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Similar to Computer Networks (20)
Computer Networks
- 1. Chapter 18
Virtual Circuit
Switching:
Frame Relay
and
ATM
McGraw-Hill ©The McGraw-Hill Companies, Inc., 2004
- 2. 18.1 Virtual Circuit Switching
Global Addressing
Virtual Circuit Identifier
Three Phases
Data Transfer Phase
Setup Phase
Teardown Phase
McGraw-Hill ©The McGraw-Hill Companies, Inc., 2004
- 3. Figure 18.1 Virtual circuit wide area network
McGraw-Hill ©The McGraw-Hill Companies, Inc., 2004
- 5. Figure 18.3 VCI phases
McGraw-Hill ©The McGraw-Hill Companies, Inc., 2004
- 6. Figure 18.4 Switch and table
McGraw-Hill ©The McGraw-Hill Companies, Inc., 2004
- 7. Figure 18.5 Source-to-destination data transfer
McGraw-Hill ©The McGraw-Hill Companies, Inc., 2004
- 8. Figure 18.6 SVC setup request
McGraw-Hill ©The McGraw-Hill Companies, Inc., 2004
- 9. Figure 18.7 SVC setup acknowledgment
McGraw-Hill ©The McGraw-Hill Companies, Inc., 2004
- 10. Frame Relay(FR)
Frame relay is a virtual circuit wide-area-network that was designed in response to
demands for a new type of WAN.
• Prior to FR, X.25 was being used. But it is being replaced by other WANs.
• X.25 has several drawbacks:
•It has a low 64-kbps data rate.
•X.25 has extensive flow and error control at both data link and network layer.
Flow and error control at both layers create a large overhead and slow down
transmission.
•Originally X.25 was designed for private use, not for the Internet.
•Disappointed with X.25, some organization started their own private WAN by
leasing T-1 0r T-3 lines from public service providers. This approach has also some
limitations:
•If an organization has n branches spread over an area, it needs n(n-1)/2 lines.
•This type of service is not suitable for bursty data. Because T-1 or T-3 provides
fixed data rate and bursty data require bandwidth-on-demand.
McGraw-Hill ©The McGraw-Hill Companies, Inc., 2004
- 12. Figure 18.8 Frame Relay network
McGraw-Hill ©The McGraw-Hill Companies, Inc., 2004
- 13. Note:
VCIs in Frame Relay are called
DLCIs.(data link connection identifier)
McGraw-Hill ©The McGraw-Hill Companies, Inc., 2004
- 14. Figure 18.9 Frame Relay layers
McGraw-Hill ©The McGraw-Hill Companies, Inc., 2004
- 15. Note:
Frame Relay operates only at the
physical and data link layers.
McGraw-Hill ©The McGraw-Hill Companies, Inc., 2004
- 16. Figure 18.10 Frame Relay frame
McGraw-Hill ©The McGraw-Hill Companies, Inc., 2004
- 19. Note:
Frame Relay does not provide flow or
error control; they must be provided by
the upper-layer protocols.
McGraw-Hill ©The McGraw-Hill Companies, Inc., 2004
- 20. Figure 18.12 FRAD
McGraw-Hill ©The McGraw-Hill Companies, Inc., 2004
- 25. Note:
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.
McGraw-Hill ©The McGraw-Hill Companies, Inc., 2004
- 28. Figure 18.17 TP, VPs, and VCs
McGraw-Hill ©The McGraw-Hill Companies, Inc., 2004
- 29. Figure 18.18 Example of VPs and VCs
McGraw-Hill ©The McGraw-Hill Companies, Inc., 2004
- 30. Note:
Note that a virtual connection is
defined by a pair of numbers:
the VPI and the VCI.
McGraw-Hill ©The McGraw-Hill Companies, Inc., 2004
- 31. Figure 18.19 Connection identifiers
McGraw-Hill ©The McGraw-Hill Companies, Inc., 2004
- 32. Figure 18.20 Virtual connection identifiers in UNIs and NNIs
McGraw-Hill ©The McGraw-Hill Companies, Inc., 2004
- 33. Figure 18.21 An ATM cell
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- 34. Figure 18.22 Routing with a switch
McGraw-Hill ©The McGraw-Hill Companies, Inc., 2004
- 36. Figure 18.24 ATM layers in endpoint devices and switches
McGraw-Hill ©The McGraw-Hill Companies, Inc., 2004
