1. Circuit Switching Circuit-switched network direct physical connection between two devices  ex) phones or computers shorter links (no, length) than point-to-point connection The circuit can not be shared by other devices circuit switches

2. Packet Switching Datagram Approach each packet is treated independently from all others packet = datagram datagrams may arrive at their destination out of order  Transport layer reorders the datagrams

3. Packet Switching SVC(Switched Virtual Circuit) A virtual circuit is created whenever needed and exists only for the duration of the specific exchange comparable conceptually to dial-up circuit switching

4. Packet Switching Circuit switching vs. Virtual Circuit Path vs. Route physical path routing table

5. Packet Switching Circuit switching vs. Virtual Circuit (cont.) Dedicated vs. Shared

6. Frame Relay  Higher data rate at lower cost  the past WAN : leased line or X.25  low data rate  Solution : T-lines, mesh network, Frame relay  Data rate of Frame relay : 1.544Mbps (T-1) / 44.376Mbps (T-3) Pure mesh T-line network vs. Frame Relay lower cost

7. Frame Relay  Less overhead due to improved transmission media  No need to have a WAN that spends time and resources checking and double checking potential errors  X.25 vs. Frame relay X.25 – extensive error checking and flow control at the network layer – station-to-station frame checking at the data link layer – overhead for reliability eats up bandwidth Frame Relay – does not provide error checking or require acknowledgment in the data link layer because network become reliable and less error – All error checking is left to network and transport layer protocols – Frame relay traffic : simplified transmission

8. X.25 traffic Frame Relay traffic

9. Frame Relay WAN Frame Relay is normally used as a WAN to connect LANs or mainframe computers. Frame Relay network

10. Frame Relay Virtual Circuits Use a virtual circuit identifier (not physical address) Virtual circuit identifiers in Frame Relay operate at the data link layer (cf. X.25: network layer)  data link connection identifier (DLCI) : local number Two type of connections in Frame Relay  PVC(Permanent Virtual Circuit) Connection  SVC(Switched Virtual Circuit) Connection DLCIs

11. Frame Relay Layers Physical Layer No specific protocol Data Link Layer A simplified version of HDLC called core LAPF  LAPF : LAP for frame mode  No extensive error and flow control fields final(1)/more(0) a switch informs that congestion has occurred frame priority for discard in bottleneck (1:high)

12. ISDN Services provides the means to transfer information (voice, data, video) between users without the network manipulating the content of that information provides additional functionality to the bearer services and Teleservices network may change or process the content of data  layer 4-7 service Layer 1-3 services Three categories

13. User Interfaces BRI: Basic Rate Interface for home or small office  2B+D = 192kbps PRI: Primary rate Interface  23B+D = 1.544Mbps (North America) = T1  30B+D = 2.048 Mbps (Europe) = E1 Subscriber Access to the ISDN TP local loop T1

14. Broadband ISDN (B-ISDN) Bit rates for different application For the services beyond the capabilities of both the BRI and PRI

15. ATM Architecture Virtual Connection Connection is accomplished through TP, VP, VC Transmission Paths (TPs)  Physical connection (wire, cable, satellite and so on) Virtual Paths (VPs)  A connection or a set of connection between Switches Virtual Circuits (VCs)  All cells belonging to a single message follow the same VC TPs > VPs > VCs

16. Example of VPs and VCs ATM Architecture TP

17. ATM