As per Relevance of the word transport, we have this rfc below:
Network Working Group D.
Request for Comments: 3094 R.
Category: Informational D.
J.
April 2001
Tekelec's Transport Adapter Layer
Status of this
This memo provides information for the Internet community. It
not specify an Internet standard of any kind. Distribution of
memo is unlimited
Copyright
Copyright (C) The Internet Society (2001). All Rights Reserved
IESG Note
Readers should note that this memo presents a vendor's alternative
standards track technology being developed by the IETF
Working Group. The technology presented in this memo has not
reviewed by the IETF for its technical soundness or completeness
Potential users of this type of technology are urged to examine
SIGTRAN work before deciding to use the technology described here
This document proposes the interfaces of a Signaling Gateway,
provides interworking between the Switched Circuit Network (SCN)
an IP network. Since the Gateway is the central point of
information, not only does it provide transportation of
from one network to another, but it can also provide
functions such as protocol translation, security screening,
information, and seamless access to Intelligent Network (IN)
on both networks
The Transport Adapter Layer Interface (TALI) is the
interface, which provides TCAP (Transaction Capability
Part), ISUP (ISDN User Part), and MTP (Mail Transport Protocol
messaging over TCP/IP. In addition, TALI provides SCCP (
Connection Control Part) Management (SCMG), MTP Primitives,
registration of circuits, and routing of call control messages
on circuit location
Sprague, et al. Informational [Page 1]
RFC 3094 Tekelec's Transport Adapter Layer Interface April 2001
Table of
1. Introduction 4
2. Overview of the TALI Protocol 6
2.1 Traditional PSTN SS7 Networks 6
2.2 Converged SS7 Networks 8
2.3 TALI Protocol Stack Overview 10
2.3.1 An Alternate TALI Protocol Stack using the SAAL Layer 13
2.3.2 An Alternate TALI Protocol Stack using SCTP 15
2.4 Inputs to the TALI Version 1.0 State Machine 15
3. TALI Version 1.0 17
3.1 Overview of the TALI Message Structure 17
3.1.1 Types of TALI Fields 19
3.2 Detailed TALI Message Structure 20
3.2.1 TALI Peer to Peer Messages 20
3.2.1.1 Test Message (test) 20
3.2.1.2 Allow Message (allo) 21
3.2.1.3 Prohibit Message (proh) 21
3.2.1.4 Prohibit Acknowledgement Message (proa) 21
3.2.1.5 Monitor Message (moni) 22
3.2.1.6 Monitor Acknowledge Message (mona) 22
3.2.2 Service Messages 23
3.2.2.1 SCCP Service Message (sccp) 23
3.2.2.1.1 SCCP Encapsulation using TALI 25
3.2.2.2 ISUP Service Message (isot) 27
3.2.2.2.1 ISUP Encapsulation using TALI 27
3.2.2.3 MTP3 Service Message (mtp3) 28
3.2.2.3.1 MTP3 Encapsulation using TALI 29
3.2.2.4 SAAL Service Message (saal) 30
3.2.2.4.1 MTP3 and SAAL Peer to Peer Encapsulation using TALI 31
3.3 TALI Timers 34
3.3.1 T1 Timer 34
3.3.2 T2 Timer 34
3.3.3 T3 Timer 34
3.3.4 T4 Timer 34
3.3.5 Recommended Defaults and Ranges for the TALI Timers 35
3.4 TALI User Events 35
3.4.1 Management Open Socket Event 35
3.4.2 Management Close Socket Event 36
3.4.3 Management Allow Traffic Event 36
3.4.4 Management Prohibit Traffic Event 36
3.5 Other Implementation Dependent TALI Events 37
3.6 TALI States 37
3.7 TALI Version 1.0 State Machine 38
3.7.1 State Machine Concepts 38
3.7.1.1 General Protocol Rules 38
3.7.1.2 Graceful Shutdown of a Socket 39
3.7.1.3 TALI Protocol Violations 39
Sprague, et al. Informational [Page 2]
RFC 3094 Tekelec's Transport Adapter Layer Interface April 2001
3.7.2 The State Machine 40
3.8 TALI 1.0 Implementation Notes 42
3.8.1 Failure on a TCP/IP Socket 42
3.8.2 Congestion on a TCP/IP Socket 43
3.9 TALI 1.0 Limitations 43
4. TALI Version 2.0 43
4.1 Overview of TALI Version 2.0 Features 45
4.2 TALI Version Identification 47
4.3 Backwards Compatibility 50
4.3.1 Generating Protocol Violations based on Received Messages 53
4.4 Overview of the TALI Message Structure 55
4.4.1 Types of TALI Fields 55
4.5 Detailed TALI Message Structures for New 2.0 Opcodes 58
4.5.1 Management Message (mgmt) 60
4.5.1.1 Routing Key Registration Primitive (rkrp) 61
4.5.1.1.1 RKRP Data Structures 65
4.5.1.1.1.1 Common Fields in all RKRP Messages 65
4.5.1.1.1.2 CIC Based Routing Key Operations 67
4.5.1.1.1.3 SCCP Routing Key Operations 71
4.5.1.1.1.4 DPC-SI, DPC and SI based Routing Key Operations 74
4.5.1.1.1.5 Default Routing Key Operations 76
4.5.1.1.1.6 Support for Multiple RKRP Registration Operations 78
4.5.1.1.1.6.1 Multiple Registrations Support 78
4.5.1.1.1.6.2 Multiple RKRP Operations in a Single Message 80
4.5.1.2 MTP3 Primitive (mtpp) 82
4.5.1.3 Socket Option Registration Primitive (sorp) 87
4.5.2 Extended Service Message (xsrv) 91
4.5.3 Special Message (spcl) 92
4.5.3.1 Special Messages Not Supported (smns) 93
4.5.3.2 Query Message (qury) 93
4.5.3.3 Reply Message (rply) 94
4.5.3.4 Unsolicited Information Message (USIM) 95
4.6 TALI Timers 95
4.7 TALI User Events 95
4.8 TALI States 96
4.9 TALI Version 2.0 State Machine 96
4.9.1 State Machine Concepts 96
4.9.1.1 General Protocol Rules 96
4.9.1.2 Graceful Shutdown of a Socket 97
4.9.1.3 TALI Protocol Violations 97
4.9.2 The State Machine 97
4.10 TALI 2.0 Specification Limitations 101
5. Success/Failure Codes 101
6. Security Considerations 102
7. References 102
8. Acknowledgments 103
9. Authors' Addresses 104
10. Full Copyright Statement 105
Sprague, et al. Informational [Page 3]
RFC 3094 Tekelec's Transport Adapter Layer Interface April 2001
1.
