draft-ietf-cuss-sip-uui-isdn-11.txt   rfc7434.txt 
CUSS K. Drage, Ed. Internet Engineering Task Force (IETF) K. Drage, Ed.
Internet-Draft Alcatel-Lucent Request for Comments: 7434 Alcatel-Lucent
Intended status: Standards Track A. Johnston Category: Standards Track A. Johnston
Expires: May 15, 2015 Avaya ISSN: 2070-1721 Avaya
November 11, 2014 January 2015
Interworking ISDN Call Control User Information with SIP Interworking ISDN Call Control User Information with SIP
draft-ietf-cuss-sip-uui-isdn-11
Abstract Abstract
The motivation and use cases for interworking and transporting ITU-T The motivation and use cases for interworking and transporting User-
DSS1 User-user information element data in SIP are described in RFC to-User Information (UUI) from the ITU-T Digital Subscriber
6567. As networks move to SIP, it is important that applications Signalling System No. 1 (DSS1) User-user information element within
requiring this data can continue to function in SIP networks as well SIP are described in RFC 6567. As networks move to SIP, it is
as the ability to interwork with this ISDN service for end-to-end important that applications requiring this data can continue to
transparency. This document defines a usage (a new package called function in SIP networks as well as have the ability to interwork
the ISDN UUI package) of the User-to-User header field to enable with this ISDN service for end-to-end transparency. This document
interworking with this ISDN service. defines a usage (a new package called the ISDN UUI package) of the
User-to-User header field to enable interworking with this ISDN
This document covers the interworking with both public ISDN and service.
private ISDN capabilities, so the potential interworking with QSIG
will also be addressed.
The package is identified by a new value "isdn-uui" of the "purpose" This document covers interworking with both public ISDN and private
header field parameter. ISDN capabilities, so the potential interworking with QSIG will also
be addressed.
Status of this Memo The package is identified by the new value "isdn-uui" of the
"purpose" header field parameter.
This Internet-Draft is submitted in full conformance with the Status of This Memo
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering This is an Internet Standards Track document.
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 This document is a product of the Internet Engineering Task Force
and may be updated, replaced, or obsoleted by other documents at any (IETF). It represents the consensus of the IETF community. It has
time. It is inappropriate to use Internet-Drafts as reference received public review and has been approved for publication by the
material or to cite them other than as "work in progress." Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 5741.
This Internet-Draft will expire on May 15, 2015. Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc7434.
Copyright Notice Copyright Notice
Copyright (c) 2014 IETF Trust and the persons identified as the Copyright (c) 2015 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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Table of Contents Table of Contents
1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Summary of the ISDN User-to-User Service . . . . . . . . . . 3
3.1. The Service . . . . . . . . . . . . . . . . . . . . . . . 3
3.2. Impacts of the ISDN Service on SIP Operation . . . . . . 6
4. Relation to SIP-T . . . . . . . . . . . . . . . . . . . . . . 6
5. Transition Away from ISDN . . . . . . . . . . . . . . . . . . 7
6. ISDN Usage of the User-to-User Header Field . . . . . . . . . 7
7. UAC Requirements . . . . . . . . . . . . . . . . . . . . . . 8
8. UAS Requirements . . . . . . . . . . . . . . . . . . . . . . 10
9. UUI Contents . . . . . . . . . . . . . . . . . . . . . . . . 11
10. Considerations for ISDN Interworking Gateways . . . . . . . . 12
11. Coding Requirements . . . . . . . . . . . . . . . . . . . . . 12
12. Media Feature Tag . . . . . . . . . . . . . . . . . . . . . . 13
13. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13
14. Security Considerations . . . . . . . . . . . . . . . . . . . 14
15. References . . . . . . . . . . . . . . . . . . . . . . . . . 15
15.1. Normative References . . . . . . . . . . . . . . . . . . 15
15.2. Informative References . . . . . . . . . . . . . . . . . 16
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 17
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 17
1. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Overview
2. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Summary of the ISDN User-to-User Service . . . . . . . . . . . 3
3.1. The service . . . . . . . . . . . . . . . . . . . . . . . 3
3.2. Impacts of the ISDN service on SIP operation . . . . . . . 5
4. Relation to SIP-T . . . . . . . . . . . . . . . . . . . . . . 6
5. Transition away from ISDN . . . . . . . . . . . . . . . . . . 6
6. ISDN Usage of the User-to-User Header Field . . . . . . . . . 7
7. UAC requirements . . . . . . . . . . . . . . . . . . . . . . . 8
8. UAS requirements . . . . . . . . . . . . . . . . . . . . . . . 9
9. UUI contents . . . . . . . . . . . . . . . . . . . . . . . . . 10
10. Considerations for ISDN internetworking gateways . . . . . . . 11
11. Coding requirements . . . . . . . . . . . . . . . . . . . . . 12
12. Media Feature Tag . . . . . . . . . . . . . . . . . . . . . . 12
13. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12
14. Security Considerations . . . . . . . . . . . . . . . . . . . 14
15. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 14
16. References . . . . . . . . . . . . . . . . . . . . . . . . . . 15
16.1. Normative References . . . . . . . . . . . . . . . . . . . 15
16.2. Informative References . . . . . . . . . . . . . . . . . . 15
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 16
1. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
2. Overview
This document describes a usage of the User-to-User header field This document describes a usage of the User-to-User header field
defined in [I-D.ietf-cuss-sip-uui] to enable the transport of User- defined in [RFC7433] to enable the transport of UUI in ISDN
to-User Information (UUI) in ISDN interworking scenarios using SIP interworking scenarios using SIP [RFC3261]. Specifically, this
[RFC3261]. Specifically, this document discusses the interworking of document discusses the interworking of the following items, which are
call control related ITU-T DSS1 User-user information element Q931 call control related: ITU-T Recommendation Q.931 DSS1 User-user
[Q931], Q957.1 [Q957.1] and ITU-T Q.763 User-to-user information information element [Q931], ITU-T Recommendation Q.957.1 DSS1 User-
parameter [Q763] data in SIP. UUI is widely used in the PSTN today to-User Signalling (UUS) supplementary service [Q957.1], and ITU-T
in contact centers and call centers which are transitioning away from Recommendation Q.763 User-to-User information parameter [Q763] data
ISDN to SIP. in SIP. Today, UUI is widely used in the Public Switched Telephone
Network (PSTN) in contact centers and call centers that are
transitioning away from ISDN to SIP.
This usage is not limited to scenarios where interworking will occur. This usage is not limited to scenarios where interworking will occur.
Rather it describes a usage where interworking is possible if Rather it describes a usage where interworking is possible if
interworking is met. That does not preclude its usage directly interworking is met. That does not preclude its usage directly
between two SIP terminals. between two SIP terminals.
