Network Working Group Muneyoshi Suzuki
INTERNET DRAFT NTT
Expires December 29, 1998 June 29, 1998
The Assignment of the Information Field and Protocol Identifier
in the Q.2941 Generic Identifier and Q.2957 User-to-user Signaling
for the Internet Protocol
<draft-ietf-mpls-git-uus-00.txt>
Status of this Memo
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Abstract
The purpose of this document is to specify the assignment of the
information field and protocol identifier in the Q.2941 Generic
Identifier and Q.2957 User-to-user Signaling for the Internet
protocol.
The assignment, that is specified in section 4 of this document, is
designed for advanced B-ISDN signaling support of the Internet
protocol, especially the B-ISDN signaling support for the connection
that corresponds to the session in the Internet protocol which is
clarified in section 2. This specification provides an indispensable
framework for the implementation of long-lived session and QoS-
sensitive session transfers over ATM.
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0. Background
In the ITU-T SG11 WP1 Kochi meeting held in January 1998, SG11 WP1,
which has responsibility for the B-ISDN signaling protocol
recommendation, decided to discuss B-ISDN signalling support for the
Internet protocol based on draft-suzuki-git-uus-assignment-00.txt.
In the ITU-T SG11 Geneva meeting held in May 1998, WP1 decided to
enhance the Q.2941 Generic Identifier Transport based on draft-
suzuki-git-uus-assignment-02.txt and developed the Awaiting-review
text (initial draft) [4]. WP1 also decided to continue discussion on
the User-to-user signaling support for the Internet protocol.
Expected standard development process (fastest case) for the
enhancement of the Generic Identifier is:
November 1998: Enhance the Awaiting-review text based on inputs and
develop the Cooling text (Draft Recommendations to be frozen in the
next meeting, if no significant technical changes are proposed in
that meeting).
March 1999: Freeze the Draft Recommendations and letter ballot is
requested.
February 2000: The Draft Recommendations are decided (final
approval).
The purpose of this document is to specify the assignment of the
information field and protocol identifier in the Q.2941 Generic
Identifier and Q.2957 User-to-user Signaling for the Internet
protocol. To enable this specification, section 6 of this document
clarifies amendments to the current User-to-user Signaling. ITU-T
SG11 will enhance the current User-to-user Signaling based on this
clarification.
Note that the assignment rule for Generic Identifer described in this
document may be subject to change.
Note that the assignment rule for the User-to-user Signaling
described in this document may be subject to change, so it should not
be implemented until ITU-T SG11 WP1 decides to enhance the User-to-
user Signaling based on this request.
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1. Purpose of Document
The purpose of this document is to specify the assignment of the
information field and protocol identifier in the Q.2941 Generic
Identifier and Q.2957 User-to-user Signaling for the Internet
protocol.
The assignment, that is specified in section 4 of this document, is
designed for advanced B-ISDN signaling support of the Internet
protocol, especially the B-ISDN signaling support for the connection
that corresponds to the session in the Internet protocol which is
clarified in section 2. Needless to say, the purpose of this
specification is not limited to this support, and it should also be
applicable to other purposes.
This specification provides an indispensable framework for the
implementation of long-lived session and QoS-sensitive session
transfers over ATM. Note that this document only specifies the
assignment of the information field and protocol identifier, and that
it may not specify complete protocol that enables interoperable
implementation. This is because it is beyond the scope of this
document and will be specified in a separate document.
2. Session-related ATM Connection
With the development of new multimedia applications on the current
Internet, the demands for multimedia support are increasing in the IP
network, which currently supports best effort communications. In
particular, demands to support QoS guaranteed communications are
increasing with the development of voice, audio, and video
communications applications. And it may also be necessary to
introduce the mechanism that can efficiently transfer the huge volume
of traffic expected with these applications.
The major features of B-ISDN are high speed, logical multiplexing
with the VP/VC, and flexible QoS management per VC, so it is quite
natural to use these distinctive functions of B-ISDN to implement a
multimedia support mechanism in the IP network. The flexible QoS
management and logical multiplexing functions in B-ISDN are the
expected method of implementing the QoS guaranteed communications in
the Internet. And when a long-lived session is supported by a
particular VC, efficient packet forwarding may be possible using the
high speed and logical multiplexing of B-ISDN.
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This section clarifies B-ISDN signaling functions that are required
when the session is supported by the VC, for advanced B-ISDN
signaling support of the Internet protocol.
2.1 Long-lived Session Signaling
An example scenario for establishing a VC for a long-lived session is
shown in Fig. 2.1.
