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Signalling Transport Working group L. Coene
Internet-Draft Siemens
Expires: January 7, 2006 J. Loughney
Nokia
July 6, 2005
SUA Implementor's guide
<draft-ietf-sigtran-sua-implementor-guide-01.txt>
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Copyright Notice
Copyright (C) The Internet Society (2005).
Abstract
This document contains a compilation of all defects found up until
the publication date for SUA [RFC3868] [1]. These defects may be of
an editorial or technical nature. This document may be thought of as
a companion document to be used in the implementation of SUA to
clarify errors in the original SUA document. This document updates
RFC3868 and text within this document supersedes the text found in
RFC3868.
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Table of Contents
1. INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1 Terminology . . . . . . . . . . . . . . . . . . . . . . . 4
1.2 Conventions . . . . . . . . . . . . . . . . . . . . . . . 4
2. Correction to RFC3868 . . . . . . . . . . . . . . . . . . . 5
2.1 Routing context list in connectionless and
connectionoriented messages . . . . . . . . . . . . . . . 5
2.1.1 Description of the problem . . . . . . . . . . . . . . 5
2.1.2 Text changes to the document . . . . . . . . . . . . . 5
2.1.3 Solution description . . . . . . . . . . . . . . . . . 5
2.2 Congestion level parameter value . . . . . . . . . . . . . 5
2.2.1 Description of the problem . . . . . . . . . . . . . . 5
2.2.2 Text changes to the document . . . . . . . . . . . . . 6
2.2.3 Solution description . . . . . . . . . . . . . . . . . 7
2.3 Segmentation parameter value . . . . . . . . . . . . . . . 7
2.3.1 Description of the problem . . . . . . . . . . . . . . 7
2.3.2 Text changes to the document . . . . . . . . . . . . . 7
2.3.3 Solution description . . . . . . . . . . . . . . . . . 8
2.4 DAUD response message ordering . . . . . . . . . . . . . . 8
2.4.1 Description of the problem . . . . . . . . . . . . . . 8
2.4.2 Text changes to the document . . . . . . . . . . . . . 8
2.4.3 Solution description . . . . . . . . . . . . . . . . . 9
2.5 Host name parameter . . . . . . . . . . . . . . . . . . . 9
2.5.1 Description of the problem . . . . . . . . . . . . . . 9
2.5.2 Text changes to the document . . . . . . . . . . . . . 9
2.5.3 Solution description . . . . . . . . . . . . . . . . . 10
2.6 ASP routing context . . . . . . . . . . . . . . . . . . . 10
2.6.1 Description of the problem . . . . . . . . . . . . . . 10
2.6.2 Text changes to the document . . . . . . . . . . . . . 10
2.6.3 Solution description . . . . . . . . . . . . . . . . . 10
2.7 Parameters should only occur once in a message . . . . . . 11
2.7.1 Description of the problem . . . . . . . . . . . . . . 11
2.7.2 Text changes to the document . . . . . . . . . . . . . 11
2.7.3 Solution description . . . . . . . . . . . . . . . . . 11
2.8 TID label parameter . . . . . . . . . . . . . . . . . . . 11
2.8.1 Description of the problem . . . . . . . . . . . . . . 11
2.8.2 Text changes to the document . . . . . . . . . . . . . 12
2.8.3 Solution description . . . . . . . . . . . . . . . . . 12
2.9 DRM label parameter . . . . . . . . . . . . . . . . . . . 13
2.9.1 Description of the problem . . . . . . . . . . . . . . 13
2.9.2 Text changes to the document . . . . . . . . . . . . . 13
2.9.3 Solution description . . . . . . . . . . . . . . . . . 14
2.10 Usage of the TID and DRN label . . . . . . . . . . . . . 14
2.10.1 Description of the problem . . . . . . . . . . . . . 14
2.10.2 Text changes to the document . . . . . . . . . . . . 15
2.10.3 Solution description . . . . . . . . . . . . . . . . 17
2.11 Address Range paramete . . . . . . . . . . . . . . . . . 18
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2.11.1 Description of the problem . . . . . . . . . . . . . 18
2.11.2 Text changes to the document . . . . . . . . . . . . 18
