Internet DRAFT - draft-liao-ss7-tcap-ip
draft-liao-ss7-tcap-ip
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Internet Engineering Task Force Monling Liao
INTERNET DRAFT Liem Le
draft-liao-ss7-tcap-ip-00.txt Emad Qaddoura
March 1999 Don Wurch
Nortel Networks
Expires: September 1999
SS7-TCAP/IP Interworking
<draft-liao-ss7-tcap-ip-00.txt>
Status of this Memo
This document is an Internet-Draft and is in full conformance with all
provisions of Section 10 of RFC2026 except that the right to produce
derivative works is not granted.
Internet-Drafts are working documents of the Internet Engineering
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Abstract
The paper defines the architectural framework, convergence solutions and
service interworking scenarios associated with SS7-TCAP/IP Interworking
between applications in PSTN/IN/Wireless and IP domains.
Note
Some aspects of this contribution are the subject of a provisional patent
application by Nortel Networks. The contributors hereby represent that they are
not personally aware of any other proprietary or intellectual property rights in
this contribution.
<draft-liao-ss7-tcap-ip-00.txt> [Page 2]
Table of Contents
1.0 Introduction
2.0 Terminology
3.0 Base Configuration
3.1 Reference Architecture
3.2 Convergence functions
3.3 Inter-domain scenario configurations
3.3.1 Voice Over IP Service
3.3.2 Short Message Service TCAP/IP Interworking
3.3.3 IP Applications and TCAP/IP Interworking
3.3.4 Signaling Transport between SS7 networks
4.0 Next Steps
5.0 References and Related Work
6.0 Authors
1.0 Introduction
Today, the telecommunications industry depends on the SS7 network for
the signaling between different entities within the system. The
technologies such as Internet Dial-up Access, Voice over IP (VoIP), etc.
have identified the need of SS7-ISUP/IP Interworking. There are several
Internet Drafts[1,2] that define how the SS7-ISUP inter-works with IP.
The other aspect of the SS7 is the use of TCAP for transaction related
applications as in 800/888, calling card, local number portability
(LNP), wireless mobility management, Intelligent Network (IN) and CLASS
services. These services are also required on VoIP convergent network.
In fact, some of these service entities have been planned and/or
implemented in the IP network without the standardization of the
TCAP/SS7 Interworking with IP.
The explosive growth of the Internet and IP networks makes the
integration of SS7 entities in the IP network more practical. The
network intelligence on voice over IP network will make the use of TCAP
on a more widespread basis. This paper proposes the integration of SS7
network services into IP networks via the TCAP/IP Interworking.
2.0 Terminology
Call Server/Controller (CS)
The Call Server performs signaling and call control functions for IP
clients, e.g., VoIP phones and Media Gateways. CS may handle the
registration and management of resources at the MG. The CS may have the
ability to authorize resource usage based on local policy, for example,
based on the attributes of both the end-user and the ISP.
Directory Number (DN)
Subscriber number or telephone number.
Global Title Translation (GTT)
SS7 network routing function that translates a logical address to a
physical SS7 network address and possibly, a subsystem number, which
identify the application that will process the message.
<draft-liao-ss7-tcap-ip-00.txt> [Page 3]
Internet Service Provider (ISP)
Group providing Internet service to customers
ISDN User Part (ISUP)
Integrated Services Digital Network User Part. The call control part of
the SS7 protocol.
Media Gateway (MG)
A MG terminates PSTN facilities (trunks, loops), packetizes the media
stream for IP, if it is not already packetized, and delivers packetized
traffic to the IP network. Examples of MGs are NAS (Network Access
Servers) and VoIP gateways. The NAS and VoIP functions may or may not be
combined in one gateway.
Public Switched Telephone Network (PSTN)
Abbreviation used by the ITU for the public telephone network.
Service Control Point (SCP)
This is a node in an SS7 network that provides centralized service logic
and data, such as call routing information.
Signaling Connection Control Part (SCCP)
The signaling layer in the SS7 protocol provides a transfer capability
for circuit related and non-circuit related signaling information.