This document is organized into the following 6 sections
- Introduction to the
- Overview of the TALI
- TALI Version 1.0
- TALI Version 2.0
- Success/Failure
- Security
The following terms are used throughout this document
Circuit Identification Code (CIC):
A field identifying the circuit being setup or released.
on SI and MSU Type, this field can be 12, 14 or 32 bits
Changeover/Changeback (co/cb):
SS7 MTP3 procedure related to link failure and re-establishment
Far End (FE):
The remote endpoint of a socket connection
Far End Allowed (FEA):
The FE is ready to use the socket for service PDUs
Far End Prohibited (FEP):
The FE is not ready to use the socket for service PDUs
Intelligent Network (IN):
A network that allows functionality to be distributed flexibly at
variety of nodes on and off the network and allows the
to be modified to control the services
Management ATM Adaptation Layer (MAAL):
This layer is a component of SAAL. This layer maps requests
indications between the System Management for the SG and the
SAAL layers. MAAL includes interfaces to/from SSCOP, SSCF,
system management. More information can be found in T1.652.
Media Gateway (MG):
A MG terminates SCN media streams, packetizes the media data, if
is not already packetized, and delivers packetized traffic to
packet network. It performs these functions in reverse order
media streams flowing from the packet network to the SCN
Sprague, et al. Informational [Page 4]
RFC 3094 Tekelec's Transport Adapter Layer Interface April 2001
Media Gateway Controller (MGC):
An MGC handles the registration and management of resources at
MG. The MGC may have the ability to authorize resource usage
on local policy. For signaling transport purposes, the MGC serves
a possible termination and origination point for SCN
protocols, such as SS7 ISDN User Part and Q.931/DSS1.
MTP3 Framing (MTP3F):
TALI does not require full MTP3 procedures support but rather
the MTP3 framing structure (ie: SIO, Routing Label, etc
Near End (NE):
The local endpoint of a socket connection
Near End Allowed (NEA):
The NE is ready to use the socket for service PDUs
Near End Prohibited (NEP):
The NE is not ready to use the socket for service PDUs
Q.BICC ISUP
An ISUP+ variant that uses 32 bit CIC codes instead of 14/12 bit
codes. ISUP+, or Q.BICC ISUP, is based on the Q.765.
specification currently being developed in ITU Study Group 11.
Signaling ATM Adaptation Layer (SAAL):
This layer is the equivalent of MTP-2 for ATM High Speed
carrying SS7 Traffic as described in GR-2878-CORE [8]. SAAL
SSCF, SSCOP and MAAL
Signaling Gateway (SG):
An SG is a signaling agent that receives/sends SCN native
at the edge of the IP network. The SG function may relay,
or terminate SS7 signaling in an SS7-Internet Gateway. The
function may also be co-resident with the MGC/MG functions to
SCN signaling associated with line or trunk terminations
by the MG (e.g., signaling backhaul).
Service Specific Coordination Function (SSCF):
This layer is a component of SAAL. This layer maps the
provided by the lower layers of the SAAL to the needs of a
higher layer user. In the case of the STP, the higher layer user
the MTP-3 protocol, and the SSCF required is that as defined
T1.645: SSCF for Support of Signaling at the Network Node
(SSCF at the NNI). More information can be found in T1.645.
provides the interface between SSCOP and MTP3 and includes
following functions
Sprague, et al. Informational [Page 5]
RFC 3094 Tekelec's Transport Adapter Layer Interface April 2001
- Local Retrieve of messages to support link changeover
- Flow control with four levels of
Switched Circuit Network (SCN):
The term SCN is used to refer to a network that carries
within channelized bearers of pre-defined sizes. Examples
Public Switched Telephone Networks (PSTNs) and Public Land
Networks (PLMNs). Examples of signaling protocols used in
include Q.931, SS7 MTP Level 3 and SS7 Application/User parts
Service Specific Connection Oriented Protocol (SSCOP):
This layer is a component of SAAL. This layer provides
point to point data transfer with sequence integrity and
recovery by selective retransmission. Protocol layer interfaces
described in T1.637. Aspects of the protocol include flow control
connection control, error reporting to layer management,
maintenance in the prolonged absence of data transfer, local
retrieval by the user of the SSCOP, error detection of
control information and status reporting. SSCOP provides the
layer functions that are
- In-Sequence
- Flow
- Error Detection/
- Keep
- Local Data
- Connection
- Protocol Error Detection and
Signaling Transfer Point (STP):
Packet switches that provide CCS message routing and transport.
are stored programmed switches that use information contained in
message in conjunction with information stored in memory to route
message to the appropriate destination signaling point
2. Overview of the TALI
2.1 Traditional PSTN SS7
The traditional PSTN SS7 network consists of 3 types of
connected via dedicated SS7 signaling links
The 3 primary device types for PSTN networks are
* SSP: Signaling Service Point. These nodes act as endpoints
the SS7 network, originating SS7 messages as users attempt
place phone calls. These nodes contain interfaces into the SS
data network and the SS7 voice network
Sprague, et al. Informational [Page 6]
RFC 3094 Tekelec's Transport Adapter Layer Interface April 2001
* STP: Signaling Transfer Point. These nodes act primarily
switches, switching SS7 traffic from node to node throughout
network until it reaches another endpoint. An important
of each STP is to provide SS7 network management
that allows messages to be delivered even when links and
fail. STPs also sometimes provide database type services, such
Global Title Translations and Local Number Portability
* SCP: Signaling Control Point. These nodes act as databases
These nodes contain stored data that is used to turn SS7
into SS7 Replies
There are 3 primary types of dedicated SS7 signaling links
* 56Kbps SS7 (DS0, V35, OCU) links. These links implement the MTP-1
and MTP-2 protocols as defined in [1].
* DS1 High Speed Links. These links use the SAAL protocol
provide an alternative to 56Kbps SS7 links that is based on newer
faster technology. These links implement the SS7 protocol
defined in [8].
* E1 Links
Figure 1 provides an overview of the traditional PSTN network.
this network, any of the links can be implemented via either 56
Kbps, DS1, or E1 links
Sprague, et al. Informational [Page 7]
RFC 3094 Tekelec's Transport Adapter Layer Interface April 2001
^
/ \
/SCP
/-----\
/ \
/ \
/ \
/ \
/---\ +---+ +---+ /---\
| SSP |-----|STP|----|STP|-----| SSP |
\---/ \ /+-+-+\ /+-+-+ \ / \---/
\/ | \/ | \/
/\ | /\ | /\
/---\ / \+-+-+/ \+-+-+ / \ /---\
| SSP |/----|STP|----|STP|/----| SSP |
\---/ +---+ +---+ \---/
\ /
\ /
\ /
\ ^ /
\/ \/
/SCP
/-----\
Figure 1: The Traditional PSTN
2.2 Converged SS7
In the converged SS7 network, SS7 devices will reside on both
traditional PSTN network (with dedicated 56 Kbps and DS1 links)
on the IP network (with Ethernet links based on IP protocol).
services of SSPs, STPs, and SCPs can be provided by new types
devices that reside on IP networks. The IP network is not
to completely replace the PSTN, rather devices on the 2 types
networks must be able to communicate with one another and
from 1 lower layer protocol to the other
Signaling Gateways are new devices that may also function as an
in the converged network. SGs provide interfaces to
* devices on the SCN (traditional SSPs, STPs, and SCPs
* other
* new devices on the IP
SGs also continue to perform STP functions such as SS7
management and some database services (such as GTT and LNP).