2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
3. Summary of the ISDN User-to-User Service 3. Summary of the ISDN User-to-User Service
3.1. The service 3.1. The Service
ISDN defines a number of related services. Firstly there is a user ISDN defines a number of related services. Firstly, there is a user
signalling bearer service, which uses the information elements / signalling bearer service that uses the information elements /
parameters in the signalling channel to carry the data, and does not parameters in the signalling channel to carry the data and does not
establish a related circuit-switched connection. For DSS1, this is establish a related circuit-switched connection. For DSS1, this is
specified in ITU-T Recommendation Q.931 section 3.3 and section 7 specified in ITU-T Recommendation Q.931, Sections 3.3 and 7 of
[Q931]. It also defines a User-to-User signalling supplementary [Q931]. Secondly, it defines a User-to-User Signalling (UUS)
service, which uses the information elements / parameters in the supplementary service that uses the information elements / parameters
signalling channel to carry additional data, but which is used in in the signalling channel to carry additional data but that is used
conjunction with the establishment of a related circuit-switched in conjunction with the establishment of a related circuit-switched
connection. This reuses the same information elements / parameters connection. This reuses the same information elements / parameters
as the user signalling bearer service, with the addition of other as the user signalling bearer service, with the addition of other
signalling information, and for DSS1 this is specified in ITU-T signalling information, and for DSS1 this is specified in ITU-T
Recommendation Q.957.1 [Q957.1]. Recommendation Q.957.1 [Q957.1].
ISDN defines three variants of the User-to-User signalling ISDN defines three variants of the UUS supplementary service as
supplementary service as follows: follows:
UUS1: User-to-User information exchanged during the setup and UUS1: User-to-User Information exchanged during the setup and
clearing phases of a call, by transporting DSS1 User-user clearing phases of a call by transporting DSS1 User-user
information elements within call control messages. This in itself information elements within call control messages. This in itself
has two subvariants, UUS1 implicit and UUS1 explicit. In UUS1 has two subvariants, UUS1 implicit and UUS1 explicit. In UUS1
implicit, it is the presence of the user signalling data itself implicit, it is the presence of the user signalling data itself
that constitutes the request for the service. UUS1 explicit uses that constitutes the request for the service. UUS1 explicit uses
additional supplementary service control information to control additional supplementary service control information to control
the request and granting of the service, as in UUS2 and UUS3. the request and granting of the service, as in UUS2 and UUS3. As
UUS1 explicit as a result also allows the requester to a result, UUS1 explicit also allows the requester to additionally
additionally specify whether the parallel circuit-switched specify whether the parallel circuit-switched connection should
connection should proceed if the UUS1 service cannot be provided proceed if the UUS1 service cannot be provided (preferred or
(preferred or required); required);
UUS2: DSS1 User-user information elements exchanged from the UUS2: DSS1 User-user information elements exchanged from the
sender's point of view during call establishment, between the DSS1 sender's point of view during call establishment, between the DSS1
ALERTING and DSS1 CONNECT messages, within DSS1 USER INFORMATION ALERTING and DSS1 CONNECT messages, within DSS1 USER INFORMATION
messages; and messages; and
UUS3: DSS1 User-user information elements exchanged while a call is UUS3: DSS1 User-user information elements exchanged while a call is
in the Active state, within DSS1 USER INFORMATION messages. in the Active state, within DSS1 USER INFORMATION messages.
The service is always requested by the calling user. The service is always requested by the calling user.
This document defines only the provision of the ISDN UUS1 implicit This document defines only the provision of the ISDN UUS1 implicit
supplementary service to interworking scenarios, this being the most supplementary service to interworking scenarios, this being the most
widely deployed and used of the various ISDN User-to-User services, widely deployed and used of the various ISDN User-to-User services,
and indeed the one that matches the requirements specified in RFC6567 and is indeed the one that matches the requirements specified in
[RFC6567]. [RFC6567].
The above come from the ISDN specifications defined for public The above comes from the ISDN specifications defined for public
networks. There are a parallel set of ISDN specifications defined networks. There is a parallel set of ISDN specifications defined for
for private networks (QSIG}. These specifications do not define a private networks (QSIG). These specifications do not define a UUS1
UUS1 implicit supplementary service. However, implementation of such implicit supplementary service. However, implementation of such a
a UUS1 implicit supplementary service for private networks can UUS1 implicit supplementary service for private networks can readily
readily be constructed in a proprietary fashion based on the be constructed in a proprietary fashion based on the specifications
specifications for public networks, and evidence suggests that some for public networks, and evidence suggests that some vendors have
vendors have done so. On this basis, there is no reason why this done so. On this basis, there is no reason why this package cannot
package cannot also be used to support interworking with such a also be used to support interworking with such a private network
private network service, on the assumption that the constraints are service, on the assumption that the constraints are exactly the same
exactly the same as those for the public network. as those for the public network.
The ISDN UUS1 service has the following additional characteristics as The ISDN UUS1 service has the following additional characteristics as
to the data that can be transported: to the data that can be transported:
The maximum number of octets of user information that can be The maximum number of octets of user information that can be
transported is 128 octets plus a protocol discriminator. It is transported is 128 octets plus a protocol discriminator. It is
noted that some early ISDN implementations had a limitation of 32 noted that some early ISDN implementations had a limitation of 32
octets, but it is understood that these are not currently octets, but it is understood that these are not currently
deployed. While this package does not prohibit longer data deployed. While this package does not prohibit longer data
fields, the mechanism at any interworking point is to discard data fields, the mechanism at any interworking point discards data
elements that are too long to handle. The handled length can elements that are too long to handle. The handled length can
normally be assumed to be 128 octets. normally be assumed to be 128 octets.
The content of the user information octets is described by a The content of the user information octets is described by a
single octet protocol discriminator (see table 4-26 of ITU-T single octet protocol discriminator (see Table 4-26 of ITU-T
Recommendation Q.931) [Q931]. That protocol descriminator may Recommendation Q.931) [Q931]. That protocol discriminator may
describe the protocol used within the user data, the structure of describe the protocol used within the user data, the structure of
the user data, or leave it entirely open. Note that not all the user data, or leave it entirely open. Note that not all
values within the protocol discriminator necessarily make sense values within the protocol discriminator necessarily make sense
for use in the ISDN User-to-User service, as the content is for use in the ISDN User-to-User service, as the content is
aligned with the protocol discriminator that appears at the start aligned with the protocol discriminator that appears at the start
of all DSS1 messages (see table 4-1 of ITU-T Recommendation Q.931) of all DSS1 messages (see Table 4-1 of ITU-T Recommendation Q.931)
[Q931]. The protocol discriminator value has no impact on the [Q931]. The protocol discriminator value has no impact on the
interworking capability. interworking capability.
Only a single user information can be transported in each message. Only a single piece of UUI data can be transported in each
message.
The ISDN service works without encryption or integrity protection. The ISDN service works without encryption or integrity protection.