IP Router ATM SW ATM SW IP Router
+----+ Default VC +----+
| WS | +------+ UNI +-----+ +-----+ UNI +------+ | WS |
+--+-+ | /->|<------+-\-/-+--------+-\-/-+------>|<-\ | +-+--+
|.....|__/ |===||==| X |========| X |==||===| \__|.....|
| | | / \ | | / \ | | |
+------+ +-----+ +-----+ +------+
A. New session initially forwarded over a default VC.
IP Router ATM SW ATM SW IP Router
+----+ Default VC +----+
| WS | +------+ UNI +-----+ +-----+ UNI +------+ | WS |
+--+-+ | /->|<------+-\-/-+--------+-\-/-+------>|<-\ | +-+--+
|.....|__/ |===||==| X |========| X |==||===| \__|.....|
| |<------+-/-\-+--------+-/-\-+------>| |
+------+ +-----+ +-----+ +------+
New VC is set up
B. New VC is set up for the long-lived session.
IP Router ATM SW ATM SW IP Router
+----+ Default VC +----+
| WS | +------+ UNI +-----+ +-----+ UNI +------+ | WS |
+--+-+ | |<------+-\-/-+--------+-\-/-+------>| | +-+--+
|.....|__ |===||==| X |========| X |==||===| __|.....|
| \-->|<------+-/-\-+--------+-/-\-+------>|<--/ |
+------+ +-----+ +-----+ +------+
New VC
C. Transfer of the long-lived session to a new VC.
Fig. 2.1: Example scenario for establishing a VC for a long-lived session.
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First, a session is multiplexed into the default VC connecting the
routers. Then, if a router detects that it is a long-lived session,
it sets up a new VC for the session. If the new VC is established
successfully, the long-lived session is moved to the new VC.
In this procedure involving an ATM VC setup, the B-ISDN signaling
entity in the called side router must detect that the incoming call
corresponds to a session of the Internet protocol and notify that
fact to the IP layer entity. Based on this information, the IP layer
entity moves the session to the new VC.
Therefore, to implement this signaling procedure, the B-ISDN
signaling must include an session identifier as an information
element. The B-LLI, B-HLI, User-user, and Generic Identifier
information elements are all capable of transferring this
information. Considering the original purposes of these information
elements, the most appropriate one to use is the Generic Identifier
information element.
2.2 QoS-sensitive Session Signaling
The major difference between QoS-sensitive session signaling and
long-lived session signaling is that call setup is not initiated by
the detection of a long-lived session, but is explicitly initiated by
the setup protocol such as ST2+ and RSVP. To implement QoS-sensitive
session signaling using ATM, the ATM network between the routers must
forward not only the session identifier but also the setup protocol.
There are two schemes for forwarding the setup protocol. One is to
multiplex the protocol into a default VC connecting the routers, or
to forward the protocol through a particular VC. In this case, the
QoS-sensitive session and the ATM VC are established sequentially.
The second scheme is to forward the setup protocol as an information
element in the B-ISDN signaling. In this case, the QoS-sensitive
session and the ATM VC are established simultaneously. The latter
scheme has the following advantages compared with the former one.
o Easier to implement.
- Admission control is simplified, because admission control for
the IP and ATM layers can be done simultaneously.
- Watchdog timer processing is simplified, because there is no need
to watch the IP layer establishment and ATM layer establishment
sequentially.
o If the setup protocol supports negotiation, then an ATM VC whose
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QoS is based on the result of negotiation can be established.
However, the latter scheme, at least, cannot support a case where a
PVC is used to support a QoS-sensitive session. Therefore, both
procedures should be taken into account.
An example of a message sequence that simultaneously establishes a
QoS-sensitive session and an ATM VC is shown in Fig. 2.2.
IP Router ATM SW ATM SW IP Router
+----+ B-ISDN Signaling +----+
| WS | +------+ UNI +-----+ Setup +-----+ UNI +------+ | WS |
+--+-+ | /->|<------+-\-/--Protocol--\-/-+------>|<-\ | +-+--+
|.....|__/ |===||==| X |========| X |==||===| \__|.....|
| \-->|<------+-/-\-+--------+-/-\-+------>|<--/ |
+------+ +-----+ Data +-----+ +------+
QoS VC
N-CONNECT | |
---------->| | | | | |
|->| SETUP | | | |
| |------------>| | | |
| |<------------| | | |
| | CALL PROC |----------->| SETUP | |
| | | |------------>| |
| | | | |->| N-CONNECT
| | | | | |---------->
| | | | | |<----------
| | | | CONN |<-| N-CONNECT-ACK
| | | |<------------| |
| | | |------------>| |
| | CONN |<-----------| CONN ACK |->|
| |<------------| | | |
| |------------>| | | |
|<-| CONN ACK | | | |
<----------| | | | | |
N-CONNECT | |
-ACK
Fig. 2.2: Example procedure for simultaneous QoS-sensitive session and
ATM VC establishment.
Both ST2+ and RSVP are currently proposed for the setup protocol and
new setup protocols are likely to be developed in the near future.