Signal Transfer Point (STP)
This is a node in an SS7 network that routes signaling messages based on
their destination address in the SS7 network.
TCAP/IP Interworking Gateway (TIPG)
The network entity that provides the interface between SS7 network and
IP network pertaining to TCAP messaging.
Transaction Capabilities Application Part (TCAP)
Transaction Capabilities in the SS7 protocol are functions that control
non-circuit-related information transfer between two or more signaling
nodes via a signaling network.
3.0 Base Configurations
SS7-TCAP/IP Interworking will provide an interface between the SS7
network TCAP messaging and IP network entities. This section presents
base configurations that serve to illustrate the architectural framework
of the SS7-TCAP/IP Interworking.
3.1 Reference Architecture
<draft-liao-ss7-tcap-ip-00.txt> [Page 4]
PSTN IP Network
+-----+
+---+ |IP |
|SCP| |Entity
+---+\ TCAP over / +-----+
\ +---+ TCAP over +----+ IP* / .
+---+ \---|STP|------SS7-------|TIPG| -------/ .
|SP |----- +---+ +----+ ------- .
+---+ / TCAP/IP \ +-----+
+-------+/ Interworking \ |IP |
|VLR/HLR| Function \ |Entity
+-------+ +-----+
Figure 1: TCAP/IP Interworking Reference Architecture
* This Reference Architecture shows an open TCAP/IP Interface between
the TIPG and the IP Entity. Please refer to the, "Simple SS7-TCAP/IP
Protocol (STIPP)" document [3] for a proposed protocol for this open
interface.
The SS7-TCAP/IP Interworking function will be performed on the TCAP/IP
Gateway (TIPG). The Reference Architecture for the TIPG is illustrated
in figure 1.
The Reference Architecture for TIPG shows the TCAP/IP Interworking,
including the interface between the SS7 network and the IP network. The
TCAP/IP Interworking function could also be performed on any gateway
that establishes an interface between the SS7 network and an IP network.
Three inter-domain scenarios are addressed:
1. SS7 entity communicating with IP server
2. IP entity (e.g. call server) communicating with SCP in SS7 network
3. IP signaling transport between two SS7 networks
To the interconnecting SS7 network, TIPG acts as a signaling endpoint.
It may, of course, include STP functions and acts as a STP. To the
interconnecting IP network, TIPG acts as a transit point for messaging
between SS7 network and IP entities. TIPG can also be an IP entity
itself, that is, a TIPG can transfer TCAP messages to a far-end TIPG for
signaling transport between two SS7 networks.
By providing TCAP/IP interworking functions, the signaling transport is
transparent to TCAP applications. Thus, TCAP applications must not be
impacted whether the signaling message is sent over SS7 network or IP
network. Within SS7 network, SCCP functions are provided for addressing
and routing. Within IP network, a convergence layer is defined for
addressing and routing functions.
The TIPG will perform the mapping function between IP entities and SS7
addresses, and bi-directional encapsulation/decapsulation function for
the TCAP/IP Interworking.
<draft-liao-ss7-tcap-ip-00.txt> [Page 5]
Depends on application needs (e.g. sequence control), it may require
either TCP/IP or UDP/IP to provide the transport functions for TCAP over
IP. Whether using TCP, UDP or a reliable transport is outside the scope
of this document. A convergence layer named Simple TCAP Interworking
Part (STIP) is defined between TCAP and UDP/IP (or TCP/IP) transport.
STIP provides connectionless control for TCAP applications.
The STIP header consists of called party address and calling party
address paraameters as defined in SCCP.
************* SS7 ******** IP ************
*SS7 Entity *--------------* TIPG *-------------* IP Entity*
************* ******** ************
+-----+ +-----+
|TCAP | |TCAP |
+-----+ +-----+
|SCCP | |STIP |
+-----+ +-----+
|MTP | |TCP/UDP/Reliable transport
+-----+ +-----+
| IP |
+-----+
Figure 2: TCAP messaging between SS7 network & IP network
I. SS7 network originates a TCAP message into the IP network:
+-----+-----+-----+ +----+ +------+----+-----+
| MTP | SCCP| TCAP|-----------> |TCAP|------------->|IP/UDP|STIP|TCAP |
+-----+-----+-----+Decapsulation+----+ Encapsulation+------+----+-----+
Figure 3.a: TCAP messaging from SS7 network to IP network
The SS7 message is decapsulated to remove the MTP and SCCP headers. The
remaining TCAP message is encapsulated with the IP header and the STIP
header, which contains the required information from the MTP and SCCP
headers.
