Cell Relay Archive

[ays@hooked.net (Alan Y. Schaevitz)]

In article <64v8gr$km7@ssbunews.ih.lucent.com>,
ronaldd@ihgp3.ih.lucent.com (-Davis,R.H.) wrote:

">"In article <ays-1711971340100001@pm3-ppp2.well.com>,
">"Alan Y. Schaevitz <ays@hooked.net> wrote:
">">In article <64pv7i$2hg@ssbunews.ih.lucent.com>,
">">ronaldd@ihgp3.ih.lucent.com (-Davis,R.H.) wrote:
">">
">">">"there is a service specific convergence sublayer defined for frame
">">">"relay service over atm (using aal 5).  if i recall correctly, it
">">">"may be found in itu recommendation i.365.1.
">">">"
">">I think you may be confusing ATM with frame relay.  There is an end-to-end
">">reliable transport protocol defined for ATM called SSCOP (Service Specific
">">Connection Oriented Protocol) that is an SSCS implementation (It is
">">specified in the Signalling AAL or SAAL) for the ATM signaling application
">">along with AAL5.  However, there is still no such mechanism defined for
">">frame relay.  So while the ATM core can have congestion/flow control and
">">end-to-end recovery, the frame relay access cannot.
">">
">"
">"no, there's no confusion in what i was saying at all, although i am
">"a bit confused by your response.  as you mentioned, sscop is the
">"sscs for saal.  i.365.1 is the sscs for frame relay interworking
">"over atm.  the associated common part convergence sublayer is aal 5
">"as i stated (but more significantly, as is stated in recommendation
">"i.365.1).  the function of the fr-sscs is to translate bits from
">"the frame relay header (e.g. de, becn, fecn) into bits in the atm
">"cell header (e.g. clp, ci) on the transmit side aal connection
">"endpoint, and performing the reverse tranlation on the receive
">"side aal-cep.
">"
What you say is accurate.  However, frame relay DE/FECN/BECN do to provide
flow control nor recovery capability and only limited congestion
control.   Thus, on the frame relay side of the FR/ATM interface, no such
capabilities exist and therefore cannot be "mapped" to equivalent ATM
services.  You are stuck with the lowest common denominator of
capabilities, ie frame relay.

-- 
Alan Y. Schaevitz
AYS Associates
ays@hooked.net