traffic uses this primitive to set the coverage length that is
checked on receive (section 1.1 of the UDP-Lite MIB [RFC5097] checked on receive (section 1.1 of the UDP-Lite MIB [RFC5097]
describes the corresponding MIB entry as describes the corresponding MIB entry as
udpliteEndpointMinCoverage). Section 3.3 of the UDP-Lite udpliteEndpointMinCoverage). Section 3.3 of the UDP-Lite
specification [RFC3828] states that "applications that wish to specification [RFC3828] states that "applications that wish to
receive payloads that were only partially covered by a checksum receive payloads that were only partially covered by a checksum
should inform the receiving system by an explicit system call". should inform the receiving system by an explicit system call".
The default is to require only minimal coverage of the datagram The default is to require only minimal coverage of the datagram
payload. payload.
4. Acknowledgements 4. Acknowledgements
This work was partially funded by the European Union's Horizon 2020 This work was partially funded by the European Union's Horizon 2020
research and innovation programme under grant agreement No. 644334 research and innovation programme under grant agreement No. 644334
(NEAT). The views expressed are solely those of the author(s). (NEAT). The views expressed are solely those of the author(s). Thanks
Thanks to all who have commented or contributed, including Joe Touch, to all who have commented or contributed, including Joe Touch, Ted
Ted Hardie and Aaron Falk. Hardie and Aaron Falk.
5. IANA Considerations 5. IANA Considerations
This memo includes no request to IANA. This memo includes no request to IANA.
The authors request the section to be removed during conversion into The authors request the section to be removed during conversion into
an RFC by the RFC Editor. an RFC by the RFC Editor.
6. Security Considerations 6. Security Considerations
skipping to change at page 12, line 4 skipping to change at page 11, line 51
The authors request the section to be removed during conversion into The authors request the section to be removed during conversion into
an RFC by the RFC Editor. an RFC by the RFC Editor.
6. Security Considerations 6. Security Considerations
Security considerations for the use of UDP and UDP-Lite are provided Security considerations for the use of UDP and UDP-Lite are provided
in the referenced RFCs. Security guidance for application usage is in the referenced RFCs. Security guidance for application usage is
provided in the UDP-Guidelines [RFC8085]. provided in the UDP-Guidelines [RFC8085].
7. References 7. References
7.1. Normative References 7.1. Normative References
[I-D.ietf-6man-rfc1981bis]
<>, J., <>, S., <>, J. and R. Hinden, "Path MTU Discovery
for IP version 6", Internet-Draft draft-ietf-6man-
rfc1981bis-06, April 2017.
[I-D.ietf-taps-transports-usage] [I-D.ietf-taps-transports-usage]
Welzl, M., Tuexen, M., and N. Khademi, "On the Usage of Welzl, M., Tuexen, M. and N. Khademi, "On the Usage of
Transport Service Features Provided by IETF Transport Transport Features Provided by IETF Transport Protocols",
Protocols", draft-ietf-taps-transports-usage-01 (work in Internet-Draft draft-ietf-taps-transports-usage-04, April
progress), July 2016. 2017.
[RFC0768] Postel, J., "User Datagram Protocol", STD 6, RFC 768, [RFC0768] Postel, J., "User Datagram Protocol", STD 6, RFC 768, DOI
DOI 10.17487/RFC0768, August 1980, 10.17487/RFC0768, August 1980, <http://www.rfc-editor.org/
<http://www.rfc-editor.org/info/rfc768>. info/rfc768>.
[RFC1122] Braden, R., Ed., "Requirements for Internet Hosts - [RFC1122] Braden, R., Ed., "Requirements for Internet Hosts -
Communication Layers", STD 3, RFC 1122, Communication Layers", STD 3, RFC 1122, DOI 10.17487/
DOI 10.17487/RFC1122, October 1989, RFC1122, October 1989, <http://www.rfc-editor.org/info/
<http://www.rfc-editor.org/info/rfc1122>. rfc1122>.