Sprague, et al. Informational [Page 8]
RFC 3094 Tekelec's Transport Adapter Layer Interface April 2001
New devices on the IP network include
* Media Gateway Controllers. In addition to other functions,
devices control Media Gateways and perform call processing
* Media Gateways. In addition to other functions, these
control voice circuits that are used to carry telephone calls
MGs + MGCs combine to provide the functionality of
SSPs
* IP based SCPs. The database services that are related to SS7
be moved onto devices on the IP network
Figure 2 provides an overview of the converged SS7 network
----- +----+
/\ / \-------------| SG |
/ \----| SCN | +----+ +----+
/SCP \ \ /------| SG | |
------ ----- +----+ |
| | | |
| | | |
| | -----
| | / \ /\
| | | IP |----/ \
| /---\ \ / /SCP \
| | SSP | ----- ------
| \---/ / \
| | / \
/---\ | / \
| SSP | | +---+ +---+
\---/ +----+ |MGC| |MGC
| | MG | +---+ +---+
| +----+\ \ /
| \ \ /
| \ -----
| \ / \
+----+ | IP |
| MG |-----------\ /
+----+ -----
Figure 2: The Converged SS7
In theory, the TALI protocol can be used between 2 nodes to carry SS
traffic across TCP/IP. Some of the areas that TALI could be
include
Sprague, et al. Informational [Page 9]
RFC 3094 Tekelec's Transport Adapter Layer Interface April 2001
- For SG to SG communication across
- For SG to MGC communication across
- For SG to IP based SCP communication across
- For communication between multiple IP based
- For communication between multiple
- For communication between MGCs and
- For other IP devices such as DNS, Policy Servers, etc
In reality, the communication between MGCs, or between MGC and MG
probably better suited to using other protocols. With respect to
Signaling Gateway implementation, the TALI protocol is used to
SS7 traffic
- For SG to SG
- For SG to MGC
- For SG to IP based SCP
2.3 TALI Protocol Stack
The Transport Adapter Layer Interface is the proposed interface
provides SCCP, ISUP, and MTP messaging encapsulation within a TCP/
packet between two switching elements. In addition, TALI
SCCP Management (SCMG), MTP Primitives, dynamic registration
circuits, and routing of call control messages based on
location
The major purpose of the TALI protocol is to provide a bridge
the SS7 Signaling Network and applications that reside within an
network. Figure 3 provides a simple illustration that highlights
protocol stacks used for transport of SS7 MSUs on both the SS7
and the IP side of the SG
Sprague, et al. Informational [Page 10]
RFC 3094 Tekelec's Transport Adapter Layer Interface April 2001
SS7 traffic SS7
via 56Kbps links via
+-----------+ +----+ +--------+
|Traditional| | SG | | IP |
|SS7 Devices|<------>| |<-------->| Devices
+-----------+ +----+ +--------+
SS7 SS7, TALI, TCP/
protocol stack protocol
+---------------+ +---------------+
|SS7 application| |SS7 application
|layer | |layer |
+-------+-------+ +-------+-------+
| TCAP | ISUP | | TCAP | ISUP |
+-------+ | +-------+ |
| SCCP | | | SCCP | |
+-------+-------+ +-------+-------+
| MTP3 | | MTP3 |
+---------------+ +---------------+
| MTP2 | | TALI |
+---------------+ +---------------+
| MTP1 | | TCP |
| (& phy. | +---------------+
| layer) | | IP |
+---------------+ +---------------+
| MAC |
| (& phy. |
| layer) |
+---------------+
Figure 3: TALI Protocol to carry SS7 over TCP/
From Figure 3, several observations can be made
* The TALI layer is used when transferring SS7 over IP
* When SS7 traffic is carried over a IP network, the MTP2 and MTP
layers of a traditional 56 Kbps link are replaced by the TALI
TCP, IP, and MAC
* The TALI layer sits on top of the TCP layer
* The TALI layer sits below the various SS7 layers (MTP3, SCCP/TCAP
ISUP, and applications). The data from these SS7 layers
carried as the data portion of TALI service data packets
Sprague, et al. Informational [Page 11]
RFC 3094 Tekelec's Transport Adapter Layer Interface April 2001
Some of the facts concerning the TALI protocol which are important
understanding how TALI works that are not evident from Figure 3
include the following
* Each TALI connection is provided over a single TCP socket
* The standard Berkeley sockets interface to the TCP is used
the TALI layer to provide connection oriented service
endpoint to peer endpoint
* TCP sockets are based on a Client/Server architecture; one
of the TALI connection must be defined as the 'server side',
the other end is a 'client'.
* The client/server roles are important only in bringing up
TCP connection between the 2 endpoint, once the connection
established both ends use the same Berkeley sockets
(send, recv) to transfer data
* The TCP socket must be connected before the 2 TALI
can begin communicating
* TALI provides user control over each TALI connection that
defined. This control
* Allows the user to control when each TALI connection will
* Allows the user to control when each TALI connection is
to carry SS7
* Allows the user to control the graceful shutdown of each
* TALI provides Peer to Peer messages. These messages
from the TALI layer of one endpoint of the connection and
terminated at the TALI layer of the other endpoint. Peer to
messages are used
* To provide test and watchdog maintenance
* To control the ability of each socket to carry SS7
* TALI provides Service messages. These messages originate from
layer above the TALI layer of one endpoint of the connection
are transferred to and terminated at the layer above the
layer of the other endpoint
Sprague, et al. Informational [Page 12]
RFC 3094 Tekelec's Transport Adapter Layer Interface April 2001
* The service messages provide several different ways
encapsulate the SS7 messages (SCCP/TCAP, ISUP, and other MTP
layer data) across the TCP/IP connection
* As we will see later, different Service opcodes are used
communicate across the TALI socket exactly how each SS7
has been encapsulated
* A set of TALI timers is defined. These timers are used
correctly implement the TALI state machine
2.3.1 An Alternate TALI Protocol Stack using the SAAL
This section presents a different, slightly more complex,