2.11.3 Solution description . . . . . . . . . . . . . . . . 19
2.12 Interpretation of the mask parameter . . . . . . . . . . 19
2.12.1 Description of the problem . . . . . . . . . . . . . 19
2.12.2 Text changes to the document . . . . . . . . . . . . 20
2.12.3 Solution description . . . . . . . . . . . . . . . . 21
2.13 Reply on errors contained in a error message . . . . . . 21
2.13.1 Description of the problem . . . . . . . . . . . . . 21
2.13.2 Text changes to the document . . . . . . . . . . . . 21
2.13.3 Solution description . . . . . . . . . . . . . . . . 22
2.14 Use of stream 0 for SSNM messages . . . . . . . . . . . 22
2.14.1 Description of the problem . . . . . . . . . . . . . 22
2.14.2 Text changes to the document . . . . . . . . . . . . 22
2.14.3 Solution description . . . . . . . . . . . . . . . . 23
2.15 Timer Ta does not exist . . . . . . . . . . . . . . . . 23
2.15.1 Description of the problem . . . . . . . . . . . . . 23
2.15.2 Text changes to the document . . . . . . . . . . . . 23
2.15.3 Solution description . . . . . . . . . . . . . . . . 24
2.16 Error response on unsupported RKM messages . . . . . . . 24
2.16.1 Description of the problem . . . . . . . . . . . . . 24
2.16.2 Text changes to the document . . . . . . . . . . . . 24
2.16.3 Solution description . . . . . . . . . . . . . . . . 25
3. Security considerations . . . . . . . . . . . . . . . . . . 26
4. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . 27
5. References . . . . . . . . . . . . . . . . . . . . . . . . . 27
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 27
A. Changes Control . . . . . . . . . . . . . . . . . . . . . . 28
A.1 Changes from v00 to v01 . . . . . . . . . . . . . . . . . 28
Intellectual Property and Copyright Statements . . . . . . . 29
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1. INTRODUCTION
This document contains a compilation of all defects found up until
the publication date for the SCCP User Adaptation Layer (SUA)
[RFC3868]. These defects may be of an editorial or technical nature.
This document may be thought of as a companion document to be used in
the implementation of SUA to clarify errors in the original SUA
document. This document updates RFC3868 and text within this
document, where noted, supersedes the text found in RFC3868. Each
error will be detailed within this document in the form of:
o The problem description,
o The text quoted from RFC3868,
o The replacement text,
o A description of the solution.
1.1 Terminology
The terms are commonly identified in related work SUA [RFC3868] [1].
1.2 Conventions
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2. Correction to RFC3868
2.1 Routing context list in connectionless and connectionoriented
messages
2.1.1 Description of the problem
The routing context parameter of a connectionless and
connectionoriented message can contain a list of routing contexts.
Normaly, the addressing info present in the message will yield only a
single routing context. A list of routing contexts is valid only for
SSNM, ASPTM and RKM messages
2.1.2 Text changes to the document
---------
Old text: (Section 3.9.6)
---------
The Routing Context parameter contains (a list of) 4-byte unsigned
integers indexing the Application Server traffic that the sending ASP
is configured/registered to receive. There is a one-to-one
relationship between an index entry and a Routing Key or AS Name.
---------
New text: (Section 3.9.6)
---------
The Routing Context parameter contains (a list of) 4-byte unsigned
integers indexing the Application Server traffic that the sending ASP
is configured/registered to receive. There is a one-to-one
relationship between an index entry and a Routing Key or AS Name.
A list of routing contexts is only valid for SSNM, ASPTM and RKM
messages. All other messages can contain only a single Routing
Context.
2.1.3 Solution description
Only 1 routing context value may be included in the routing context
parameter of a connectionless and connectionoriented message.
