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