Cell Relay Archive

["Johannes Krohn" <KROHN@ffm.pandacom.de>]

SAR devices for SONET rates up to do OC12 exist.

> ATM provides circuit emulation services to carry DS1 type traffic. And ATM cells are further
> embedded into SONET frames. Isnt this kind of redundant...increasing overhead.?
>  Isnt it better to just support DS1 type
> circuits on regular SONET Payload instead of carrying it inside ATM cells.?

as long as you only think of pure CES for full E1/T1 links there
certainly is no advantage in using ATM CES over SDH/SONET. The first
advantage of using ATM takes effect if you start using channelized
CES for partly used E1/T1 circuits. Then you might need lesss
bandwith on the STS level compared to using full DS1 mappings in the
SONET frame. The bandwidth argument gets more important when
thinking of voice services (compressed, silence removal etc) that
can be trunked over ATM VCCs using the AAL-2 taking full
advantage of the VBR character of the compressed  voice data. In this 
scenario you can support a large number of voice connections over 
only a fraction of the full STS-3c bandwidth you might have needed 
using standard DS1 to STS-1 mappings. While taking advantage out of 
this bandwidth reduction you still can guarantee a certain quality of 
service for the voice connections in terms of delay (major impact 
on talker/listener echo!) and degradations due to loss of data in the 
network. This is even valid for service over ATM in MANs or WANs 
where is gets really difficult to guarante limited frame delays for 
IP datagrams when using VoIP.

    Johannes

---------------------------------------------------------------------------
Pan Dacom GmbH
Training/Consulting
Johannes Krohn
Robert-Bosch-Str. 32
D-63303 Dreieich

Tel.: +49-6103/932-137
Fax: +49-6103/932-400
Email: krohn@ffm.pandacom.de