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CCNP BCRAN Self-Study: Managing Network Performance with Queuing and Compression

Chapter Description

To help you prepare for the CCNP BCRAN exam, Brian Morgan and Craig Dennis discuss some of the advanced queuing techniques offered in Cisco IOS and compression techniques that are possible from Cisco routers.

Foundation Summary

This section is a collection of information that provides a convenient review of many key concepts in this chapter. If you are already comfortable with the topics in this chapter, this summary can help you recall a few details. If you just read this chapter, this review should help solidify some key facts. If you are doing your final preparation before the exam, these tables are a convenient way to review the day before the exam.

Table 15-5 summarizes the various advanced queuing techniques discussed in this chapter.

Table 15-5 Queuing Summary


Class-Based Weighted Fair


No configuration

Define flows (class-map), policy per flow (policy-map), and assign to an interface (service-policy)

Same configuration as CBWFQ, but add a priority queue for delay-sensitive traffic

No priority traffic

Administrator-defined policies

High-priority traffic has its own priority queue—guarantee of service

Traffic dispatched on first-come, first-served basis

Traffic dispatched using WFQ between flows, FIFO within flows

Priority queue is sent first, then remaining queues are WFQ, with FIFO within a queue

Table 15-6 summarizes the various queuing commands discussed in this chapter.

Table 15-6 Queuing Command Summary



class-map { match-all | match-any } class-map-name

Creates a data structure to select specific traffic.

match-all is an AND of all conditions within the class-map.

match-any is an OR of the conditions within the class-map.


Matches specific traffic within a class-map (defined below).

access-group {number | name}

Matches a numbered or named IP access list.


Matches all traffic.

class-map class-map-name

Creates a nested class-map.

cos IP-TOS

Matches the IP ToS bits.

destination-address mac MAC-address

Matches a specific destination MAC address.

input-interface interface

Matches the interface the traffic arrived on.

ip {dscp value | precedence value | rtp start-port port-range}

Matches various IP header values.

mpls experimental value

Matches the MPLS experimental bits.

protocol value

Matches any given protocol.

qos-group value

Matches traffic from a specific QoS group.

source-address mac MAC-address

Matches a specific source MAC address.

policy-map policy-map-name

Creates a data structure to reference one or more class-maps and is assigned to an interface.

class class-map-name

Maps the class-map (defined earlier) to the policy-map. There are many parameters (below) to reference only specific traffic within the class map.

bandwidth {Kbps-value | percent value}

Defines how traffic is handled during congested situation (CBWFQ).

priority Kbps-value

Defines how traffic is handled at all times (LLQ).

queue-limit #-packets

Defines how many packets may reside in a particular queue.

service-policy policy-map-name

Creates nested policy maps.

shape {average bps-value | max-buffers buffer-value | peak bps-value}

Defines traffic shaping (buffering) parameters.

police bps-value

Defines traffic policing (discarding) parameters.

set {cos value | ip value | mpls experimental value | qos-group value}

Allows marking of various parameters.

service-policy { input | output } policy-map-name

Assigns a policy map to an interface. Packet queuing is normally done outbound.

Table 15-7 summarizes the various advanced queuing techniques discussed in this chapter.

Table 15-7 Compression Summary





TCP Header

Compresses OSI Layers 2–7

Very CPU intensive

Memory intensive

Compresses OSI Layers 3–7

Compresses OSI Layers 3–4

Two algorithms = Stac and Predictor

Replaces redundant strings with tokens

Replaces text with smaller codes


Compresses ONLY IP and TCP headers


Does not expand encrypted or compressed data (no redundant strings)

Could possibly expand compressed data


Good for very small data packets


Open standard

Cisco proprietary

Open standard


Used across point-to-point circuits only

Can be used on both PPP and HDLC links

Can be used on PPP links only

Can be used on HDLC, PPP, and Frame Relay links

Can be used on any links