II. IP network originates a TCAP message into the SS7 network:
+------+-----+-----+ +----+ +----+-----+-----+
|IP/UDP| STIP|TCAP |-----------> |TCAP|------------> |MTP | SCCP| TCAP|
+------+-----+-----+Decapsulation+----+Encapsulation +----+-----+-----+
Figure 3.b: TCAP messaging from IP network to SS7 network
The IP message is decapsulated to remove the IP header and the STIP
header. The remaining TCAP message is encapsulated with the MTP and SCCP
headers with the required information from the STIP header.
III. IP network provides TCAP message transport between two SS7
networks:
<draft-liao-ss7-tcap-ip-00.txt> [Page 6]
The TCAP message is originated from one SS7 network and is terminated to
a far-end SS7 network. The IP network provides signaling transport
functions. Each TIPG at the edge of IP network performs the
encapsulation/decapsulation functions as described above.
3.2 Convergence functions
STIP convergence functions are required in both TIPG gateway and IP
entity that requires the TCAP over IP function.
Note that TIPG may be deployed as a STP and thus some of IP servers,
e.g. call servers, are provisioned as pseudo signaling end point
to the SS7 network. The routing in this case is based on mapping
between point codes and IP addresses. The STIP functions described
below assume that no point codes are provisioned for IP entities
except the TIPG.
3.2.1 TIPG STIP functions
TIPG acts as a signaling end point to the SS7 network and as a transit
signaling point to the IP network. IP entities are TIPG's subsystems.
TIPG needs to maintain the mapping between Subsystem number (SSN) and
the address of IP servers after IP servers logging in [3].
In addition to encapsulation and decapsulation functions described in
section 3.1, STIP convergence layer performs SCCP addressing and
routing to SS7 network and also SCCP-like addressing and routing
to IP network.
3.2.1.1 Global Title Translation (GTT) function
Global Title (GT) Address in SS7 network refers E.164 DN and E.214
Mobile number. The GTT function performed by SCCP is to translate GT to
find a destination node in SS7 network. Since TIPG is acting as a
transit signaling point to IP entities, the GTT function may be required
and extended in TIPG. Possible GTT outcomes:
- a destination node in SS7 network - DPC (+SSN or +GT)
- a destination node in IP network - IP address + port number
3.2.1.2 Incoming TCAP messages from SS7 network
STIP determines the destination IP entity based on Destination Point
Code (DPC) and the called party address.
<draft-liao-ss7-tcap-ip-00.txt> [Page 7]
1. If DPC of the incoming message is TIPG itself, the destination is a
TCAP application that may reside in one IP server or another TIPG (for
signaling transport between two SS7 networks) depends on the Routing
Indicator in Called Party Address (CDPA).
- SSN routing: If SSN is available, forward the message to the IP server
that has logged in with the same SSN, otherwise the SCCP message return
procedure is initiated.
- GT routing: This indicates translation is required. STIP performs GTT
to obtain a far end TIPG's IP address and forwards the message.
2. If DPC is not TIPG itself, the signaling transport function is
requested. STIP retrieves the IP address of a far end TIPG based on the
DPC. The mapping between DPC and IP address is described in section
3.2.1.4.
The SCCP Called Party Address (CdPA) and Calling Party Address (CgPA)
are copied into STIP CdPA and CgPA with the following exceptions:
- CdPA: If DPC is not TIPG itself and SCCP.CdPA contains SSN only, the
DPC must be added to STIP.CdPA in order for the far end TIPG to send out
the message to its interconnecting SS7 network.
- CgPA: If SCCP.CgPA contains SSN only, the OPC must be added to
STIP.CgPA in order for the response message to be sent back to the
originator.
