Cisco 4G-LTE-ANTM-O-3 Installation Guide download pdf (Page 425)

and latency (required by some real-time and interactive traffic), and improved loss characteristics. QoS

technologies provide the elemental building blocks for future business applications in campus, WAN, and

service provider networks.

QoS must be configured throughout your network, not just on your router running VoIP, to improve voice

network performance. Not all QoS techniques are appropriate for all network routers. Edge routers and

backbone routers in your network do not necessarily perform the same operations; the QoS tasks they perform

might differ as well. To configure your IP network for real-time voice traffic, you need to consider the functions

of both edge and backbone routers in your network.

QoS software enables complex networks to control and predictably service a variety of networked applications

and traffic types. Almost any network can take advantage of QoS for optimum efficiency, whether it is a small

corporate network, an Internet service provider, or an enterprise network.

IP Precedence

You can partition traffic in up to six classes of service using IP Precedence (two others classes are reserved

for internal network use). The queuing technologies throughout the network can then use this signal to expedite

handling.

Features such as policy-based routing and committed access rate (CAR) can be used to set precedence based

on extended access-list classification. This allows considerable flexibility for precedence assignment, including

assignment by application or user, by destination and source subnet, and so on. Typically this functionality

is deployed as close to the edge of the network (or administrative domain) as possible, so that each subsequent

network element can provide service based on the determined policy.

IP Precedence can also be set in the host or network client with the signaling used optionally. IP Precedence

enables service classes to be established using existing network queuing mechanisms (such as class-based

weighted fair queueing [CBWFQ]) with no changes to existing applications or complicated network

requirements.

PPP Fragmentation and Interleaving

With multiclass multilink PPP interleaving, large packets can be multilink-encapsulated and fragmented into

smaller packets to satisfy the delay requirements of real-time voice traffic; small real-time packets, which are

not multilink encapsulated, are transmitted between fragments of the large packets. The interleaving feature

also provides a special transmit queue for the smaller, delay-sensitive packets, enabling them to be transmitted

earlier than other flows. Interleaving provides the delay bounds for delay-sensitive voice packets on a slow

link that is used for other best-effort traffic.

In general, multilink PPP with interleaving is used in conjunction with CBWFQ and RSVP or IP Precedence

to ensure voice packet delivery. Use multilink PPP with interleaving and CBWFQ to define how data is

managed; use Resource Reservation Protocol (RSVP) or IP Precedence to give priority to voice packets.

CBWFQ

In general, class-based weighted fair queuing (CBWFQ) is used in conjunction with multilink PPP and

interleaving and RSVP or IP Precedence to ensure voice packet delivery. CBWFQ is used with multilink PPP

to define how data is managed; RSVP or IP Precedence is used to give priority to voice packets.

Cisco 800 Series Integrated Services Routers Software Configuration Guide

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Concepts

IP Precedence

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Cisco 4G-LTE-ANTM-O-3 Installation Guide Page 425