[RFC1123] Braden, R., Ed., "Requirements for Internet Hosts - [RFC1123] Braden, R., Ed., "Requirements for Internet Hosts -
Application and Support", STD 3, RFC 1123, Application and Support", STD 3, RFC 1123, DOI 10.17487/
DOI 10.17487/RFC1123, October 1989, RFC1123, October 1989, <http://www.rfc-editor.org/info/
<http://www.rfc-editor.org/info/rfc1123>. rfc1123>.
[RFC1191] Mogul, J.C. and S.E. Deering, "Path MTU discovery", RFC
1191, DOI 10.17487/RFC1191, November 1990, <http://www
.rfc-editor.org/info/rfc1191>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/
DOI 10.17487/RFC2119, March 1997, RFC2119, March 1997, <http://www.rfc-editor.org/info/
<http://www.rfc-editor.org/info/rfc2119>. rfc2119>.
[RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6 [RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", RFC 2460, DOI 10.17487/RFC2460, (IPv6) Specification", RFC 2460, DOI 10.17487/RFC2460,
December 1998, <http://www.rfc-editor.org/info/rfc2460>. December 1998, <http://www.rfc-editor.org/info/rfc2460>.
[RFC2553] Gilligan, R., Thomson, S., Bound, J., and W. Stevens, [RFC2553] Gilligan, R., Thomson, S., Bound, J. and W. Stevens,
"Basic Socket Interface Extensions for IPv6", RFC 2553, "Basic Socket Interface Extensions for IPv6", RFC 2553,
DOI 10.17487/RFC2553, March 1999, DOI 10.17487/RFC2553, March 1999, <http://www.rfc-
<http://www.rfc-editor.org/info/rfc2553>. editor.org/info/rfc2553>.
[RFC3168] Ramakrishnan, K., Floyd, S., and D. Black, "The Addition [RFC3168] Ramakrishnan, K., Floyd, S. and D. Black, "The Addition of
of Explicit Congestion Notification (ECN) to IP", Explicit Congestion Notification (ECN) to IP", RFC 3168,
RFC 3168, DOI 10.17487/RFC3168, September 2001, DOI 10.17487/RFC3168, September 2001, <http://www.rfc-
<http://www.rfc-editor.org/info/rfc3168>. editor.org/info/rfc3168>.
[RFC3493] Gilligan, R., Thomson, S., Bound, J., McCann, J., and W. [RFC3493] Gilligan, R., Thomson, S., Bound, J., McCann, J. and W.
Stevens, "Basic Socket Interface Extensions for IPv6", Stevens, "Basic Socket Interface Extensions for IPv6", RFC
RFC 3493, DOI 10.17487/RFC3493, February 2003, 3493, DOI 10.17487/RFC3493, February 2003, <http://www
<http://www.rfc-editor.org/info/rfc3493>. .rfc-editor.org/info/rfc3493>.
[RFC3828] Larzon, L-A., Degermark, M., Pink, S., Jonsson, L-E., Ed., [RFC3828] Larzon, L-A., Degermark, M., Pink, S., Jonsson, L-E.Ed.,
and G. Fairhurst, Ed., "The Lightweight User Datagram and G. Fairhurst, Ed., "The Lightweight User Datagram
Protocol (UDP-Lite)", RFC 3828, DOI 10.17487/RFC3828, July Protocol (UDP-Lite)", RFC 3828, DOI 10.17487/RFC3828, July
2004, <http://www.rfc-editor.org/info/rfc3828>. 2004, <http://www.rfc-editor.org/info/rfc3828>.
[RFC6864] Touch, J., "Updated Specification of the IPv4 ID Field", [RFC6864] Touch, J., "Updated Specification of the IPv4 ID Field",
RFC 6864, DOI 10.17487/RFC6864, February 2013, RFC 6864, DOI 10.17487/RFC6864, February 2013, <http://www
<http://www.rfc-editor.org/info/rfc6864>. .rfc-editor.org/info/rfc6864>.
