User's Manual 280 Document #: LTRT-27055
Mediant 1000B Gateway & E-SBC
Once the device receives the resultant destination hop from the Routing server, it sends
the call to that destination. The Routing server can provide the device with an appropriate
route or reject the call. However, if for the initial request (first sent Get Route request for
the call) the Routing server cannot find an appropriate route for the call or it does not
respond, for example, due to connectivity loss (i.e., the Routing server sends an HTTP 404
"Not Found" message), the device routes the call using its routing tables. If the Get Route
request is not the first one sent for the call (e.g., in call forwarding or alternative routing)
and the Routing server responds with an HTTP 404 "Not Found" message, the device
rejects the call.
This HTTP request-response transaction for the routing path occurs between Routing
server and each device in the route path (hops) as the call traverses the devices to its final
destination. Each device in the call path connects to the Routing server, which responds
with the next hop in the route path. Each device considers the call as an incoming call from
an IP Group or Trunk Group. The session ID (SID) is generated by the first device in the
path and then passed unchanged down the route path, enabling the Routing server to
uniquely identify requests belonging to the same call session.
Communication between the device and the Routing server is through the device's
embedded Representational State Transfer (RESTful) API. The RESTful API is used to
manage the routing-related information exchanged between the Routing server (RESTful
server) and the device (RESTful client). When you have configured the device with
connection settings of the Routing sever and the device starts-up, it connects to the
Routing server and activates the RESTful API, which triggers the routing-related API
commands.
The following figure provides an example of information exchange between devices and a
Routing server for routing calls:
Figure 15-43: Example of Call Routing Information Exchange between Devices and Routing
Server
The Routing server can also manipulate call data such as calling name, if required. It can
also create new IP Groups and associated configuration entities, if necessary for routing.
Multiple Routing servers can also be employed, whereby each device in the chain path can
use a specific Routing server. Alternatively, a single Routing server can be employed and
used for all devices ("stateful" Routing server).
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