2.2 Congestion level parameter value
2.2.1 Description of the problem
The value of the congestion level is dependant on which info is
present in the SCON message. If the SCON only contains the affected
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pointcode, then the congestion level has values ranging between 0 and
3. If affected pointcode and subsystemnumber is included in the SCON
message, then the value of the congestion level can be between 1 and
8.
2.2.2 Text changes to the document
---------
Old text: (Section 3.10.24)
---------
When the Congestion Level parameter is included in a SCON message
that corresponds to an N-PCSTATE primitive, the Congestion Level
field indicates the MTP congestion level experienced by the local or
affected signalling point as indicated by the Affected Point Code(s)
also in the SCON message. In this case, valid values for the
Congestion Level field are as follows:
0 No Congestion or Undefined
1 Congestion Level 1
2 Congestion Level 2
3 Congestion Level 3
When the Congestion Level parameter is included in a SCON messagethat
corresponds to an N-STATE primitive, the Congestion Level field
indicates the SCCP restricted importance level experienced by the
local or affected subsystem as indicated by the Affected Point Code
and Subsystem Number also in the SCON message. In this case, valid
values for the Congestion Level field range from 0 to 7, where 0
indicates the least congested and 7 indicates the most congested
subsystem.
---------
New text: (Section 3.10.24)
---------
2 different congestion levels ranges can be used accoring to ITU and
ANSI congestion control algorithms.
When the ANSI congestion control algorithm is used, the Congestion
Level field indicates the MTP congestion level as experienced by the
local or affected subsystem indicated by the Affected Point Code and
Subsystem Number. In this case, valid values for the Congestion
Level field range from 0 to 3, where 1 indicates the least congested
and 3 indicates the most congested condition.
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0 No Congestion or Undefined
1 Congestion Level 1
2 Congestion Level 2
3 Congestion Level 3
When the ITU congestion control algorithm is used, the Congestion
Level field indicates the SCCP restricted importance level
experienced by the local or affected subsystem as indicated by the
Affected Point Code and Subsystem Number also in the SCON message.
In this case, valid values for the Congestion Level field range from
1 to 8, where 1 indicates the least congested and 8 indicates the
most congested condition.
2.2.3 Solution description
The ITU SCCP congestion control procedures are described in SCCP
procedures [Q.714] [4] paragraph 2.6. The ANSI SCCP congestion
control procedures are described in SCCP procedures [T1.112.4] [5]
paragraph 5.2.4.
The SCC message in SCCP takes the value range 1..8, so the
corresponding SCON should also be in that range. To indicate no
congestion, it is sufficient to send only a DAVA.
2.3 Segmentation parameter value
2.3.1 Description of the problem
The original sequence delivery option as original demanded(= before
the segementing) by the SCCP application is not preserved after
segmentation. The receiving SCCP application will always receive the
message with sequenced delivery option set to 1.
2.3.2 Text changes to the document
---------
Old text: (Section 3.10.23)
---------
The first/remaining segments field is formatted as follows:
o bit 8 (MSB) : indicates whether this is the first segment (1) or
not (0)
o bits 1-7: indicate the number of remaining segments, value between
0 and 15
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---------
New text: (Section 3.10.23)
---------
The segmentation paramter consists of the following:
o bit 0: first/remaing segment bit: first = 1, remaining = 0
o bit 1: sequence delivery option as original demanded(= before the
segementing) by the SCCP application. class 0 = 0, class 1 = 1.
o bit 2-3: spare
o bit 4-7: number of remaining segments(4 bits, values 0 -15)
o bit 8-31:segmentation reference(3 byte integer)
2.3.3 Solution description
The segmentation parameter gets a extra bit(out of the spare bits
present) indicating the original requested sequence delivery option
as originally demanded by the sending SCCP application.
2.4 DAUD response message ordering
2.4.1 Description of the problem
Should a SCON be send before the DAVA or DRST or after? The SCON is
send first and DAVA/DRST after in M3UA.