[RFC6935] Eubanks, M., Chimento, P., and M. Westerlund, "IPv6 and [RFC6935] Eubanks, M., Chimento, P. and M. Westerlund, "IPv6 and UDP
UDP Checksums for Tunneled Packets", RFC 6935, Checksums for Tunneled Packets", RFC 6935, DOI 10.17487/
DOI 10.17487/RFC6935, April 2013, RFC6935, April 2013, <http://www.rfc-editor.org/info/
<http://www.rfc-editor.org/info/rfc6935>. rfc6935>.
[RFC6936] Fairhurst, G. and M. Westerlund, "Applicability Statement [RFC6936] Fairhurst, G. and M. Westerlund, "Applicability Statement
for the Use of IPv6 UDP Datagrams with Zero Checksums", for the Use of IPv6 UDP Datagrams with Zero Checksums",
RFC 6936, DOI 10.17487/RFC6936, April 2013, RFC 6936, DOI 10.17487/RFC6936, April 2013, <http://www
<http://www.rfc-editor.org/info/rfc6936>. .rfc-editor.org/info/rfc6936>.
[RFC8085] Eggert, L., Fairhurst, G., and G. Shepherd, "UDP Usage [RFC8085] Eggert, L., Fairhurst, G. and G. Shepherd, "UDP Usage
Guidelines", BCP 145, RFC 8085, DOI 10.17487/RFC8085, Guidelines", BCP 145, RFC 8085, DOI 10.17487/RFC8085,
March 2017, <http://www.rfc-editor.org/info/rfc8085>. March 2017, <http://www.rfc-editor.org/info/rfc8085>.
7.2. Informative References 7.2. Informative References
[POSIX] "IEEE Std. 1003.1-2001, , "Standard for Information [POSIX] "IEEE Std. 1003.1-2001, , "Standard for Information
Technology - Portable Operating System Interface (POSIX)", Technology - Portable Operating System Interface (POSIX)",
Open Group Technical Standard: Base Specifications Issue Open Group Technical Standard: Base Specifications Issue
6, ISO/IEC 9945:2002", December 2001. 6, ISO/IEC 9945:2002", December 2001.
[RFC1191] Mogul, J. and S. Deering, "Path MTU discovery", RFC 1191, [RFC2474] Nichols, K., Blake, S., Baker, F. and D. Black,
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>.
[RFC2474] Nichols, K., Blake, S., Baker, F., and D. Black,
"Definition of the Differentiated Services Field (DS "Definition of the Differentiated Services Field (DS
Field) in the IPv4 and IPv6 Headers", RFC 2474, Field) in the IPv4 and IPv6 Headers", RFC 2474, DOI
DOI 10.17487/RFC2474, December 1998, 10.17487/RFC2474, December 1998, <http://www.rfc-
<http://www.rfc-editor.org/info/rfc2474>. editor.org/info/rfc2474>.
[RFC2475] Blake, S., Black, D., Carlson, M., Davies, E., Wang, Z., [RFC2475] Blake, S., Black, D., Carlson, M., Davies, E., Wang, Z.
and W. Weiss, "An Architecture for Differentiated and W. Weiss, "An Architecture for Differentiated
Services", RFC 2475, DOI 10.17487/RFC2475, December 1998, Services", RFC 2475, DOI 10.17487/RFC2475, December 1998,
<http://www.rfc-editor.org/info/rfc2475>. <http://www.rfc-editor.org/info/rfc2475>.
[RFC3260] Grossman, D., "New Terminology and Clarifications for [RFC3260] Grossman, D., "New Terminology and Clarifications for
Diffserv", RFC 3260, DOI 10.17487/RFC3260, April 2002, Diffserv", RFC 3260, DOI 10.17487/RFC3260, April 2002,
<http://www.rfc-editor.org/info/rfc3260>. <http://www.rfc-editor.org/info/rfc3260>.
[RFC3376] Cain, B., Deering, S., Kouvelas, I., Fenner, B., and A. [RFC3376] Cain, B., Deering, S., Kouvelas, I., Fenner, B. and A.
