Cell Relay Archive

[Marc Delvaux <mdel@globespan.net>]

ATM makes a distinction between (terminology maybe slightly off)
the QoS or service class (here CBR) and the possible way to
transport this service class e.g. different AAL or CES.  The two
are a priori orthogonal.  It is true that AAL1 (with normally a 47
bytes payload per ATM cell) is normally associated with CBR,
but this is somehow an user choice.
  So to answer your question, no you are not forced to use
AAL1 for CBR and you are allowed to use a 48 bytes payload for
a CBR QoS class.  In general the use of the ATM payload is
completely defined by end point processing, so if your ATM connection
is between two end user, nobody will look inside your ATM
cell so to speak, so the cell format is your responsibility.

michael_silver@my-dejanews.com wrote:

> Is the payload (data) of CBR cells always 47 bytes?  I know that it is
> for CES since you need that extra byte for a timestamp, but what if I
> just have data that I want to be prioritized higher than other data.
> Do I have to waste that one byte in each cell?  (And I have lots of VBR
> traffic, so making it VBR with the SCR equal to my expected PCR won't
> really help very much.)
>
> Mike
>
> --== Sent via Deja.com http://www.deja.com/ ==--
> ---Share what you know. Learn what you don't.---



begin:          vcard
fn:             Marc Delvaux
n:              Delvaux;Marc
org:            GlobeSpan Semiconductors
adr:            100 Schulz Drive;;;Red Bank;NJ;07701;USA
email;internet: mdel@globespan.net
title:          LSI designer
tel;work:       +1 (732) 345 7502
tel;fax:        +1 (732) 345 7592
tel;home:       +1 (732) 578 9255
x-mozilla-cpt:  ;0
x-mozilla-html: TRUE
version:        2.1
end:            vcard