RFC 5133 PROPOSED STANDARD ISDN · SIGNALING · ERRATA

IUA TEI Query Change: Terminal Endpoint Identifier (TEI) Query Request Number Change

A one-number fix: the ISDN IUA TEI Query Request message moves from type 5 to type 8 to stop clashing with DUA.

On rfc-editor.org ↗
PUBLISHED
December 2007
AUTHORS
M. Tuexen, K. Morneault
STREAM
IETF
BUILDS ON
RFC 4233 — IUA
OLD TEI QUERY TYPE
5
NEW TEI QUERY TYPE
8
CLASHING DLC STATUS TYPES
5, 6, 7
DOI
10.17487/RFC5133

RFC text

Contents
Original text · RFC Editor View on rfc-editor.org ↗
Network Working Group                                          M. Tuexen
Request for Comments: 5133            Muenster Univ. of Applied Sciences
Updates: 4233                                               K. Morneault
Category: Standards Track                            Cisco Systems, Inc.
                                                           December 2007


     Terminal Endpoint Identifier (TEI) Query Request Number Change

Status of This Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Abstract

   The Integrated Services Digital Network (ISDN) Q.921-User Adaptation
   Layer (IUA) Protocol, described in RFC 4233, defines the message type
   of Terminal Endpoint Identifier (TEI) Query Request messages as 5.
   However, this number is already being used by the Digital Private
   Network Signaling System (DPNSS)/Digital Access Signaling System 2
   (DASS 2) Extensions (DUA) to the IUA Protocol described in RFC 4129.
   This document updates RFC 4233 such that the message type of TEI
   Query Request messages is 8.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 2
   2.  Conventions Used in This Document . . . . . . . . . . . . . . . 2
   3.  New Message Type of the TEI Query Message . . . . . . . . . . . 2
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 2
   5.  Security Considerations . . . . . . . . . . . . . . . . . . . . 2
   6.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 2
   7.  Normative References  . . . . . . . . . . . . . . . . . . . . . 3

1.  Introduction

   The Integrated Services Digital Network (ISDN) Q.921-User Adaptation
   Layer (IUA) protocol, described in [RFC3057], does not define a
   Terminal Endpoint Identifier (TEI) Query Request message.  The
   Digital Private Network Signaling System (DPNSS)/Digital Access
   Signaling System 2 (DASS 2) Extensions (DUA) to the IUA Protocol,
   described in [RFC4129], introduces Data Link Connection (DLC) Status
   messages of type 5, 6, and 7.  Then, [RFC4233] was published, which
   updates [RFC3057].  [RFC4233] also introduces the TEI Query Request
   message and uses the message type of 5 for it.  This makes it
   impossible to differentiate the DLC Status request from a TEI Query
   Request.

   This document updates [RFC4233].

2.  Conventions Used in This Document

   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.  New Message Type of the TEI Query Message

   This document updates [RFC4233] by introducing the following change:

   Terminal Endpoint Identifier (TEI) Query messages MUST be encoded
   with a message type of 8 instead of 5 as described in [RFC4233].

4.  IANA Considerations

   In the "Message Types" section of the "Signaling User Adaptation
   Layer Assignments" registry, IANA has reserved the message type 8 of
   Management Messages for Terminal Endpoint Identifier (TEI) Query
   Request messages.

5.  Security Considerations

   This document does not require any security considerations in
   addition to the ones given in [RFC4233].

6.  Acknowledgments

   The authors wish to thank Jon Peterson and Christian Vogt for their
   invaluable comments.

7.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC3057]  Morneault, K., Rengasami, S., Kalla, M., and G.
              Sidebottom, "ISDN Q.921-User Adaptation Layer", RFC 3057,
              February 2001.

   [RFC4129]  Mukundan, R., Morneault, K., and N. Mangalpally, "Digital
              Private Network Signaling System (DPNSS)/Digital Access
              Signaling System 2 (DASS 2) Extensions to the IUA
              Protocol", RFC 4129, September 2005.

   [RFC4233]  Morneault, K., Rengasami, S., Kalla, M., and G.
              Sidebottom, "Integrated Services Digital Network (ISDN)
              Q.921-User Adaptation Layer", RFC 4233, January 2006.

Authors' Addresses

   Michael Tuexen
   Muenster Univ. of Applied Sciences
   Stegerwaldstr. 39
   48565 Steinfurt
   Germany

   EMail: tuexen@fh-muenster.de


   Ken Morneault
   Cisco Systems, Inc.
   13615 Dulles Technology Drive
   Herndon, VA  20171
   US

   Phone: +1-703-484-3323
   EMail: kmorneau@cisco.com

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AI ELI5

On this page
PROBLEMRFC 4233 gave the TEI Query Request message the type 5, but the DUA extension in RFC 4129 already used type 5 for a DLC Status message, so the two could not be told apart.
MECHANISMThis document says TEI Query messages MUST be encoded with message type 8 instead of 5, and IANA reserved type 8 for them.
WHY IT MATTERSIt updates RFC 4233 and is a Proposed Standard with no replacement listed.

§1Introduction

The ISDN Q.921-User Adaptation Layer (IUA) is described in RFC 3057, which has no Terminal Endpoint Identifier (TEI) Query Request message. The DPNSS/DASS 2 Extensions (DUA) in RFC 4129 add Data Link Connection (DLC) Status messages of types 5, 6 and 7.

Then RFC 4233 updated RFC 3057 and introduced the TEI Query Request message, also using type 5. That made it impossible to tell a DLC Status request from a TEI Query Request.

Two different messages ended up with the same number, so a receiver could not tell which one it got.

§2The Message Type Change

The whole change is one rule: TEI Query messages MUST be encoded with a message type of 8 instead of 5 as described in RFC 4233. Nothing else in RFC 4233 is altered by this document.

The rule is simple: the TEI Query message now uses number 8, not 5.

TEI QUERY REQUEST TYPE BEFORE AND AFTER
DocumentMessageType
RFC 4129 (DUA)DLC Status messages5, 6, 7
RFC 4233TEI Query Request5
RFC 5133 THIS RFCTEI Query Request8

§3IANA Registry Entry

In the Message Types section of the Signaling User Adaptation Layer Assignments registry, IANA has reserved message type 8 of Management Messages for TEI Query Request messages. This keeps the registry consistent with the new encoding.

The official list of numbers now shows 8 as taken by the TEI Query message.

§4Security Considerations

The document does not require any security considerations in addition to the ones given in RFC 4233, because it only renumbers one message type.

Changing a label number does not add any new danger.

§5References