protocol stack that can be used in place of the protocol stack in
previous section
Figure 3 in the previous section provided a simple illustration
highlighted the basic TALI protocol stack that can be used
transport SS7 MSUs between 56 Kbps links on the SS7 side of an SG
the IP devices
Figure 4 below illustrates an alternate TALI protocol stack
includes the SAAL layer as part of the data transferred across
TCP/IP connection
Sprague, et al. Informational [Page 13]
RFC 3094 Tekelec's Transport Adapter Layer Interface April 2001
SS7 traffic SS7
via DS1 links via
+-----------+ +----+ +--------+
|Traditional| | SG | | IP |
|SS7 Devices|<------>| |<-------->| Devices
+-----------+ +----+ +--------+
SS7 DS1 SS7, TALI, TCP/
protocol stack protocol
+-----------------+ +-----------------+
| SS7 application | | SS7 application |
| layer | | layer |
+--------+--------+ +--------+--------+
| TCAP | ISUP | | TCAP | ISUP |
+--------+ | +--------+ |
| SCCP | | | SCCP | |
+--------+--------+ +--------+--------+
| MTP3 | | MTP3 |
+-----------------+ +-----------------+
| SAAL | | SAAL |
|(SSCF,MAAL,SSCOP)| |(SSCF,MAAL,SSCOP)|
+-----------------+ +-----------------+
| AAL5 | | TALI |
+-----------------+ +-----------------+
| ATM | | TCP |
| (& phy. | +-----------------+
| layer) | | IP |
+-----------------+ +-----------------+
| MAC |
| (& phy. |
| layer) |
+-----------------+
Figure 4: An Alternate TALI Protocol Stack with
The following bullets provide a discussion regarding the
between these 2 protocol stacks, the reasons for having 2
stacks, and the advantages of each
* When the TALI protocol stack is implemented without the
layer, as in Figure 3, the SEQUENCE NUMBER of the SS7 MSU is
part of the data transferred across the TCP/IP connection. In 56
Kbps SS7 links, the MTP2 header contains an 8 bit sequence
for each MSU. The sequence number is used to preserve
sequencing and to support complex SS7 procedures involving
retrieval during link changeover and changeback. As indicated
Figure 3, the MTP2 header is NOT part of the data
Sprague, et al. Informational [Page 14]
RFC 3094 Tekelec's Transport Adapter Layer Interface April 2001
across the TCP/IP connection. The TALI protocol stack
SAAL still guarantees correct sequencing of SS7 data (
sequencing is provided by sequence numbers in the TCP layer),
however that protocol stack can not support SS7 changeover
changeback procedures
* When the TALI protocol stack is implemented with the SAAL layer
as in Figure 4, the SEQUENCE NUMBER of the SS7 MSU IS part of
data transferred across TCP/IP. In SS7 DS1 links, the
trailer contains a 24 bit sequence number for each MSU. This 24
bit sequence number serves the same purposes as the 8 bit SS
sequence number. As indicated in Figure 4, the SSCOP trailer
part of the data transferred across the TCP/IP connection.
protocol stack in Figure 4 can support SS7 changeover
changeback procedures
* Implementing the TALI protocol with SAAL therefore
support for SS7 co/cb and data retrieval and can help to
MSU loss as SS7 links are deactivated. However, implementing
is not a trivial matter. The SAAL layer consists of 3
(SSCF, SSCOP, and MAAL), one of which (SSCOP) is quite involved
It is envisioned that most SS7 to TCP/IP applications will
choose to implement SAAL
2.3.2 An Alternate TALI Protocol Stack using
The TALI protocol is dependent on a reliable transport layer
it. At the initial design of TALI, TCP was the only reliable,
transport layer. Simple Control Transport Protocol (SCTP)
currently being designed as a transport later specifically
signalling. Once SCTP is a proven and accepted transport protocol
SCTP can then be used in place of TCP as shown in Figures 3 and 4.
2.4 Inputs to the TALI Version 1.0 State
Figure 5 illustrates the inputs that affect the TALI State Machine
Inputs to the state machine include
* Management events (ie: requests from the human user of the
connection) to control the operation of a particular TALI session
* TALI messages received from the Peer. These messages include
to peer messages as well as service data messages
* Events from the User of the TALI layer. The user is the
above TALI in the protocol stack, either the SS7 or SAAL layer
Sprague, et al. Informational [Page 15]
RFC 3094 Tekelec's Transport Adapter Layer Interface April 2001
* Implementation Dependent Events. Each implementation must
inputs into the TALI state machine such as
* Socket
* TALI protocol violations. The TALI state machine must
protocol violations and act accordingly
* Timer events
Sprague, et al. Informational [Page 16]
RFC 3094 Tekelec's Transport Adapter Layer Interface April 2001
+====+ +============+
| | +---------+ +-------------+ | |
|User| | Service | | Mgmt. Open | | MANAGEMENT |
|Part|<-->| Message | | Mgmt. Close |<-->| |
| | | | | Mgmt. Proh. | | |
| | +---------+ | Mgmt. Allow | +============+
+====+ ^ +-------------+
| ^
| |
v
+========================================================+
| TALI State Machine |
+========================================================+
^ ^ ^ ^
| | | |
| | | |
v | | |
+---------+ +-----------------+ +-----------+ +------------+
| Received| | Connection est. | | Protocol | | T1 Expired |
| 'test' | | Connection lost | | Violation | | T2 Expired |
| 'allo' | | | | | | T3 Expired |
| 'proh' | +-----------------+ +-----------+ | T4 Expired |
| 'proa' | ^ ^ +------------+
| 'moni' | | | ^
| 'mona' | | | |
| or | | | |
| Service | | | |
| Message | +========================================+
+---------+ | IMPLEMENTATION |
^ | DEPENDENT |
| +========================================+
|
+============+
| PEER |
| |
+============+
Figure 5: Overview of Inputs to the TALI 1.0 State
Sprague, et al. Informational [Page 17]
RFC 3094 Tekelec's Transport Adapter Layer Interface April 2001
3. TALI Version 1.0
This chapter provides the states, messages, message exchange
and state machine that must be implemented to provide a TALI
1.0 protocol layer
3.1 Overview of the TALI Message
Table 2 provides a summary of the messages and message structure
in TALI version 1.0.
