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Please confirm my priority queue setting

Posted on 2000-04-18
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Last Modified: 2010-04-17
   I wanted to modify the cisco2501's priority queue setting, but  I am not sure if I did the right thing. Please help to analyze it.
    The IOS is 11.2. Serial0 link to ISP through DDN, Ethernet0 link to company network.  I wanted to let the iis/proxy server(Internet ip address is 10.0.0.3,for example) be the high priority, email server(Internet ip address is 10.0.0.4,for example) be the medium, others be normal or even low.
What the command I am going to type is:

#conf t                                                                  .......line 1
(config)#access-list 2 permit 10.0.0.3                   .......line 2
(config)#access-list 3 permit 10.0.0.4                   .......line 3
(config)#access-list 4 permit 10.0.0.0 0.0.0.15     .......line 4
(config)#int e0                                                      .......line 5
(config-if)#ip access-group 4                                .......line 6
(config-if)#exit                                                      .......line 7
(config)#priority-list 1 protocol ip high list 2          .......line 8
(config)#priority-list 1 protocol ip medium list 3     .......line 9
(config)#priority-list 1 protocol ip normal list4        .......line 10
(config)#int e0                                                       .......line 11
(config-if)#priority-group 1                                     .......line 12

I doubt if I make some mistake in design or miss some setting to achieve my goal. Please give me some advice. Any is welcome. Thanks a lot! BTW, if you think this question should worth more point, please info me.
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Question by:maixp
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Expert Comment

by:cdukes
ID: 2726835


priority-list protocol
----------------------------------------
To establish queuing priorities based on the protocol type, use the priority-list protocol global configuration command. Use the no form of this command with the appropriate list number to remove an entry from the list.

priority-list list -number protocol protocol-name {high | medium | normal | low}
queue-keyword keyword-value
no priority-list list -number protocol
Syntax Description
list-number  Arbitrary integer between 1 and 10 that identifies the priority list selected by the user.  
protocol-name  Specifies the protocol type: aarp, arp, apollo, appletalk, bridge (transparent), clns, clns_es, clns_is, compressedtcp, cmns, decnet, decnet_node, decnet_router-l1, decnet_router-l2, ip, ipx, pad, rsrb, stun, vines, xns, and x25.  
high | medium | normal | low  Priority queue level.  
queue-keyword keyword-value  Possible keywords are fragments, gt, lt, list, tcp, and udp. See Table 13-4.  

Default
No queuing priorities are established.

Command Mode
Global configuration.

Usage Guidelines
When using multiple rules for a single protocol, remember that the system reads the priority settings in order of appearance. When classifying a packet, the system searches the list of rules specified by priority-list commands for a matching protocol type. When a match is found, the packet is assigned to the appropriate queue. The list is searched in the order it is specified, and the first matching rule terminates the search.

The decnet_router-l1 keyword refers to the multicast address for all level-1 switches, which are inter-area switches, and the decnet_router-l2 keyword refers to all level 2 switches, which are inter-area switches.

Use Table 13-4, Table 13-5, and Table 13-6 to configure the queuing priorities for your system.


Table  13-4: Protocol Priority Queue Keywords and Values Option  Description  
fragments  Assigns the priority level defined to fragmented IP packets (for use with IP protocol only). More specifically, IP packets whose fragment offset field is nonzero are matched by this command. The initial fragment of a fragmented IP packet has a fragment offset of zero, so such packets are not matched by this command.
Note: Packets with a nonzero fragment offset do not contain TCP or UDP headers, so other instances of this command that use the tcp or udp keyword always fail to match such packets.
 
gt byte-count  Specifies a greater-than count. The priority level assigned goes into effect when a packet exceeds the value entered for the argument byte-count. The size of the packet must also include additional bytes due to MAC encapsulation on the outgoing interface.  
lt byte-count  Specifies a less-than count. The priority level assigned goes into effect when a packet size is less than the value entered for byte-count. The size of the packet must also include additional bytes due to MAC encapsulation on the outgoing interface.  
list list-number  Assigns traffic priorities according to a specified list when used with Appletalk, bridging, IP, IPX, VINES, or XNS. The list-number argument is the access list number as specified by the access-list global configuration command for the specified protocol-name. For example, if the protocol is AppleTalk, list-number should be a valid AppleTalk access list number.  
tcp port  Assigns the priority level defined to TCP segments originating from or destined to a specified port (for use with the IP protocol only). Table 13-5 lists common TCP services and their port numbers.  
udp port  Assigns the priority level defined to UDP packets originating from or destined to the specified port (for use with the IP protocol only). Table 13-6 lists common UDP services and their port numbers.  

