Introduction Reading Assignment : Stallings Chapter 1

1. IntroductionReading Assignment : Stallings Chapter 1 • A communication model • Source • e.g., telephone, computer • Transmitter • transforms and encodes the information to produce electromagnetic signals • Transmission system • a single transmission line or a complex network • Receiver • opposite of transmitter • Destination • Communication tasks • Transmission system utilization • interfacing • signal generation • synchronization • exchange management • error detection and correction • flow control • addressing

2. routing • recovery • message formatting • security • network management • Data communications networking • networks vs. dedicated links • Wide-area networks • interconnecting / switching nodes • circuit switching • fixed data rate circuits • dedicated path, minimal delay • telephone network • packet switching • brief delay • designed for older networks (64 kbps) • overhead • redundancy, addressing, error checking for high error rate of equipment • computer to computer communication • frame relay • high speed networks ( 2 Mbps ) with low error rates • strip out most error control fields in packet switching • variable length packets • Asynchronous transfer mode (ATM) • combination of circuit and packet switching • also called cell relay • fixed length cells (packets) • 100 Mbps • multiple virtual channels (circuits) with dynamically defined data rates

3. Integrated Service Digital Network (ISDN) • intended to be a new worldwide digital telecommunication network • all types of data • narrowband ISDN : frame relay technology • broadband ISDN : ATM • Local-area networks • small scope, single building / floor • owned by single organization • capital investment • network management responsibilities • broadcast network • packets • shared medium, only one station can transmit at a time • Protocols and protocol architecture • cooperation between source and destination entities in separate systems • protocol • convention of cooperation • a set of rules governing the exchange of data between entities • key elements • syntax • data format, signal level • semantics • meaning of each field in data format, control information, error handling • timing

4. Protocol architecture • simplified architecture for file transfer • passwords, file commands • reliability requirements • network access • Basic three-layer model • application • transport • destination service access point (SAP) • sequence number • error-detection code • network access • destination computer address • facilities requests : priorities, etc. • TCP/IP protocol architecture • physical layer • interface between computer and network • transmission medium, nature of signals, data rate, etc. • network access layer • within same network • addressing, priority • software depends on particulars of physical layer, such as circuit/packet switching, LAN • internet layer / Internet protocol (IP) • routing across multiple networks • also implemented in routers • transport layer / Transmission control protocol (TCP) • host-to-host layer • end-to-end reliability • sequencing • application layer • The open systems interconnection (OSI) model • International Organization for Standardization (ISO)