Popular Articles

At one time Russia rivaled the USA as a global power, but then came Gorbochov and we all know that Russia broke up into 18 states. This was also the end
From the 8th century the Muslim invaders began to make forays into Hindustan and by the 12th century the entire North India and the throne at Delhi had
Privacy is an important thing in every section. Same goes for mobile phones too. People always have something to hide from others on their mobile phone

Latest Articles

Subhas Chandra Bose was a rival of Gandhi and during the war he threw his lot with the Fascist powers and joined them. He had a one point agenda to overthrow
At one time Russia rivaled the USA as a global power, but then came Gorbochov and we all know that Russia broke up into 18 states. This was also the end
I had in an earlier post pointed out that the great Hindu warrior  Hemu was struck by an arrow in his eye in the third battle of Panipat and lost


#)ATM provides elaborate signaling support for dynamic establishment and release of Switched Virtual Circuits (SVC).

#)The information necessary for traffic contracting is exchanged between the user and the network through these signaling messages .

#)The signaling information includes Qos parameters (like cell delay variation and cell loss ratio) and traffic descriptor (like PCR , SCR and MBS) .

#)ATM forum has also published recommendations for signaling at the UNI. Both point-to-point and point-to-multipoint signaling procedures are laid out in ATM forum’s UNI Signalling Specification Version 4.0

#)Besides the UNI specification, ATM Forum has also come up with an elaborate recommendation for the Network-Network Interface(NNI).


#)The signaling procedures for ATM are defined for both User-Network Interface (UNI) as well as Network-Network Interface (NNI) .

#)The signaling layer sits on top of the Signaling Adaptation ATM Layer (SAAL).

#)The SAAL can be viewed as a special AAL used for the purpose of signaling.

#)SAAL is divided into two parts – Segmentation and Reassembly (SAR) and Convergence Sublayer (CS).

#)The CS is further divided into Common Part Convergence Sublayer (CPCS) and Service Specific Convergence Sublayer (SSCS).

#)Further, SSCS is divided into Service Specific Connection-Oriented Part (SSCOP) and service Specific Coordination Function (SCCF).

#)SSCOP is the core sublayer of SAAL and provides connection-oriented transfer of PDUs.

#)It may be noted that among different layers of ATM, SSCOP is the only layer where retransmission is done.

#)This is because signaling messages require reliability, as against normal user cells which may not require it.



#)SSCF provides a mapping between the primitives provided by SSCOP to that required by specific-user applications.

#)SAAL Provides an assured delivery of signaling messages on an otherwise unreliable ATM layer.

#)AAL5 forms a part of SAAL and thus, all nodes carrying the signaling message from source to destination must support AAL5.

#)Intermediate switches primarily concerned with switching of cells should support at least AAL5 in order to support signalling operations.

#)It is customary to refer to the ATM signalling layer as Layer 3.

#)This is because of a direct mapping between the functionality of SAAL and that of layer 2 of the OSI reference model.

#)Thus, SAAL is commonly referred to as Layer 2 and the ATM signalling layer as Layer 3.

#)ATM provides support for both channel-associated signalling as well as channel, non-associated signalling. Thus, all signalling messages are carried on VPI = 0 and VCI = 5.


  • No comments found