Thyagarajan, "Internet Group Management Protocol, Version Thyagarajan, "Internet Group Management Protocol, Version
3", RFC 3376, DOI 10.17487/RFC3376, October 2002, 3", RFC 3376, DOI 10.17487/RFC3376, October 2002, <http://
<http://www.rfc-editor.org/info/rfc3376>. www.rfc-editor.org/info/rfc3376>.
[RFC3678] Thaler, D., Fenner, B., and B. Quinn, "Socket Interface [RFC3678] Thaler, D., Fenner, B. and B. Quinn, "Socket Interface
Extensions for Multicast Source Filters", RFC 3678, Extensions for Multicast Source Filters", RFC 3678, DOI
DOI 10.17487/RFC3678, January 2004, 10.17487/RFC3678, January 2004, <http://www.rfc-editor.org
<http://www.rfc-editor.org/info/rfc3678>. /info/rfc3678>.
[RFC3810] Vida, R., Ed. and L. Costa, Ed., "Multicast Listener [RFC3810] Vida, R.Ed., and L. Costa, Ed., "Multicast Listener
Discovery Version 2 (MLDv2) for IPv6", RFC 3810, Discovery Version 2 (MLDv2) for IPv6", RFC 3810, DOI
DOI 10.17487/RFC3810, June 2004, 10.17487/RFC3810, June 2004, <http://www.rfc-editor.org/
<http://www.rfc-editor.org/info/rfc3810>. info/rfc3810>.
[RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session [RFC4566] Handley, M., Jacobson, V. and C. Perkins, "SDP: Session
Description Protocol", RFC 4566, DOI 10.17487/RFC4566, Description Protocol", RFC 4566, DOI 10.17487/RFC4566,
July 2006, <http://www.rfc-editor.org/info/rfc4566>. July 2006, <http://www.rfc-editor.org/info/rfc4566>.
[RFC4604] Holbrook, H., Cain, B., and B. Haberman, "Using Internet [RFC4604] Holbrook, H., Cain, B. and B. Haberman, "Using Internet
Group Management Protocol Version 3 (IGMPv3) and Multicast Group Management Protocol Version 3 (IGMPv3) and Multicast
Listener Discovery Protocol Version 2 (MLDv2) for Source- Listener Discovery Protocol Version 2 (MLDv2) for Source-
Specific Multicast", RFC 4604, DOI 10.17487/RFC4604, Specific Multicast", RFC 4604, DOI 10.17487/RFC4604,
August 2006, <http://www.rfc-editor.org/info/rfc4604>. August 2006, <http://www.rfc-editor.org/info/rfc4604>.
[RFC4821] Mathis, M. and J. Heffner, "Packetization Layer Path MTU [RFC4821] Mathis, M. and J. Heffner, "Packetization Layer Path MTU
Discovery", RFC 4821, DOI 10.17487/RFC4821, March 2007, Discovery", RFC 4821, DOI 10.17487/RFC4821, March 2007,
<http://www.rfc-editor.org/info/rfc4821>. <http://www.rfc-editor.org/info/rfc4821>.
[RFC5082] Gill, V., Heasley, J., Meyer, D., Savola, P., Ed., and C. [RFC5082] Gill, V., Heasley, J., Meyer, D., Savola, P.Ed., and C.
Pignataro, "The Generalized TTL Security Mechanism Pignataro, "The Generalized TTL Security Mechanism
(GTSM)", RFC 5082, DOI 10.17487/RFC5082, October 2007, (GTSM)", RFC 5082, DOI 10.17487/RFC5082, October 2007,
<http://www.rfc-editor.org/info/rfc5082>. <http://www.rfc-editor.org/info/rfc5082>.
[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, DOI 10.17487/RFC5097, January 2008, protocol", RFC 5097, DOI 10.17487/RFC5097, January 2008,
<http://www.rfc-editor.org/info/rfc5097>. <http://www.rfc-editor.org/info/rfc5097>.