Therefore, to generalize the discussion, the procedure for the setup
protocol in this example is the general connection setup procedure
using confirmed service.
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To implement this signaling procedure, the B-ISDN signaling must
include the User-user information element that the capacity is
sufficient to forward the setup protocol.
3. Overview of the Generic Identifier and User-to-user Signaling
3.1 Overview of the Generic Identifier
The Generic Identifier enables the transfer of identifiers between
end-to-end users in the ATM network, and it is defined in the Q.2941
Part 1 (Q.2941.1) and Part 2 (Q.2941.2) as an optional information
element for the Q.2931 and Q.2971 UNI signaling protocol. The SETUP,
ALERTING, CONNECT, RELEASE, RELEASE COMPLETE, ADD PARTY, PARTY
ALERTING, ADD PARTY ACK, ADD PARTY REJECT, DROP PARTY, and DROP PARTY
ACK messages that are transferred between end-to-end users in the ATM
network may contain up to three Generic Identifier information
elements. The ATM network transfers the Generic Identifier
information element transparently if it contains no coding rule
errors.
The format of the Generic Identifier information element specified in
the Q.2941 is shown in Fig. 3.1.
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Bits
8 7 6 5 4 3 2 1 Octets
+-----+-----+-----+-----+-----+-----+-----+-----+
| Information element identifier |
| = Generic identifier transport IE (0x7F) | 1
+-----+-----+-----+-----+-----+-----+-----+-----+
| 1 | Coding | IE instruction field |
| Ext | standard |Flag |Res. | IE action ind. | 2
+-----+-----+-----+-----+-----+-----+-----+-----+
| Length of contents of information element | 3-4
+-----+-----+-----+-----+-----+-----+-----+-----+
| Identifier related standard/application | 5
+-----+-----+-----+-----+-----+-----+-----+-----+
| Identifier type | 6
+-----+-----+-----+-----+-----+-----+-----+-----+
| Identifier length | 7
+-----+-----+-----+-----+-----+-----+-----+-----+
| Identifier value | 8-
= =
+-----+-----+-----+-----+-----+-----+-----+-----+
= =
+-----+-----+-----+-----+-----+-----+-----+-----+
| Identifier type |
+-----+-----+-----+-----+-----+-----+-----+-----+
| Identifier length |
+-----+-----+-----+-----+-----+-----+-----+-----+
| Identifier value |
= =
+-----+-----+-----+-----+-----+-----+-----+-----+
Fig. 3.1: Format of the Generic Identifier information element.
The usage of the first 4 octets of fields is specified in section 4
of the Q.2931.
The Identifier related standard/application field identifies the
standard or application that uses the identifier. Assignment of the
Identifier related standard/application field for the Intenet
protocol is as follows. A leading 0x means hexadecimal.
0x03: IPv4.
0x04: ST2+.
0x05: IPv6.
0x06: MPLS.
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Note: DSM-CC, H.310/H.321, and AAL2 application are also supported.
A transferred identifier is given by the combination of the
Identifier type, length and value fields, and a Generic Identifier
information element may contain multiple identifiers.
Assignment of the Identifier type field for the Intenet protocol is
as follows. A leading 0x means hexadecimal.
0x01: Session.
0x02: Resource.
0x03-0xFD: Reserved for IANA assignment.
0xFE: Experiment/Organization specific.
The maximum length of the Generic Identifier information element is
63 octets. (See Draft Q.2941.2.)
See the Q.2941.1 and Draft Q.2941.2 for detailed protocol
specifications of the Generic Identifier.
3.2 Overview of the User-to-user Signaling
The User-to-user Signaling enables the transfer of information
between end-to-end users in the ATM network, and it is defined in
Q.2957 and in Q.2971 annex D as an optional information element for
the Q.2931 and Q.2971 UNI signaling protocol. The SETUP, ALERTING,
CONNECT, RELEASE, RELEASE COMPLETE, PROGRESS, ADD PARTY, PARTY
ALERTING, ADD PARTY ACK, ADD PARTY REJECT, DROP PARTY, and DROP PARTY
ACK messages that are transferred between end-to-end users in the ATM
network may contain a User-user information element. The ATM network
transfers the User-user information element transparently if it
contains no coding rule errors.
From the viewpoint of B-ISDN signaling applications, it seems the
Generic Identifier and User-to-user Signaling are similar functions.
But their rules for processing exceptions are not completely the
same, because their purposes are different. The Generic Identifier is
designed for the transfer of identifiers between the c-planes, while
the User-to-user Signaling is designed for the transfer of user data
via the c-planes. Another difference is that the latter supports
interworking with the user-user information element in the Q.931 N-
ISDN signaling, but the Generic Identifier does not. Note that the
ATM network may check the contents of the Generic Identifier
information element, but does not check the contents of the User-to-
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user information element.