2.4.2 Text changes to the document
---------
Old text: (Section 4.5.3)
---------
The SGP SHOULD respond to a DAUD message with the availability and
congestion status of the subsystem. The status of each SS7
destination or subsystem requested is indicated in a DUNA message (if
unavailable), a DAVA message (if available), or a DRST (if restricted
and the SGP supports this feature). If the SS7 destination or
subsystem is available and congested, the SGP responds with an SCON
message in addition to the DAVA message. If the SS7 destination or
subsystem is restricted and congested, the SGP responds with an SCON
message in addition to the DRST. If the SGP has no information on
the availability / congestion status of the SS7 destination or
subsystem, the SGP responds with a DUNA message, as it has no routing
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information to allow it to route traffic to this destination or
subsystem.
---------
New text: (Section 4.5.3)
---------
The SGP SHOULD respond to a DAUD message with the availability and
congestion status of the subsystem. The status of each SS7
destination or subsystem requested is indicated in a DUNA message (if
unavailable), a DAVA message (if available), or a DRST (if restricted
and the SGP supports this feature). If the SS7 destination or
subsystem is available and congested, the SGP responds with an SCON
message and a DAVA message. If the SS7 destination or subsystem is
restricted and congested, the SGP responds with an SCON message and a
DRST. If the SGP has no information on the availability / congestion
status of the SS7 destination or subsystem, the SGP responds with a
DUNA message, as it has no routing information to allow it to route
traffic to this destination or subsystem.
2.4.3 Solution description
The DAVA/DUNA/DRST/SCON messages may be send in random order.
However if a SCON is send first and the destination is inaccessible,
the SCON will be dropped. So it might be better to send the DAVA
first followed by the SCON.
2.5 Host name parameter
2.5.1 Description of the problem
The hostname is actually a Fully Qualified Domain Name(FQDN) as
defined in RFC1983. The definition of the hostname(as found in
RFC1983) would only allow for a part of the FQDN and that does not
uniquely identify a endpoint. Also the encoding of the FQDN is not
clear.
2.5.2 Text changes to the document
---------
Old text: (Section 3.10.2.7)
---------
This field contains a host name in "host name syntax" per RFC 1123
Section 2.1 [1123]. The method for resolving the host name is out of
scope for this document.
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---------
New text: (Section 3.10.2.7)
---------
This field contains a host name in "Fully Qualified Domain Name
syntax" per RFC 1035 section 3.1 [RFC1035] [3]. The method for
resolving the host name is out of scope for this document.
2.5.3 Solution description
The hostname is actually a Fully Qualified Domain Name(FQDN) which
should be encoded following the RFC1035 section 3.1 coding rules.
2.6 ASP routing context
2.6.1 Description of the problem
An ASP routes responses to the SGP that it received messages from;
within the routing context which it is currently active and receiving
traffic.
2.6.2 Text changes to the document
---------
Old text: (Section 1.5.2)
---------
An ASP routes responses to the SGP that it received messages from;
within the routing context which it is currently active and receiving
traffic.
---------
New text: (Section 1.5.2)
---------
An ASP routes responses to the SGP that it received messages from.
The reponse will utilize the routing context from the received
messages.
2.6.3 Solution description
a. A routing context is an integer which is significant only for a
given SGP-ASP pair. So it is circular logic to say that the ASP
should use the RC to select the SGP - an RC value is meaningful only
after the SGP has already assigned the RC for the the msg send to the
ASP.
b. An ASP can be active vis-a-vis an SGP for more than one RC - so
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it is not meaningful to say that the ASP uses "the" RC for which it
is active. If the ASP response to a messages, it has to use the RC
of that received message in the reponse.
2.7 Parameters should only occur once in a message
2.7.1 Description of the problem
Parameters in SUA messages can be repeated as many times as possible.
This would lead to inconsistencies, such as 2 or more destination
addresses.
