CHAPTER 3: NETWORKING AND INTERNETWORKINGDr. Saddaf RubabNATIONAL UNIVERSITY OF SCIENCES AND TECHNOLOGY, PAKISTANSPRING, 2020[email protected]
BRIEFDist systems use LANs, WANs and internetworking for communication.Networking Issues: Performance, reliability, scalability, mobility and quality of servicePrinciples of networking: protocol layering, packet switching, routing and data streamingInternetworking techniques enable heterogeneous networks to be integrated, e.g., Internet (IP addressing and routing schemes)Case studies discussed (Ethernet, IEEE 802.11 (WiFi), and Bluetooth wireless networking)
3.1 INTRODUCTIONDist systems/networks built from:1.Transmission media– wire, cables, fibre and wireless channels2.Hardware devices– routers, switches, bridges, hubs, repeaters, network interfaces3.Software components– protocols, stacks, drivers, communication handlers3Communication SubsystemHardware and Software ComponentsHosts: computers and devices that use network for communication purposeNode: computer or device attached to networkSubnet: collection of nodes can be reached on same physical network, e.g., Internet (integrate diverse subnets to make communication possible between all hosts)
3.1.1 NETWORKING ISSUES FOR DIST SYSTEMS4Performance: network performance parameters that are of primary interest are those affecting the speed with which individual messages can be transferred between two interconnected computers. 1.Latency is the delay that occurs after a send operation is executed and before data starts to arrive at the destination computer. Measured as the time required to transfer an empty message. Here we are considering only network latency2.Data transfer rate is the speed at which data can be transferred between two computers in the network once transmission has begun, usually quoted in bits per second.
Performance:1.Message Transmission time: Following from these definitions, the time required for a network to transfer a message containing lengthbits between two computers is: Message transmission time = latency + length ⁄ data transfer rateThe above equation is valid for messages whose length does not exceed a maximum that is determined by the underlying network technology. Longer messages have to be segmented and the transmission time is the sum of the times for the segments.Transfer Rate is determined by network physical characteristics and latency is determined by overheads, routing delays, load dependency etc.