Adaptation of different broadband services into ATM cells requires a suitable
layer. It is called ATM Adaptation Layer (AAL). Broadband signalling is one
of the users of AAL-service. For that purpose has been developped a special
Signalling AAL (SAAL). SAAL is responsible about reliable signalling connection
between two signalling entities. As an introduction we briefly describe the
sublayers and functions of SAAL. The main interest is dedicated for the error
correction part of the protocol, named Service Specific Connection Oriented
Protocol (SSCOP).
First of all the protocol operation principles are outlined with an imaginary
sample. The main part of the study concentrates on SSCOP delay characteristics
which gives the background for buffer calculations. We present two proposals
made for SSCOP which will decrease the buffer size requirements. The last part
includes the description of two ATM applications in which SAAL and SSCOP has
an interesting part. The first one describes how SAAL is implemented in an
early phase ATM node. The latter one presents a real ATM exchange where SSCOP
is used, besides network signalling, also for inter-unit connections. Finally
we take a short look at the future where the ideas of next steps are proposed.
Keywords: ATM adaptation layer, broadband ISDN, selective repeat, service
specific connection oriented protocol, service specific coordination function,
signalling AAL
Updated 4.1.1996 by
anne.saarinen@hut.fi