2.7.2 Text changes to the document
---------
Old text: (Section x.x)
---------
---------
New text: (Section x.x)
---------
2.7.3 Solution description
Unless explicitly stated or shown in a message format diagram, only
one parameter of the same type is allowed in a message.
2.8 TID label parameter
2.8.1 Description of the problem
The clarity of the definition of TID label parameters is unclear.
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2.8.2 Text changes to the document
---------
Old text: (Section 3.10.16)
---------
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Tag = 0x0110 | Length = 8 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| start | end | label value |
+---------------+---------------+-------------------------------+
The Start parameter is the start position of label, between 0 (LSB)
and 31 (MSB).
The End parameter is the end position of label, between 0 (LSB) and
31 (MSB).
Label value is a 16-bit integer, which is unique across an AS.
---------
New text: (Section 3.10.16)
---------
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Tag = 0x0110 | Length = 8 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| label mask |
+---------------------------------------------------------------+
Label mask value is a 32-bit integer. The mask is logically
ANDed onto the received TCAP transaction ID. And if the result
of the AND operation exactly matches the "Label mask" field,
then the message is sent to the ASP that registered for this
label via the ASPAC msg.
An ASP that registers a label will be sent only those TID-bearing
messages that match its label.
An ASP that does not register a label may be sent any TID-bearing
message.
2.8.3 Solution description
The clarity of the definition of the TID and DRM label parameters is
improved by removing the start and end field. It is assumed that
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these labels are simply xx-bit masks that are logically ANDed onto
the received TID or DRN. If the result of the AND operation exactly
matches the "Label" field, then the message is sent to the ASP that
registered for this label via the ASPAC msg. An ASP that registers a
label will be sent only those TID-bearing messages that match its
label.
2.9 DRM label parameter
2.9.1 Description of the problem
See problem description TID label parameter
2.9.2 Text changes to the document
---------
Old text: (Section 3.10.15)
---------
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Tag = 0x010F | Length = 8 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| start | end | label value |
+---------------+---------------+-------------------------------+
The Start parameter is the start position of label, between 0 (LSB)
and 23 (MSB).
The End parameter is the end position of label, between 0 (LSB) and
23 (MSB).
Label value is a 16-bit integer, which is unique across an AS.
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---------
New text: (Section 3.10.15)
---------
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Tag = 0x010F | Length = 8 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| padding | label value |
+---------------+-----------------------------------------------+
Label mask value is a 24-bit integer. The mask is logically
ANDed onto the received SCCP DRN. And if the result
of the AND operation exactly matches the "Label mask" field,
then the message is sent to the ASP that registered for this
label via the ASPAC msg.
An ASP that registers a label will be sent only those DRN-bearing
messages that match its label.
An ASP that does not register a label may be sent any DRN-bearing
message.
2.9.3 Solution description
See solution description TID label parameter.
2.10 Usage of the TID and DRN label
2.10.1 Description of the problem
The use of the TID and DRM label parameters is unclear.
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2.10.2 Text changes to the document
---------
Old text: (Section 4.7.2.1)
---------
After association setup and registration, an ASP normally goes active
for each AS it registered for. In the ASPAC message, the ASP
includes a TID and/or DRN Label Parameter, if applicable for the AS
in question. All the ASPs within the AS must specify a unique label
at a fixed position in the TID or DRN parameter. The same ASPAC
message is sent to each SG used for interworking with the SS7
network.
The SG builds, per RK, a list of ASPs that have registered for it.
The SG can now build up and update a distribution table for a certain
Routing Context, any time the association is (re-)established and the
ASP goes active. The SG has to perform some trivial plausibility
checks on the parameters:
- Start and End parameters values are between 0 and 31 for TID.
- Start and End parameters values are between 0 and 23 for DRN
- ...
- Start values are the same for each ASP within a RC
- End values are the same for each ASP within a RC
- TID and DRN Label values must be unique across the RC
If any of these checks fail, the SG refuses the ASPAC request, with
an error: Invalid loadsharing label .
