SS7 / SIGTRAN

Signaling System 7 is also the protocol that defines the procedures to transport and process database queries necessary for providing today’s advanced intelligent network (AIN) features and services. SS7 is increasingly being used to bridge the PSTN with next-generation Internet Protocol (IP) and 3G Wireless networks.
Designed to improve network operation and to provide enhanced services, SS7 carries packetized data to form a low-delay, highly secure and reliable infrastructure that supports voice transport and services over the circuit-switched network.
The SS7 standard has been extended for multiple country-specific variations, such as the American National Standards Institute (ANSI) and Telcordia Technologies (formerly Bellcore) standards within North America, and the European Telecommunications Standards Institute (ETSI) standard in Europe.
Broadband standards have been defined to support transferring Signaling System 7 messages over ATM to take advantage of the higher speeds and Quality of Service (QoS) available in broadband networks. The SS7-over-IP standards support transporting SS7 messages over IP-based networks, which enables seamless convergence and inter-working of PSTN and IP protocols within a unified architecture.

SS7 STACK DIAGRAM

SS7 NETWORK ARCHITECTURE

FASTER TIME TO MARKET

• Fully portable, platform-independent software
• Simple yet flexible interfaces with a large base of trained developers
• Mature, field-proven products integrated into a wide variety of network elements

REDUCED COSTS

• Multi-threaded software solutions that provide optimal performance scalability
• Consistent TAPA architecture to facilitate integration
• Integrated systems that enable customers to focus on apps

REDUCED RISK

• Standards-based products and processes
• Expert Trillium Professional Services and global technical support
• Robust fault-tolerant and distributed fault-tolerant solutions

The Trillium SS7 product line includes the following protocol layers:

INTELLIGENT NETWORK APPLICATION PROTOCOL (INAP)

• Capability Set 1 (CS1), as defined by the ITU, ETSI, and the Generic Requirement (GR) standards of the Telcordia Advanced Intelligent Network (AIN)
• The interaction between the SSF, SCF, Specialized Resource Function (SRF), and the Service Data Function (SDF)

ISDN USER PART (ISUP)

• The signaling protocol to establish, maintain and release circuit-switched network connections across an SS7 network; can act as originating, destination or intermediate exchange
• ITU-T, Telcordia (formally Bellcore), ANSI, Singapore, Q.767, ETSI, FTZ, Russia, Italy, NTT (Japan), and other variants

MOBILE APPLICATION PART (MAP)

• Used by the Mobile Switching Center (MSC), Serving GPRS Support Node (SGSN), and Gateway GPRS Support Node (GGSN) in wireless networks to query the Home Location Register (HLR) or Visitor Location Register (VLR) to determine and/or verify subscriber services

MTP1

• Defines the physical and functional characteristics of the digital signaling link

MTP2

• Reliable transfer of signaling messages over signaling links
• ITU-T, ANSI, TTC (Japan), NTT (Japan), China, and other variants

MTP3

• Broadband and narrowband signaling traffic management, signaling link and route management
• Functionality as an SSP or STP; Direct inter-working with Trillium Q.2140 ATM
• ITU-T, ANSI, TTC (Japan), NTT (Japan), Singapore, China, B-ICI, and other variants
• Connection-oriented and/or connection-less services (Class 0, 1, 2, and 3) for transferring data across an SS7 network
• ITU-T, ANSI, and China variants
• End-to-end, connectionless network service protocol between transaction capability users across an SS7 network
• An ASN.1 encoding/decoding engine to encode/decode all operation codes and dialog parameters
• ITU-T, ANSI, ETSI, and TTC (Japan) variants
• Convergence functions necessary to map the SS7 MTP Level 3 protocol to the ATM Q.SAAL protocol
• ITU-T Q.2140, B-ISDN – ATM Adaptation Layer – SSCF at NNI and Q.2110, B-ISDN – ATM Adaptation Layer – SSCOP
• Establishing, maintaining and releasing circuit-switched network connections across an SS7 network; can act as the originating, destination, or intermediate exchange
• ITU-T and China variants
• The Motorola MC68360 SCC Driver portable software product supports the HDLC and SS7 interfaces. It can be directly used with Trillium LAPB, LAPD, Frame Relay, and MTP2 products.
• The Motorola MPC8260 Driver and MPC860 Driver portable software product supports the HDLC, AAL5, and SS7 interfaces. It can be directly used with the Trillium LAPB, LAPD, Frame Relay, ATM, and MTP2 products.

Signaling Connection Control Part (SCCP)

Transaction Capabilities Application Part (TCAP)

Q.2140

Telephone User Part (TUP)

Drivers

Trillium SIGTRAN software source code solutions enable seamless convergence and inter-working of PSTN and IP protocols under a unified architecture.
SIGTRAN is an Internet Engineering Task Force (IETF) standard for transporting message-based Public Switched Telephone Network (PSTN) Signaling System 7 (SS7) traffic over IP networks. The SIGTRAN framework defines a modular structure that uses a common reliable transport protocol and allows the definition of adaptation modules for different PSTN control protocols.
The transport protocol, Stream Control Transmission Protocol (SCTP), allows carriers to use the IP infrastructure to transport SS7 telephony traffic over an IP network. Its generic design also provides a reliable transport delivery mechanism for other multimedia and wireless frameworks such as H.323, MGCP, H.248/MEGACO, SIP and 3G.
SCTP supports node-to-node transport of SS7/ISDN traffic between Signaling Gateways (SGs)/Media Gateways (MGs) and Media Gateway Controllers (MGCs). It works on the basic concept of associations and streams.

