Cisco VN 2900 Series Video Networking Systems

Document ID: 12509

Contents

Introduction
Prerequisites
      Requirements
      Components Used
      Conventions
General Guidelines
ATM Guidelines
IP Guidelines
Related Information

Introduction

This document provides guidelines for calculating the buffer size, or maximum transmission unit (MTU), for any Cisco Video Networking (VN) product.

Prerequisites

Requirements

There are no specific requirements for this document.

Components Used

This document is not restricted to specific software and hardware versions.

Conventions

Refer to Cisco Technical Tips Conventions for more information on document conventions.

General Guidelines

• MTU is often dependent on the specific requirements of the Set Top Box (STB).

• The MTU must be divisible by 188. A value that is divisible by 376 is ideal. The default value for IP is 1316; the default for ATM is 1504.

ATM Guidelines

• The maximum MTU value is approximately 9000. However, this value can be further limited by the STB.

• The minimum MTU value is 1316.

• The pace value is approximately 8000.

• The Next Level Communications (NLC) value must be 376. No other NLC value is acceptable.

• The larger the MTU, the better the performance.

IP Guidelines

• The maximum MTU for Cisco switches is 1316.

• When you use multicast, use the same MTU value on each stream, or use an even multiple of the lowest MTU value. For example, if you use IP, MTU values of 1316 and 2632 work, or if you use ATM, 1504 and 3008.

• The default MTU of the Cisco PS2000 decoder is 2632.

• Setting a IP sink to Real-Time Transport Protocol (RTP) over User Datagram Protocol (UDP) sets the default MTU size to 1452.

Related Information

• Technical Support & Documentation - Cisco Systems