[RFC5790] Liu, H., Cao, W., and H. Asaeda, "Lightweight Internet [RFC5790] Liu, H., Cao, W. and H. Asaeda, "Lightweight Internet
Group Management Protocol Version 3 (IGMPv3) and Multicast Group Management Protocol Version 3 (IGMPv3) and Multicast
Listener Discovery Version 2 (MLDv2) Protocols", RFC 5790, Listener Discovery Version 2 (MLDv2) Protocols", RFC 5790,
DOI 10.17487/RFC5790, February 2010, DOI 10.17487/RFC5790, February 2010, <http://www.rfc-
<http://www.rfc-editor.org/info/rfc5790>. editor.org/info/rfc5790>.
[RFC6633] Gont, F., "Deprecation of ICMP Source Quench Messages", [RFC6633] Gont, F., "Deprecation of ICMP Source Quench Messages",
RFC 6633, DOI 10.17487/RFC6633, May 2012, RFC 6633, DOI 10.17487/RFC6633, May 2012, <http://www.rfc-
<http://www.rfc-editor.org/info/rfc6633>. editor.org/info/rfc6633>.
[RFC7657] Black, D., Ed. and P. Jones, "Differentiated Services [RFC7657] Black, D.Ed., and P. Jones, "Differentiated Services
(Diffserv) and Real-Time Communication", RFC 7657, (Diffserv) and Real-Time Communication", RFC 7657, DOI
DOI 10.17487/RFC7657, November 2015, 10.17487/RFC7657, November 2015, <http://www.rfc-
<http://www.rfc-editor.org/info/rfc7657>. editor.org/info/rfc7657>.
[STEVENS] "Stevens, W., Fenner, B., and A. Rudoff, "UNIX Network [STEVENS] "Stevens, W., Fenner, B., and A. Rudoff, "UNIX Network
Programming, The sockets Networking API", Addison- Programming, The sockets Networking API", Addison-
Wesley.", 2004. Wesley.", 2004.
Appendix A. Multicast Primitives Appendix A. Multicast Primitives
This appendix describes primitives that are used when UDP and UDP- This appendix describes primitives that are used when UDP and UDP-
Lite support IPv4/IPv6 Multicast. Guidance on the use of UDP and Lite support IPv4/IPv6 Multicast. Guidance on the use of UDP and
UDP-Lite for multicast services is provided in the UDP UDP-Lite for multicast services is provided in the UDP
Guidelines[RFC8085]. Guidelines[RFC8085].
IP multicast may be supported using the Any Source Multicast (ASM) IP multicast may be supported using the Any Source Multicast (ASM)
model or by the Source-Specific Multicast (SSM) model. The latter model or by the Source-Specific Multicast (SSM) model. The latter
requires use of a Multicast Source Filter (MSF) when specifying an IP requires use of a Multicast Source Filter (MSF) when specifying an IP
multicast group destination address. multicast group destination address.
skipping to change at page 15, line 37 skipping to change at page 15, line 21
requires use of a Multicast Source Filter (MSF) when specifying an IP requires use of a Multicast Source Filter (MSF) when specifying an IP
multicast group destination address. multicast group destination address.
Use of multicast requires additional primitives at the transport API Use of multicast requires additional primitives at the transport API
that need to be called to coordinate operation of the IPv4 and IPv6 that need to be called to coordinate operation of the IPv4 and IPv6
network layer protocols. For example, to receive datagrams sent to a network layer protocols. For example, to receive datagrams sent to a
group, an endpoint must first become a member of a multicast group at group, an endpoint must first become a member of a multicast group at
the network layer. Local multicast reception is signalled for IPv4 the network layer. Local multicast reception is signalled for IPv4
by the Internet Group Management Protocol (IGMP) [RFC3376] [RFC4604]. by the Internet Group Management Protocol (IGMP) [RFC3376] [RFC4604].
IPv6 uses the equivalent Multicast Listener Discovery (MLD) protocol IPv6 uses the equivalent Multicast Listener Discovery (MLD) protocol
[RFC3810] [RFC5790], carried over ICMPv6. A lightweight version of [RFC3810] [RFC5790], carried over ICMPv6. A lightweight version of
these protocols has also been specified [RFC5790]. these protocols has also been specified [RFC5790].