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---------
New text: (Section 4.7.2.1)
---------
After association setup and registration, an ASP normally goes active
for each AS it registered for. In the ASPAC message, the ASP can include
a TID and/or DRN Label Parameter, if applicable for the AS
in question.
If at least one of the ASPs within an AS specifies a label, then all the
ASPs within the AS must specify a unique label in the ASPAC's msg they
send.
Each of the ASPs within the AS must specify a unique label
in the TID or DRN parameter. The ASP must send the same ASPAC to each
SG it is attached to, for interworking with the SS7 network.
The SG builds, per RC, a list of ASPs that have registered for it.
The SG can now build up and update a distribution table for a certain
Routing Context, any time the association is (re-)established and the
ASP goes active. The SG has to perform some trivial plausibility
checks on the parameters:
- TID and/or DRN Label values must be unique across the RC
If any of these checks fail, the SG refuses the ASPAC request, with
an error, "Invalid loadsharing label."
---------
Old text: (Section 4.7.3.1)
---------
Messages not containing a destination (or "responding") TID, i.e.,
Query, Begin, Unidirectional, are loadshared among the available
ASPs. Any scheme permitting a fair load distribution among the ASPs
is allowed (e.g., round robin).
When a destination TID is present, the SG extracts the label and
selects the ASP that corresponds with it.
If an ASP is not available, the SG may generate (X)UDTS "routing
failure", if the return option is used.
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---------
New text: (Section 4.7.3.1)
---------
Messages not containing a destination (or "responding") TID, i.e.,
Query, Begin, Unidirectional, are loadshared among the available
ASPs. Any scheme permitting a fair load distribution among the ASPs
is allowed (e.g., round robin).
When a destination TID is present, the SG extracts the label and
if the result of the AND operation exactly matches the "Label" field,
then the message is sent to the ASP that registered for this label via the
ASPAC msg.
An ASP that registers a label will be sent only those TID-bearing
messages that match its label.
An ASP that does not register a label may be sent any TID-bearing
message.
If an ASP is not available, the SG may generate (X)UDTS "routing
failure", if the return option is used.
2.10.3 Solution description
Improving the clarity of the use of the TID and DRM label parameters:
If the result of the AND operation exactly matches the "Label" field,
then the message is sent to the ASP that registered for this label
via the ASPAC msg.
An ASP that registers a label will be sent only those TID-bearing
messages that match its label. An ASP that does not register a label
may be sent any TID-bearing message.
Redundancy - The label values are fixed length (16 bits). So why do
we need both a "Start" and an "End" position for applying the mask?
One or the other would seem to be enough.
Simplicity - Why bother with a partial-sized mask at a specified
"start" bit. Why not just specify a "full-sized" 32-bit (TID) or 23-
bit (DRM) mask? Then we do not need a "start" and "end" position.
Contradictions - Section 4.7.2.1 states that "All the ASPs within the
AS _must_ specify a unique label at a fixed position in the TID or
DRN parameter." The "must" here contradicts that fact the the TID
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and DRM parameters are listed as Optional in the ASPAC msg. Thus if
a label is present, then all ASP's belonging to that AS, must
specifiy a label in the ASPAC msg.
2.11 Address Range paramete
2.11.1 Description of the problem
It should explicitly state the order of the minimum and maximum
addresses in this parameter. The most logical order would probably
be first the min, followed by the max.
2.11.2 Text changes to the document
---------
Old text: (Section 3.10.17)
---------
Address field:
The Address field the following parameters:
Parameter
Source Address Optional *1
Destination Address Optional *1
Note 1: The Address field must contain pairs of Source Addresses
or pairs of Destination Addresses but MUST NOT mix Source
Addresses with Destination Addresses in the same Address
field.
