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ATM CES

What aal5 encapsulations is recommended to use with CES?

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New Member

Re: ATM CES

If you are doing CES, then there is only one type of encapsulation. It's going to be AAL1. CES is defined by the ATM Forum AF-VTOA-0078.000. CES uses the ATM AAL1 mechanism to encapsulate, segment and reassemble the incoming T1 traffic into the cell. So it's using the ATM network as a replacement of the network in place. Constant Bit Rate is a requirement because it forces bandwidth reservation regardless if voice traffic is present or not.

A good example is located here:

http://www.cisco.com/en/US/tech/tk39/tk103/technologies_tech_note09186a0080094402.shtml

The ATM forum spec is here:

ftp://ftp.atmforum.com/pub/approved-specs/af-vtoa-0078.000.pdf

A good document on CES concept is here:

http://www.cisco.com/en/US/tech/tk39/tk103/technologies_tech_note09186a0080094569.shtml

..and it has the following to say:

"CES is typically used to transfer voice or video traffic across an ATM network. Voice and video, unlike data traffic, is very sensitive to delay and delay variance. CES uses virtual circuits (VCs) of the CBR ATM service category, which guarantees acceptable delay and delay variation. Therefore, it satisfies both voice and video traffic requirements. ATM adaptation layer one (AAL1) specified by ITU-T.I.363.1 is used at CES-IWF."

-Tim

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