The user trusts the intermediate network elements, and therefore The user trusts the intermediate network elements, and therefore
the operator of those elements, not to modify the data, and to the operator of those elements, not to modify the data and to
deliver all the data to the remote user. On a link by link basis, deliver all the data to the remote user. On a link-by-link basis,
message contents are protected at layer 2 by standard CRC message contents are protected at Layer 2 by standard cyclic
mechanisms - this allows loss on a link level basis to be redundancy check mechanisms -- this allows loss on a link-level
detected, but does not guard against fraudulent attacks on the basis to be detected but does not guard against fraudulent attacks
link itself. This does not prevent the use of additional on the link itself. This does not prevent the use of additional
encryption or integrity protection within the UUI data itself, encryption or integrity protection within the UUI data itself,
although the limit on the size of the UUI data (protocol although the limit on the size of the UUI data (protocol
discriminator plus 128 octets) will restrict this. discriminator plus 128 octets) will restrict this.
3.2. Impacts of the ISDN service on SIP operation 3.2. Impacts of the ISDN Service on SIP Operation
The ISDN service has the following impacts that need to be understood The ISDN service has the following impacts that need to be understood
within the SIP environment. within the SIP environment.
Call transfer: ISDN call transfer cancels all ISDN User-to-User Call transfer: ISDN call transfer cancels all ISDN User-to-User
supplementary services. In the ISDN, if User-to-User data is supplementary services. In the ISDN, if User-to-User data is
required after call transfer, then UUS3 has to be renegotiated, required after call transfer, then UUS3 has to be renegotiated,
which is not provided by this SIP extension. The impact of this which is not provided by this SIP extension. The impact of this
restriction on the SIP environment is that UUI header fields restriction on the SIP environment is that UUI header fields
cannot be exchanged in transactions clearing down the SIP dialog cannot be exchanged in transactions clearing down the SIP dialog
after call transfer has occurred. after call transfer has occurred.
Conference: ISDN conferencing allows the user to still exchange Conference: ISDN conferencing allows the user to still exchange
User-to-User data after the conference is created. As far as UUS1 User-to-User data after the conference is created. As far as UUS1
is concerned, it is not permitted. The ISDN three-party is concerned, it is not permitted. The ISDN three-party
supplementary service is similar in many ways to conferencing, but supplementary service is similar in many ways to conferencing but
is signalled using a different mechanism. This means that on is signalled using a different mechanism. This means that on
clearing, the controller using UUS1 implicit does have the choice clearing, the controller using UUS1 implicit does have the choice
of sending data to either or both remote users. Because SIP of sending data to either or both remote users. Because SIP
conferencing cannot completely emulate the ISDN three-party conferencing cannot completely emulate the ISDN three-party
supplementary service at the served user, UUS1 implicit is not supplementary service at the served user, UUS1 implicit is not
possible. possible.
Diversion: When ISDN diversion occurs, any UUS1 User-to-User data is Diversion: When ISDN diversion occurs, any UUS1 User-to-User data is
sent to the forwarded-to-user (assuming that the call meets sent to the forwarded-to-user (assuming that the call meets
requirements for providing the service - this is impacted by the requirements for providing the service -- this is impacted by the
explicit service only). If the type of diversion is such that the explicit service only). If the type of diversion is such that the
call is also delivered to the forwarding user, they will also call is also delivered to the forwarding user, they will also
receive any UUS1 User-to-User data. receive any UUS1 User-to-User data.
4. Relation to SIP-T 4. Relation to SIP-T
A method of transport of ISDN User-to-User data is to use SIP-T A method of transport of ISDN User-to-User data is to use SIP-T
[RFC3372] and transport the UUI information end-to-end, as part of an [RFC3372] and transport the UUI information end-to-end (as part of an
ISUP message or QSIG message) as a MIME body. If the SIP-T method of ISUP message or QSIG message) as a MIME body. If the SIP-T method of
encapsulation of ISDN instead of interworking is used, this is a encapsulation of ISDN instead of interworking is used, this is a
reasonable mechanism and does not require any extensions to existing reasonable mechanism and does not require any extensions to existing
SIP-T. However, if true ISDN interworking is being done, and SIP-T. However, if true ISDN interworking is being done, and
therefore SIP-T would not otherwise be used, this approach is not therefore SIP-T would not otherwise be used, this approach is not
reasonable, because then implementation of the many elements of ISUP reasonable because then implementation of the many elements of the
syntax would be required to understand one element of data. Instead, ISUP syntax would be required to understand one element of data.
the better approach is to interwork the ISDN User-to-User data using Instead, the better approach is to interwork the ISDN User-to-User
the native SIP UUI transport mechanism, the User-to-User header data using the native SIP UUI transport mechanism, the User-to-User
field. The rest of this document describes this approach. header field. The rest of this document describes this approach.
5. Transition away from ISDN 5. Transition Away from ISDN
This interworking usage of the SIP UUI mechanism will likely begin This interworking usage of the SIP UUI mechanism will likely begin
with one User Agent being an ISDN gateway while the other User Agent with one UA as an ISDN gateway while the other UA is a native SIP
is a native SIP endpoint. As networks transition away from ISDN, it endpoint. As networks transition away from ISDN, it is possible that
is possible that both User Agents could become native SIP endpoints. both UAs could become native SIP endpoints. In this case, there is
In this case, there is an opportunity to transition away from this an opportunity to transition away from this ISDN usage to a more
ISDN usage to a more general usage of [I-D.ietf-cuss-sip-uui]. general usage of [RFC7433].
The SIP UUI mechanism provides a way to achieve this transition. As The SIP UUI mechanism provides a way to achieve this transition. As
an endpoint moves from being an ISDN gateway to a native SIP an endpoint moves from being an ISDN gateway to a native SIP
endpoint, and a future package for some form of enhanced UUI has been endpoint, and a future package for some form of enhanced UUI has been
standardized, the endpoint can carry the UUI data both as ISDN and as standardized, the endpoint can carry the UUI data both as ISDN and as
the future package in parallel, and in the same messages or in the future package in parallel and in the same messages or in
different messages depending on the needs of the application. This different messages depending on the needs of the application. This
will permit the other endpoint to use the UUI according to the ISDN will permit the other endpoint to use the UUI according to the ISDN
UUI package if it is an ISDN gateway or the future package if it is a UUI package if it is an ISDN gateway or according to the future
native SIP endpoint. package if it is a native SIP endpoint.
6. ISDN Usage of the User-to-User Header Field 6. ISDN Usage of the User-to-User Header Field
This document defines the package for the ISDN interworking of UUI This document defines the package for the ISDN interworking of UUI
which is to interoperate with ISDN User-to-User Signaling (UUS), a that interoperates with ISDN UUS, a supplementary service in which
supplementary service in which the user is able to send/receive a the user is able to send/receive a limited amount of information to/
limited amount of information to/from another ISDN user over the from another ISDN user over the signalling channel in association
signalling channel in association with a call to the other ISDN user. with a call to the other ISDN user.
