Custom Queueing vs Rate-limit

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Jan 30th, 2004
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I was wondering which to use.


My goal is simple, I want businnes applications (Telnet, Oracle) to have priority over other protocols over a WAN link?


Just wanting to get some ideas as to which to use, which is more effective. The WAN link is a 256Kbps Frame-Relay connection.


Regards.

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cntp Fri, 01/30/2004 - 10:08
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I believe rate limit is more suitable for you

Shahzad Rasheed

Pakistan

michaeljmorris Sun, 02/01/2004 - 07:01
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No, queueing (be it custom, class-based, or priority) is what you need. Rate-limiting will not order traffic for you, it simply sets a ceiling for the amount of traffic that can be sent. So, let's say you use rate-limiting and set your "limit" to be 500K. Then, 400K of FTP traffic needs to be sent, followed by 200K of Oracle. The 400K of FTP would be sent, but then only 100K of Oracle would be sent. The other 100K would be dropped. Thus, you have not achieved your goal.


When you use queueing, the router will get the 400K of FTP and the 200K of Oracle and send the Oracle first. After the Oracle traffic has been sent, the FTP traffic will be sent. Now, you have achieved your goal.


If there is a need to "limit" the traffic, you can use queuing and rate-limiting. First, queue the traffic correctly so the Oracle and telnet goes first, but limit the overall traffic to a certain bandwidth. So, back to our example, you can still rate-limit to 500K, but queue the traffic so the 200K of Oracle traffic goes first, then 300K of FTP traffic is sent. The remaining 100K of FTP traffic will be dropped and re-transmitted by the server, but this is ok since it's not mission critical traffic.


Here is a good link to start reading about Cisco QoS


http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122cgcr/fqos_c/index.htm


Hope this helps...


samsam_wang Sun, 02/01/2004 - 07:16
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in my opinion, if you only care Oracle and telnet, maybe you can try PQ


just like


priority-list 1 protocol ip high tcp 1521(Oracle port?)

priority-list 1 protocol ip high tcp 23

priority-list 1 default normal


Just to let you know what I have tried, which seems to work ok, however would still appreciate any comments.


Here is an excerpt from the config


interface Serial0/0.17 point-to-point

ip address 192.168.xxx.xxx 255.255.255.252

ip nat inside

no cdp enable

frame-relay class fr_cha_pir

frame-relay interface-dlci 17

frame-relay ip tcp header-compression

frame-relay ip rtp header-compression

ip rsvp bandwidth 24 24

.....


map-class frame-relay fr_cha_pir

frame-relay adaptive-shaping becn

frame-relay cir 256000

frame-relay mincir 256000

frame-relay custom-queue-list 1

frame-relay ip rtp priority 16384 16383 48


.......


queue-list 1 protocol ip 1 tcp telnet

queue-list 1 protocol ip 2 tcp 7778

queue-list 1 default 3

queue-list 1 queue 1 limit 35

queue-list 1 queue 2 limit 40


So I give precedence to the application which runs on 7778, and then telnet and then what ever is left over.


So now, even if I start an ftp download, telnet is only slightly affected.


Any comments?

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