+------------------------------------------------------------------+
| OCTET | DESCRIPTION | SIZE | VALUE | TYPE |
+------------------------------------------------------------------+
| 0..3 | SYNC | 4 Octets | | 4 byte |
| | | | | ASCII |
+------------------------------------------------------------------+
| | TALI | | 'TALI' | |
+------------------------------------------------------------------+
| 4..7 | OPCODE | 4 Octets | | 4 byte |
| | | | | ASCII |
+------------------------------------------------------------------+
| | Test Service | | 'test' | |
| | Allow Service | | 'allo' | |
| | Prohibit Service | | 'proh' | |
| | Prohibit Service Ack | | 'proa' | |
| | Monitor Socket | | 'moni' | |
| | Monitor Socket Ack | | 'mona' | |
| | SCCP Service | | 'sccp' | |
| | ISUP Service over TALI | | 'isot' | |
| | MTP3 Service over TALI | | 'mtp3' | |
| | Service over SAAL | | 'saal' | |
+------------------------------------------------------------------+
| 8..9 | LENGTH | 2 Octets | | integer |
| | (least significant | | | |
| | byte first) non-0 | | | |
| | if Service or | | | |
| | Socket monitor message| | | |
+------------------------------------------------------------------+
| 10..X | DATA PAYLOAD | variable | | variable |
+------------------------------------------------------------------+
Table 2: Message Structure for TALI 1.0
Table 3 indicates the valid values of the LENGTH field for
version 1.0 opcode. The LENGTH field is always an indication of
# of bytes contained in the DATA PAYLOAD portion of a general
message
Sprague, et al. Informational [Page 18]
RFC 3094 Tekelec's Transport Adapter Layer Interface April 2001
+------------------------------------------------------------------+
| OPCODE | VALID LENGTH VALUES | COMMENTS |
+------------------------------------------------------------------+
| test | 0 bytes | |
+------------------------------------------------------------------+
| allo | 0 bytes | |
+------------------------------------------------------------------+
| proh | 0 bytes | |
+------------------------------------------------------------------+
| proa | 0 bytes | |
+------------------------------------------------------------------+
| moni | 0-200 bytes | A maximum length is provided so |
| | | that the maximum ethernet frame |
| | | size is not exceeded. |
+------------------------------------------------------------------+
| mona | 0-200 bytes | Mona reply length and content must
| | | match the original moni (with the |
| | | exception of the opcode) |
+------------------------------------------------------------------+
| sccp | 12-265 bytes | These are the valid sizes for the |
| | | SCCP-ONLY portions of SCCP UDT |
| | | MSUs |
+------------------------------------------------------------------+
| isot | 8-273 bytes | The length is the number of octets
| | | in the MTP3 and higher layer(s) of
| | | the SS7 MSU. This length includes
| | | the SIO byte, the MTP3 routing |
| | | label, the CIC code, and the |
| | | ISUP Message Type field, and any |
| | | other bytes that may exist as part
| | | of the SIF (Service Information |
| | | Field) |
+------------------------------------------------------------------+
| mtp3 | 5-280 bytes | The length is the number of octets
| | | in the MTP3 and higher layer(s) of
| | | the SS7 MSU. This length includes
| | | the SIO byte and the MTP3 routing |
| | | labeld, and any other bytes that |
| | | may exist as part of the SIF |
| | | (Service Information Field) |
+------------------------------------------------------------------+
| saal | 11-280 bytes | The length is the number of octets
| | | in the MTP3 and higher layer(s) of
| | | the SS7 MSU. This length includes
| | | the SIO byte and all bytes in the |
| | | SIF (Service Information Field) |
| | | field. The MTP3 routing label is |
| | | part of the SIF field. Seven (7) |
Sprague, et al. Informational [Page 19]
RFC 3094 Tekelec's Transport Adapter Layer Interface April 2001
| | | octets of SSCOP trailer is added |
| | | to the message. The SSCOP trailer
| | | bytes are also included in the |
| | | length. |
+------------------------------------------------------------------+
Table 3: Valid Length Fields for Each Opcode in TALI 1.0
3.1.1 Types of TALI
Several field types are used in the general TALI message structure
+------------------------------------------------------------------+
|Field Type | Implementation Notes for that Type |
+------------------------------------------------------------------+
|4 byte | * 4 byte ASCII text strings are used to define the |
|ASCII text | sync code and the opcode of the basic TALI message.|
| | * These fields are case sensitive, the coding for |
| | each sync and opcode literal needs to match the |
| | case specified in Table 2. |
| | * The standard ASCII conversion table is used to |
| | transform each character into a byte. |
| | * The order of the ASCII characters is important. |
| | The first character in the string must be the |
| | first character transmitted across the wire. |
| | * For example, if the string being encoded is 'abCD',|
| | the order of the bytes as they are transferred |
| | over the wire must be: |
| | 1st byte: 0x61 ('a') 3rd byte: 0x43 ('C') |
| | 2nd byte: 0x62 ('b') 4th byte: 0x44 ('D') |
| | * The software for each implementation should be |
| | written in a manner that accounts for the required |
| | byte order of transmission (ie: the Big Endian/ |
| | Little Endian characteristics of the processor |
| | need to be dealt with in the software. |
+------------------------------------------------------------------+
|Integer | * A 1, 2 or 4 byte field to be treated as an integer |
| | value. Integer fields should be transmitted Least |
| | Significant Byte first across the wire. |
| | * The software for each implementation should be |
| | written in a manner that accounts for the required |
| | byte order of transmission (ie: the Big Endian/ |
| | Little Endian characteristics of the processor |
| | need to be dealt with in the software. |
+------------------------------------------------------------------+
|Variable | * The definition of the message structure for this |
| | field is governed by other specifications. |
| | * For example, when transferring MTP3 service data |
Sprague, et al. Informational [Page 20]
RFC 3094 Tekelec's Transport Adapter Layer Interface April 2001
| | via a 'mtp3' opcode, the DATA PAYLOAD begins with |
| | the SIO byte of the MTP3 routing label. The |
| | structure for the entire DATA PAYLOAD is governed |
| | by the MTP3 message structure defined in [1]. |
+------------------------------------------------------------------+
|X byte | * ASCII text fields of sizes other than 4 bytes |
|ASCII text | should be supported according to the same rules |
| | presented for the 4 byte ASCII text fields. For |
| | instance, an 8 byte string such as 'ab01cd23' could
| | be used, where the 'a' would be the first byte of |
| | the field transmitted out the wire. |
+------------------------------------------------------------------+
Table 4: Implementation Notes for each Type of TALI
3.2 Detailed TALI Message
3.2.1 TALI Peer to Peer
The following subsections provide more information regarding the
Peer to Peer messages that are implemented in version 1.0. The
peer to peer messages originate at the TALI layer of 1 end of
socket connection (the near end) and are terminated at the TALI
of the far end of the connection
3.2.1.1 Test Message (test
The 'test' message is used by a TALI implementation to query
remote end of the TALI connection with respect to the willingness
the remote end to carry SS7 service data. This message asks
other end: are you ready to carry service data? This message is
periodically by each TALI implementation based on a T1
interval. Upon receiving 'test', a TALI implementation must
with either 'proh' or 'allo' to indicate the nodes willingness
carry SS7 service data over that TALI connection
+------------------------------------------------------------------+
| Octets | Field Name | Description |
+------------------------------------------------------------------+
| 0..3 | SYNC | 'TALI' |
+------------------------------------------------------------------+
| 4..7 | OPCODE | 'test' |
+------------------------------------------------------------------+
| 8..9 | LENGTH | Length = 0 |
+------------------------------------------------------------------+
Sprague, et al. Informational [Page 21]
RFC 3094 Tekelec's Transport Adapter Layer Interface April 2001
3.2.1.2 Allow Message (allo
The 'allo' message is sent in reply to a 'test' query, or in
to some internal implementation event, to indicate that a
implementation IS willing to carry SS7 service data over the
session. This message informs the far end that SS7 traffic can
transmitted on the socket. 'allo' is one of the 2 possible
to a 'test' message. Before SS7 traffic can be carried over
socket, both ends of the connection need to send 'allo' messages
+------------------------------------------------------------------+
| Octets | Field Name | Description |
+------------------------------------------------------------------+
| 0..3 | SYNC | 'TALI' |
+------------------------------------------------------------------+
| 4..7 | OPCODE | 'allo' |
+------------------------------------------------------------------+
| 8..9 | LENGTH | Length = 0 |
+------------------------------------------------------------------+
3.2.1.3 Prohibit Message (proh
The 'proh' message is sent in reply to a 'test' query, or in
to some internal implementation event, to indicate that a
implementation is NOT willing to carry SS7 service data over the
session. This message informs the far end that SS7 traffic can
be transmitted on the socket. 'proh' is one of the 2
replies to a 'test' message. As long as 1 end of the
remains in the 'prohibited' state, SS7 traffic can not be
over the socket
+------------------------------------------------------------------+
| Octets | Field Name | Description |
+------------------------------------------------------------------+
| 0..3 | SYNC | 'TALI' |
+------------------------------------------------------------------+
| 4..7 | OPCODE | 'proh' |
+------------------------------------------------------------------+
| 8..9 | LENGTH | Length = 0 |
+------------------------------------------------------------------+
3.2.1.4 Prohibit Acknowledgement Message (proa
The 'proa' message is sent by a TALI implementation each time
'proh' is received from the far end. This message is sent
indicate to the far end that his 'prohibit' message was
correctly and will be acted on accordingly
Sprague, et al. Informational [Page 22]
RFC 3094 Tekelec's Transport Adapter Layer Interface April 2001
+------------------------------------------------------------------+
| Octets | Field Name | Description |
+------------------------------------------------------------------+
| 0..3 | SYNC | 'TALI' |
+------------------------------------------------------------------+
| 4..7 | OPCODE | 'proa' |
+------------------------------------------------------------------+
| 8..9 | LENGTH | Length = 0 |
+------------------------------------------------------------------+
3.2.1.5 Monitor Message (moni
The 'moni' message provides a generic ECHO capability that can
used by each TALI implementation as that implementation sees fit.