Table  13-5: Common TCP Services and Their Port Numbers Service  Port  
Telnet  23  
SMTP  25  

Table  13-6: Common UDP Services and Their Port Numbers Service  Port  
TFTP  69  
NFS  2049  
SNMP  161  
RPC  111  
DNS  53  

--------------------------------------------------------------------------------
Note The TCP and UDP ports listed in Table 13-5 and Table 13-6 include some of the more common port numbers. However, you can specify any port number to be prioritized; you are not limited to those listed.
--------------------------------------------------------------------------------

Use the no priority-list global configuration command followed by the appropriate list-number argument and the protocol keyword to remove a priority list entry assigned by protocol type.

Examples
The following example assigns a high-priority level to traffic that matches IP access list 10.

Switch# priority-list 1 protocol ip high list 10

The following example assigns a medium-priority level to Telnet packets.

Switch# priority-list 4 protocol ip medium tcp 23

The following example assigns a medium-priority level to UDP Domain Name Service packets.

Switch# priority-list 4 protocol ip medium udp 53

The following example assigns a high-priority level to traffic that matches Ethernet type code access list 201.

Switch# priority-list 1 protocol bridge high list 201

Related Commands
precedence
show queueing

priority-list queue-limit

--------------------------------------------------------------------------------
Note This command or some of its parameters might not function as expected in the LightStream 1010 ATM switch environment.
--------------------------------------------------------------------------------

To specify the maximum number of packets that can be waiting in each of the priority queues, use the priority-list queue-limit global configuration command.The no form of this command selects the normal queue.

priority-list list-number queue-limit high-limit medium-limit normal-limit low-limit
no priority-list list-number queue-limit
Syntax Description
list-number  Arbitrary integer between 1 and 16 that identifies the priority list selected by the user.  
high-limit medium-limit
normal-limit low-limit  Priority queue maximum length. A value of 0 for any of the four arguments means that the queue can be of unlimited size for that particular queue.  

Default
The default queue limit arguments are listed in Table 13-7.


Table  13-7: Priority Queue Packet Limits Priority Queue Argument  Packet
Limits  
high-limit  20  
medium-limit  40  
normal-limit  60  
low-limit  80  

Command Mode
Global configuration.

Usage Guidelines
If a priority queue overflows, excess packets are discarded and quench messages can be sent, if appropriate, for the protocol.

Example
The following example sets the maximum packets in the priority queue to 10.

Switch# priority-list 2 queue-limit 10 40 60 80





priority-group

----------------------------------------To assign the specified priority list to an interface, use the priority-group interface configuration command. Use the no form of this command to remove the specified priority group assignment.

priority-group list
no priority-group
Syntax Description
list  Priority list number assigned to the interface.  

Default
None.

Command Mode
Interface configuration.

Usage Guidelines
Only one list can be assigned per interface. Priority output queueing provides a mechanism to prioritize packets transmitted on an interface.

Example
The following example causes packets on interface auxiliary 0 to be classified by priority list 1.

Switch(config)# interface aux 0
Switch(config-if)# priority-group 1

Related Commands
priority-list interface
priority-list queue-limit
privilege level (global)


priority-list default

----------------------------------------To assign a priority queue for those packets that do not match any other rule in the priority list, use the priority-list default global configuration command. Use the no form of this command to return to the default or assign normal as the default.

priority-list list-number default {high | medium | normal | low}
no priority-list list-number default {high | medium | normal | low}
Syntax Description
list-number  Arbitrary integer between 1 and 10 that identifies the priority list selected by the user.  
high | medium | normal | low  Priority queue level.  

