Signaling System No.7 Protocol Architecture And Sevices part 67 pps

SCCP Messages ANSI/ETSI/ITU-T The table in this appendix summarizes Signaling Connection Control Part SCCP messages and the purpose of each.. Only used when the optional field in XUDT is

Appendix C SCCP Messages (ANSI/ETSI/ITU-T)

The table in this appendix summarizes Signaling Connection Control Part (SCCP) messages and the purpose of each For an introduction to SCCP, refer to Chapter 9,

"Signaling Connection Control Part (SCCP)."

Table C-1 SCCP Messages

MESSAGE/CODE

FULL MESSAGE NAME PURPOSE

CR

0 0 0 0 0 0 0 1

Connection Request

Sent by SCCP to another SCCP peer to request a setup of a logical signaling connection between them so that data transfer can take place in a connection-orientated fashion

CC

0 0 0 0 0 0 1 0

Connection Confirm

Sent in response to a CR message to indicate that the node has performed the setup of the requested logical signaling connection

CREF

0 0 0 0 0 0 1 1

Connection Refused

Sent by the destination or an intermediate SCCP node in response to

a CR message to indicate a refusal to set up a logical signaling connection

AK (NE)

0 0 0 0 1 0 0 0

Data Acknowledgment

May be sent when using protocol class

3 to control the window flow

DT1

0 0 0 0 0 1 1 0

Data Form 1 Sent by either end of a logical

signaling connection to pass SCCP user data transparently between two SCCP nodes DT1 is only used in protocol class 2

DT2 (NE)

0 0 0 0 0 1 1 1

Data Form 2 Sent by either end of a logical

signaling connection to pass SCCP user data transparently between two SCCP nodes DT2 is only used in

protocol class 3

ED (NE)

0 0 0 0 1 0 1 1

Expedited Data Performs the same function as the DT2

message, but includes the capability to bypass the flow control mechanism and

is, therefore, only used in protocol class 3

EA (NE)

0 0 0 0 1 1 0 0

Expedited Data Acknowledgment

Used to acknowledge an ED message Each ED message must be

acknowledged before another is sent XUDT

0 0 0 1 0 0 0 1

Extended Unitdata Used by SCCP to transmit data with

optional parameters, using connectionless classes 0 and 1

XUDTS

0 0 0 1 0 0 1 0

Extended Unitdata Service

Sent back in response to a XUDT message if the XUDT message cannot

be delivered to its destination Only used when the optional field in XUDT

is set to "return on error." Protocol class indeterminate due to absence of protocol class parameter

IT

0 0 01 0 0 0 0

Inactivity Test May be sent periodically by either end

of a logical signaling connection to make sure the logical signaling connection is active and to audit the consistency of connection data at both ends Used in connection-orientated classes 2 and 3

LUDT

0 0 0 1 0 0 1 1

Long Unitdata Used by SCCP to transmit data with

optional parameters, using connectionless 0 and 1 If ATM is the underlying network, it allows sending

of Network Service Data Unit (NSDU) sizes up to 3952 octets without

segmentation

LUDTS

0 0 0 1 0 1 0 0

Long Unitdata Service

Sent back in response to a LUDT message if the LUDT message cannot

be delivered to its destination Only

used when the optional field in LUDT

is set to "return on error." Protocol class indeterminate due to absence of protocol class parameter

ERR

0 0 0 0 1 1 1 1

Protocol Data Unit Error

Sent on detection of any protocol errors Used during the data transfer phase in connection-orientated classes

2 and 3

RLC

0 0 0 0 0 1 0 1

Release Complete Sent in response to the Released

(RLSD) message to indicate that the RLSD message was received and that the necessary procedures have been performed Used during connection release phase in connection-orientated classes 2 and 3

RLSD

0 0 0 0 0 1 0 0

Released Sent to indicate that the sending SCCP

wishes to release a logical signaling connection and that the associated resources have been brought into the disconnect pending condition Also indicates that the receiving node should release the logical signaling connection and its associated resources

Used during connection release phase

in connection-orientated classes 2 and

3

RSC (NE)

0 0 0 0 1 1 1 0

Reset Confirm Sent in response to a Reset Request

(RSR) message to indicate that RSR has been received and that the

necessary procedure has been performed

Used during the data transfer phase in connection-orientated class 3

RSR (NE) Reset Request Sent to indicate that the sending SCCP

wishes to initiate a reset procedure

(re-0 (re-0 (re-0 (re-0 1 1 (re-0 1 initialization of sequence numbers)

with the receiving SCCP

Used during the data transfer phase in protocol class 3

SBR (M)(A)

1 1 1 1 1 1 0 1

Subsystem Backup Routing

Optional message sent before rerouting traffic to the backup subsystem

Provides more connectivity information so the end node can determine the traffic mix received for a subsystem

SNR (M)(A)

1 1 1 1 1 1 1 1 0

Subsystem Normal Routing

Optional message sent prior to rerouting traffic to the primary subsystem, to the backup of the subsystem that is now allowed Allows the end node to update the traffic mix information that the subsystem is receiving

SRT (A)

1 1 1 1 1 1 1 1

Subsystem Routing Status Test

Optional message sent to verify the routing status of a subsystem marked

as under backup routing

SSA (M)

0 0 0 0 0 0 0 1

Subsystem Allowed

Used by SCCP subsystem management (SCMG) to inform SCMG at

concerned destinations that a formerly prohibited subsystem (such as

VLR/HLR) is now available, or that a previously unavailable SCCP is now available As a result, the node receiving the SSA updates its translation tables

SSP (M)

0 0 0 0 0 0 1 0

Subsystem Prohibited

Used by SCCP subsystem management (SCMG) to inform SCMG at

concerned destinations that a subsystem (such as VLR/HLR) has failed The receiving end of an SSP message updates its translation tables;

as a result, traffic could be re-routed to

a backup subsystem, if available

SST (M)

0 0 0 0 0 0 1 1

Subsystem Status Test

Used by SCCP subsystem management (SCMG) to verify the status of a

subsystem marked prohibited or the status of an SCCP marked unavailable The receiving node checks the status of the named subsystem and, if the

subsystem is allowed, sends an SSA message in response If the subsystem

is prohibited, no reply is sent

SOR (M)

0 0 0 0 0 1 0 0

Subsystem Out-of-Service Request

Used by SCCP subsystem management (SCMG) to allow subsystems to go out-of-service without degrading performance of the network

SOG (M)

0 0 0 0 0 1 0 1

Subsystem Out-of-service-grant

Used by SCCP subsystem management (SCMG) in response to a Subsystem Out-of-Service Request (SOR) message to the requesting SCCP if both the requested SCCP and the backup of the affected subsystem agree to the request

SSC (M)(I)

0 0 0 0 0 0 1 0

SCCP/subsystem-congested

Sent when an SCCP node experiences congestion

UDT

0 0 0 0 1 0 0 1

Unitdata Used by SCCP to transmit data, using

connectionless classes 0 and 1

UDTS

0 0 0 0 1 0 1 0

Unitdata Service Sent in response to a UDT message if

the UDT message cannot be delivered

to its destination Only used when the optional field in UDT is set to "return

on error." Used in connectionless protocol classes 0 and 1

KEY: (A)—Messages supported in ANSI SCCP Messages not supported in ETSI SCCP [].cellular network, does not seem place to define them as reader should

know them only [2]

(I)—Messages supported in ITU-T SCCP only [60]

(NE)—Messages not supported in ETSI SCCP [10]

(M)—SCCP subsystem management (SCMG) These are transmitted within the data parameter a UDT, XUDT or LUDT message