Nework Components 3 (part 4)

Signaling Gateway

The Signaling Gateway is located in the service provider’s network and acts as a gateway between the call agent signaling and the SS7-based PSTN. It can also be used as a signaling gateway between different packetbased carrier domains. It may provide signaling translation, for example between SIP and SS7 or simply signaling transport conversion e.g. SS7 over IP to SS7 over TDM.

 

Trunking Gateway

The Trunking Gateway is located in the service provider’s network and as a gateway between the carrier IP network and the TDM (Time Division Multiplexing)-based PSTN. It provides transcoding from the packetbased voice, VoIP onto a TDM network. Typically, it is under the control of the Call Agent / Media Gateway Controller through a device control protocol such as H.248 (Megaco) or MGCP.

Access Gateway

The Access Gateway is located in the service provider’s network. It provides support for POTS phones and typically, it is under the control of the Call Agent / Media Gateway Controller through a device control protocol such as H.248 (Megaco) or MGCP.

Access Concentrator

The Access Concentrator is located in the service provider’s network and terminates the service provider end of the WAN links used over the “last mile”. For example, in a DSL network, this is a DSLAM; in a cable network, a CMTS.  The Access Concentrator may also include the Access Gateway function, for example a Next-Generation DLC that combines DSLAM capability with direct POTS termination. 

Bandwidth Manager

The Bandwidth Manager is located in the service provider’s network and is responsible for providing the required QoS from the network. It is responsible for the setting up and tearing down of bandwidth within the network and for controlling the access of individual calls to this bandwidth. It is responsible for installing the appropriate policy in edge routers to police the media flows on a per call basis. 

Edge Router

The Edge Router is located in the service provider’s network and routes IP traffic onto the carrier backbone network. Typically the edge router will provide many other functions and can be combined with the Access Concentrator.

Subscriber Gateway

The Subscriber Gateway is located at the customer premises and terminates the WAN (Wide Area Network) link (DSL, T1, fixed wireless, cable etc) at the customer premises and typically provides both voice ports and data connectivity. Usually, it uses a device control protocol, such as H.248 (Megaco) or MGCP/NCS, under the control of the Call Agent. It provides similar function to the Access Gateway but typically supports many fewer voice ports.  Subscriber Gateways are also known as IADs, Residential Gateways, or MTAs (in a cable network). 

Bridge/Router

The Bridge/Router is located at the customer premises and terminates the WAN (Wide Area Network) link (DSL, T1, fixed wireless, cable etc) at the customer premises. The difference between this and the Subscriber Gateway is a bridge/router does not provide any native voice support, although voice services for example SIP phones, can be bridged/routed via this device. 

IP Phone/PBX

IP Phones and PBX systems are located at customer premises and provide voice services. They interact with the Call Agent/SIP Server using a signaling protocol such as SIP, H.323 or a device control protocol such as H.248 (Megaco) or MGCP.