Specifications

ShoreTel Architecture Distributed Call Control
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ShoreTel 14 Maintenance Guide 17
The voice switches communicate on a peer-to-peer basis, eliminating any single point of failure. For
instance, if one ShoreTel voice switch goes offline, all other ShoreTel voice switches continue
operating. When the voice switch comes back online, it rejoins the voice network. There is no server
involved with the basic telephony, so the system delivers levels of availability unmatched by even
legacy vendors.
ShoreTel voice switches build an internal routing database from the peer-to-peer communication with
other switches. Each ShoreTel voice switch contains routing information for all endpoints in the
system, including information regarding trunk selection for outbound calls. (The exception is when
Distributed Routing Service is enabled. For more information, see Distributed Routing Service.) When
a user places a call from any extension, each switch can route the call to the correct ShoreTel voice
switch based on its internal routing database. Sites can typically support up to 500 ShoreTel voice
switches, depending on the system configuration.
The heart of the ShoreTel system is the distributed call control software that runs on the ShoreTel voice
switches, which run the VxWorks
®
real-time operating system, and on the ShoreTel voicemail-enabled
switches, which run the Linux operating system. Each call control element manages the call setup and
call teardown, including features such as transfer, conference, forward, call permissions, and call
routing.
Distributed Routing Service
Distributed Routing Service (DRS) allows larger systems to scale beyond 60 switches to a total of 500
switches (including softswitches). DRS is optional, but the following guidelines can help you determine
when to enable it:
 For deployments of 0 to 10,000 users, you can have a maximum of 100 switches without enabling
DRS.
 For deployments of 10,000 to 20,000 users, you can have a maximum of 60 switches without
enabling DRS.
 In a single-system image with more than 50 voice switches installed at sites that span continents
or are connected by an unreliable WAN, enabling DRS is recommended regardless of the number
of users.
When Distributed Routing Service is enabled:
 ShoreTel voice switches exchange routing information only with other switches configured in the
same site, rather than exchanging information with every switch in the system. Although each
ShoreTel voice switch maintains routing information for only the switches within its site, each
ShoreTel server also includes an instance of the Distributed Routing Service that maintains
system-wide routing information. When site-to-site calls are initiated, ShoreTel voice switches
contact the Distributed Routing Service to find the ShoreTel voice switch or switches necessary to
complete the call.
 The switch connectivity matrix in ShoreTel Director is organized by site.
 All trunk calls are first resolved using DRS.