Default
The normal queue is assumed if you use the no form of the command.

Command Mode
Global configuration.

Example
The following example sets the priority queue for those packets that do not match any other rule in the priority list to a low priority.

Switch# priority-list 1 default low

Related Commands
precedence
show queueing


priority-list interface
----------------------------------------

To establish queuing priorities on packets entering from a given interface, use the priority-list interface global configuration command. Use the no form of this command with the appropriate arguments to remove an entry from the list.

priority-list list-number interface interface-type interface-number {high | medium |
normal | low}
no priority-list list-number interface interface-type interface-number {high | medium |
normal | low}
Syntax Description
list-number  Arbitrary integer between 1 and 10 that identifies the priority list selected by the user.  
interface-type  Specifies the name of the interface.  
interface-number  Number of the specified interface.  
high | medium | normal | low  Priority queue level.  

Default
No queuing priorities are established.

Command Mode
Global configuration.

Example
The following example sets any packet type entering on Ethernet interface 2/0/0 to a medium priority.

Switch# priority-list 3 interface ethernet 2/0/0 medium

Related Commands
precedence
show queueing
0
 

Author Comment

by:maixp
ID: 2729200
   Sorry, Cdukes, I have to reject your answer. I am a beginner in Cisco Router but I can check the Cisco Tech Documents like ACRC myself. So, I don't need the PURE documents at this moment. It seems that I should describe my request more detail:
    What I mostly want  to know is that IF MY DESIGN, PLAN AND COMMAND IS  RIGHT.  Please notice my question title: PLEASE CONFIRM MY PRIORITY QUEUE SETTING. The answer/comment, I hope, should be one of these 2 type:
1) Yes, you setting is right. But I have a better idea.....if you change/add the line * to .... that will be much better.
2) No, you won't reach your goal. The command line * is wrong. The correct design and command should be ..... instead of line *'s command.
I am waiting for other experts.
Thanks a lot!
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Accepted Solution

by:
apadua earned 50 total points
ID: 2729327
Looking good. The only thing I see is that you forgot in line six, to specify if this access-list is "in" or "out". Don't really remember which one, if any, Cisco defaults to.

Anyways, seems like it's perfect.

The other thing you need to worry about is if this is a good thing. Other machines may never get to use the net during peak times, because the proxy server is so busy, it never leaves room for others. Also, make sure you don't overrun the buffer size for each queue. The queue size for each priority, by default, is high=20, med=40, norm=60 and low=80. This means that when you get 20 packets in the high buffer, the router will drop packets and your machine will receive "quench" signalling, to slow down its comm. During these moments, be sure that folks on other queues will be suffering to get any type of network attention.

It's a matter of installing, measuring improvement during peak hours, then customizing until you're satisfied.

The command for setting up the buffer size is:

priority-list 1 queue-limit 20 40 60 80

Make sure you replace the numbers with the appropriate sizes for each one of the queues.

If I think of anything else, I'll let you know.


Cheers,

Andre
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Author Comment

by:maixp
ID: 2729500
To Andre:
Thank you for your help!
Yes, I forgot the "in" in command line 6.
   For the peak hour, if I set the high-limit too small, the iis/proxy server will receive "quench" signalling, to slow down its communications, or even lost some packages, right? So I have to increase the value to a proper one, like 40 or above, right?
    Besides, I think that most of the users in company network will access Internet via proxy during working hour, and the emails and be delivered at non-peak hour, at night, for example. Then other Internet IP computers have no necessary to access the router. They can be the backup machine in case the proxy server or email server fails. Does my thinking right?
   

Regards

Maixp
0
 
LVL 3

Expert Comment

by:apadua
ID: 2730985
I'd start with the default values for the queues.

Leave it at 20 40 60 80 to begin.

If you find out that it's slower than before, then you start altering things.

Good luck,


Andre
0
 

Author Comment

by:maixp
ID: 2732767
Since I just wanted to get a confirm from the experts. Who can give me the confirm and advice, I will recept it as answer. Of course, they should be active.
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