The following are defined: The following are defined:
JoinLocalGroup: 1 of the basic socket extensions for IPv6 [RFC3493] JoinLocalGroup: 1 of the basic socket extensions for IPv6 [RFC3493]
provides a function that allows receivi9ng traffic from a local provides a function that allows receivi9ng traffic from a local
IPv4 multicast group. IPv4 multicast group.
IPV6_MULTICAST_IF: Section 5.2 of the basic socket extensions for IPV6_MULTICAST_IF: Section 5.2 of the basic socket extensions for
IPv6 [RFC2553] states that this sets the interface that will be IPv6 [RFC2553] states that this sets the interface that will be
used for outgoing multicast packets. used for outgoing multicast packets.
IP_MULTICAST_TTL: This sets the time to live field t to use for IP_MULTICAST_TTL: This sets the time to live field t to use for
outgoing IPv4 multicast packets. This is used to limit scope of outgoing IPv4 multicast packets. This is used to limit scope of
multicast datagrams. Methods such as GTSM [RFC5082], set this multicast datagrams. Methods such as GTSM [RFC5082], set this
value to ensure link-local transmission. GTSM also requires the value to ensure link-local transmission. GTSM also requires the
UDP receiver API to pass the received value of this field to the UDP receiver API to pass the received value of this field to the
application. application.
IPV6_MULTICAST_HOPS: Section 5.2 of the basic socket extensions for IPV6_MULTICAST_HOPS: Section 5.2 of the basic socket extensions for
IPv6 [RFC2553] states that sets the hop count to use for outgoing IPv6 [RFC2553] states that sets the hop count to use for outgoing
multicast IPv6 packets. (This is equivalent to IP_MULTICAST_TTL multicast IPv6 packets. (This is equivalent to IP_MULTICAST_TTL
used for IPv4 multicast). used for IPv4 multicast).
IPV6_MULTICAST_LOOP: Section 5.2 of the basic socket extensions for IPV6_MULTICAST_LOOP: Section 5.2 of the basic socket extensions for
IPv6 [RFC2553] states that this sets whether a copy of a datagram IPv6 [RFC2553] states that this sets whether a copy of a datagram
is looped back by the IP layer for local delivery when the is looped back by the IP layer for local delivery when the
datagram is sent to a group to which the sending host itself datagram is sent to a group to which the sending host itself
belongs). belongs).
IPV6_JOIN_GROUP: Section 5.2 of the basic socket extensions for IPv6 IPV6_JOIN_GROUP: Section 5.2 of the basic socket extensions for IPv6
[RFC2553] provides a function that allows an endpoint to join an [RFC2553] provides a function that allows an endpoint to join an
IPv6 multicast group. IPv6 multicast group.
SIOCGIPMSFILTER: Section 8.1 of the socket interface for MSF SIOCGIPMSFILTER: Section 8.1 of the socket interface for MSF
[RFC3678] provides a function that allows reading the multicast [RFC3678] provides a function that allows reading the multicast
source filters. source filters.
SIOCSIPMSFILTER: Section 8.1 of the socket interface for MSF SIOCSIPMSFILTER: Section 8.1 of the socket interface for MSF
[RFC3678] provides a function that allows setting/modifying the [RFC3678] provides a function that allows setting/modifying the
multicast source filters. multicast source filters.
IPV6_LEAVE_GROUP: Section 5.2 of the basic socket extensions for IPV6_LEAVE_GROUP: Section 5.2 of the basic socket extensions for IPv6
IPv6 [RFC2553] provides a function that allows leaving an IPv6 [RFC2553] provides a function that allows leaving an IPv6
multicast group. multicast group.
LeaveHostGroup: Section 7.1 of the basic socket extensions for IPv6 LeaveHostGroup: Section 7.1 of the basic socket extensions for IPv6
[RFC3493] provides a function that allows leaving an IPv4 [RFC3493] provides a function that allows leaving an IPv4
multicast group. multicast group.
