3.2 Overview of Multisite Connection Options

This topic describes multisite connection options.

The figure shows a Cisco Unified Communications Manager cluster at the main site with these connections:

  • ICT to another cluster located at a different site
  • An H.323 gateway that is located at a remote site
  • A SIP trunk that is connected to an ITSP via a Cisco Unified Border Element

In addition to the connection to the main site cluster, the remote cluster has the following connections:

  • Local MGCP gateway
  • Connection to the Internet through Cisco Expressway Series

Cisco Unified Communications Manager Connection Options Overview

In Cisco Unified Communications Manager, you can configure gateways and trunks for connections to the PSTNor to other call control systems.

  • Trunks
    1. SIP
      • Connection to any SIP device
    2. H.323
      • Direct connection to another Cisco Unified Communications Manager cluster
      • Connection to any H.323 device via a gatekeeper
  • Gateways
    • H.323 (any H.323 device when not using a gatekeeper)
    • MGCP
    • SCCP

You can configure trunks and gateways when you connect to devices that allow access to multiple endpoints. If the destination is a single endpoint, you can configure a phone as SCCP, SIP, or H.323.

Gateways are configured by the signaling protocol that they use. Cisco Unified Communications Manager supports H.323, MGCP, and SCCP gateways. Trunks can be configured as H.323 trunks (three types are available) or SIP trunks.

You can use H.323 trunks only when connecting to another Cisco Unified Communications Manager cluster, to Cisco Unified Communications Manager Business Edition, or when using an H.323 gatekeeper.

You can configure an H.323 gateway when you connect to any other H.323 device that is not an endpoint. Such devices can be Cisco IOS H.323 gateways or H.323 gateways of other vendors.

Cisco IOS Gateway Protocol Functions Review

The table shows Cisco IOS gateway protocol functions by protocol.

Function MGCP H.323 SIP
Clients Dumb Intelligent Intelligent
NFAS Not supported Supported Supported
QSIG Supported Not supported Not supported
Fractional T1/E1 More effort to implement Easy to implement Easy to implement
Signaling protocol TCP and UDP TCP TCP or UDP
Code basis ASCII Binary (ASN.1) ASCII
Call survivability No Yes Yes
Call applications usable No Yes Yes

As shown in the table, the three main gateway signaling protocols—MGCP, H.323, and SIP—provide various features and functions when implemented with Cisco Unified Communications Manager and Cisco IOS gateways.