QoS Information

[dukenukem]

Hi all,

I would like some help and suggestions no a QoS issue.

Consider the following scenario.

Two remote locations are connected via a 2Mbps link.

This link is FR at one location on a 1721 router, and the other end is an ATM interface ona 3600 series router.

Two siemens tel systems each at either location will be communicating.

I would like to configure QoS, so that i ensure that the VoIP traffic leaving the siemens VoIP cards, is given highest priority and forwared ahead of other packets.

I have read about using RTP and cRTP.

I have also read about CB-WFQ .

I am puzzled as to which one to use.

I know that RTP will forward VoIP packets at high priority, but i also know that i can specify many classes for different services such as email, web browsing etc with CB-WFQ.

In my scenario, i would like to dedicate 200Kbps for Voice, and divide the rest for Internet usage, POP3 mail, and other data transfer services.

Can you give me your lights concerning this, and which method do you think its best.

Also, are there other issues, as i am connecting FR to ATM ???

I hope to get some answers.

Ig u think you need clarification please ask whatever info you think is vital.

Thanks,

George

[Georg Pauwen]

Hello George,

you could indeed use a class to specify the voice traffic and attach a policy to both the Frame Relay and the ATM VCs, the class and the policy would look like this:

ip access-list extended VoIP

permit tcp any any eq 1720

permit udp any any range 16384 32767

class-map match-all VoIP_CLASS

match access-group name VoIP

policy-map VoIP_POLICY

class VoIP_CLASS

priority 200

When you apply the policy to your Frame Relay interface and your ATM VC, the voice traffic would get 200K of guaranteed bandwidth, and all other traffic would be equally shared amongst the other protocols.

AFAIK, the Frame Relay to ATM should have no effect on this configuration, but you might want to test this and see if it works.

Does that make sense ?

Regards,

GP

[dukenukem]

Hi GP,

Happy Christmas to you and everyone that reads this thread.

Your answer does make sense. I understand that i create this class that will classify all packets with the VoIP UDP port range, and say that this will be given 200 Kbps of the bandwidth.

But how does this compare to using RTP???

Is one better than the other? or to be more correct,

what are the advantages-disdvantages between CB-WFQ and RTP.

Failing to get an answer to this i will go ahead and prioritize traffic clases with the solution you mention.

Thanks again,

and i wish u all and your family a Happy and Prosperous New Year.

George

[thisisshanky]

CRTP is used only in p-p links. It compresses UDP/RTP header sizes from 40 bytes to 2 bytes..tremendous improvement on a p-p link...

CBWFQ allocates how much min. bandwidth is guaranteed during congestion for each traffic class that is defined. Usually for VoIP LLQ is what is recommended. LLQ is Priority queueing + CBWFQ. So you define various classes..including one for voice and one for video (if neede) along with data classes. For voice and video you apply strict priority queueing. So voice and video traffic are sent out first compared to data during congestion.

You can use both CRTP and LLQ on the same link..independent of each other. Both are recommended to use in case you have VoIP traversing the link..