Two examples of ISDN UUI with redirection (transfer and diversion) Two examples of ISDN UUI with redirection (transfer and diversion)
are defined in [ANSII] and [ETSI]. are defined in [ANSII] and [ETSI].
One objective of the design of this package has been to keep the One objective of the design of this package has been to keep the
functionality at the interworking point as simple as possible. As a functionality at the interworking point as simple as possible. As a
result there is also only one encoding value specified. result, there is also only one encoding value specified.
Responsibility for respecting the limits has been transferred to the Responsibility for respecting the limits has been transferred to the
end UA. If an interworking point is reached, and the limitations of end UA. If an interworking point is reached, and the limitations of
the ISDN (see section 3.1) are not met, then the UUI data will not be the ISDN (see Section 3.1) are not met, then the UUI data will not be
transferred, although the SIP request will otherwise be interworked. transferred, although the SIP request will otherwise be interworked.
This is rather than have the interworking point attempt to resolve This is rather than have the interworking point attempt to resolve
the non- compliance with the limitations of ISDN. the non-compliance with the limitations of ISDN.
The general principals of this package of the UUI mechanism are The general principals of the UUI mechanism package are, therefore,
therefore as follows: as follows:
That the sending application is expected to limit their sending The sending application is expected to limit their sending
requirements to the subset provided by the ISDN User-to-User requirements to the subset provided by the ISDN User-to-User
service. service.
That the SIP UA will not allow the reception of more that one The SIP UA will not allow the reception of more than one
User-to-User header field relating to the "isdn-uui" package in User-to-User header field relating to the "isdn-uui" package in
the same SIP request or response, and will only allow it in a the same SIP request or response; it will only allow it in a
request or response of the appropriate method (INVITE or BYE). request or response of the appropriate method (INVITE or BYE).
What happens to User-to-User header fields relating to other What happens to User-to-User header fields relating to other
packages is outside the scope of this document. packages is outside the scope of this document.
That an interworking point trying to interwork UUI data that is An interworking point trying to interwork UUI data that is too
too long will discard the UUI data, but proceed with the long will discard the UUI data but proceed with the interworking.
interworking. There is no notification of such discard back to There is no notification of such discard back to the sending user.
the sending user. If the SIP user knows that it is interworking If the SIP user knows that it is interworking with the ISDN, then
with the ISDN, then the UUI application at the SIP endpoint should the UUI application at the SIP endpoint should limit its
limit its communication to 128 octet packets plus the protocol communication to packets of 128 octets plus the protocol
discriminator, in the knowledge that discard will occur if it does discriminator, with the knowledge that discard will occur if it
not. The UUI application at the SIP endpoint has complete control does not. The UUI application at the SIP endpoint has complete
over what occurs. It should be noted that this was exactly the control over what occurs. It should be noted that this was
envisaged operation when early ISDN implementations that only exactly the envisaged operation when early ISDN implementations
supported 32 octets interworked with those supporting 128 octets. that only supported 32 octets interworked with those supporting
It also corresponds to the interworking with ISDNs that do not 128 octets. It also corresponds to the interworking with ISDNs
support the supplementary service at all, as discard will occur in that do not support the supplementary service at all, as discard
these circumstances as well. Note that failure to include the will occur in these circumstances as well. Note that failure to
User-to-User data into the ISDN SETUP message (when discard include the User-to-User data into the ISDN SETUP message (when
occurs) will result in the service being unavailable for the discard occurs) will result in the service being unavailable for
remainder of the call when UUS1 implicit operation is used. the remainder of the call when UUS1 implicit operation is used.
7. UAC requirements 7. UAC Requirements
The UAC MUST meet the requirements of [I-D.ietf-cuss-sip-uui] in The User Agent Client (UAC) MUST meet the requirements of [RFC7433]
addition to the requirements defined in this document. in addition to the requirements defined in this document.
The UAC MUST only use this package of the UUI mechanism extension in The UAC MUST only use this UUI mechanism extension package in
association with the initial INVITE method and the BYE method association with the initial INVITE method and the BYE method
relating to an INVITE dialog. Usage on transactions associated with relating to an INVITE dialog. Usage on transactions associated with
any other type of dialog, or on methods not associated with a dialog any other type of dialog, or on methods not associated with a dialog,
is precluded. Usage on other methods within the INVITE dialog, and is precluded. Usage on other methods within the INVITE dialog, and
on re-INVITE transactions with the INVITE dialog, is also precluded. on re-INVITE transactions with the INVITE dialog, is also precluded.
If the UAC wishes to use or permit the sending of UUI data at any If the UAC wishes to use or permit the sending of UUI data at any
point in the dialog, the UAC MUST include in the INVITE request for point in the dialog, the UAC MUST include in the INVITE request for
that dialog a User-to-User header field. The UAC SHOULD set the that dialog a User-to-User header field. The UAC SHOULD set the
"purpose" header field parameter to "isdn-uui". Non-inclusion of the "purpose" header field parameter to "isdn-uui". Non-inclusion of the
"purpose" header field parameter is permitted, but this is primarily "purpose" header field parameter is permitted, but this is primarily
to allow earlier implementations to support this package. This to allow earlier implementations to support this package. This
initial header field constitutes the implicit request to use the UUI initial header field constitutes the implicit request to use the UUI
service, and is therefore included even when there is no data except service and is, therefore, included even when there is no data except
the protocol discriminator octet to send at that point in time. the protocol discriminator octet to send at that point in time.
The UAC MUST NOT include the User-to-User header field with a The UAC MUST NOT include the User-to-User header field with a
"purpose" header field parameter set to "isdn-uui", or with no "purpose" header field parameter set to "isdn-uui", or with no
"purpose" header field parameter, in any message of an INVITE dialog "purpose" header field parameter, in any message of an INVITE dialog
if the original INVITE request did not include the User-to-User if the original INVITE request did not include the User-to-User
header field, either with a "purpose" header field parameter set to header field, either with a "purpose" header field parameter set to
"isdn-uui", or with no "purpose" header field parameter included. "isdn-uui" or with no "purpose" header field parameter included.
When sending UUI for the ISDN UUI package, if the "purpose" header When sending UUI for the ISDN UUI package, if the "purpose" header
field is included, the UAC MUST set the User-to-User "purpose" header field is included, the UAC MUST set the User-to-User "purpose" header
field parameter to "isdn-uui". The UAC MUST NOT include more than field parameter to "isdn-uui". The UAC MUST NOT include more than
one User-to-User header field for this package in any SIP request or one User-to-User header field for this package in any SIP request or
response. response.
