11-19-2007 05:11 AM - edited 03-05-2019 07:30 PM
Hi all, can anyone tell me the differences in the above, and what is the tos value, is that used for precedence where as diffserv uses the dscp value ? whats the difference ?
11-19-2007 05:49 AM
Precedence uses 3 bits of the TOS field in IP header. Thus Ip precedence can classify trafic in to 8 different categories.
Whereas diffserv modifies the IP header to include 6 bit field, thus helping in classifying traffic in to 64 different categories. DSCP has backward compatibility with precedence or intserv.
Both of these are marking tools used for marking packets which are later serviced accordingly.
Pls refer this link for detailed study.
http://www.cisco.com/en/US/tech/tk543/tk545/technologies_q_and_a_item09186a00800cdfab.shtml
pls rate if helped.
11-19-2007 06:20 AM
HI,
As i know TOS and DSCP are only Marking Tools.
DSCP has certain chart to follow inorder to mark various kinds of Packet Types.
Refer Cisco QOS Configuration Guide for the same.
Do Rate all Helpful POsts
Best Regards,
Guru Prasad R
11-19-2007 09:25 AM
When we talk about RED/WRED, are these different that WFQ ?, Are all these to do with how the queues are serviced ?
11-19-2007 11:12 AM
RED/WRED are different from WFQ, essentially RED and WRED are congestion avoidance techniques whereas WFQ is a queuing technique.
RED/WRED simply monitor network traffic in an effort to anticipate and avoid congestion at common network and internetwork bottlenecks before it becomes a problem.
If supported on the hardware, WRED would be recommended instead of RED as it services queues and drops packets based on IP precedence value. The higher the value the less likely it will be dropped.
WFQ simply queues traffic in order to ensure that latency sensitive traffic such voice for example can be forwarded before less critical.
Regards
Allan.
WFQ
11-20-2007 05:01 AM
Hi there
thanks for that, so do you have to configure your router for WRED, or is this default behaviour ?
11-20-2007 05:26 AM
As I have mentioned previously, you will firstly need to determine whether your hardware or more specifically your interfaces supports WRED.
You have to specifically enable or configure WRED on the interface, it is not the default. If WRED was enabled by default then this would be indicated on the 'show interface' or 'show queueing' commands.
Please review the following link, which explains in more detail about WRED and also has configuration examples if interested:-
Regards
Allan.
Pls rate this post and others if you find the information provided helpful.
11-21-2007 03:59 AM
Hi there
so can you tell me how the queues work ? what kind of things do we assign to the queues ? and then what do we do with the queues?
also is RED/WRED part of QOS
can you put me a step by step info on what to do when configuring qos, ie 1, decide what traffic, 2 classify etc?
this would be very helpful
thanks
Carl
11-21-2007 05:28 AM
The links provided here & in the other post by you for a question on QoS, are god enough for understanding most of the QoS concepts.
Also, QoS guide from Cisco press by Wendell Odom is a Bible for this topic.All topics have been covered very extensively. I'm currently spending most of my time on this book for last few days.
This book can help meet your quench for deeper understanding of these topics.
Have a great reading.
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