Network Infrastructure Guide for Cisco Collaboration System 10.x

Quick Guide to Network Infrastructure

This document provides design and configuration guidelines for network infrastructure supporting Cisco Collaboration System 10.x. It covers the requirements for LAN, WAN, and Wireless LAN environments to ensure high availability and quality of service (QoS) for voice and video traffic.

LAN Infrastructure Design

Proper LAN design is essential for Unified Communications. It should be structured as a layered model consisting of the Access, Distribution, and Core layers. Key recommendations include:

• Access Layer: Assign a single IP subnet per VLAN. Limit the number of devices per VLAN to approximately 512 to manage broadcast traffic and ARP cache.
• Redundancy: Implement redundant links and devices to ensure high availability. Use Layer 3 links between redundant distribution switches to avoid topological loops.
• QoS: Enable end-to-end QoS. Classify traffic as close to the edge as possible. Use multiple egress queues on switches to prioritize voice and video traffic.

Network Services Configuration

Reliable network services are critical for collaboration endpoints:

• DNS: Use geographically redundant DNS servers. For basic deployments without DNS, configure endpoints to use IP addresses.
• DHCP: Use redundant DHCP servers. Configure DHCP Option 150 to provide TFTP server addresses to IP phones.
• TFTP: Used for configuration files and firmware. For large deployments, distribute TFTP servers and use load balancing by assigning different ordered lists of TFTP servers to different subnets.
• NTP: Synchronize all network devices to a common time source (Stratum 1, 2, or 3) to ensure accurate time-stamping of logs and CDRs.

WAN Infrastructure and QoS

WAN design must account for bandwidth limitations and potential link failures:

• Design: Choose topologies (hub-and-spoke, meshed) that provide fault tolerance. Use redundant WAN links where possible.
• QoS: Implement traffic shaping, link fragmentation and interleaving (LFI), and low-latency queuing (LLQ) to manage traffic on low-speed links.
• Bandwidth Provisioning: Provision bandwidth for both bearer traffic (voice/video) and call control signaling. Use the 75% rule (total bandwidth for applications should not exceed 75% of link capacity).

Wireless LAN Infrastructure

Wireless networks require specific considerations for voice and video:

• Architecture: Wireless access points (APs) and wireless LAN controllers (WLCs) are central components.
• High Availability: Ensure a 20% to 30% cell boundary overlap on non-adjacent channels for seamless roaming.
• Capacity Planning: Size the solution based on the supported capacity of the wireless endpoints.
• QoS: Use Wi-Fi Multimedia (WMM) and Traffic Specification (TSPEC) for call admission control. Configure QoS policies on APs to prioritize voice and video traffic.