When receiving UUI, when multiple User-to-User header fields are When receiving UUI, when multiple User-to-User header fields are
received in the same response with the "purpose" header field received in the same response with the "purpose" header field
parameter to "isdn-uui", or with no "purpose" header field parameter, parameter set to "isdn-uui", or with no "purpose" header field
or with some combination of these, the UAC MUST discard all these parameter, or with some combination of these, the UAC MUST discard
header fields. There are no mechanisms for determining which was the all these header fields. There are no mechanisms for determining
intended UUI data so all are discarded. which ones are the intended UUI data, so all are discarded.
The application designer will need to take into account the ISDN The application designer will need to take into account the ISDN
service restrictions; failure to do so can result in information service restrictions; failure to do so can result in information
being discarded at any interworking point with the ISDN. This being discarded at any interworking point with the ISDN. This
document makes no further normative requirements based on those document makes no further normative requirements based on those
constraints, because those constraints may vary from one ISDN to constraints because those constraints may vary from one ISDN to
another. It is reasonable to expect that a limitation of 128 octets another. It is reasonable to expect that a limitation of 128 octets
(plus a protocol discriminator) can be imposed by the ISDN, and (plus a protocol discriminator) can be imposed by the ISDN;
therefore UUI data longer than this will never reach the destination therefore, UUI data longer than this will never reach the destination
if such interworking occurs. Note that the 128 octet limit (plus a if such interworking occurs. Note that the 128-octet limit (plus a
protocol discriminator) applies before the encoding (or after the protocol discriminator) applies before the encoding (or after the
decoding) using the "hex" encoding. The "hex" encoding is defined in decoding) using the "hex" encoding. The "hex" encoding is defined in
[I-D.ietf-cuss-sip-uui]. [RFC7433].
[I-D.ietf-cuss-sip-uui] defines a "uui" option tag for use with the A "uui" option tag for use with the UUI mechanism extension is
UUI mechanism extension. Because for the ISDN User-to-User service, defined in [RFC7433]. Because the service is UUS1 implicit for the
the service is UUS1 implicit, the inclusion of the "uui" option tag ISDN User-to-User service, the inclusion of the "uui" option tag in a
in a Supported header field conveys no additional information over Supported header field conveys no additional information over and
and above the presence, in the INVITE request, of the User-to-User above the presence, in the INVITE request, of the User-to-User header
header field with the "purpose" header field parameter set to "isdn- field with the "purpose" header field parameter set to "isdn-uui".
uui". While there is no harm in including the "uui" option tag, and While there is no harm in including the "uui" option tag, and
strictly it should be included if the extension is supported, it strictly it should be included if the extension is supported, it
performs no function. The presence of the "uui" option tag in the performs no function. The presence of the "uui" option tag in the
Require header field of an INVITE request will cause the request to Require header field of an INVITE request will cause the request to
fail if it reaches a UAS or ISDN interworking gateway that does not fail if it reaches a UAS or ISDN interworking gateway that does not
support this extension; such a usage is not precluded although it support this extension; such usage is allowed but will produce
does not form part of the package. results that are inconsistent with the mechanisms defined in the ISDN
UUS supplementary service.
8. UAS requirements 8. UAS Requirements
The UAS MUST meet the requirements of [I-D.ietf-cuss-sip-uui] in The UAS MUST meet the requirements of [RFC7433] in addition to the
addition to the requirements defined in this document. requirements defined in this document.
The UAS MUST only use this package of the UUI mechanism extension in The UAS MUST only use this UUI mechanism extension package in
association with the initial INVITE method and the BYE method association with the initial INVITE method and the BYE method
relating to an INVITE dialog. Usage on transactions associated with relating to an INVITE dialog. Usage on transactions associated with
any other type of dialog, or on methods not associated with a dialog any other type of dialog, or on methods not associated with a dialog,
is precluded. Usage on other methods within the INVITE dialog, and is precluded. Usage on other methods within the INVITE dialog, and
on re-INVITE transactions with the INVITE dialog, is also precluded. on re-INVITE transactions with the INVITE dialog, is also precluded.
The UAS MUST NOT include the User-to-User header field with a The UAS MUST NOT include the User-to-User header field with a
"purpose" header field parameter set to "isdn-uui", or with no "purpose" header field parameter set to "isdn-uui", or with no
"purpose" header field parameter, in any message of an INVITE dialog "purpose" header field parameter, in any message of an INVITE dialog
if the original INVITE request did not include the User-to-User if the original INVITE request did not include the User-to-User
header field, either with a "purpose" header field parameter set to header field, either with a "purpose" header field parameter set to
"isdn-uui", or with no "purpose" header field parameter included. "isdn-uui" or with no "purpose" header field parameter included.
The UAS MAY include the User-to-User header field in responses to the The UAS MAY include the User-to-User header field in responses to the
initial INVITE request, or the BYE requests or responses for the initial INVITE request, or the BYE requests or responses for the
dialog, only where the original INVITE request included a User-to- dialog, only where the original INVITE request included a
User header field with the "purpose" header field parameter set to User-to-User header field with the "purpose" header field parameter
"isdn-uui", or where no "purpose" header field parameter was set to "isdn-uui" or where no "purpose" header field parameter was
included. When sending UUI for the ISDN UUI package, the UAS SHOULD included. When sending UUI for the ISDN UUI package, the UAS SHOULD
set the User-to-User "purpose" header field parameter to "isdn-uui". set the User-to-User "purpose" header field parameter to "isdn-uui".
Non-inclusion of the "purpose" header field parameter is permitted, Non-inclusion of the "purpose" header field parameter is permitted,
but this is primarily to allow earlier implementations to support but this is primarily to allow earlier implementations to support
this package. this package.
When sending UUI for the ISDN UUI package, if the "purpose" header When sending UUI for the ISDN UUI package, if the "purpose" header
field is included, the UAS MUST set the User-to-User "purpose" header field is included, the UAS MUST set the User-to-User "purpose" header
field parameter to "isdn-uui". The UAS MUST NOT include more than field parameter to "isdn-uui". The UAS MUST NOT include more than
one User-to-User header field for this package in any SIP request or one User-to-User header field for this package in any SIP request or
response. response.
The "isdn-interwork" value for "purpose" header field parameter was The "isdn-interwork" value for the "purpose" header field parameter
used in Internet-Drafts that have led to the publication of the was used in documents that led to the publication of the present
present document. Although these documents had no other status than document. Although these documents had no other status than "Work in
"work in progress", this value is implemented by some vendors. While Progress", this value is implemented by some vendors. While not
not defined by this document, implementations could find it useful defined by this document, implementations could find it useful for
for interoperability purposes to support parsing and interpreting interoperability purposes to support parsing and interpreting
"isdn- interwork" the same way as "isdn-uui" when receiving messages. "isdn-interwork" the same way as "isdn-uui" when receiving messages.
Where the UAS is acting as a redirect server, the UAS MUST NOT Where the UAS is acting as a redirect server, the UAS MUST NOT
include the User-to-User header field in the header URI parameter in include the User-to-User header field in the header URI parameter in
a 3xx response to an incoming request. a 3xx response to an incoming request.
