Queuing Overview - FTP Directory Listing

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24 Οκτ 2013 (πριν από 3 χρόνια και 7 μήνες)

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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

IPX

IP

SNA

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

Step1

Step2

Step3

Step4

Yes

Yes

Yes

Yes

No

No

No

No

Custom
Queuing

Configuring Weighted

Fair Queuing

Data Stream Classification

Low
-
Volume Traffic

FIFO Queuing

High
-
Volume Traffic

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 1

Session 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

6

4

1

5

2

3

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.)

6

4

1

2

5

3

Packets fair queued

Fair queue

3

1

2

4

5

6


Messages are transmitter in a fair order


High
-
volume conversations share the link

Fair Queuing Operation (cont.)

6

1

2

5

3

4

Weighted Fair Queue Example

Frame Relay
Network


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

No

No

No

No

No

To

Yes

Yes

Yes

Yes

Yes

Yes

More?

Queue selection

WAN

Telnet


IPX



AppleTalk



Default

Priority Queuing Configuration Tasks

LOW

HIGH

MEDIUM

NORMAL

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

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

S0

Configuring Custom

Queuing

Custom Queuing


Queues handled in round
-
robin fashion

S0

2

1

(system)

3

14

15

16

High priority
(keepalive)

Custom Queue
List for S0

Deliver x number of
bytes per cycle

0

Default

20 entires

Custom Queuing Operation

2

1

3

14

15

16

Custom Queue
List for S0

Traffic Filtering

S0

Next
Queue

Current
Queue

Dispatch
Packet

To

WAN

Over
Service
Threshold
?

More ?

Queued Message Forwarding

No

Yes

Custom Queuing Configuration

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

2

3

4

. .

5

. .

14

16

15

Default
Queue

Custom Queue Configuration
Commands

Router(config)#

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



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



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



Assigns a default queue priority

Router(config
-
if)#

custom
-
queue
-
list
list



Assigns a queue list to an interface

Custom Queuing Example 1

1

2

3

4

5

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 2

1

2

3

4

5

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