ICSA 745 Transmission Systems Foundations for Emerging Technologies

1. ICSA 745 Transmission SystemsFoundations for Emerging Technologies Nirmala Shenoy Dept. of Information Technology Rochester Institute of Technology

2. Scope • Virtual circuits • Connection oriented and connectionless services • Variable and constant bit rate services • Flow control and congestion management

3. Scope • User payload integrity management • Address and identification schemes • Multiplexing methodologies • Switching, routing and relaying

4. Virtual Circuits • Physical circuit • two users communicate directly with each other through a circuit • Virtual circuit • User unaware of sharing • Intermediate systems relay information as they arrive

5. Types of Virtual Circuits • Permanent Virtual Circuit - PVC Allocated by contract • Switched Virtual Circuits - SVCallocated on demand • Semi-Permanent Virtual Circuits – SPVC • Not guaranteed continuous service

6. Permanent Virtual Circuits • Requires a contract agreement • Provisioned on a continuous basis • Entries stored at intermediate nodes for appropriate handling • Payloads should carry assigned identifier • Quality of service - throughput, delay, security, error-rates, etc. specified

7. Switched Virtual Circuit • Not pre-provisioned • Call setup essential • Connection request -virtual circuit number allocation, connection tear down • Virtual circuit number is used during the session to route information – • Resources released when session is over

8. Semi-permanent Virtual Circuits • Pre-provisioned similar to PVC • Does not guarantee that users will obtain level of requested service

9. Connection-Oriented System • Systems using virtual circuits • Connection setup, connection tear down • Forwarding nodes maintain connection information for packet handling • Processing overheads • Normally in-sequence delivery

10. Connectionless Systems • Does not employ virtual circuits • No information maintained by intermediate nodes • Ad hoc processing • Known as datagram networks

11. Connection-Oriented more control over traffic and servicing user’s QOS Faster payload processing Low end-to-end delays Connectionless No Qos guarantees Robust forwarding decisions to be made Comparison updated 12/2001

12. Coexistence • Telephone networks – throughout connection oriented • TCP/IP based transfers – end-to-end connection oriented, within the network connection less • UDP/IP – connectionless throughout • Protocol Layer based

13. Traffic Characteristics • Different applications have different patterns of traffic • Continuous • Bursty • Highly Bursty

14. Variable Bit Rate • Service preferred by bursty traffic • Periods of lull and periods of heavy traffic • Transmit and receive traffic asynchronously • Loose timing and synchronisation between sender and receiver • Traffic may be queued during bursts • Non-real-time, Real time • Example: email, client-server apps, video(?)

15. Constant Bit Rate • Can be used by services requiring continuous bandwidth • Predictable and bound delay, low jitter • Normally preferred by real-time services • Example: voice, video, video-conferencing (?)

16. Virtual Multiple Networks • Integrated VBR and CBR service support • All traffic is digitized • Manage the different traffic and provide fair and suitable service for all traffic • User perspective – one network

17. Flow Control • Network QoS Requirement – • traffic should not saturate a network • Should not exceed the network’s capacity • Methods of flow control • Explicit • Implicit • None

18. Explicit Flow Control • Network explicitly informs end systems via “explicit messages” on the amount of traffic the end systems can send • Users can increase traffic on congestion clearance

19. Implicit Flow Control • Informs user about congestion • Packet dropping, messages • User should reduce traffic, else data will be dropped • Control messages • user is violating service contract • network is congested

20. No Flow Control • Network discards any traffic that is creating congestion • Simple for network to implement • User service requirements not met • Connectionless networks have traffic regulation mechanisms • carrier-sense collision • issuance of tokens

21. User Payload Integrity Mgmt • All payload correctly received • Network responsibility? • End system responsibility? • Do all applications need this feature? • EFT, voice, video, data – service based?

22. Addresses & Labels • Connectionless systems – Explicit Address • each PDU uses explicit addresses for routing • IP address - network/subnetwork/device • Connection-oriented systems - Labels • uses a short label or Virtual Circuit Identifier • label used to index into state tables to determine the explicit location or forwarding information

23. Multiplexing • Frequency Division Multiplexing (FDM) • each user has fixed portion of freq. spectrum • Time Division Multiplexing (TDM) • each user is given a slot • slots are rotated among the attached users • Statistical TDM (STDM) • dynamically allocate time slots • Code Division Multiplexing • Usage of codes

24. Network Interface • User-to-Network Interface - UNI or SNI • protocol that governs the interface between the user and the network • Network-to-Network Interface - NNI or ICI • protocol that governs the interface between networks

25. Switching, Routing and Relaying • Relaying – forward data as it comes • Switching – comes in at one input is switched on to another • Routing – decision made on which path to take • Source routing • Non-source routing

26. Network Interfaces • UNI or SNI • User network interface, subscriber network interface • NNI or INSI – within network • Network- network interface, intra-network switching interface • NNI or ICI – between networks • inter-carrier interface

27. Convergence Operations • Performed at UNI • Add synchronization and accommodate different transfer rates • Convergence Sublayer - CS • Application specific • Example: error detection, synchronization

28. Segmentation and Reassembly • Segmentation is performed on the user traffic before it enters the network • Reassembly is performed before data reaches end user