When receiving UUI, when a User-to-User header field is received in a When receiving UUI, when a User-to-User header field is received in a
request that is not from the originating user with the "purpose" request that is not from the originating user with the "purpose"
header field parameter to "isdn-uui", or with no "purpose" header header field parameter set to "isdn-uui", or with no "purpose" header
field parameter, the UAS MUST discard this header field. field parameter, the UAS MUST discard this header field.
When receiving UUI, when multiple User-to-User header fields are When receiving UUI, when multiple User-to-User header fields are
received from the originating user in the same request with the received from the originating user in the same request with the
"purpose" header field parameter to "isdn-uui", or with no "purpose" "purpose" header field parameter set to "isdn-uui", or with no
header field parameter, or with some combination of these, the UAS "purpose" header field parameter, or with some combination of these,
MUST discard all these header fields. There are no mechanisms for the UAS MUST discard all these header fields. There are no
determining which was the intended UUI data so all are discarded. mechanisms for determining which ones are the intended UUI data, so
all are discarded.
9. UUI contents 9. UUI Contents
These requirements apply when the "purpose" header field parameter is These requirements apply when the "purpose" header field parameter is
set to "isdn-uui", or with no "purpose" header field parameter. set to "isdn-uui" or when there is no "purpose" header field
parameter.
Processing for User-to-User header fields sent or received with Processing for User-to-User header fields sent or received with
values other than this value are outside the scope of this document, values other than this value are outside the scope of this document,
and the appropriate package document for that value applies. and the appropriate package document for that value applies.
The default and only content defined for this package is "isdn-uui". The default and only content defined for this package is "isdn-uui".
When sending UUI, the sending SIP entity MAY, but need not, include a When sending UUI, the sending SIP entity MAY, but need not, include a
"content" header field with a value set to "isdn-uui". A receiving "content" header field with a value set to "isdn-uui". A receiving
SIP entity MUST ignore a received User-to-User header field if the SIP entity MUST ignore a received User-to-User header field if the
"content" header field parameter is present and the value is some "content" header field parameter is present and the value is some
other value than "isdn-uui". other value than "isdn-uui".
The default and only encoding defined for this package is "hex". The default and only encoding defined for this package is "hex".
When sending UUI, the sending SIP entity MAY, but need not, include When sending UUI, the sending SIP entity MAY, but need not, include
an "encoding" header field with a value set to "hex". A receiving an "encoding" header field with a value set to "hex". A receiving
SIP entity MUST ignore a received User-to-User header field if the SIP entity MUST ignore a received User-to-User header field if the
"encoding" header field parameter is present and the value is some "encoding" header field parameter is present and the value is some
other value that "hex". other value than "hex".
When sending UUI, the sending application MUST include a protocol When sending UUI, the sending application MUST include a protocol
discriminator octet, conforming to table 4-26 of ITU-T Recommendation discriminator octet, conforming to Table 4-26 of ITU-T Recommendation
Q.931 [Q931] as the first octet of the UUI data. It is up to the Q.931 [Q931], as the first octet of the UUI data. It is up to the
receiving application what it does with this value. This document receiving application what it does with this value. This document
places no other normative requirement on the use of the protocol places no other normative requirement on the use of the protocol
discriminator; it is required at interworking gateways to allow discriminator; it is required at interworking gateways to allow
mapping into the appropriate fields in the ISDN protocols, but mapping into the appropriate fields in the ISDN protocols; otherwise,
otherwise the usage is entirely up to the application, and outside the usage is entirely up to the application and is outside the scope
the scope of this document. Valid values are identified and of this document. Valid values are identified and documented by
documented by ITU-T, and there is no IANA registry for these values. ITU-T, and there is no IANA registry for these values.
10. Considerations for ISDN internetworking gateways 10. Considerations for ISDN Interworking Gateways
ISDN interworking gateways MUST support the requirements defined for ISDN interworking gateways MUST support the requirements defined for
UAS and UAC operation. UAS and UAC operation.
ISDN interworking gateways MUST support only the "isdn-uui" package ISDN interworking gateways MUST support only the "isdn-uui" package
on dialogs that are interworked. on dialogs that are interworked.
ISDN interworking gateways will take octet structured data from the ISDN interworking gateways will take octet-structured data from the
ISDN side and encode it using the "hex" encoding scheme defined in ISDN side and encode it using the "hex" encoding scheme defined in
[I-D.ietf-cuss-sip-uui] for inclusion as the UUI data in the User-to- [RFC7433] for inclusion as the UUI data in the User-to-User header
User header field. In the reverse direction, it will take valid UUI field. In the reverse direction, it will take valid UUI data
data according to the "hex" encoding scheme, and decode it to octet according to the "hex" encoding scheme and decode it to octet-
structured data for sending to the ISDN side. structured data to send to the ISDN side.
When mapping data content from the ISDN to the SIP signalling, or When mapping data content from the ISDN to SIP signalling, or from
from SIP signalling to the ISDN, the gateway needs to assume that all SIP signalling to the ISDN, the gateway needs to assume that all
content is octet structured binary, irrespective of the value of the content is octet-structured binary, irrespective of the value of the
received protocol discriminator. There are no requirements in the received protocol discriminator. There are no requirements in the
ISDN to ensure that the content matches the value of the protocol ISDN to ensure that the content matches the value of the protocol
discriminator, and it is for the application usage to sort out any discriminator; the application usage sorts out any discrepancy. The
discrepancy. The same applies to the ISDN protocol discrimination same applies to the ISDN protocol discriminator as the first octet of
defined table 4-26 of ITU-T Recommendation Q.931 [Q931] as the first the UUI data, as defined in Table 4-26 of ITU-T Recommendation Q.931
octet of the UUI data; the interworking gateway will not perform any [Q931]; the interworking gateway will not perform any additional
additional checking of this value. checking of this value.
[I-D.ietf-cuss-sip-uui] defines a "uui" option tag for use with the A "uui" option tag for use with the UUI mechanism extension is
UUI mechanism extension. The option tag is not interworked at an defined in [RFC7433]. The option tag is not interworked at an ISDN
ISDN interworking gateway. The ISDN interworking gateways MUST NOT interworking gateway. The ISDN interworking gateways MUST NOT take
take the omission of the "uui" option tag in a received INVITE the omission of the "uui" option tag in a received INVITE request to
request to indicate that interworking of a received header field is indicate that interworking of a received header field is not to be
not to be performed. performed.
