which codec to use over wan link?

[lukeprimm]

Im about to implement an SRST connection from the east coast (CUCM) to the west coast (CUCME) over our 6mb MPLS link (80ms latency).  Should I use G.729 or G.711 over the WAN link?  I'm reading through one book that says I should use G.729 since its a WAN, though they don't give a connection speed/latency chart.  Thoughts?

The phones being used are: 7960, 61, and 65 along with communicator

thanks

[acampbell]

Hi,

The G729 was recommended accross the WAN as they used to be low bandwidth.

With the advent of ethernet and high speed/bandwidth serial  WANs the codec selection is less of an issue.

You really need to know how many simultaneous calls you want to flow.

As a guide 1 G711 call will consume App 80Kbps

G729 call will consume App 24Kbps

What ever you select make sure you have QOS across the WAN to givethe VOIP traffic prioty

Regards

Alex

[lukeprimm]

"What ever you select make sure you have QOS across the WAN to givethe VOIP traffic prioty" Is this handled through our MPLS service provider?  thanks

luke

[Maxim Denisov]

Hi,

G.711 provides better voice quality and less sensitive to packet loss. Using it is preferred if you have enough bandwidth. Between IP phones I recommend using G.722 codec. It provides better voice quality with the same bandwidth requirements as G.711.

Sent from Cisco Technical Support iPad App

[acampbell]

Luke,

QOS needs to be provided end to end

You need QOS on the CE/Gwy routers at both ends along with

the MPLS provider having QOS on their PE/P network.

Maxim is correct too.(+5 M)

G711 is better quality G722 is newer not all devices support it.

G729 quality is perhaps the quality og mobile/cellphones

HTH

Alex

Please rate useful posts

[lukeprimm]

thanks, I checked with our provider and they are providing (and we are paying for) full 6mb "Real-Time" Class of Service on the MPLS link, so I think we should be good.  THe last part I guess is at our hand off of MPLS at each location.  Here at the head end, the MPLS terminates into a Cisco 6509 and at the branch office, it terminates into a Cisco 3750.  Your saying we need to apply QOS marking on the exiting interfaces at each location?  Thanks

[acampbell]

Luke

Yes you need to config your WAN ports on your LAN switches at both ends.

They will be acting as CE routers

Not sure what your IOS versionare etc.

Here is alink for the 3750 IOS 12.2.52 QOS section

http://www.cisco.com/en/US/docs/switches/lan/catalyst3750/software/release/12.2_52_se/configuration/guide/swqos.html

6500s are more tricky as the QOS can be type of SUPY and Line card dependant

Regards

Alex