📄 rfc3331.txt
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Parameter Tag | Parameter Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
\ \
/ Parameter Value /
\ \
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Mandatory parameters MUST be placed before optional parameters in a
message.
Parameter Tag: 16 bits (unsigned integer)
The Type field is a 16 bit identifier of the type of parameter. It
takes a value of 0 to 65534. The common parameters used by the
adaptation layers are in the range of 0x00 to 0xff. The M2UA
specific parameters have Tags in the range 0x300 to 0x3ff.
Morneault, et. al. Standards Track [Page 19]
RFC 3331 SS7 MTP2 User Adaptation Layer September 2002
The common parameter tags (used by all User Adaptation layers) that
M2UA uses are defined below:
Parameter Value Parameter Name
--------------- --------------
0 (0x00) Reserved
1 (0x01) Interface Identifier (Integer)
2 (0x02) Unused
3 (0x03) Interface Identifier (Text)
4 (0x04) Info String
5 (0x05) Unused
6 (0x06) Unused
7 (0x07) Diagnostic Information
8 (0x08) Interface Identifier (Integer Range)
9 (0x09) Heartbeat Data
10 (0x0a) Unused
11 (0x0b) Traffic Mode Type
12 (0x0c) Error Code
13 (0x0d) Status Type/Information
14 (0x0e) Unused
15 (0x0f) Unused
16 (0x10) Unused
17 (0x11) ASP Identifier
18 (0x12) Unused
19 (0x13) Correlation Id
18-255 Reserved
Morneault, et. al. Standards Track [Page 20]
RFC 3331 SS7 MTP2 User Adaptation Layer September 2002
The M2UA specific parameter Tags defined are as follows:
Parameter Value Parameter Name
--------------- --------------
768 (0x0300) Protocol Data 1
769 (0x0301) Protocol Data 2 (TTC)
770 (0x0302) State Request
771 (0x0303) State Event
772 (0x0304) Congestion Status
773 (0x0305) Discard Status
774 (0x0306) Action
775 (0x0307) Sequence Number
776 (0x0308) Retrieval Result
777 (0x0309) Link Key
778 (0x030a) Local-LK-Identifier
779 (0x030b) Signalling Data Terminal (SDT) Identifier
780 (0x030c) Signalling Data Link (SDL) Identifier
781 (0x030d) Registration Result
782 (0x030e) Registration Status
783 (0x030f) De-Registration Result
784 (0x0310) De-Registration Status
Parameter Length: 16 bits (unsigned integer)
The Parameter Length field contains the size of the parameter in
bytes, including the Parameter Tag, Parameter Length, and Parameter
Value fields. Thus, a parameter with a zero-length Parameter Value
field would have a Length field of 4. The Parameter Length does not
include any padding bytes.
Parameter Value: variable-length.
The Parameter Value field contains the actual information to be
transferred in the parameter.
The total length of a parameter (including Tag, Parameter Length and
Value fields) MUST be a multiple of 4 bytes. If the length of the
parameter is not a multiple of 4 bytes, the sender pads the Parameter
at the end (i.e., after the Parameter Value field) with all zero
bytes. The length of the padding is NOT included in the parameter
length field. A sender MUST NOT pad with more than 3 bytes. The
receiver MUST ignore the padding bytes.
Morneault, et. al. Standards Track [Page 21]
RFC 3331 SS7 MTP2 User Adaptation Layer September 2002
3.2 M2UA Message Header
In addition to the common message header, there will be a M2UA
specific message header. The M2UA specific message header will
immediately follow the common message header, but will only be used
with MAUP messages.
This message header will contain the Interface Identifier. The
Interface Identifier identifies the physical interface at the SG for
which the signalling messages are sent/received. The format of the
Interface Identifier parameter can be text or integer, the values of
which are assigned according to network operator policy. The values
used are of local significance only, coordinated between the SG and
ASP.
The integer formatted Interface Identifier MUST be supported. The
text formatted Interface Identifier MAY optionally be supported.
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Tag (0x1) | Length=8 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Interface Identifier (integer) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3 M2UA Message Header (Integer-based Interface Identifier)
The Tag value for the Integer-based Interface Identifier is 0x1. The
length is always set to a value of 8.
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Tag (0x3) | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/ \
\ Interface Identifier (text) /
/ \
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4 M2UA Message Header (Text-based Interface Identifier)
The Tag value for the Text-based Interface Identifier is 0x3. The
encoding of the Identifier is ANSI X3.4-1986 [7]. The maximum string
length of the text-based Interface Identifier is 255 octets. The tag
length is equal to the string length of the Interface Identifier name
plus four bytes for the Tag and Length fields.
Morneault, et. al. Standards Track [Page 22]
RFC 3331 SS7 MTP2 User Adaptation Layer September 2002
3.3 M2UA Messages
The following section defines the messages and parameter contents.
The M2UA messages will use the common message header (Figure 2) and
the M2UA message header (Figure 3 and Figure 4).
3.3.1 MTP2 User Adaptation Messages
3.3.1.1 Data
The Data message contains an SS7 MTP2-User Protocol Data Unit (PDU).
The Data message contains the following parameter:
Protocol Data (mandatory)
Correlation Id (optional)
The format for the Data Message parameters is as follows:
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Tag (0x300) | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/ \
\ Protocol Data /
/ \
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Tag (0x13) | Length = 8 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Correlation Id |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The Protocol Data field contains the MTP2-User application message in
network byte order starting with the Signalling Information Octet
(SIO). The Correlation Id parameter uniquely identifies the MSU
carried in the Protocol Data within an AS. This Correlation Id
parameter is assigned by the sending M2UA. The purpose of the
Correlation Id is to permit the newly active ASP to synchronize its
processing of the traffic in each ordered stream with other ASPs in
the broadcast group.
Morneault, et. al. Standards Track [Page 23]
RFC 3331 SS7 MTP2 User Adaptation Layer September 2002
The format for a Data Message with TTC PDU parameters is as follows:
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Tag (0x301) | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/ \
\ TTC Protocol Data /
/ \
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Tag (0x13) | Length = 8 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Correlation Id |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The Protocol Data field contains the MTP2-User application message in
network byte order starting with the Length Indicator (LI) octet.
The Japanese TTC variant uses the spare bits of the LI octet for
priority.
The length of the Protocol Data and TTC Protocol Data MUST NOT exceed
the length of a MTP2-User application message [2,3,5].
3.3.1.2 Data Acknowledge Message
The Data Acknowledge message contains the Correlation Id of the Data
message that the sending M2UA is acknowledging as successfully
processed to the peer M2UA.
The Data Acknowledge message contains the following parameter:
Correlation Id Mandatory
The following format MUST be used for the Data Ack Message:
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Tag (0x13) | Length = 8 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Correlation Id |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The Correlation Id parameter of the Data message and the Data Ack
message provide a mechanism, for those SG implementations capable of
taking advantage of them, to obtain an acknowledgment that the MSU
has been transferred to the M2UA peer before acknowledging the MSU to
Morneault, et. al. Standards Track [Page 24]
RFC 3331 SS7 MTP2 User Adaptation Layer September 2002
the SS7 peer, removing the risk of losing messages due to association
failure or SCTP congestion.
The Data Ack message MUST be sent if a Correlation Id parameter is
received from the peer. Otherwise, the Data Ack message MUST NOT be
sent.
If the Data Acknowledge is not sent for Correlation Id(s) or is sent
with Invalid Correlation Id(s), the SS7 link will eventually fail due
to lack of MTP Level 2 acknowledgments of the SS7 peer's MSUs.
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