An SCTP association:

• is similar to a TCP connection
• supports multiple IP addresses at either or both ends (multi-homing)
• supports multiple logical streams (multi-streaming)
• provides sequenced delivery for user datagrams within a single stream

SCTP’s design includes the appropriate congestion-avoidance behavior, message validation and path management capabilities required by the PSTN.
Adaptation modules may be added as extensions to the transport protocol. The IETF SIGTRAN working group has defined adaptation modules for ISDN Q.921, MTP Level 2, MTP Level 3 and SCCP.
The Trillium SIGTRAN software family extends the value of a carrier’s legacy telephone network by carrying signaling traffic across SS7 and IP-based networks. Trillium SIGTRAN software also facilitates seamless and ubiquitous deployment of applications and services regardless of the underlying network infrastructure. Trillium SIGTRAN software plays a crucial role in these coexisting and converging SS7/IP signaling networks and is being deployed in an ever-growing number of network integration scenarios.

SIGTRAN SOFTWARE STACK DIAGRAM

SIGTRAN SOFTWARE NETWORK ARCHITECTURE

Trillium SIGTRAN software encompasses the SCTP, IUA, M2UA, M3UA and SUA functionality defined by the IETF SIGTRAN Working Group.

STREAM CONTROL TRANSMISSION PROTOCOL (SCTP)

• Network level fault tolerance through support of multi-homing
• Persistent associations
• Reliable data transport to handle missing and duplicated datagrams
• Elimination of head-of-line blocking
• Immediate delivery of out-of-band data
• Detection of session failure
• User-controlled heartbeat generation
• Congestion control algorithms
• Bundling of multiple application PDUs into a single message for improved transport efficiency
• Data segmentation to conform to discovered path MTU size
• Random tag and authentication cookie security mechanisms

ISDN USER ADAPTATION LAYER (IUA)

• Backhauls Q.921 user messages (X.25, Q.931, Q.SIG) over IP using SCTP
• Transport of Q.921/Q.931 (Q.921/X.25, Q.921/Q.SIG) boundary primitives
• Communication between protocol management modules on the SG and MGC
• Supports management of active associations between the SGs and MGCs

LAPV USER ADAPTATION LAYER (V5UA)

• Backhauls LAPV user signaling (i.e. V5) messages over IP using SCTP
• Management of active associations between SGP and ASP
• Mapping between a V5 interface ID and the physical interface (E1), and the associated signaling channel at the SGP

DPNSS/DASS2 USER ADAPTATION LAYER (DUA)

• Backhauls DPNSS or DASS2 user (i.e. DPNSS Layer 3) signaling messages over IP using SCTP
• Management of active associations between SGP and ASP
• Mapping between a DPNSS/DASS2 user type and the physical interface (E1), and the associated signaling channel at the SGP

MTP LEVEL 2 USER ADAPTATION LAYER (M2UA)

• Backhauls SS7 MTP Level 3 user signaling messages over IP using SCTP
• Transport of MTP Level 2/MTP Level 3 boundary primitives
• Communication between protocol management modules on the SG and MGC
• Supports management of active associations between the SGs and MGCs

MTP2-USER PEER-TO-PEER ADAPTATION LAYER (MTP2)

• Backhauls SS7 MTP Level 3 user signaling messages over IP using SCTP in peer-to-peer architectures
• Transport of MTP Level 2/MTP Level 3 boundary primitives
• Used between
  • SG and MGC
  • SG and IPSP
  • IPSP and IPSP
• Supports management of active associations between the SGs, MGCs, and IPSPs

MTP LEVEL 3 USER ADAPTATION LAYER (M3UA)

• Supports the transport of any SS7 MTP Level 3 user signaling (ISUP and SCCP) messages over IP using SCTP
• Mapping of primitives received from the MTP Level 3 user layer to the corresponding SCTP primitives, associations, streams and vice-versa
• Same upper interface as MTP Level 3
• Carries MTP Level 3 User Part Signaling, such as ISUP, SCCP and TUP
• Management of SCTP transport associations between the SG and MGC/IP databases
• Nodal Interworking Function that provides seamless mapping between MTP Level 3 and M3UA
• Active association control and failover
• Seamless interworking of MTP Level 3 network management functions between SS7 and IP domains
• Dynamic routing key registration
• Ability to distribute user traffic to multiple application server processors within an application server

SCCP USER ADAPTATION LAYER (SUA)

• Supports the transport of SCCP user signaling (TCAP, RANAP) messages over IP using SCTP.
• Carries SCCP User Part signaling such as TCAP and RANAP
• Allows seamless interworking between SCCP in both the SS7 and IP domains
• Supports operation between SCCP peers in an all-IP domain