Cisco Unified Contact Center Enterprise Solution Reference ...

Bandwidth and Latency Requirements
Private Network Traffic Flow
11-8
Cisco Unified Contact Center Enterprise 7.x SRND
Chapter 11 Bandwidth Provisioning and QoS Considerations
Low-priority traffic — Includes historical data traffic, configuration traffic from the Central
Controller, and call close notifications. The low-priority traffic is sent in TCP with the public
high-priority IP address.
Administrative Workstations (AWs) are typically deployed at ACD sites, and they share the physical
WAN/LAN circuits that the PGs use. When this is the case, network activity for the AW must be factored
into the network bandwidth calculations. This document does not address bandwidth sizing for AW
traffic.
Traffic destined for the critical Message Delivery Service (MDS) client (Router or OPC) is copied to the
other side over the private link.
The private traffic can be summarized as follows:
High-priority traffic — Includes routing, MDS control traffic, and other traffic from MDS client
processes such as the PIM CTI Server, Logger, and so forth. It is sent in TCP with the private
high-priority IP address.
Heartbeat traffic — UDP messages with the private high-priority IP address and in the port range of
39500 to 39999. Heartbeats are transmitted at 100-ms intervals bidirectionally between the duplexed
sides. In Unified ICM Release 7.0, the UDP heartbeat is replaced with TCP keep-alive if QoS is
enabled on the private network interface through the Unified ICM setup.
Medium-priority and low-priority traffic — For the Central Controller, this traffic includes shared
data sourced from routing clients as well as (non-route control) call router messages, including call
router state transfer (independent session). For the OPC (PG), this traffic includes shared non-route
control peripheral and reporting traffic. This class of traffic is sent in TCP sessions designated as
medium-priority and low-priority, respectively, with the private non-high priority IP address.
State transfer traffic — State synchronization messages for the Router, OPC, and other synchronized
processes. It is sent in TCP with a private non-high-priority IP address.
Bandwidth and Latency Requirements
The amount of traffic sent between the Central Controllers (call routers) and Peripheral Gateways is
largely a function of the call load at that site, although transient boundary conditions (for example,
startup configuration load) and specific configuration sizes also affect the amount of traffic. A rule of
thumb that works well for Unified ICM software prior to Release 5.0 in steady-state operation is:
1,000 bytes (8 kb) of data is typically sent from a PG to the Central Controller for each call that arrives
at a peripheral. Therefore, if a peripheral is handling 10 calls per second, we would expect to need
10,000 bytes (80 kb) of data per second to be communicated to the Central Controller. The majority of
this data is sent on the low-priority path. The ratio of low to high path bandwidth varies with the
characteristics of the deployment (most significantly, the degree to which post-routing is performed), but
generally it is roughly 10% to 30%. Each post-route request generates between 200 and 300 additional
bytes of data on the high-priority path. Translation routes incur per-call data flowing in the opposite
direction (Central Controller to PG), and the size of this data is fully dependent upon the amount of call
context presented to the desktop.
A site that has an ACD as well as a VRU has two peripherals, and the bandwidth requirement calculations
should take both peripherals into account. As an example, a site that has 4 peripherals, each taking 10
calls per second, should generally be configured to have 320 kbps of bandwidth. The 1,000 bytes per call
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