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---------
New text: (Section 3.10.17)
---------
Address field:
The Address field the following parameters:
Parameter
Source Address Optional *1
Destination Address Optional *1
Note 1: The Address field must contain pairs of Source Addresses
or pairs of Destination Addresses but MUST NOT mix Source
Addresses with Destination Addresses in the same Address
field. The minimum address must be first and the maximun
address must follow the minimum.
2.11.3 Solution description
State the order of the minimum and maximum addresses in this
parameter. The logical order is first the min, followed by the max.
2.12 Interpretation of the mask parameter
2.12.1 Description of the problem
The mask paramater in the DAUD, DAVA and DUNA SUA messages can be in
the range from 0 to 255 bits. This can go over the maximun pointcode
range of 24 bits. Also if a ASP request via DAUD with a mask
parameter of 24, the SG would need to return all pointcodes it know
in his network to the ASP. (Which could be a lot).
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2.12.2 Text changes to the document
---------
Old text: (Section 3.9.18)
---------
Mask: 8-bits
The Mask parameter can be used to identify a contiguous range of
Affected Destination Point Codes, independent of the point code
format. Identifying a contiguous range of Affected PCs may be useful
when reception of an MTP3 management message or a linkset event
simultaneously affects the availability status of a series of
destinations at an SG.
The Mask parameter is an integer representing a bit mask that can be
applied to the related Affected PC field. The bit mask identifies
how many bits of the Affected PC field are significant and which are
effectively "wild-carded". For example, a mask of "8" indicates that
the last eight bits of the PC is "wild-carded". For an ANSI 24-bit
Affected PC, this is equivalent to signalling that all PCs in an ANSI
Cluster are unavailable. A mask of "3" indicates that the last three
bits of the PC is "wild-carded". For a 14-bit ITU Affected PC, this
is equivalent to signalling that an ITU Region is unavailable.
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---------
New text: (Section 3.9.18)
---------
Mask: 8-bits
The Mask parameter can be used to identify a contiguous range of
Affected Destination Point Codes, independent of the point code
format. Identifying a contiguous range of Affected PCs may be useful
when reception of an MTP3 management message or a linkset event
simultaneously affects the availability status of a series of
destinations at an SG.
The Mask parameter is an integer representing a bit mask that can be
applied to the related Affected PC field. The bit mask identifies
how many bits of the Affected PC field are significant and which are
effectively "wild-carded". For example, a mask of "8" indicates that
the last eight bits of the PC is "wild-carded". For an ANSI 24-bit
Affected PC, this is equivalent to signalling that all PCs in an ANSI
Cluster are unavailable. A mask of "3" indicates that the last three
bits of the PC is "wild-carded".
The range of mask parameter is limited to 0-24 for ANSI networks and
is NOT used for ITU networks.
2.12.3 Solution description
The parameter is limited to 14 bits for ANSI networks and is NOT USED
in ITU networks.
2.13 Reply on errors contained in a error message
2.13.1 Description of the problem
If a error message arrives with a error in it, what should be send
out? Nothing in the RFC3868 describes this possibility.
2.13.2 Text changes to the document
---------
Old text: (Section 3.7.1)
---------
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---------
New text: (Section 3.7.1)
---------
Error messages MUST NOT be generated in response to other Error messages.
2.13.3 Solution description
No error msg must be send back in response on a received error
message(containing a error). This would otherwise possibly lead to a
storm of exchange error messages.
2.14 Use of stream 0 for SSNM messages
2.14.1 Description of the problem
There seems to be some confusion in paragraph 4.5.1. First it is
mentioned NOT to use stream 0 but a few lines later you MUST use
stream 0 and that happen all in the same context of sending SSNM
messages(DAUD, DUNA, DAVA..). It also contradicts statements made in
paragraph 4.1.1.
2.14.2 Text changes to the document
---------
Old text: (Section 4.5.1)
---------
DUNA, DAVA, SCON, and DRST messages are sent sequentially and
processed at the receiver in the order sent. SCTP stream 0 SHOULD
NOT be used. The Unordered bit in the SCTP DATA chunk MAY be used
for the SCON message.
