Cisco Cisco Unified Customer Voice Portal 10.0(1)

For redundancy, Gatekeepers can be deployed in pairs using the HSRP (Hot Standby Routing
Protocol), one redundant pair per site.

Additionally, the VBAdmin SetGatekeeper command allows multiple IP addresses to be
configured. The H.323 Service then keeps track of a currently active Gatekeeper from that list,
beginning with the first, and sends all requests to that Gatekeeper. If the currently active
Gatekeeper fails, it moves to the next one in the list, and that one becomes current. The H.323
Service continues to use it until it too fails, at which time it begins using the subsequent
Gatekeeper in the list. When the list is exhausted, the next failover is back to the top.

Note that for sizing purposes, each individual Gatekeeper should be sized to handle the entire
load.

DNS Server

This optional component can be installed anywhere in the network. Its purpose, in general, is
to resolve hostnames to IP addresses. However, it can also be configured with multiple IP
addresses for the same hostname. Successive requests for a given hostname can be configured
to return IP addresses in a round-robin fashion. Unified CVP’s SIP design can make use of this
capability in order to implement a sort of load balancing among multiple like components.

The DNS (Domain Name System) Server comes into play during SIP interactions in the following
situations:

•

When a call arrives at an Ingress Gateway, the dial peer can use DNS to alternate calls between
the two SIP Proxy Servers. The SIP Proxy Servers can also use DNS to distribute incoming
calls among multiple SIP Services. If SIP Proxy Servers are not being used, then the Ingress
Gateway can use DNS directly to distribute inbound calls among multiple SIP Services.

•

When the SIP Service is instructed by Unified ICME to transfer the call to the VRU leg, it
can use DNS to alternate such requests between two SIP Proxy Servers, and the SIP Proxy
Servers can use DNS to distribute VRU legs among multiple VXML Gateways. If SIP Proxy
Servers are not being used, the SIP Service can use DNS directly to distribute VRU legs
among multiple VXML Gateways.

•

When transferring a call to an agent using a SIP Proxy Server, the SIP Proxy Server can use
DNS to identify the IP address target for that agent. Also, the SIP Service can use DNS to
alternate such requests between the two SIP Proxy Servers. If SIP Proxy Servers are not
being used, then the SIP Service can use DNS to locate the target agent’s IP address.

Note that use of the DNS Server for SIP routing is entirely optional in Unified CVP.

Content Services Switch

The Content Services Switch (CSS) is the focus for high availability design in the TCP
(Transmission Control Protocol) arena. The CSS can be placed between one (or more) VXML
Gateways and all its IVR Services, VoiceXML Servers, Media Servers, and ASR/TTS Servers.
Various mechanisms allow it to implement transparent load balancing and failover across these
types of devices.

Planning Guide for Cisco Unified Customer Voice Portal 4.0(1)