LeaveLocalGroup: Section 7.1 of the basic socket extensions for IPv6 LeaveLocalGroup: Section 7.1 of the basic socket extensions for IPv6
[RFC3493] provides a function that allows leaving a local IPv4 [RFC3493] provides a function that allows leaving a local IPv4
multicast group. multicast group.
Section 4.1.1 of the Socket Interface Extensions for MSF [RFC3678] Section 4.1.1 of the Socket Interface Extensions for MSF [RFC3678]
updates the multicast interface to add support for MSF for IPv4 and updates the multicast interface to add support for MSF for IPv4 and
IPv6 required by IGMPv3. Three sets of API functionality are IPv6 required by IGMPv3. Three sets of API functionality are defined:
defined:
1. IPv4 Basic (Delta-based) API. "Each function call specifies a 1. IPv4 Basic (Delta-based) API. "Each function call specifies a
single source address which should be added to or removed from single source address which should be added to or removed from
the existing filter for a given multicast group address on which the existing filter for a given multicast group address on which
to listen." to listen."
2. IPv4 Advanced (Full-state) API. "This API allows an application 2. IPv4 Advanced (Full-state) API. "This API allows an application
to define a complete source-filter comprised of zero or more to define a complete source-filter comprised of zero or more
source addresses, and replace the previous filter with a new source addresses, and replace the previous filter with a new
one." one."
3. Protocol-Independent Basic MSF (Delta-based) API 3. Protocol-Independent Basic MSF (Delta-based) API
4. Protocol-Independent Advanced MSF (Full-state) API 4. Protocol-Independent Advanced MSF (Full-state) API
It specifies the following primitives: It specifies the following primitives:
IP_ADD_MEMBERSHIP: This is used to join an ASM group. IP_ADD_MEMBERSHIP: This is used to join an ASM group.
IP_BLOCK_SOURCE: This MSF can block data from a given multicast IP_BLOCK_SOURCE: This MSF can block data from a given multicast
source to a given ASM or SSM group. source to a given ASM or SSM group.
IP_UNBLOCK_SOURCE: This updates an MSF to undo a previous call to IP_UNBLOCK_SOURCE: This updates an MSF to undo a previous call to
IP_UNBLOCK_SOURCE for an ASM or SSM group. IP_UNBLOCK_SOURCE for an ASM or SSM group.
IP_DROP_MEMBERSHIP: This is used to leave an ASM or SSM group. (In IP_DROP_MEMBERSHIP: This is used to leave an ASM or SSM group. (In
SSM, this drops all sources that have been joined for a particular SSM, this drops all sources that have been joined for a particular
group and interface. The operations are the same as if the socket group and interface. The operations are the same as if the socket
had been closed.) had been closed.)
Section 4.1.2 of the socket interface for MSF [RFC3678] updates the Section 4.1.2 of the socket interface for MSF [RFC3678] updates the
interface to add IPv4 MSF support to IGMPv3 using ASM: interface to add IPv4 MSF support to IGMPv3 using ASM:
IP_ADD_SOURCE_MEMBERSHIP: This is used to join an SSM group. IP_ADD_SOURCE_MEMBERSHIP: This is used to join an SSM group.
IP_DROP_SOURCE_MEMBERSHIP: This is used to leave an SSM group. IP_DROP_SOURCE_MEMBERSHIP: This is used to leave an SSM group.
Section 4.1.2 of the socket interface for MSF [RFC3678] defines the Section 4.1.2 of the socket interface for MSF [RFC3678] defines the
Advanced (Full-state) API: Advanced (Full-state) API:
setipv4sourcefilter This is used to join an IPv4 multicast group, or setipv4sourcefilter This is used to join an IPv4 multicast group, or
to enable multicast from a specified source. to enable multicast from a specified source.
getipv4sourcefilter: This is used to leave an IPv4 multicast group, getipv4sourcefilter: This is used to leave an IPv4 multicast group,
or to filter multicast from a specified source. or to filter multicast from a specified source.