The format of the User-user information element is shown in Fig. 3.2.
Bits
8 7 6 5 4 3 2 1 Octets
+-----+-----+-----+-----+-----+-----+-----+-----+
| Information element identifier |
| = User-user information element (0x7E) | 1
+-----+-----+-----+-----+-----+-----+-----+-----+
| 1 | Coding | IE instruction field |
| Ext | standard |Flag |Res. | IE action ind. | 2
+-----+-----+-----+-----+-----+-----+-----+-----+
| Length of contents of information element | 3-4
+-----+-----+-----+-----+-----+-----+-----+-----+
| Protocol discriminator | 5
+-----+-----+-----+-----+-----+-----+-----+-----+
| User information | 6-
= =
| |
+-----+-----+-----+-----+-----+-----+-----+-----+
Fig. 3.2: Format of the User-user information element.
The usage of the first 4 octets of fields is specified in section 4
of the Q.2931.
The Protocol discriminator field identifies the upper layer protocol
that uses the user-user information.
The User information field contains the user-user information to be
transferred.
The maximum length of the User-user information element is currently
133 octets.
See Q.2957 and Q.2971 annex D for detailed protocol specifications of
the User-to-user Signaling.
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4. Information Field and Protocol Identifier Assignment
4.1 Assignment in the Generic Identifier Information Element
4.1.1 Use of Generic Identifier
The information field and protocol identifier assignment principle
for the Internet protocol in the Generic Identifier information
element is shown in Fig. 4.1.
Bits
8 7 6 5 4 3 2 1 Octets
+-----+-----+-----+-----+-----+-----+-----+-----+
| Information element identifier |
| = Generic identifier transport IE (0x7F) | 1
+-----+-----+-----+-----+-----+-----+-----+-----+
| 1 | Coding | IE instruction field |
| Ext | standard |Flag |Res. | IE action ind. | 2
+-----+-----+-----+-----+-----+-----+-----+-----+
| Length of contents of information element | 3-4
+-----+-----+-----+-----+-----+-----+-----+-----+
| Identifier related standard/application |
| = IPv4, ST2+, IPv6, or MPLS | 5
+-----+-----+-----+-----+-----+-----+-----+-----+
| Identifier type |
| = Session, Resource, or Experiment | 6
+-----+-----+-----+-----+-----+-----+-----+-----+
| Identifier length | 7
+-----+-----+-----+-----+-----+-----+-----+-----+
| Identifier value | 8-
= =
+-----+-----+-----+-----+-----+-----+-----+-----+
= =
+-----+-----+-----+-----+-----+-----+-----+-----+
| Identifier type |
| = Session, Resource, or Experiment |
+-----+-----+-----+-----+-----+-----+-----+-----+
| Identifier length |
+-----+-----+-----+-----+-----+-----+-----+-----+
| Identifier value |
= =
+-----+-----+-----+-----+-----+-----+-----+-----+
Fig. 4.1: Principle of assignment in the Generic Identifier
information element.
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The Identifier related standard/application field is the IPv4, ST2+,
IPv6, or MPLS.
The Identifier type field is the Session, Resource, or
Experiment/Organization specific.
The Identifier value field is assigned to Internet protocol related
information which is identified by the Identifier related
standard/application field and Identifier type field. The following
identifiers are specified.
Std./app. Id type
IPv4 session identifier IPv4 Session
ST2+ session identifier ST2+ Session
IPv6 session identifier IPv6 Session
MPLS VCID MPLS Resource
Exp./Org. specific IPv4/ST2+/IPv6/MPLS Experiment
As described in section 3.1, the B-ISDN signaling message transferred
between end-to-end users may contain up to three Generic Identifier
information elements. These elements may contain multiple
identifiers. This document does not specify the order of identifiers
when multiple identifiers appear in a signaling message.
This document also does not specify the semantics when multiple
identifiers having the same Identifier type appear in a signaling
message, or when a signaling message contains a Generic Identifier
information element that does not contain identifiers.
When a B-ISDN signaling message containing a Generic Identifier
information element enters an ATM network that does not support the
Generic Identifier, the network clears the call, discards the
information element, or discards the signaling message. (See
sections 4.5.1 and 5.6.8.1 of Q.2931 and section 9.3 of Q.2941.1 for
details.)
To enable reliable Generic Identifier information element transfer,
when the calling party sends a SETUP or ADD PARTY message with up to
three Generic Identifier information elements, the CONNECT or ADD
PARTY ACK message returned by the called party must contain at least
one Generic Identifier information element. The called party may not
respond with the same identifiers received from the calling party.
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The calling party should confirm that the response message contains
at least one Generic Identifier information element.