TALI version 1.0 implementation does not have to originate a 'moni
message to be compliant with the 1.0 specification. The
intent of this message is to provide a way for the TALI layer to
the round-trip message transfer time on a socket. A 'mona'
must be sent in reply to each received 'moni' message. The
portion of a 'moni' message is vendor implementation dependent.
DATA portion of each 'mona' reply must exactly match the DATA
of the 'moni' that is replied to. Regardless of whether
implementation chooses to send 'moni' or not, 'mona' must be sent
response to each 'moni' in order to remain compliant with the
protocol
+------------------------------------------------------------------+
| Octets | Field Name | Description |
+------------------------------------------------------------------+
| 0..3 | SYNC | 'TALI' |
+------------------------------------------------------------------+
| 4..7 | OPCODE | 'moni' |
+------------------------------------------------------------------+
| 8..9 | LENGTH | Length |
+------------------------------------------------------------------+
| 10..X | DATA PAYLOAD| Vendor Dependent |
+------------------------------------------------------------------+
3.2.1.6 Monitor Acknowledge Message (mona
As mentioned above, the 'mona' must be sent in reply to each
'moni'. The contents of the 'mona' DATA area must match the
area of the received 'moni' message
Sprague, et al. Informational [Page 23]
RFC 3094 Tekelec's Transport Adapter Layer Interface April 2001
+------------------------------------------------------------------+
| Octets | Field Name | Description |
+------------------------------------------------------------------+
| 0..3 | SYNC | 'TALI' |
+------------------------------------------------------------------+
| 4..7 | OPCODE | 'mona' |
+------------------------------------------------------------------+
| 8..9 | LENGTH | Length |
+------------------------------------------------------------------+
| 10..X | DATA PAYLOAD| Vendor Dependent |
+------------------------------------------------------------------+
3.2.2 Service
The following subsections provide more information regarding the
Service messages that are implemented in version 1.0. TALI
messages are used to carry SS7 MSUs across the IP network.
information in this section includes details with respect to how
encapsulate SS7 MSUs into TCP/IP frames using each of the
service opcodes. The TALI service messages originate at the
above TALI, are transported across the IP network via a TALI
message, and are delivered to the layer above TALI at the far end
the TALI connection
3.2.2.1 SCCP Service Message (sccp
The 'sccp' opcode is used to deliver SS7 MSUs with a
Indicator of 3 (SCCP) over a TALI connection. This opcode is
used on TALI protocol stacks that are implemented without SAAL.
MTP3 layer of the SS7 MSU is NOT part of the data transferred
TCP/IP for this opcode; the data portion of the TALI 'sccp'
begins with the first byte of the SCCP data area in the SS7
(after the MTP3 routing label). The first byte in the SCCP data
is an SCCP message type field
Several restrictions on the SCCP messages that this TALI opcode
carry exist. These restrictions are as follows
* SCCP messages contain an SCCP message type field. The
messages that are supported by TALI 1.0 implementations
limited to Class 0 and Class 1 SCCP messages with a message
field of either
*
*
*
*
Sprague, et al. Informational [Page 24]
RFC 3094 Tekelec's Transport Adapter Layer Interface April 2001
* SCCP messages must contain a Point Code in the 'calling party
area in order to be transferred across the TCP/IP connection as
'sccp' message. An implementation may choose to modify
original SCCP MSU to add an appropriate calling party point
before transmission across TALI if desired
* SCCP messages must contain a Point Code in the 'called party'
in order to be transferred across the TCP/IP connection as
'sccp' message. An implementation may choose to modify
original SCCP MSU to add an appropriate called party point
before transmission across TALI if desired
* The encoding of the SS7 SCCP MSUs, as they are transmitted
TALI via 'sccp', should remain compliant with the
specifications (T1.112 and T1.114) that apply to the SCCP and
portions of the message respectively
NOTE 1: SCCP Subsystem Management for the IP based SCP's is
via this 'sccp' opcode. SS7 SCCP Management messages are
by an SCMG SS7 process. SCMG sends the management messages via
UNITDATA (UDT) messages. Therefore, the SCMG messages can be
across the TALI connection
NOTE 2: 'sccp' TALI messages will not include the MTP3 header
therefore will not retain the original DPC/OPC of the SS7 MSU.
