Chapter 6. Configuring Queuing to Manage Traffic

Queuing Overview  Prioritizes traffic through router  Cisco IOS offers weighted fair queuing,priority queuing, and custom queuing SNA IPX IP IPXIPSNA

The Need for Traffic Prioritization  Delay-sensitive applications may require higher priority than others File Transfer Interactive Traffic

Effective Use of Traffic Priorization  Priorization is most effective on bursty WAN links (T1/E1 or below) that experience temporary congestion IPX IP AppleTalk S0 T1/E1

IPX IP AppleTalk Establishing a Queuing Policy  Determines which packets get through first  Helps provide acceptable service levels and control WAN costs Traffic Queue Bottleneck

Determine traffic priorities Choosing a Cisco IOS Queuing Option No need for queuing WAN congested ? Strict control needed? Queuing policy? Delay OK? Use weighted fair queuing Use priority queuing Step1Step2Step3Step4 Yes No Custom Queuing

Configuring Weighted Fair Queuing

Data Stream Classification Low-Volume Traffic FIFO Queuing High-Volume Traffic Low-Volume Traffic

Discriminates between sessions Automatically “fairly” allocates bandwidth for each session Priority users get needed bandwidth Other users share remaining bandwidth Session 1Session 2 Session 3 Session 4 Premium Gets what it needs. Standard Shares remaining bandwidth Premium Gets what it needs Standard Shares remaining bandwidth Weighted Fair Queuing

Fair Queuing Operation  Messages are sorted into conversations Packets in order of arrival

 Conversations are assigned a channel  Sorts the queu by order of the last bit crossing its channel Fair Queuing Operation (cont.) Packets fair queuedFair queue

 Messages are transmitter in a fair order  High-volume conversations share the link Fair Queuing Operation (cont.)

Weighted Fair Queue Example Frame Relay Network interface Serial1 encapsulation frame-relay fair-queue 128 bandwidth 56 interface Serial1 encapsulation frame-relay fair-queue 128 bandwidth 56

Configuring Priority Queuing

Priority Queuing LOW Packet arrives Selects one of these Priority List for S0 HIGH MEDIUM NORMAL S0

Priority Queuing Operation Dispatch Packet Place in Queue Incoming Packet Select Queue NORMAL Packet? HIGH Packet? MEDIUM Packet? LOW Packet? Timeout ? Queue full? Queue service No To Yes More? Queue selectionWAN

Telnet IPX AppleTalk Default Telnet IPX AppleTalk Default Priority Queuing Configuration Tasks LOW HIGH MEDIUM NORMAL Telnet IPX AppleTalk Default Telnet IPX AppleTalk Default To configure priority queuing perform the following tasks: 1. Create priority list based on protocol or interface 2. Assign a default queue 3. Specify the queue sizes (optional) 4. Assign the priority list to an interface To configure priority queuing perform the following tasks: 1. Create priority list based on protocol or interface 2. Assign a default queue 3. Specify the queue sizes (optional) 4. Assign the priority list to an interface S0 Priority List for S0

Priority List Configuration Commands  Sets queue priority by protocol type Router (config) # Priority-list list-munber protocol protocol-name { high | medium | normal | low} queue/keyword keyword-value Sets priority by incoming interface type Router (config) # Priority-list list-munber interface interface-type interface-number { high | medium | normal | low}

Priority List Configuration Commands (cont.)  Assigns a default queue Router (config) # priority-list list-munber default { high | medium | normal | low} Specifies the queue sizes Router (config) # priority-list list-munber queue-limit high-limit medium-limit normal-limit low-limit Links priority list to an interafce Router (config) # Priority-group list

Priority Queuing Example LOW HIGH MEDIUM NORMAL priority-list 1 protocol ip high tcp 23 priority-list 1 protocol appletalk medium priority-list 1 protocol ipx medium priority-list 1 protocol ip normal priority-list 1 default low ! Interface serial 0 priority-group 1 priority-list 1 protocol ip high tcp 23 priority-list 1 protocol appletalk medium priority-list 1 protocol ipx medium priority-list 1 protocol ip normal priority-list 1 default low ! Interface serial 0 priority-group 1 S0

Configuring Custom Queuing

Custom Queuing  Queues handled in round-robin fashion S0 2 1 (system) High priority (keepalive) Custom Queue List for S0 Deliver x number of bytes per cycle 0 Default 20 entires

Custom Queuing Operation Custom Queue List for S0 Traffic Filtering S0 Next Queue Current Queue Dispatch Packet To WAN Over Service Threshold ? More ? Queued Message Forwarding NoYes

Custom Queuing Configuration 1 1 S0 To configure custom queuing perform the following tasks: 1. Set custom queuing filtering for protocols or interfaces 2. Assign a default queue 3. Change queue capacity (optional) 4. Configure the transfer rate per queue 5. Assign the custom queue-list to an interface To configure custom queuing perform the following tasks: 1. Set custom queuing filtering for protocols or interfaces 2. Assign a default queue 3. Change queue capacity (optional) 4. Configure the transfer rate per queue 5. Assign the custom queue-list to an interface Default Queue

Custom Queue Configuration Commands Router(config)# queue-list list-number protocol protocol-name queue-number queue-keyword keyword-value queue-list list-number protocol protocol-name queue-number queue-keyword keyword-value Sets queue priority by protocol type Router(config)# queue-list list-number interface interface-type interface-number queue-number queue-list list-number interface interface-type interface-number queue-number Sets priority by interface type

Custom Queue Configuration Commands (cont.) Router(config)# queue-list list-number default queue-number Assigns a default queue priority Router(config)# queue-list list-number queue queue-numer limit limit-number queue-list list-number queue queue-numer limit limit-number Changes the capacity of a queue

Custom Queue Configuration Commands (cont.) Router(config)# queue-list list-number queue queue-number byte-count byte-count-number queue-list list-number queue queue-number byte-count byte-count-number Assigns a default queue priority Router(config-if)# custom-queue-list list Assigns a queue list to an interface

Custom Queuing Example queue-list 1 interface E0 1 queue-list 1 protocol ip 2 queue-list 1 protocol ipx 3 queue-list 1 protocol vines 4 queue-list 1 default 5 ! interface serial 3/2 custom-queue-list 1 queue-list 1 interface E0 1 queue-list 1 protocol ip 2 queue-list 1 protocol ipx 3 queue-list 1 protocol vines 4 queue-list 1 default 5 ! interface serial 3/2 custom-queue-list 1 S0

Custom Queuing Example queue-list 1 protocol ip tcp 20 queue-list 1 protocol ip 2 queue-list 1 protocol ipx 3 queue-list 1 protocol vines 4 queue-list 1 default 5 queue-list 1 queue 1 byte-count 3000 ! interface serial 3/2 custom-queue-list 1 queue-list 1 protocol ip tcp 20 queue-list 1 protocol ip 2 queue-list 1 protocol ipx 3 queue-list 1 protocol vines 4 queue-list 1 default 5 queue-list 1 queue 1 byte-count 3000 ! interface serial 3/2 custom-queue-list 1 S0 2 datagrams per cycle

Queuing Comparison Weighted Fair Queuing No queue lists Low volume given priority Conversation dispatching Interactive traffic gets priority File transfers get balanced access Enabled by default Priority Queuing 4 queues High queue serviced first Packet dispatching Critical traffic gets through Designed for low-bandwidth links Custom Queuing 16 queues Round-robin serviced Threshold dispatching Allocation of available bandwidth Best suited for high-bandwidth links