4.1.2 IPv4 session identifier
If the Identifier related standard/application field in the Generic
Identifier information element is the IPv4, and the Identifier type
field in the identifier is the Session, the identifier is the IPv4
session identifier. The format of the IPv4 session identifier is
shown in Fig. 4.2.
Bits Octet
8 7 6 5 4 3 2 1 length
+-----+-----+-----+-----+-----+-----+-----+-----+
| Identifier type |
| = Session (0x01) | 1
+-----+-----+-----+-----+-----+-----+-----+-----+
| Identifier length |
| = 13 octets (0x0D) | 1
+-----+-----+-----+-----+-----+-----+-----+-----+
| Source IPv4 address | 4
+-----+-----+-----+-----+-----+-----+-----+-----+
| Destination IPv4 address | 4
+-----+-----+-----+-----+-----+-----+-----+-----+
| Protocol | 1
+-----+-----+-----+-----+-----+-----+-----+-----+
| Source Port | 2
+-----+-----+-----+-----+-----+-----+-----+-----+
| Destination Port | 2
+-----+-----+-----+-----+-----+-----+-----+-----+
Fig. 4.2: IPv4 session identifier.
The Identifier type field is the Session (0x01).
The Identifier length is 13 octets.
The Source IPv4 address, Destination IPv4 address, Protocol, Source
Port, and Destination Port [6, 8, 9] are assigned in that order to
the Identifier value field.
Note: This specific session identifier is intended for use only with
the explicit reservation. If wild card associations are needed at a
later date, another identifier type will be used.
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4.1.3 ST2+ session identifier
If the Identifier related standard/application field in the Generic
Identifier information element is the ST2+, and the Identifier type
field in the identifier is the Session, the identifier is the ST2+
session identifier. The format of the ST2+ session identifier is
shown in Fig. 4.3.
Bits Octet
8 7 6 5 4 3 2 1 Length
+-----+-----+-----+-----+-----+-----+-----+-----+
| Identifier type |
| = Session (0x01) | 1
+-----+-----+-----+-----+-----+-----+-----+-----+
| Identifier length |
| = 6 octets (0x06) | 1
+-----+-----+-----+-----+-----+-----+-----+-----+
| Stream ID (SID) | 6
+-----+-----+-----+-----+-----+-----+-----+-----+
Fig. 4.3: ST2+ session identifier.
The Identifier type field is the Session (0x01).
The Identifier length is 6 octets.
The Stream ID (SID) [10] is assigned to the Identifier value field.
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4.1.4 IPv6 session identifier
If the Identifier related standard/application field in the Generic
Identifier information element is the IPv6, and the Identifier type
field in the identifier is the Session, the identifier is the IPv6
session identifier. The format of the IPv6 session identifier is
shown in Fig. 4.4.
Bits Octet
8 7 6 5 4 3 2 1 length
+-----+-----+-----+-----+-----+-----+-----+-----+
| Identifier type |
| = Session (0x01) | 1
+-----+-----+-----+-----+-----+-----+-----+-----+
| Identifier length |
| = 37 octets (0x25) | 1
+-----+-----+-----+-----+-----+-----+-----+-----+
| Source IPv6 address | 16
+-----+-----+-----+-----+-----+-----+-----+-----+
| Destination IPv6 address | 16
+-----+-----+-----+-----+-----+-----+-----+-----+
| Protocol | 1
+-----+-----+-----+-----+-----+-----+-----+-----+
| Source Port | 2
+-----+-----+-----+-----+-----+-----+-----+-----+
| Destination Port | 2
+-----+-----+-----+-----+-----+-----+-----+-----+
Fig. 4.4: IPv6 session identifier.
The Identifier type field is the Session (0x01).
The Identifier length is 37 octets.
The Source IPv6 address, Destination IPv6 address, Protocol, Source
Port, and Destination Port [7, 8, 9] are assigned in that order to
the Identifier value field.
Note: This specific session identifier is intended for use only with
the explicit reservation. If wild card associations are needed at a
later date, another identifier type will be used.
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4.1.5 MPLS VCID
If the Identifier related standard/application field in the Generic
Identifier information element is the MPLS, and the Identifier type
field in the identifier is the Resource, the identifier is the MPLS
VCID. The format of the MPLS VCID is shown in Fig. 4.5.
Bits Octet
8 7 6 5 4 3 2 1 length
+-----+-----+-----+-----+-----+-----+-----+-----+
| Identifier type |
| = Resource (0x02) | 1
+-----+-----+-----+-----+-----+-----+-----+-----+
| Identifier length |
| = 4 octets (0x04) | 1
+-----+-----+-----+-----+-----+-----+-----+-----+
| MPLS VCID | 4
+-----+-----+-----+-----+-----+-----+-----+-----+
Fig. 4.5: MPLS VCID.
The Identifier type field is the Resource (0x02).
The Identifier length is 4 octets.