3.2.1.3 Incoming TCAP messages from IP network
If STIP.CdPA indicates GT routing, then perform GTT to obtain a
destination address:
- the destination is an IP address, forward the message to the IP
entity.
- the destination is a SS7 point code then set DPC to the SS7
point code.
The STIP CdPA and CgPA are copied into SCCP CdPA and CgPA with the
following exceptions:
- CdPA: If STIP.CdPA contains PC and SSN, copy the SSN to SCCP.CdPA and
uses the PC for DPC.
- CgPA: If STIP.CdPA indicates GT routing, and STIP.CgPA contains SSN
only, this indicates the message is originated from an IP server. STIP
adds TIPG's PC into SCCP.CgPA in order for a response message to be sent
back to the TIPG.
The OPC is set to TIPG's PC unless the STIP.CgPA contains a different PC
that indicates it is a signaling transport message. In this case, the
OPC must be set to the PC from STIP.CgPA.
<draft-liao-ss7-tcap-ip-00.txt> [Page 8]
3.2.1.4 Mapping between point code and IP address
To provide signaling transport over IP function between two SS7
networks, it requires mapping of SS7 point codes to a TIPG's IP address.
This mapping information is needed when a response message needs to be
sent back to the originating SS7 network. STIP needs to record the DPC
with incoming IP address and port number when it first sends out the
query message with an OPC other than its own PC to SS7 network.
To prevent the overload with the point code mapping information,
TIPG may add a 'clean-up' procedure to periodically delete
the mapping records that are not referenced/used over a period of time.
3.2.2 STIP in IP entity (non TIPG)
STIP provides addressing and routing functions for TCAP applications in
IP entities. The STIP CgPA and CdPA contain the same type of SCCP
routing addresses: GT and PC/SSN. Since the IP entity is not an SS7
entity, it does not have SS7 point code nor does it utilizes any point
code that may be sent to it in CgPA from the homed TIPG. The point code
if any contained in CgPA in a query message is used as CdPA in a
subsequent response message to the originator via TIPG.
STIP provides three primitives as described in SS7 SCCP to the TCAP
user:
1. N-UNITDATA request - used by the TCAP user to request data transport
to another user.
2. N-UNITDATA indication - informs the TCAP user that data is being
delivered to it.
3. N-NOTICE indication - informs the TCAP user that data could not reach
the final destination.
3.2.2.1 Incoming STIP TCAP Data message from TIPG
STIP TCAP Data message is defined in STIPP document [3]. The routing
indicator in CdPA must be set to SSN routing. The message is passed to
the application using N-UNITDATA indication primitive with parameters:
- CdPA
- CgPA
- TCAP data
3.2.2.2 Outgoing message from subsystem
STIP received the data parameters from the TCAP user via N-UNITDATA
request primitive. The data parameters are:
- CdPA
- CgPA
- TCAP data
<draft-liao-ss7-tcap-ip-00.txt> [Page 9]
The addressing information may take the following forms:
- DPC+SSN (from the CgPA of the received message from SS7 network)
- GT
It's optional for TCAP user to set CgPA. The CgPA is set to its own SSN.
STIP sends the message via UDP/IP to the homed TIPG.
3.2.2.3 STIP TCAP Error message from TIPG
Upon receiving the TCAP Error message (defined in STIPP protocol [3]),
STIP informs the TCAP user via N-NOTICE indication primitive.
3.3 Inter-domain scenarios configurations
3.3.1 Voice Over IP Services Configuration
The Voice-Over-IP (VoIP) services configuration illustrates the
application of the TCAP/IP Interworking functionality. The TCAP/IP
Interworking functionality will be performed within the TIPG.
+---+ ------------
|SCP|--- |SS7 network|----------
+---+ ------------ \
ss7 / \ \
/ \ss7 \
+------+ +-------+ \+-----+
| TIPG | |ISUP GW| |CO/SP|---PSTN phone
+------+ +-------+ +-----+
STIP\ / IP /
+-------+ /
------ | CS | /
/IP +-------+ /
/ |IP /
----------- +-------+ ----------
|IP network|------| MG |---------| PSTN |
------------ RTP +-------+ IMT ----------
| stream
|
IP phone
Figure 4: VoIP Services TCAP/IP Interworking Configuration
Note:
1. TIPG and ISUP Gateway are two different logical entities that can
physically be located on the same physical box.
