Version 7.2  281  Mediant 1000B Gateway & E-SBC 
 
User's Manual   15. Services 
The device automatically updates (sends) the Routing server with its' configuration 
topology regarding SIP routing-related entities (Trunk Groups, SRDs, SIP Interfaces, and 
IP Groups) that have been configured for use by the Routing server. For example, if you 
add a new IP Group and enable it for use by the Routing server, the device sends this 
information to the Routing server. Routing of calls associated with routing-related entities 
that are disabled for use by the Routing server (default) are handled only by the device (not 
the Routing server). 
In addition to regular routing, the Routing server also supports the following: 
  Alternative Routing: If a call fails to be established, the device "closest" to the failure 
and configured to send "additional" routing requests (through REST API - 
"additionalRoute" attribute in HTTP Get Route request) to the Routing server, sends a 
new routing request to the Routing server. The Routing server may respond with a 
new route destination, thereby implementing alternative routing. Alternatively, it may 
enable the device to return a failure response to the previous device in the route path 
chain and respond with an alternative route to this device. Therefore, alternative 
routing can be implemented at any point in the route path. If the Routing server sends 
an HTTP 404 "Not Found" message for an alternative route request, the device rejects 
the call. If the Routing server is configured to handle alternative routing, the device 
does not make any alternative routing decisions based on its alternative routing tables. 
  Call Status: The device can report call status to the Routing server to indicate 
whether a call has successfully been established and/or failed (disconnected). The 
device can also report when an IP Group (Proxy Set) is unavailable, detected by the 
keep-alive mechanism, or when the CAC thresholds permitted per IP Group have 
been crossed. For Trunk Groups, the device reports when the trunk's physical state 
indicates that the trunk is unavailable. 
  Credentials for Authentication: The Routing Server can provide user (e.g., IP Phone 
caller) credentials (username-password) in the Get Route response, which can be 
used by the device to authenticate outbound SIP requests if challenged by the 
outbound peer, for example, Microsoft Skype for Business (per RFC 2617 and RFC 
3261). If multiple devices exist in the call routing path, the Routing server sends the 
credentials only to the last device ("node") in the path. 
  QoS: The device can report QoS metrics per IP Group to the Routing server, which 
the Routing server can use to determine the best route (i.e., QoS-based routing). For 
more information, see Configuring QoS-Based Routing by Routing Server on page 
282. 
  Call Preemption for Emergency Calls: If you enable call preemption for emergency 
calls (e.g., 911) on the device, the routing server determines whether or not the 
incoming call is an emergency call and if so, handles the routing decision accordingly 
(i.e., preempts a non-emergency call if the maximum call capacity of the device is 
reached in order to allow the emergency call to be routed). To enable call preemption 
for emergency calls, use the parameter SBCPreemptionMode for SBC calls and 
CallPriorityMode for Gateway calls. 
  To configure routing based on Routing server: 
1.  For each configuration entity (e.g., IP Group) that you want routing done by the 
Routing server, configure the entity's 'Used By Routing Server' parameter to Used: 
Figure  15-44: Configuring Entity to Use Routing Server 
 
2.  Configure an additional Security Administrator user account in the Local Users table 
(see  ''Configuring Management User Accounts'' on page 74), which is used by the 
Routing server (REST client) to log in to the device's management interface. 
3.  Configure the address and connection settings of the Routing server, referred to as a