Cisco Cisco Customer Response Solution Downloads 设计指南
C H A P T E R
8-1
Cisco IPCC Express Solution Reference Network Design
9560890308
8
Bandwidth, Security, and QoS Considerations
This chapter presents some design considerations for provisioning network bandwidth, providing
security and access to corporate data stores, and ensuring Quality of Service (QoS) for IPCC Express
applications.
security and access to corporate data stores, and ensuring Quality of Service (QoS) for IPCC Express
applications.
Estimating Bandwidth Consumption
Bandwidth plays a large role in deployments involving:
•
The centralized call processing model (IPCC Express at either the central site or remote sites)
•
Any call deployment model that uses call admission control or a gatekeeper
Remote Agent Traffic Profile
IPCC Express signaling represents only a very small portion of control traffic (Cisco CallManager CTI
and ICD subsystems) in the network. For information on TCP ports and Differentiated Services Code
Point (DSCP) marking for IPCC Express ICD and CTI traffic, see the sections on
and ICD subsystems) in the network. For information on TCP ports and Differentiated Services Code
Point (DSCP) marking for IPCC Express ICD and CTI traffic, see the sections on
, and
.
Bandwidth estimation becomes an issue when voice is included in the calculation. Because WAN links
are usually the lowest-speed circuits in an IP Telephony network, particular attention must be given to
reducing packet loss, delay, and jitter where voice traffic is sent across these links. G.729 is the preferred
codec for use over the WAN because the G.729 method for sampling audio introduces the least latency
(only 30 msecs) in addition to any other delays caused by the network.
are usually the lowest-speed circuits in an IP Telephony network, particular attention must be given to
reducing packet loss, delay, and jitter where voice traffic is sent across these links. G.729 is the preferred
codec for use over the WAN because the G.729 method for sampling audio introduces the least latency
(only 30 msecs) in addition to any other delays caused by the network.
Where voice is included in bandwidth, system architects should consider the following factors:
•
Total delay budget for latency (taking into account WAN latency, serialization delays for any local
area network traversed, and any forwarding latency present in the network devices). The generally
agreed-upon limit for total (one-way) latency for applications in a network is 150 msecs.
area network traversed, and any forwarding latency present in the network devices). The generally
agreed-upon limit for total (one-way) latency for applications in a network is 150 msecs.
•
Impact of delays inherent in the applications themselves. 25 seconds is the initial IPCC Express
agent login setup time with no WAN delay. The overall time to log in agents and base delay adds
approximately 30 secs of delay per 70 msecs of WAN delay.
agent login setup time with no WAN delay. The overall time to log in agents and base delay adds
approximately 30 secs of delay per 70 msecs of WAN delay.
•
Impact of routing protocols. For example, Enhanced Interior Gateway Routing Protocol (EIGRP)
uses quick convergence times and conservative use of bandwidth. EIGRP convergence also has a
negligible impact on call processing and IPCC Express agent logins.
uses quick convergence times and conservative use of bandwidth. EIGRP convergence also has a
negligible impact on call processing and IPCC Express agent logins.
Use
to estimate the number of IPCC Express agents that can be maintained across the WAN
(with IP Telephony QoS enabled). These numbers are derived from testing where an entire call session
to IPCC Express agents, including G.729 RTP streams, is sent across the WAN. Approximately 30% of
bandwidth is provisioned for voice. Voice drops are more of an issue when you are running RTP in
to IPCC Express agents, including G.729 RTP streams, is sent across the WAN. Approximately 30% of
bandwidth is provisioned for voice. Voice drops are more of an issue when you are running RTP in