N-GEN Communications Web-based Seminars ©NGCS

Seminar - An Overview of Communications Technologies

Module 4 - ATM Technology                                                                                                                      Slide 24 of 46 _________________                                                                                  __________

                                                  QOS Addressed by ATM                               

                                                User Contract

                                                Traffic Contract

                                                Traffic Shaping

                                                Traffic Policing

_________________                                                                                  __________

QOS  is maintained by the customer entering into a contract with the network to use the network services. The contract specifies customer subscribed service (CBR, VBR, ABR, UBR), required QOS and traffic characteristics of the connection. The QOS guarantees are comprised of Traffic Contract, Traffic Shaping and Traffic Policing. 

Traffic Contract - Specifies Cell Loss Ratio, maximum Cell Transfer Delay and peak-to-peak cell delay variation, peak cell rate and sustained cell rates.

Traffic Shaping - Use of queues to constrain data bursts, limit peak data rate and smooth jitters

Traffic Policing - ATM switch measures the actual traffic against agreed-upon traffic. Any cells out side agreed-upon parameters are dropped during the period of congestion.