CIT 307 OnlineData Communications

Virtual Circuit SwitchingVirtual Circuit Switching

Module 15 Module 15 Kevin Siminski, InstructorKevin Siminski, Instructor

Virtual circuit wide area network

VCI- Virtual Channel Index

Phases of VCI

Switch and table

Source – destination transfer

Switched Virtual Circuit request

SVC acknowledgement

Frame Relay

Architecture Frame Relay Layers FRAD VOFR LMI

Frame Relay Network

Frame Relay- DLCIs

VCIs in Frame Relay are called DLCIs.

Frame Relay Layers

Frame relay operation

Frame Relay operates only at the physical and data link layers. Therefore, it can be considered a

Layer 2 technology

Architecture of a Frame Relay fram

Flow control & Frame Relay

Frame Relay does not provide flow or error control; they must be provided by the

upper-layer protocols.

FRAD

ATM – NOT YOUR CASH MACHINES!

Design Goals Problems Architecture Switching Layers

Multiplexing using different frame sizes

ATM Cell

A cell network uses the cell as the basic unit of data exchange. A cell is defined as

a small, fixed-sized block of information.

Multiplexing using Cells

ATM Multiplexing

Architecture on an ATM Network

TP, VPs, and VCs

VPs and VCs example

Virtual Connection

Note that a virtual connection is defined by a pair of numbers: the VPI and the VCI.

Connection Identifiers

UNIs and NNIs

ATM Cell

Routing with an ATM switch

ATM Header

ATM Services

Predecessor to IP Quality of Service (QoS)– Constant Bit Rate– Variable Bit Rate– Available Bit Rate– Unspecified Bit Rate

Some still maintain ATM offers superior QoS control plane

ATM Today?

IP QoS has matured to a production level technology

ATM networks very expensive Limited interface speeds Overhead limits steal valuable bandwidth

– appx. 12% - 14% overhead