The MPLS VCID [12] is assigned to the Identifier value field.
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4.1.6 Experiment/Organization specific
If the Identifier related standard/application field in the Generic
Identifier information element is the IPv4, ST2+, IPv6, or MPLS, and
the Identifier type field in the identifier is the
Experiment/Organization specific, the identifier is the
Experiment/Organization specific. The format of the
Experiment/Organization specific is shown in Fig. 4.6.
Bits Octet
8 7 6 5 4 3 2 1 length
+-----+-----+-----+-----+-----+-----+-----+-----+
| Identifier type |
| = Experiment/Organization specific (0xFE) | 1
+-----+-----+-----+-----+-----+-----+-----+-----+
| Identifier length | 1
+-----+-----+-----+-----+-----+-----+-----+-----+
| Organizationally unique identifier (OUI) | 3
+-----+-----+-----+-----+-----+-----+-----+-----+
| Experiment/Organization specific info. |
= =
| |
+-----+-----+-----+-----+-----+-----+-----+-----+
Fig. 4.6: Experiment/Organization specific.
The Identifier type field is the Experiment/Organization specific
(0xFE).
The first 3 octets in the Identifier value field must contain the
Organizationally unique identifier (OUI) (as specified in IEEE 802-
1990; section 5.1).
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4.2 Assignment in the User-user Information Element
4.2.1 Use of User-to-user Signaling
The information field and protocol identifier assignment principle
for the Internet protocol in the User-user information element is
shown in Fig. 4.7.
Bits
8 7 6 5 4 3 2 1 Octets
+-----+-----+-----+-----+-----+-----+-----+-----+
| Information element identifier |
| = User-user information element (0x7E) | 1
+-----+-----+-----+-----+-----+-----+-----+-----+
| 1 | Coding | IE instruction field |
| Ext | standard |Flag |Res. | IE action ind. | 2
+-----+-----+-----+-----+-----+-----+-----+-----+
| Length of contents of information element | 3-4
+-----+-----+-----+-----+-----+-----+-----+-----+
| Protocol discriminator |
| = Internet protocol/application (TBD) | 5
+-----+-----+-----+-----+-----+-----+-----+-----+
| Internet protocol/application identifier | 6
+-----+-----+-----+-----+-----+-----+-----+-----+
| Internet protocol/application related info. | 7-
= =
| |
+-----+-----+-----+-----+-----+-----+-----+-----+
Fig. 4.7: Principle of assignment in the User-user information element.
The Protocol discriminator field is the Internet protocol/application
(TBD). In this case, the first 1 octet in the User information field
is the Internet protocol/application identifier field.
Assignment of the Internet protocol/application identifier field is
as follows. A leading 0x means hexadecimal.
0x00: Reserved.
0x01: ST2+ SCMP.
0x02: RSVP message.
0x03-0xFD: Reserved for IANA assignment.
0xFE: Experiment/Organization specific.
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0xFF: Reserved.
The field that follows the Internet protocol/application identifier
field is assigned to Internet protocol/application related
information that is identified by the Internet protocol/application
identifier field.
4.2.2 ST2+ SCMP
The format of the ST2+ SCMP is shown in Fig. 4.8.
Bits
8 7 6 5 4 3 2 1 Octets
+-----+-----+-----+-----+-----+-----+-----+-----+
| Information element identifier |
| = User-user information element (0x7E) | 1
+-----+-----+-----+-----+-----+-----+-----+-----+
| 1 | Coding | IE instruction field |
| Ext | standard |Flag |Res. | IE action ind. | 2
+-----+-----+-----+-----+-----+-----+-----+-----+
| Length of contents of information element | 3-4
+-----+-----+-----+-----+-----+-----+-----+-----+
| Protocol discriminator |
| = Internet protocol/application (TBD) | 5
+-----+-----+-----+-----+-----+-----+-----+-----+
| Internet protocol/application identifier |
| = ST2+ SCMP (0x01) | 6
+-----+-----+-----+-----+-----+-----+-----+-----+
| ST2+ SCMP | 7-
= =
| |
+-----+-----+-----+-----+-----+-----+-----+-----+
Fig. 4.8: ST2+ SCMP.
The Internet protocol/application identifier field is the ST2+ SCMP
(0x01).
The ST2+ SCMP [10] is assigned to the Internet protocol/application
related information field. The SETUP and ADD PARTY messages may
contain the ST2+ SCMP CONNECT message. The CONNECT and ADD PARTY ACK
messages may contain the ST2+ SCMP ACCEPT message. The RELEASE and
DROP PARTY messages may contain the ST2+ SCMP DISCONNECT message.
The RELEASE, RELEASE COMPLETE, ADD PARTY REJECT, and DROP PARTY
messages may contain the ST2+ SCMP REFUSE message.