2. IMT- Inter-Machine Trunk
<draft-liao-ss7-tcap-ip-00.txt> [Page 10]
Sample TCAP message headers:
1. Query message
STIP message sent by IP entity
Dest.IP+port = TIPG's IP+port
Src.IP+port = IP entity's IP+port
STIP.CdPA = GT + Translation Type (TT), GT routing
STIP.CgPA = IP entity's SSN, SSN routing
TIPG's STIP sends the TCAP message with SCCP & MTP header
DPC = STP's PC
OPC = TIPG's PC
SCCP.CdPA = GT + TT, GT routing
SCCP.CgPA = TIPG's PC + SSN, SSN routing
2. Response message
SS7 TCAP message to TIPG
DPC = TIPG's PC
OPC = SCP's PC
SCCP.CdPA = IP entity's SSN, SSN routing
SCCP.CgPA = SCP's LNP SSN, SSN routing
TIPG's STIP sends the TCAP message with STIP header
Dest.IP+port = IP entity's IP+port
Src.IP+port = TIPG's IP+port
STIP.CdPA = IP entity's SSN, SSN routing
STIP.CgPA = SCP's PC + SCP's LNP SSN, SSN routing
3. If a return result message is required
STIP message sent by IP entity
Dest.IP+port = TIPG's IP+port
Src.IP+port = IP entity's IP+port
STIP.CdPA = SCP's PC + SCP's LNP SSN, SSN routing
STIP.CgPA = IP entity's SSN, SSN routing
TIPG's STIP sends the TCAP message with SCCP & MTP header
DPC = SCP's PC
OPC = TIPG's PC
SCCP.CdPA = SCP's LNP SSN, SSN routing
SCCP.CgPA = IP entity's SSN, SSN routing
<draft-liao-ss7-tcap-ip-00.txt> [Page 11]
Scenario for an VoIP phone making a call to PSTN user with LNP:
1. VoIP phone sends a "Make Call" to its carrier with PSTN number as
destination DN.
2. The IP carrier CS determines the destination DN is in an
interconnecting PSTN with LNP deployment, so it sends a TCAP message for
LNP number translation to the TIPG over IP.
3. TIPG decapsulates the IP header, encapsulates the TCAP message with
the SS7 header, and delivers to the SS7 network.
4. GTT is performed at STP to determine the destination SCP. Upon
receiving the message, LNP SCP responds with a TCAP message that
contains the local routing DN to the TIPG.
5. TIPG decapsulates the SS7 header, encapsulates the TCAP message with
the IP header, and deliver to the CS.
6. CS acquires E.164/IP address conversion to locate a MG that has IMT
to the destination PSTN. Note: for simplicity of illustration, the same
CS provides media gateway control function for the identified MG.
7. CS commands MG to reserve trunk resources and sends ISUP-IAM message
to the ISUP Gateway over IP.
8. ISUP Gateway decapsulates the IP header, encapsulates the ISUP
message with the SS7 header, and deliver to the destination PSTN.
9. The destination CO sends back a response message to the ISUP gateway.
10. The ISUP gateway decapsulates the SS7 header, encapsulates with the
IP header, and sends to the CS.
11. CS/MG completes the call setup with the VoIP phone.
The steps 2 to 5 involve the TCAP/IP interworking functionality. The
other steps involve either Q.931 or ISUP functionality and are not the
concern of this paper. Also note that there is the need for the mapping
between IP Address/Port Number and the assigned TDM channel that is
performed at the CS/MG.
3.3.2 Short Message Service TCAP/IP Interworking Configuration
The TCAP/IP Interworking function can be applied to a Short Message
Service Center (SMSC) Application. Again, the TCAP/IP Interworking
function will be performed within the TIPG.