11. Coding requirements 11. Coding Requirements
This document defines "isdn-uui" as a new value of the User-to-User This document defines "isdn-uui" as a new value of the User-to-User
"purpose" header field parameter. The following ABNF adds to the "purpose" header field parameter. The following ABNF adds to the
production in [I-D.ietf-cuss-sip-uui]: production in [RFC7433]:
pkg-param-value =/ "isdn-uui" pkg-param-value =/ "isdn-uui"
This document defines "isdn-uui" as a new value of the User-to-User This document defines "isdn-uui" as a new value of the User-to-User
"content" header field parameter. A content value of "isdn-uui" "content" header field parameter. A content value of "isdn-uui"
indicates that the contents have a first octet that is a protocol indicates that the contents have a first octet that is a protocol
discriminator (see table 4-26 of ITU-T Recommendation Q.931 [Q931]) discriminator (see Table 4-26 of ITU-T Recommendation Q.931 [Q931])
followed by UUI data that can be subject to a length limitation followed by UUI data that can be subject to a length limitation
(before encoding or after decoding) that is generally 128 octets. (before encoding or after decoding) that is generally 128 octets.
The following ABNF adds to the production in [I-D.ietf-cuss-sip-uui].
The following ABNF adds to the production in [RFC7433].
cont-param-value =/ "isdn-uui" cont-param-value =/ "isdn-uui"
12. Media Feature Tag 12. Media Feature Tag
This document defines a new media feature tag "sip.uui-isdn". This This document defines the new media feature tag "sip.uui-isdn". This
feature tag indicates that this ISDN UUI package is supported by the feature tag indicates that this ISDN UUI package is supported by the
sender, and its usage is entirely in accordance with RFC 3840 sender, and its usage is entirely in accordance with [RFC3840]. This
[RFC3840]. This document makes no additional provisions for the use document makes no additional provisions for the use of this feature
of this feature tag. tag.
13. IANA Considerations 13. IANA Considerations
This document adds the following row to the "UUI packages" sub- Per this document, the following row has been added to the "UUI
registry of the SIP parameter registry: Packages" subregistry of the SIP parameter registry:
Value: isdn-uui Value: isdn-uui
Description: The associated application is being used with Description: The associated application is being used with
constraints suitable for interworking with the ISDN User-to-User constraints suitable for interworking with the ISDN User-to-User
service, and therefore can be interworked at ISDN gateways. service, and therefore can be interworked at ISDN gateways.
Reference: RFCXXXX Reference: RFC 7434
Contact: Keith Drage
This document adds the following row to the "UUI content" subregistry Per this document, the following row has been added to the "UUI
of the SIP parameter registry: Content" subregistry of the SIP parameter registry:
Value: isdn-uui Value: isdn-uui
Description: The associated contents conforms to the content Description: The associated contents conform to the content
associated with the ISDN User-to-User service. In the presence of associated with the ISDN User-to-User service. In the presence of
the "purpose" header field parameter set to "isdn-uui" (or the the "purpose" header field parameter set to "isdn-uui" (or the
absence of any "purpose" header field parameter) this is the absence of any "purpose" header field parameter), this is the
default meaning and therefore need not be included in this case. default meaning and therefore need not be included in this case.
Reference: RFCXXXX Reference: RFC 7434
Contact: Keith Drage
This document defines the following media feature tag which is added This document defines the following media feature tag, which has been
to the features.sip-tree of the Media feature tags registry: added to the features.sip-tree of the Media feature tags registry:
Media feature tag name: sip.uui-isdn Media feature tag name: sip.uui-isdn
ASN.1 Identifier: 1.3.6.1.8.4.x ASN.1 Identifier: 1.3.6.1.8.4.x
Summary of the media feature indicated by this tag: This media Summary of the media feature indicated by this tag: This media
feature tag when used in a Contact header field of a SIP request feature tag when used in a Contact header field of a SIP request
or a SIP response indicates that the entity sending the SIP or a SIP response indicates that the entity sending the SIP
message supports the package "uui-isdn". message supports the package "uui-isdn".
Values appropriate for use with this feature tag: none Values appropriate for use with this feature tag: none
Examples of typical use: Indicating that a mobile phone supports Examples of typical use: Indicating that a mobile phone supports
SRVCC for calls in alerting phase. Single Radio Voice call Continuity (SRVCC) for calls in the
alerting phase.
Related standards or documents: RFCXXXX Related standards or documents: RFC 7434
Security Considerations: Security considerations for this media Security Considerations: Security considerations for this media
feature tag are discussed in section 11.1 of [RFC3840] feature tag are discussed in Section 11.1 of [RFC3840]
Editor's Note: [RFCXXXX] should be replaced with the designation of
this document.
14. Security Considerations 14. Security Considerations
This document contains no specific requirements in regard to security This document contains no specific requirements in regard to security
over and above those specified in [I-D.ietf-cuss-sip-uui]. However, over and above those specified in [RFC7433]. However, since this
since this capability is designed to interwork with the ISDN, the capability is designed to interwork with the ISDN, the general
general security considerations of SIP to ISUP (ISDN User Part) security considerations of SIP to ISDN User Part (ISUP) interworking
interworking defined in [RFC3398] apply. Any SIP/PSTN gateway defined in [RFC3398] apply. Any SIP/PSTN gateway implementing the
implementing the ISDN User-to-User service should not blindly trust ISDN User-to-User service should not blindly trust ISUP from the
ISUP from the PSTN. In general, the overlying use case will define PSTN. In general, the overlying use case will define the security
the security measures required. The underlying User-to-User header measures required. The underlying User-to-User header field
field extension provides a number of tools that can meet certain extension provides a number of tools that can meet certain security
security requirements. requirements.
Information that might otherwise reveal private information about an Information that might otherwise reveal private information about an
individual, or where a level of authenticity needs to be guaranteed, individual, or where a level of authenticity needs to be guaranteed,
may need a higher level of protection, and may indeed not be suitable may need a higher level of protection and may indeed not be suitable
for this package, particularly taking into account the statement in for this package, particularly taking into account the statement in
the following paragraph. the following paragraph.
As this capability is defined to interwork with the ISDN, if the ISDN As this capability is defined to interwork with the ISDN, if the ISDN
forms part of the route, any usage needs to be aware that the forms part of the route, any usage needs to be aware that the
security level of the ISDN service may be lower than the security of security level of the ISDN service may be lower than the security of
the SIP service. The ISDN security is itself not definable on an the SIP service. The ISDN security is itself not definable on an
end-to-end basis, and exists on a hop-by-hop basis. This can be high end-to-end basis and exists on a hop-by-hop basis. This can be high
in some places (e.g. it can require physical access to a secure in some places (e.g., it can require physical access to a secure
building) and in other places it can be low (e.g. the point where an building) and in other places it can be low (e.g., the point where an
ISDN access enters a building). If this level of security is not ISDN access enters a building). If this level of security is not
sufficient, then either a different package, or indeed, a different sufficient, then either a different package or indeed a different
method of data transfer, needs to be selected by the application method of data transfer needs to be selected by the application user.
user.
15. Acknowledgments
Joanne McMillen was a major contributor and co-author of earlier
versions of this document.
