Campus Architecture; Figure 14. Simplified Remote Campus Architecture - Aastra Clearspan Product Overview

2.4

Campus Architecture

In either premises-base or hosted PBX deployments, support for the remote campus or remote
office is largely the same. The campus may range from a couple of endpoints to over 10,000
endpoints. The figure below shows a simplified architectural view of the campus equipment.
The campus SBC, also known as the Enterprise SBC (ESBC), establishes a point-of-service within
the site. The SBC is usually paired with one or more media gateways that connect the campus to
the Public Switched Telephone Network (PSTN). Finally, one or more SIP endpoints (desktop or
soft clients) are deployed within the site.
The ESBC is a critical element and performs the following functions:

Serves as a service demarcation for hosted PBX service as well as SIP trunks from a
carrier

Monitors health of the WAN connection

Acts as a registration proxy

Maintains Address-of-Record (AOR) for all campus endpoints

Provides survivability features when the WAN is down

Routes calls to the media gateway for off-net calls or in support of E911

Throttles registration
Endpoints register with the local ESBC, which then registers with the SBCs in the core call
platform. The SIP Option method is used to ensure the WAN is available and if not, the ESBC may
be configured to pass calls to the local media gateway. See the E911 section for an overview of
the deployment option and support for 911/E911.
In addition to SIP terminals, the basic campus architecture can expand to include the following
items:

Analog phones

Fax machines

Overhead paging systems

Credit card processing machines
Clearspac® Product Overview R19
2014 Clearspan® is a Registered Trademark of Aastra Technologies Ltd.

Figure 14. Simplified Remote Campus Architecture.

Aastra – 2740-007
Page 29 of 93