TALI implementation needs to consider if/how to provide this DPC/
information in the SCCP portion of the message. For example the
can be replicated to the point code in the SCCP Called Party
area and the OPC can be replicated to the point code in the
Calling Party Address area
+------------------------------------------------------------------+
| Octets | Field Name | Description |
+------------------------------------------------------------------+
| 0..3 | SYNC | 'TALI' |
+------------------------------------------------------------------+
| 4..7 | OPCODE | 'sccp' |
+------------------------------------------------------------------+
| 8..9 | LENGTH | Length |
+------------------------------------------------------------------+
| 10..X | SCCP Data | SCCP data starting at the first byte after
| | | the Layer 3 Routing Label (data does not |
| | | include the SIO or Routing Label) |
+------------------------------------------------------------------+
Sprague, et al. Informational [Page 25]
RFC 3094 Tekelec's Transport Adapter Layer Interface April 2001
3.2.2.1.1 SCCP Encapsulation using
When an SCCP MSU arrives at an SG from a 56 Kbps or DS1 link and
routed within the SG for transmission to an IP device, the
performs the following processing on the SS7 MSU
* discards the MTP Layer 2 information, CRC and
* places the DPC from MTP Layer 3 into the Called Party
field of the SCCP layer; the Calling Party Address field
created if it does not exist and then
* places the OPC from MTP Layer 3 into the Calling Party
field of the SCCP layer if there is no Calling Party Point
* places the modified SCCP and unchanged TCAP data in the
payload area of the TALI
* The SYNC field is
* The OPCODE is set to 'sccp
* The LENGTH is set to the number of octets in the SERVICE
Once the fully formed 'sccp' TALI packet is created, it is handed
the TCP socket layer and transmitted. The transmission process
add TCP, IP and MAC header information
Since the routing information from MTP Layer 3 is placed in the
part of the outgoing message, no routing information needs to
saved by the SG
Sprague, et al. Informational [Page 26]
RFC 3094 Tekelec's Transport Adapter Layer Interface April 2001
SS7
| Layer 3 | Layer 2 |
| | |
+----+---+-----+-----+-------+---+--+---+---+---+---+----+
|Flag|FCS|TCAP |SCCP |Routing|SIO|LI|FIB|FSN|BIB|BSN|Flag
| | |Layer|Layer| Label | | | | | | | |
+----+---+-----+-----+-------+---+--+---+---+---+---+----+
| |
| |
| |
TALI +-----------+---+------+----+
Packet | Service |LEN|Opcode|SYNC
+-----------+---+------+----+
| |
| |
| |
+---------------------------+------+------+------+
IP | TALI Packet |TCP | IP | MAC |
Packet | |Header|Header|Header
+---------------------------+------+------+------+
Figure 6: Encapsulation of SCCP MSUs using the TALI 'sccp'
When an 'sccp' TALI packet is received on by an SG from an IP device
the SG performs the following processing on the 'sccp' packet
* validates the TALI
* Allocates space for a new SS7
* Regenerates the SIO with the Sub-Service Field set to
Network, priority of zero (0), Service Indicator set to
* extracts the SCCP/TCAP data from the SERVICE area and places it
the new SS7
* sets the DPC to the SCCP Called Party Point
* sets the OPC to the SCCP Calling Party Point
* randomly generates the
Once the 'sccp' packet is transformed back into a normal SS7 MSU,
MSU is routed within the SG according to the normal SS7
procedures
Sprague, et al. Informational [Page 27]
RFC 3094 Tekelec's Transport Adapter Layer Interface April 2001
3.2.2.2 ISUP Service Message (isot
The 'isot' opcode is used to deliver SS7 MSUs with a
Indicator of 5 (ISUP) over a TALI connection. This opcode is
used on TALI protocol stacks that are implemented without SAAL.
MTP3 layer of the SS7 MSU IS part of the data transferred
TCP/IP for this opcode; the data portion of the TALI 'isot'
begins with the SIO byte of the MTP3 header in the SS7 MSU
+------------------------------------------------------------------+
| Octets | Field Name | Description |
+------------------------------------------------------------------+
| 0..3 | SYNC | 'TALI' |
+------------------------------------------------------------------+
| 4..7 | OPCODE | 'isot' |
+------------------------------------------------------------------+
| 8..9 | LENGTH | Length |
+------------------------------------------------------------------+
| 10..X | ISUP Data | Raw ISUP data starting at the Layer 3 SIO |
| | | field. |
+------------------------------------------------------------------+
3.2.2.2.1 ISUP Encapsulation using
When an ISUP MSU arrives at an SG from a 56 Kbps or DS1 link and
routed within the SG to a IP device, the SG performs the
processing on the SS7 MSU
* discards the MTP Layer 2 information, CRC and
* places MTP Layer 3 into the SERVICE payload area of the
* The SYNC field is
* The OPCODE is set to 'isot
* The LENGTH is set to the number of octets in the SERVICE
Once the fully formed 'isot' TALI packet is created, it is handed
the TCP socket layer and transmitted. The transmission process
add TCP, IP and MAC header information
Since the routing information is placed in the TALI Packet,
routing information needs to be saved by the SG
Sprague, et al. Informational [Page 28]
RFC 3094 Tekelec's Transport Adapter Layer Interface April 2001
SS7
| Layer 3 | Layer 2 |
| | |
+----+---+----+----+---+-------+---+--+---+---+---+---+----+
|Flag|FCS|ISUP|Msg.|CIC|Routing|SIO|LI|FIB|FSN|BIB|BSN|Flag
| | |Part|Type| |Label | | | | | | | |
+----+---+----+----+---+-------+---+--+---+---+---+---+----+
| /
| /
| |
TALI +-----------------------+---+------+----+
Packet | Service |LEN|Opcode|SYNC
+-----------------------+---+------+----+
| /
| ---------
| /
+----------------------------+------+------+------+
IP | TALI Packet |TCP | IP | MAC |
Packet | |Header|Header|Header
+----------------------------+------+------+------+
Figure 7: Encapsulation of ISUP MSUs using the TALI 'isot'
When an 'isot' TALI packet is received on an SG from an IP device
the SG performs the following processing on the 'isot' packet
* validates the TALI
* Allocates space for a new SS7
* extracts the MTP Layer 3 data from the SERVICE area and places
in the new SS7
Once the 'isot' packet is transformed back into a normal SS7 MSU,
MSU is routed within the SG according to the normal SS7
procedures
3.2.2.3 MTP3 Service Message (mtp3)
The 'mtp3' opcode is used to deliver SS7 MSUs with a
Indicator of 0-2, 4, 6-15 (non-SCCP, non-ISUP) over a
connection. This opcode is only used on TALI protocol stacks
are implemented without SAAL. The MTP3 layer of the SS7 MSU IS
of the data transferred across TCP/IP for this opcode; the
portion of the TALI 'mtp3' message begins with the SIO byte of
MTP3 header in the SS7 MSU
Sprague, et al. Informational [Page 29]
RFC 3094 Tekelec's Transport Adapter Layer Interface April 2001
+------------------------------------------------------------------+
| Octets | Field Name | Description |
+------------------------------------------------------------------+
| 0..3 | SYNC | 'TALI' |
+------------------------------------------------------------------+
| 4..7 | OPCODE | 'mtp3' |
+------------------------------------------------------------------+
| 8..9 | LENGTH | Length |
+------------------------------------------------------------------+
| 10..X | Layer 3 MSU | Raw MSU data starting at the Layer 3 SIO |
| | Data | field. |
+------------------------------------------------------------------+
