1. Telecommunications Essentials Chapter 7 Wide Area Networking

2. WANs Networks connected over long distances Integrate voice, data, & video Can be circuit or packet switched

3. DDS Equipment Digital Data Service Leased lines operate at 56 or 64 kbps (or multiples) DDS Hub is a digital circuit switch DSU/CSU acts as a digital modem

4. WAN Switching Circuit Switched Leased lines ISDN Packet Switched X.25 Frame Relay ATM

5. WAN Equipment DSU – Controls the flow between the CPE and CSUDSU CSU – Performs the line conditioningCSU Mux – Intelligent time division multiplexerMux Routers – Forward the packetsRouters Backbones – T1/T3 or SONET paths

6. Point to Point Circuit switched i.e. A head office has links to each subsidiary No contention Limited expansion capability

7. Multipoint Circuit Switched A backbone network is shared by all offices Competition for resources

8. WAN Example 1 Enterprise with 4 separate networks

9. WAN Example 2 Enterprise backbone network Requires intelligent multiplexers

10. Fractional T-1 Multiple DS-0s can be concatenated Supports high speed LAN interconnect Supports video conferencing 384 kbps required for full motion video Frame rate is lowered to 10-15 fps on lower speed links

11. Bandwidth Allocation Static Bandwidth is assigned in 64 kbps chunks Dynamic Bandwidth can be assigned in any increment

12. ISDN Circuit switched BRI – 2B+D Lots of different configurations PRI – 23B+D (30B+D in Europe) LAN/WAN integration www.cisco.com

13. X.25 First generation packet system A virtual circuit system Designed for data over analog networks Packet size: 128 or 256 bytes Error checking occurs at every intermediate node www.cisco.com

14. X.25 Advantages Addressing capabilities Can be statistically multiplexed Basic congestion control Error control Disadvantages Queuing delays Small packet size No QoS guarantees Data only

15. Frame Relay Second generation packet system Used by 60,000 enterprises worldwide Used in burst environments Supports SVC & PVC servicesSVCPVC

16. Frame Relay Removes the error correcting from X.25 Digital transmission media is assumed noise free The packet is dropped if an error is detected The end-user application requests a retransmission Can carry voice and video Can encapsulate any type of data into the frame Maximum packet size - 4096 bytes Cannot predict delay/congestion Frame Relay Forum

17. Frame Relay Advantages Cheaper than leased lines Runs on multiprotocol networks Bandwidth efficient Disadvantages Variable delay Assumed high quality digital links

18. ATM Designed to handle data, video, etc. Can support voice Provides QoS 80% of Internet backbones use ATM www.cisco.com

19. ATM Cell 5 byte header 48 byte payload Connection oriented All cells follow the same route as defined by the VPI and VCI

20. AAL Service Classes AAL 1 => Service Class A (used for streams) AAL 2 => Service Class B AAL 3/4 => Service Class C or D AAL 5 => Service Class C (used for most other packets)

21. ATM Advantages Supports bandwidth on demand Provides QoS Scales in speed and network size Disadvantages High overhead High service cost