Sequencing is not required for the DUPU or DAUD messages, which MAY
be sent unordered. SCTP stream 0 is used, with optional use of the
Unordered bit in the SCTP DATA chunk.
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---------
New text: (Section 4.5.1)
---------
DUNA, DAVA, SCON, and DRST messages are sent sequentially and
processed at the receiver in the order sent. The Unordered bit
in the SCTP DATA chunk MAY be used for the SCON message.
Sequencing is not required for the DUPU or DAUD messages, which MAY
be sent unordered. SCTP stream 0 is used, with optional use of the
Unordered bit in the SCTP DATA chunk.
2.14.3 Solution description
The SSNM messages should be send on stream 0 of the association.
2.15 Timer Ta does not exist
2.15.1 Description of the problem
Timer Ta is mentioned in paragraph 8 but nowhere specified.
2.15.2 Text changes to the document
---------
Old text: (Section 8)
---------
8. Timer Values
Ta 2 seconds
Tr 2 seconds
T(ack) 2 seconds
T(ias) Inactivity Send timer 7 minutes
T(iar) Inactivity Receive timer 15 minutes
T(beat) Heartbeat Timer 30 seconds
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---------
New text: (Section 8)
---------
8. Timer Values
Tr 2 seconds
T(ack) 2 seconds
T(ias) Inactivity Send timer 7 minutes
T(iar) Inactivity Receive timer 15 minutes
T(beat) Heartbeat Timer 30 seconds
2.15.3 Solution description
Timer Ta is removed.
2.16 Error response on unsupported RKM messages
2.16.1 Description of the problem
If RKM messages are not supported by a implementation, a error
message is send back with error cause "unsupported message Type". We
should send back a error message with error cause "unsupported
message class" .
2.16.2 Text changes to the document
---------
Old text: (Section 4.4.1)
---------
If the SGP does not support the registration procedure, the SGP
returns an Error message to the ASP, with an error code of
"Unsupported Message Type".
---------
New text: (Section 4.4.1)
---------
If the SGP does not support the registration procedure, the SGP
returns an Error message to the ASP, with an error code of
"Unsupported Message Class".
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2.16.3 Solution description
Send back a error message with "unsupported message class". If >RKM
messages are not supported, the implementation actually rejects a
whole class of messages, not just a single one.
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3. Security considerations
No new treats have been identified besides the already known in SUA
[RFC3868] [1].
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4. Acknowledgments
The authors wish to thank B. Nagelberg, B. Bidulock, T. Asveren, S.
Karl, K. Morneault and many others for their invaluable comments.
5. References
[1] Loughney, J., Sidebottom, G., Verwimp, G., Coene, L., Keller,
J., and B. Bidulock, "Signalling Connection Control Part User
Adaptation Layer (SUA)", RFC 22222, June 2004.
[2] Malkin, G., "Internet Users' Glossary", RFC 1983, August 1996.
[3] Mockapetris, P., "Domain names - Implementation and
Specification", RFC 1035, November 1987.
[4] ITU, "Q.714 : SCCP procedures", Q. 714, July 1997.
[5] ANSI, "T1.112.4 : SCCP procedures", T. 1.112.4, December 1993.
Authors' Addresses
Lode Coene
Siemens
Atealaan 32
Herentals 2200
Belgium
Phone: +32-14-252081
Email: [email protected]
John Loughney
Nokia
Itdmerenkatu 11-13
Espoo 00180
Finland
Phone: +358 50 483 6242
Email: [email protected]
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Appendix A. Changes Control
A.1 Changes from v00 to v01
- Change of boilerplate
- Typos.
- Paragraph 2.6 ASP routing context: replacement text for section
1.5.2
- Paragraph 2.1 Usage of TID and DRM label parameter: text
clarification for solution description
- Paragraph 2.8 Use of ANSI intermediate signaling network
identification (ISNI) parameter: Removed, no text proposed.
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