Cell Relay Archive

["Beckerhof, Onno" <Onno.Beckerhof@alcatel.nl>]

Yep,
Have experience using CES for mainly PBX connections. What is your
specific questions about it ? Recently ATMF released a new type of CES
called Dynamic Circuit Emulation. It is brand new so to say but it
offers more intelligent bandwidth management. With standard CES you
claim a constant pipe of bandwidth reserved 100 % of the time, No
sharing of the bandwidth is allowed by other users. For example if
physical speed of the line is T3 and you claim one CES using T3 you
effectively claim the whole T3 for one connection. ATM is at that moment
a simple mux environment. To solve this problem DCES is introduced. DCES
is based on the knowledge that PBX systems are using signalling for
claiming a timeslot for voice. DBCES is special in that way that it
understands the signalling from the PBX and based on the type of
signalling message (for example call setup) a timeslot based on CES is
claimed. During the call a normal CES bandwidth pipe is claimed. When
the PBX signals that the voice call has ended this bandwidth pipe is
released also. 
There are however some minor problems here. For example if bandwidth is
not reserved how are you going to guarantee bandwidth at any moment in
time? Most of the time the ATM bandwidth is not only used for CES, so
other classes are also claiming bandwidth in some way. Using guaranteed
and non guaranteed bandwidth for those other classes could statistically
reserve some bandwidth for DCES. If for example all other classes are
based on UBR DBCES would perform wonderful. Using ABR you could
guarantee a minimum bandwidth to this users while the PCR is not
guaranteed (and therefor this space is available by CES which has
priority).

Cheers Onno