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4.2.3 RSVP message
The format of the RSVP message is shown in Fig. 4.9.
Bits
8 7 6 5 4 3 2 1 Octets
+-----+-----+-----+-----+-----+-----+-----+-----+
| Information element identifier |
| = User-user information element (0x7E) | 1
+-----+-----+-----+-----+-----+-----+-----+-----+
| 1 | Coding | IE instruction field |
| Ext | standard |Flag |Res. | IE action ind. | 2
+-----+-----+-----+-----+-----+-----+-----+-----+
| Length of contents of information element | 3-4
+-----+-----+-----+-----+-----+-----+-----+-----+
| Protocol discriminator |
| = Internet protocol/application (TBD) | 5
+-----+-----+-----+-----+-----+-----+-----+-----+
| Internet protocol/application identifier |
| = RSVP message (0x02) | 6
+-----+-----+-----+-----+-----+-----+-----+-----+
| RSVP message | 7-
= =
| |
+-----+-----+-----+-----+-----+-----+-----+-----+
Fig. 4.9: RSVP message.
The Internet protocol/application identifier field is the RSVP
message (0x02).
The RSVP message [11] is assigned to the Internet
protocol/application related information field. The SETUP message
may contain the RSVP Resv message. The CONNECT message may contain
the RSVP ResvConf message. The RELEASE message may contain the RSVP
ResvErr or ResvTear message.
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4.2.4 Experiment/Organization specific
The format of the Experiment/Organization specific is shown in Fig.
4.10.
Bits
8 7 6 5 4 3 2 1 Octets
+-----+-----+-----+-----+-----+-----+-----+-----+
| Information element identifier |
| = User-user information element (0x7E) | 1
+-----+-----+-----+-----+-----+-----+-----+-----+
| 1 | Coding | IE instruction field |
| Ext | standard |Flag |Res. | IE action ind. | 2
+-----+-----+-----+-----+-----+-----+-----+-----+
| Length of contents of information element | 3-4
+-----+-----+-----+-----+-----+-----+-----+-----+
| Protocol discriminator |
| = Internet protocol/application (TBD) | 5
+-----+-----+-----+-----+-----+-----+-----+-----+
| Internet protocol/application identifier |
| = Experiment/Organization specific (0xFE) | 6
+-----+-----+-----+-----+-----+-----+-----+-----+
| Organizationally unique identifier (OUI) | 7-9
+-----+-----+-----+-----+-----+-----+-----+-----+
| Experiment/Organization specific info. | 10-
= =
| |
+-----+-----+-----+-----+-----+-----+-----+-----+
Fig. 4.10: Experiment/Organization specific.
The Internet protocol/application identifier field is the
Experiment/Organization specific (0xFE).
The first 3 octets in the Internet protocol/application related
information field must contain the Organizationally unique identifier
(OUI) (as specified in IEEE 802-1990; section 5.1).
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5. Open Issues
The following issues are still remain in this document.
o Generic Identifier support for session aggregation.
Session aggregation support may be needed in a backbone
environment. Wild card style aggregated session identifier may be
feasible. However, before specifying Generic Identifier support
for it, session aggregation model in ATM VCs should be clarified.
o Generic Identifier support for the IPv6 flow label and traffic
classes.
The IPv6 flow label and traffic classes support may be needed in
future. However, currently their semantics are not clear.
6. Required Amendments to the User-to-user Signaling
The information field and protocol identifier assignment in the
Generic Identifier information element and User-user information
element, which are described in section 4, are required for advanced
B-ISDN signaling support of the Internet protocol.
To enable advanced B-ISDN signaling support for the Internet
protocol, the following amendments should be applied to the Q.2957
and Q.2971 annex D User-to-user Signaling.
o Add the Internet protocol/application to the Protocol
discriminator.
o Increase the maximum length of the User-user information element to
sufficiently long, e.g. 262 octets, to forward the setup protocol
such as ST2+ and RSVP. This amendment is not applied and remains
133 octets when the User-user information element interworks with
the N-ISDN user-user information element.
7. Security Considerations
This document specifies the information field and protocol identifier
assignment in the Q.2941 Generic Identifier and Q.2957 User-to-user
Signaling for the Internet protocol, so these do not weaken the
security of the B-ISDN signaling.
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In a called party of the B-ISDN signaling, if the incoming SETUP
message contains the calling party number and if it is verified and
passed by the ATM network or it is provided by the network, then it
is feasible to use the calling party number for part of the calling
party authentication to strengthen security.
References
[1] ITU-T, "Broadband Integrated Services Digital Network (B-
ISDN)-Digital Subscriber Signaling System No. 2 (DSS 2)-User-
Network Interface (UNI) Layer 3 Specification for Basic
Call/Connection Control," ITU-T Recommendation Q.2931, September
1995.
