The size of an enterprise network drives the design and placement of certain
types of devices. If the network is designed according to the Enterprise
Composite Network model, there will be distinct devices separating the access,
distribution and backbone areas of the network. The network design and the
types of applications supported will determine where certain traffic sources
are located. In the case of multicast and IP telephony applications, they do
share some common traffic types. Specifically, if a Cisco CallManager is
providing music on hold, it may need to multicast that traffic stream.
Similarly, if there is an IPTV broadcast server on the network it will also be
sending information via multicast to a specific set of devices. Use these
considerations when determining where to place the servers:
- IP multicast servers may exist within a server farm, or be distributed
through the network at appropriately designed locations. Select distribution
layer switches to act as rendezvous points and which are central to the
location of the largest distribution of receiving nodes.
- Cisco CallManager servers must be accessible throughout the network at all
times. Ensure redundant NICs in the publisher and subscriber servers and
redundant connections between those NICs and the upstream switch from the
server. It is recommended that voice traffic be configured on its own
VLAN.
- VLAN trunks must be configured appropriately to carry IP telephony traffic
throughout the network, or to specific destinations.