Section 5.1 of the socket interface for MSF [RFC3678] specifies Section 5.1 of the socket interface for MSF [RFC3678] specifies
Protocol-Independent Multicast API functions: Protocol-Independent Multicast API functions:
MCAST_JOIN_GROUP This is used to join an ASM group. MCAST_JOIN_GROUP This is used to join an ASM group.
MCAST_JOIN_SOURCE_GROUP This is used to join an SSM group. MCAST_JOIN_SOURCE_GROUP This is used to join an SSM group.
MCAST_BLOCK_SOURCE: This is used to block a source in an ASM group. MCAST_BLOCK_SOURCE: This is used to block a source in an ASM group.
MCAST_UNBLOCK_SOURCE: This removes a previous MSF set by MCAST_UNBLOCK_SOURCE: This removes a previous MSF set by
MCAST_BLOCK_SOURCE. MCAST_BLOCK_SOURCE.
MCAST_LEAVE_GROUP: This leaves a SSM group. MCAST_LEAVE_GROUP: This leaves a SSM group.
MCAST_LEAVE_GROUP: This leaves an ASM or SSM group. MCAST_LEAVE_GROUP: This leaves an ASM or SSM group.
Section 5.2 of the socket interface for MSF [RFC3678] specifies the Section 5.2 of the socket interface for MSF [RFC3678] specifies the
Protocol-Independent Advanced MSF (Full-state) API applicable for Protocol-Independent Advanced MSF (Full-state) API applicable for
both IPv4 and IPv6: both IPv4 and IPv6:
setsourcefilter This is used to join an IPv4 or IPv6 multicast setsourcefilter This is used to join an IPv4 or IPv6 multicast group,
group, or to enable multicast from a specified source. or to enable multicast from a specified source.
getsourcefilter: This is used to leave an IPv4 or IPv6 multicast getsourcefilter: This is used to leave an IPv4 or IPv6 multicast
group, or to filter multicast from a specified source. group, or to filter multicast from a specified source.
The Lightweight IGMPv3 (LW_IGMPv3) and MLDv2 protocol [RFC5790] The Lightweight IGMPv3 (LW_IGMPv3) and MLDv2 protocol [RFC5790]
updates this interface (in Section 7.2 of RFC5790). updates this interface (in Section 7.2 of RFC5790).
Appendix B. Revision Notes Appendix B. Revision Notes
Note to RFC-Editor: please remove this entire section prior to Note to RFC-Editor: please remove this entire section prior to
publication. publication.
skipping to change at page 19, line 35 skipping to change at page 18, line 56
o Editorial changes were make to complete the document for a WGLC. o Editorial changes were make to complete the document for a WGLC.
o Rephrasing to eliminate using references as nouns, and to make o Rephrasing to eliminate using references as nouns, and to make
text more consistent. text more consistent.
o One appendix was incorporated. o One appendix was incorporated.
o This appendix was moved to the end (for later deletion by the RFC- o This appendix was moved to the end (for later deletion by the RFC-
Ed). Ed).
TAPS WG draft -02:
o Updated to align with latest taps-transport-usage ID.
o Revised to clarify MTU usage and track work in IPv6 PMTU
o Usage of DF clarified.
Authors' Addresses Authors' Addresses
Godred Fairhurst Godred Fairhurst
University of Aberdeen University of Aberdeen
School of Engineering School of Engineering
Fraser Noble Building Fraser Noble Building
Fraser Noble Building Aberdeen AB24 3UE Fraser Noble Building Aberdeen, AB24 3UE
UK UK
Email: gorry@erg.abdn.ac.uk Email: gorry@erg.abdn.ac.uk
Tom Jones Tom Jones
University of Aberdeen University of Aberdeen
School of Engineering School of Engineering
Fraser Noble Building Fraser Noble Building
Aberdeen AB24 3UE Aberdeen, AB24 3UE
UK UK
Email: tom@erg.abdn.ac.uk Email: tom@erg.abdn.ac.uk
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