Thanks to Spencer Dawkins, Vijay Gurbani, Laura Liess, and Roland
Jesske for their reviews of this document. The authors wish to thank
Francois Audet, Denis Alexeitsev, Paul Kyzivat, Cullen Jennings,
Mahalingam Mani and Celine Serrut-Valette for their comments.
The death of Francois Audet occurred before this document was 15. References
finalised, and the authors would like to identify the significant
contribution of Francois to this and a number of important RFCs, and
to express their condolences to his family. It was always a pleasure
to work with Francois.
16. References 15.1. Normative References
16.1. Normative References [Q931] ITU-T, "ISDN user-network interface layer 3 specification
for basic call control", ITU-T Recommendation Q.931,
<http://www.itu.int/rec/T-REC-Q.931-199805-I/en>.
[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, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, [RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
A., Peterson, J., Sparks, R., Handley, M., and E. A., Peterson, J., Sparks, R., Handley, M., and E.
Schooler, "SIP: Session Initiation Protocol", RFC 3261, Schooler, "SIP: Session Initiation Protocol", RFC 3261,
June 2002. June 2002, <http://www.rfc-editor.org/info/rfc3261>.
[RFC3372] Vemuri, A. and J. Peterson, "Session Initiation Protocol [RFC3372] Vemuri, A. and J. Peterson, "Session Initiation Protocol
for Telephones (SIP-T): Context and Architectures", for Telephones (SIP-T): Context and Architectures", BCP
BCP 63, RFC 3372, September 2002. 63, RFC 3372, September 2002,
<http://www.rfc-editor.org/info/rfc3372>.
[RFC3398] Camarillo, G., Roach, A., Peterson, J., and L. Ong,
"Integrated Services Digital Network (ISDN) User Part
(ISUP) to Session Initiation Protocol (SIP) Mapping", RFC
3398, December 2002,
<http://www.rfc-editor.org/info/rfc3398>.
[RFC3840] Rosenberg, J., Schulzrinne, H., and P. Kyzivat, [RFC3840] Rosenberg, J., Schulzrinne, H., and P. Kyzivat,
"Indicating User Agent Capabilities in the Session "Indicating User Agent Capabilities in the Session
Initiation Protocol (SIP)", RFC 3840, August 2004. Initiation Protocol (SIP)", RFC 3840, August 2004,
<http://www.rfc-editor.org/info/rfc3840>.
[I-D.ietf-cuss-sip-uui] [RFC7433] Johnston, A. and J. Rafferty, "A Mechanism for
Johnston, A. and J. Rafferty, "A Mechanism for Transporting User-to-User Call Control Information in
Transporting User to User Call Control Information in SIP", RFC 7433, December 2014,
SIP", draft-ietf-cuss-sip-uui-17 (work in progress), <http://www.rfc-editor.org/info/rfc7433>.
June 2014.
[Q931] "ITU-T Recommendation Q.931: Digital subscriber Signalling 15.2. Informative References
System No. 1 - Network layer; ISDN user-network interface
layer 3 specification for basic call control",
ITU-T http://www.itu.int/rec/T-REC-Q.931-199805-I/en.
[RFC3398] Camarillo, G., Roach, A., Peterson, J., and L. Ong, [ANSII] ANSI, "Integrated Services Digital Network (ISDN) -
"Integrated Services Digital Network (ISDN) User Part Explicit Call Transfer Supplementary Service", ANSI-
(ISUP) to Session Initiation Protocol (SIP) Mapping", T1.643A - SUP A, December 1996.
RFC 3398, December 2002.
16.2. Informative References [ETSI] ETSI, "Integrated Services Digital Network (ISDN);
Diversion supplementary services; Digital Subscriber
Signalling System No. one (DSS1) protocol; Part 1:
Protocol specification", ETSI ETS 300 207-1, Ed. 1,
December 1994.
[Q957.1] "ITU-T Recommendation Q.957.1: Digital subscriber [Q763] ITU-T, "Signalling System No. 7 - ISDN User Part formats
Signalling System No. 1 - Stage 3 description for and codes", ITU-T Recommendation Q.763,
supplementary services using DSS 1; Stage 3 description <http://www.itu.int/rec/T-REC-Q.763-199912-I/en>.
for additional information transfer supplementary services
using DSS 1: User-to-User Signalling (UUS)",
ITU-T http://www.itu.int/rec/T-REC-Q.957.1-199607-I.
[Q763] "ITU-T Q.763 Signaling System No. 7 - ISDN user part [Q957.1] ITU-T, "Digital subscriber Signalling System No. 1 - Stage
formats and codes", 3 description for supplementary services using DSS 1;
ITU-T http://www.itu.int/rec/T-REC-Q.931-199805-I/en. Stage 3 description for additional information transfer
supplementary services using DSS 1: User-to-User
Signalling (UUS)", ITU-T Recommendation Q.957.1,
<http://www.itu.int/rec/T-REC-Q.957.1-199607-I>.
[RFC6567] Johnston, A. and L. Liess, "Problem Statement and [RFC6567] Johnston, A. and L. Liess, "Problem Statement and
Requirements for Transporting User-to-User Call Control Requirements for Transporting User-to-User Call Control
Information in SIP", RFC 6567, April 2012. Information in SIP", RFC 6567, April 2012,
<http://www.rfc-editor.org/info/rfc6567>.
[ANSII] "ANSI T1.643-1995, Telecommunications-Integrated Services Acknowledgments
Digital Network (ISDN)-Explicit Call Transfer
Supplementary Service", ANSI T1.643-1995 .
[ETSI] ""ETSI ETS 300 207-1 Ed.1 (1994), Integrated Services Joanne McMillen was a major contributor and coauthor of earlier
Digital Network (ISDN); Diversion supplementary versions of this document.
services"", ETSI ETF 300 207-1 .
Thanks to Spencer Dawkins, Vijay Gurbani, Laura Liess, and Roland
Jesske for their reviews of this document. The authors wish to thank
Francois Audet, Denis Alexeitsev, Paul Kyzivat, Cullen Jennings,
Mahalingam Mani, and Celine Serrut-Valette for their comments.
The death of Francois Audet occurred before this document was
finalized, and the authors would like to identify the significant
contribution of Francois to this and a number of important RFCs and
to express their condolences to his family. It was always a pleasure
to work with Francois.
Authors' Addresses Authors' Addresses
Keith Drage (editor) Keith Drage (editor)
Alcatel-Lucent Alcatel-Lucent
Quadrant, Stonehill Green, Westlea Quadrant, Stonehill Green, Westlea
Swindon Swindon
UK United Kingdom
Email: keith.drage@alcatel-lucent.com EMail: keith.drage@alcatel-lucent.com
Alan Johnston Alan Johnston
Avaya Avaya
St. Loius, MO St. Louis, MO
US United States
Email: alan.b.johnston@gmail.com EMail: alan.b.johnston@gmail.com
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