+------+ IP +------+
| TIPG |-----------| SMSC |
+------+ +------+
/ \
/ ss7 \
/ \
+-----+ +-------+
| MSC | |HLR/VLR|
+-----+ +-------+
Figure 6: Short Message Service TCAP/IP Interworking Configuration
<draft-liao-ss7-tcap-ip-00.txt> [Page 12]
Scenario for the SS7 sending the SMS message to the SMSC:
1. SMS message arrives at the TIPG from the SS7 network destined for the
SMSC.
2. TIPG decapsulates the SS7 header, encapsulates the TCAP message with
the IP header, and delivers it to the SMSC.
3. SMSC saves the content of SMS message for the future delivery.
Scenario for the SMSC delivering the SMS to the SS7 network:
1. TCAP message arrives at the TIPG from the SMSC.
2. TIPG puts its PC/SSN in the originating PC/SSN field of the SS7
message. It also examines the STIP header for the destination SS7
address of the SS7 message.
3. TIPG decapsulates the IP header and encapsulates the TCAP message
with the SS7 header, and then delivers it to the SS7 network.
3.3.3 IP Applications and TCAP/IP Interworking Configuration
+----+ +------+ ss7 +------+
|SCP |----| STP |-----------| TIPG |
+----+ +------+ -- +------+
ss7 / / \
+------+ ----- / IP \
| SP | / \
+------+ +------+ +------+
| IP | |IP |
|Entity| |Entity|
+------+ +------+
Figure 7: IP Applications and TCAP/IP Interworking Configuration
Note: The IP Entity can be any IP-based application such as: Directory
Service, Location Service, etc.
An important aspect of this scenario is the need for the address
translation between the subsystem number and the IP address/Port Number.
The TIPG must have a table that records the mapping between these two
addresses.
Scenario for the SS7 originating the TCAP message into the IP network:
1. TCAP message arrives at the TIPG from the SS7 network. This TCAP
message is destined for one of the IP Entities homed to the TIPG.
2. TIPG examines the destination SSN in the SS7 message and maps this
SSN into IP address/port number of the destination IP Entity.
3. TIPG decapsulates the SS7 header, encapsulates the TCAP message with
the IP header, and delivers it to the destination IP Entity.
<draft-liao-ss7-tcap-ip-00.txt> [Page 13]
Scenario for the IP Entity originating the TCAP message into the SS7
network:
1. TCAP message arrives at the TIPG from the IP Entity. This TCAP
message is destined for one of the SS7 Entities within the SS7 network.
2. TIPG adds its PC in the originating PC/SSN of the SS7 message. It
also examines the STIP header for the destination SS7 address of the SS7
message, which can be specified as the PC/SSN or the Global Title. The
TCAP response message to a TCAP invoke message is an example of the
PC/SSN specified in the STIP header. The delivery of the short message
to a Short Message Entity (SME) is an example of the Global Title
specified in the STIP header. In this case, the Global Title can
possibly be an E.164 or E.214 number.
3. TIPG decapsulates the IP header and encapsulates the TCAP message
with the SS7 header, and then delivers it to the SS7 network.
3.3.4 PSTN Signaling Transport Configuration
For VoIP services, an IP network may provide signaling transport
functions for two PSTN networks. For example, a PSTN user makes a call
via an interconnecting IP network to another PSTN user who has
subscribed Calling Name Delivery (CNAM) service. The TCAP query message
launched by the terminating switch may be transported via the IP network
to the originating network to retrieve the calling name information.
This intermediate signaling transport function can also support queries
between the originating and terminating PSTN networks for CLASS
Automatic Recall and Automatic Callback services.
Each TIPG in the edge of IP network performs the
encapsulation/decapsulation functions for converting of a TCAP/SS7
message to a TCAP/IP message and of a TCAP/IP message to a TCAP/SS7
message.