[2] ITU-T, "Broadband Integrated Services Digital Network (B-
ISDN)-Digital Subscriber Signaling System No. 2 (DSS 2)-User-
Network Interface Layer 3 Specification for Point-to-Multipoint
Call/Connection Control," ITU-T Recommendation Q.2971, October
1995.
[3] ITU-T, "Broadband Integrated Services Digital Network (B-ISDN)
Digital Subscriber Signaling System No. 2 (DSS 2): Generic
Identifier Transport," Draft ITU-T New Recommendation Q.2941.1,
September 1997.
[4] ITU-T, "Broadband Integrated Services Digital Network (B-ISDN)
Digital Subscriber Signaling System No. 2 (DSS 2): Generic
Identifier Transport," Draft ITU-T New Recommendation Q.2941.2,
May 1998. (http://www.nal.ecl.net/SG11WP1/itu-t-sg11-tmp-doc-
td55r2.ps)
[5] ITU-T, "Stage 3 Description for Additional Information
Transfer Supplementary Service Using B-ISDN Digital Subscriber
Signaling System No. 2 (DSS 2)-Basic Call Clause 1-User-to-User
Signalling (UUS)," ITU-T Recommendation Q.2957, February 1995.
[6] J. Postel Ed., "Internet Protocol," RFC 791, September 1981.
[7] S. Deering and R. Hinden, "Internet Protocol, Version 6 (IPv6)
Specification," Internet Draft, July 1997, <draft-ietf-ipngwg-
ipv6-spec-v2-00.txt>.
[8] J. Postel, "User Datagram Protocol," RFC 768, August 1980.
[9] J. Postel Ed., "Transmission Control Protocol," RFC 793,
September 1981.
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[10] L. Delgrossi and L. Berger, Ed., "Internet Stream Protocol
Version 2 (ST2) Protocol Specification - Version ST2+," RFC 1819,
August 1995.
[11] R. Braden Ed., "Resource ReSerVation Protocol (RSVP)-Version
1 Functional Specification," RFC 2205, September 1997.
[12] K. Nagami, N. Demizu, H. Esaki, and P. Doolan, "VCID
Notification over ATM link," Internet Draft, March 1998, <draft-
ietf-mpls-vcid-atm-00.txt>.
[13] P. Newman, T. Lyon, and G. Minshall, "Flow Labelled IP: A
Connectionless Approach to ATM," Proc. IEEE Infocom, March 1996.
[14] S. Damaskos and A. Gavras, "Connection Oriented Protocols
over ATM: A case study," Proc. SPIE, Vol. 2188, pp.226-278,
February 1994.
[15] ITU-T, "Integrated Services Digital Network (ISDN) Overall
Network Aspects and Functions ISDN Protocol Reference Model,"
ITU-T Recommendation I.320, November 1993.
[16] ITU-T, "Digital Subscriber Signaling System No. 1 (DSS 1)
Specification of a Synchronization and Coordination Function for
the Provision of the OSI Connection-mode Network Service in an
ISDN Environment," ITU-T Recommendation Q.923, February 1995.
[17] K. Kitami, "Proposed Direction for B-ISDN & Multimedia
Signaling," ITU-T SG11 Delayed Contribution D.647, January 1998,
(http://www.nal.ecl.net/SG11WP1/itu-t-sg11-del-contrib-d647.ps).
Acknowledgments
I would like to thank Kenichi Kitami of the NTT Network Innovation
Planning and Promotion Dept., who is also the chair of ITU-T SG11
WP1, Shinichi Kuribayashi of the NTT Business Communications Hqs.,
Hiroshi Yao and Takumi Ohba of the NTT Network Service Systems
Labs., and Noriyuki Takahashi of the NTT Multimedia Networks Labs.
for their valuable comments and discussions.
And I would also like to thank the active members of IETF, ITU-T,
and ATM Forum, especially Joel Halpern of Newbridge Networks,
Andrew Malis of Ascend Communications, George Swallow and Bruce
Davie of Cisco Systems, Rao Cherukuri of IBM, Rajiv Kapoor of
AT&T, Greg Ratta of Lucent, Hiroshi Esaki and Kenichi Nagami of
Toshiba, and Noritoshi Demizu of NAIST for their valuable comments
and suggestions.
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Also this specification is based on various discussions during the
ST2+ over ATM project at the NTT Multimedia Joint Project with
NACSIS. I would like to thank Professor Shoichiro Asano of the
National Center for Science Information Systems for his invaluable
advice in this area.
Author's Address
Muneyoshi Suzuki
NTT Multimedia Networks Laboratories
3-9-11, Midori-cho
Musashino-shi, Tokyo 180-8585, Japan
Phone: +81-422-59-2119
Fax: +81-422-59-2829
EMail: suzuki@nal.ecl.net
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