3.2.2.3.1 MTP3 Encapsulation using
When an SS7 MSU with SI=0-2,4,6-15 arrives at an SG from a 56 Kbps
DS1 link and is routed within the SG to an IP device, the SG
the following processing on the SS7 MSU
* discards the MTP Layer 2 information, CRC and
* places MTP Layer 3 into the SERVICE payload area of TALI
* The SYNC field is
* The OPCODE is set to 'mtp3'
* The LENGTH is set to the number of octets in the SERVICE
Once the fully formed 'mtp3' TALI packet is created, it is handed
the TCP socket layer and transmitted. The transmission process
add TCP, IP and MAC header information
Sprague, et al. Informational [Page 30]
RFC 3094 Tekelec's Transport Adapter Layer Interface April 2001
SS7
| Layer 3 | Layer 2 |
| | |
+----+---+-----------+-------+---+--+---+---+---+---+----+
|Flag|FCS|Other Layer|Routing|SIO|LI|FIB|FSN|BIB|BSN|Flag
| | |3 Data |Label | | | | | | | |
+----+---+-----------+-------+---+--+---+---+---+---+----+
| /
| ------
| /
TALI +----------------+---+------+----+
Packet | Service |LEN|Opcode|SYNC
+----------------+---+------+----+
| /
| --
| /
+----------------------------+------+------+------+
IP | TALI Packet |TCP | IP | MAC |
Packet | |Header|Header|Header
+----------------------------+------+------+------+
Figure 8: Encapsulation of SS7 MSUs with SI!=3,5,13 using 'mtp3'
When an 'mtp3' TALI packet is received by an SG from an IP device
the SG performs the following processing on the 'mtp3' packet
* validates the TALI
* Allocates space for a new SS7
* extracts the MTP Layer 3 data from the SERVICE area and places
in the new SS7
Once the 'mtp3' packet is transformed back into a normal SS7 MSU,
MSU is routed within the SG according to the normal SS7
procedures
3.2.2.4 SAAL Service Message (saal
The 'saal' opcode is used to deliver SS7 MSUs with any
Indicator over a TALI connection. This opcode is only used on
protocol stacks that are implemented with SAAL. The 'saal' opcode
also used to transmit SAAL peer to peer packets (SSCF peer to
packets and SSCOP peer to peer packets other than SS7 service data
over a TALI connection
Sprague, et al. Informational [Page 31]
RFC 3094 Tekelec's Transport Adapter Layer Interface April 2001
When used to transfer SS7 MSUs, the MTP3 layer of the SS7 MSU IS
of the data transferred across TCP/IP for this opcode; the
portion of the TALI 'saal' message begins with the SIO byte of
MTP3 header in the SS7 MSU and ends with the last byte of the
trailer
When used to transfer SSCF/SSCOP peer to peer messages the
portion of the TALI 'saal' message includes the entire SSCOP PDU
+------------------------------------------------------------------+
| Octets | Field Name | Description |
+------------------------------------------------------------------+
| 0..3 | SYNC | 'TALI' |
+------------------------------------------------------------------+
| 4..7 | OPCODE | 'saal' |
+------------------------------------------------------------------+
| 8..9 | LENGTH | Length |
+------------------------------------------------------------------+
| 10..X | Layer 3 | Raw MSU data starting at the Layer 3 SIO |
| | Data | field. |
+------------------------------------------------------------------+
| (X+1) | SSCOP | Zero (0) to three (3) octets of padding |
| ..Y | Trailer | plus 4 octets for the trailer data. The |
| | | total length of the Layer 3 Data and the |
| | | SSCOP trailer must be a multiple of 4. |
+------------------------------------------------------------------+
+------------------------------------------------------------------+
| Octets | Field Name | Description |
+------------------------------------------------------------------+
| 0..3 | SYNC | 'TALI' |
+------------------------------------------------------------------+
| 4..7 | OPCODE | 'saal' |
+------------------------------------------------------------------+
| 8..9 | LENGTH | Length |
+------------------------------------------------------------------+
| 10..X | SAAL Peer | Raw SSCF/SSCOP peer to peer packets are |
| | to Peer | also transferred over the TALI connection |
| | message | using this 'saal' opcode. |
+------------------------------------------------------------------+
3.2.2.4.1 MTP3 and SAAL Peer to Peer Encapsulation using
When an SS7 MSU (with any SI) arrives at an SG from a 56 Kbps or DS
link and is routed within the SG for transmission to an IP device
the SG performs the following processing on the SS7 MSU
Sprague, et al. Informational [Page 32]
RFC 3094 Tekelec's Transport Adapter Layer Interface April 2001
* discards the MTP Layer 2 information, CRC and
* the MSU is passed from an MTP3 processing software layer to
SSCF and SSCOP layers (the SAAL layers). These layers convert
SS7 MSU into an SSCOP PDU. Part of this conversion
adding an SSCOP trailer
* the SSCOP PDU (whether it is a peer to peer SAAL message or SS
MSU in an SSCOP PDU) is copied into the SERVICE payload area
the TALI
* The SYNC field is
* The OPCODE is set to 'saal
* The LENGTH is set to the number of octets in the SERVICE
Once the fully formed 'saal' TALI packet is created, it is handed
the TCP socket layer and transmitted. The transmission process
add TCP, IP and MAC header information
Since the routing information is placed in the TALI Packet,
routing information needs to be saved by the SG
Sprague, et al. Informational [Page 33]
RFC 3094 Tekelec's Transport Adapter Layer Interface April 2001
SS7
| Layer 3 | Layer 2 |
| | |
+----+---+-----------+-------+---+--+---+---+---+---+----+
|Flag|FCS|Other Layer|Routing|SIO|LI|FIB|FSN|BIB|BSN|Flag
| | |3 Data |Label | | | | | | | |
+----+---+-----------+-------+---+--+---+---+---+---+----+
| |
| |
| |
+-------+-----------------------+
|SSCOP | Service |
|Trailer| |
+-------+-----------------------+
| |
+-------+-----------------------+---+------+----+
|Service with SSCOP Trailer |LEN|Opcode|SYNC
+-------+-----------------------+---+------+----+
| /
| -----------------
| /
+----------------------------+------+------+------+
| TALI Packet |TCP | IP | MAC |
| |Header|Header|Header
+----------------------------+------+------+------+
Figure 9: Encapsulation of SAAL PDUs using the TALI 'saal'
When an 'saal' TALI packet is received at the SG from an IP device
the SG performs the following processing on the 'saal' packet
* validates the TALI
* Allocates space for a new SSCOP PDU
* extracts the SSCOP PDU data from the SERVICE area and places it
the new SSCOP PDU
Once the 'saal' packet is transformed back into a normal DS1
PDU, the SSCOP PDU is passed to the SAAL layer for
processing. If the SSCOP PDU is a peer to peer pdu, it is
completely in the appropriate SAAL layer. If the SSCOP PDU is an SS
MSU, the MSU is transformed back to a normal SS7 MSU and is
within the SG according to the normal SS7 routing procedures
Sprague, et al. Informational [Page 34]
RFC 3094 Tekelec's Transport Adapter Layer Interface April 2001
3.3 TALI
Version 1.0 of the TALI specification defined 4 TALI timers that
used as part of the TALI state machine. These timers are
named 'T1' through 'T4'. Brief descriptions of each timer
provided in the following subsections. Timer expiration events
each of the T1-T4 timers appear as inputs to the TALI state machine
For exact processing of each timer (when to start/stop, how
process timer expirations), refer to the TALI state machine
Both ends of the TALI connection have there own T1-T4 timers.
T1-T4 timer values can be set on each end of the
independent of the settings on 