+---+ ------------ ------------
|SCP|--- |SS7 network| |SS7 network|
+---+ ------------ ------------
ss7 / \ / \
/ \ss7 ss7/ \
+------+ +-------+ +-------+ +-----+
|CO/SP | |TIPG-2 | |TIPG-1 | |CO/SP|
+------+ +-------+ +-------+ +-----+
| \ / IP |
| IP \ / |
PSTN ----------- Called Pary
Caller |IP network| with CNAM
------------
Figure 5: Signaling Transport TCAP/IP Interworking Configuration
<draft-liao-ss7-tcap-ip-00.txt> [Page 14]
Scenario for Calling Name Delivery service for a PSTN-IP-PSTN call:
1. A PSTN to PSTN call via an interconnecting IP network. This call is
connected from the originating PSTN via IP carrier's gateways such as
ISUP gateway, CS & MG to the terminating PSTN switch.
2. The terminating PSTN checks the called party service profile and
sends a TCAP message towards the originating carrier for CNAM
information.
3. The SS7 network performs Global Title Translation (GTT) on calling
party number and sends the TCAP message to TIPG-1 over SS7.
4. TIPG-1 acquires E164/IP address conversion (GTT function) based on
SCCP routing information and determines the far-end TIPG-2.
5. TIPG-1 decapsulates the SS7 header, encapsulates the TCAP message
with the IP header, and deliver to TIPG-2 over IP.
6. Upon receiving the TCAP message, TIPG-2 records the mapping between
the originating PC and IP address of the far end TIPG-1, decapsulates
the IP header, encapsulates the TCAP message with the SS7 header, and
delivers to the interconnecting SS7 network.
7. The interconnecting SS7 network performs the final GTT and forwards
the TCAP message to CNAME SCP.
8. SCP responds with a TCAP message that contains the requested CNAME
information via the interconnecting SS7 network to TIPG-2.
9. TIPG-2 retrieves the IP address of the far end TIPG-1 based on DPC in
SCCP routing information.
10. TIPG-2 decapsulates the SS7 header, encapsulates the TCAP message
with the IP header, and deliver to TIPG-1.
11. Upon receiving the TCAP message, TIPG-1 decapsulates the IP header,
encapsulates the TCAP message with the SS7 header, and delivers to the
interconnecting SS7 network.
12. The terminating switch delivers calling name to alert called party.
4.0 Next Steps
The goal of this document is to present the importance of the SS7-
TCAP/IP Interworking function in providing an interface between SS7 TCAP
and IP networks. The next step is to identify the problems/issues
associated with the SS7-TCAP/IP Interworking and to define a protocol
for the open interface between the TIPG and the IP entity that will
resolve these problems/issues.
<draft-liao-ss7-tcap-ip-00.txt> [Page 15]
There are a number of issues to be addressed in providing the
Interworking function. The resolution of these issues will require
continuing research.
* Assignment of a specific port number for the application performing
the TCAP/IP Interworking function.
* Security issues involving Encryption/Decryption (at the TIPG and
Endpoint Applications), Firewall Transversal, etc. at the IP interface
of the TIPG will need to be addressed.
* Encapsulation, decapsulation, fragmentation and sequence control
issues for multiple messages.
5.0 References and Related Work
[1] N. Greene, et al, "SS7-Internet Interworking - Architectural
Framework", draft-greene-ss7-arch-frame-01.txt, July 1998, work in
progress
[2] M. Arango, C. Huitema, "Simple Gateway Control Protocol (SGCP)",
draft-huitema-sgcp-v1-02.txt, July 1998, work in progress
[3] M. Liao, E. Qaddoura, L. Le, R. Tummula, and D. Wurch, "Simple SS7-
TCAP/IP Protocol (STIPP)", draft-liao-stipp-v0.text, March 1999, work
in progress
6.0 Authors
Monling Liao
Nortel
RTP, NC
Phone: (919) 991-2704
email: monling@nortelnetworks.com
Emad Qaddoura
Nortel
Richardson, TX
Phone: (972) 684-2705
email: EmadQ@nortelnetworks.com
Liem Le
Nortel
Richardson, TX
Phone: (972) 684-0689
email: LiemLe@nortelnetworks.com
Donald Wurch
Nortel
Richardson, TX
Phone: (972) 684-1049
email: DWurch@nortelnetworks.com
INTERNET DRAFT EXPIRES September 1999 INTERNET DRAFT
