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FUNDAMENTALS OF COMMUNICATION NETWORKS

FUNDAMENTALS OF COMMUNICATION NETWORKS. Presented By: Vasantha Lakshmi Gutha Graduate student (CS) Course: CENG 5931 University of Houston-Clear Lake Guthav6317@uhcl.edu Spring 2011. INTRODUCTION SWITCHING TECHNOLOGIES ENCAPSULATION AND MULTIPLEXING NAMING AND ADDRESSING

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FUNDAMENTALS OF COMMUNICATION NETWORKS

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  1. FUNDAMENTALS OF COMMUNICATION NETWORKS Presented By: Vasantha Lakshmi Gutha Graduate student (CS) Course: CENG 5931 University of Houston-Clear Lake Guthav6317@uhcl.edu Spring 2011

  2. INTRODUCTION • SWITCHING TECHNOLOGIES • ENCAPSULATION AND MULTIPLEXING • NAMING AND ADDRESSING • MULTIPLE ACCESS • ROUTING AND FORWARDING • CONGESTION CONTROL AND FLOW CONTROL • NEW CHALLENGES IN WIRELESS NETWORKS • MULTIPLE ACCESS SCHEMES • CONGESTION CONTROL IN WIRELESS NETWORKS • CONCLUSION

  3. Introduction • A communication network consists of a set of interconnected nodes that exchange data with each other. • Network nodes exchange control information from a source device to a destination device. • The task of information exchange among communication networks involves tremendous complexity. • The communication task is broken down into subtasks. • These subtasks are organized into a number of layers. • Each Higher layer uses the service provided by the lower layer and in turn provides service to the layer above it.

  4. SWITCHING TECHNOLOGIES Communication networks can be classified into three categories: • Circuit switching: • Dedicated communication path is established between two stations. • Communication session involves three phases: • Circuit establishment • Data transfer • Circuit termination • Packet switching: • Data are transmitted as packets or datagrams, appended with a header or trailer.

  5. SWITCHING TECHNOLOGIES(Continued…) • Each packet carries routing information and is forwarded through the network from node to node. • Virtual circuit switching: • It is a hybrid technology combining features of both circuit switching and packet switching. • As in circuit switching, a virtual circuit is established. • As in packet switching, data are transmitted as packets. • As in circuit switching, all packets of the same session follow the same path. • As in packet switching, packets from different virtual circuits may be interleaved.

  6. Encapsulation and multiplexing • When the packets arrives at the destination, it is sent up through the protocol stack. • At each layer, the corresponding header and trailer are stripped. • A communication process running in a host is assigned a unique port number. • This unique port number is carried by all the packets generated by or designed to this process. • A field called frame type in the Ethernet header is used for multiplexing and demultiplexing.

  7. Naming and addressing • A domain name is used to identify a host, such as www.google.com identifies a Google server. • A domain name is more user friendly. • Domain names are organized into a tree structure. • Port numbers are as addresses for user processes running in the application layer. • In a client-server architecture, a server uses a well-known port number(smaller than 1024). • A client uses ephemeral port numbers that are randomly chosen and are larger than 1023.

  8. Multiple access • Simplest way of interconnecting two computer hosts is using a point-to-point link with a host on each end. • As the number of hosts increases, this approach may be inadequate. • To share the common media efficiently, all hosts must follow a set of rules to access the media. • Each host should have a fair chance to access the media. • Hosts should not be allowed to take the access media forever.

  9. Routing and forwarding • Internet routers are responsible for delivering packets from source to destination. • Routing and forwarding consists of two closely related parts • Maintaining network topology • Forwarding packets. • Routing information is derived from network topology and stored in a data structure called routing tables. • When there is a packet to deliver, a router consults the routing table to find out where to forward the packet.

  10. Congestion control and flow control • The receiver will notify the sender how much data it can receive without causing buffer overflow. • Then the sender will not send more data than the amount allowed by the receiver. • The sender may be explicitly notified about the congestion in the router. • then the source will reduce its sending rate until congestion is dissolved. • TCP uses slow start and congestion avoidance to react to congestion in the network.

  11. New challenges in wireless networks • Wireless Transmissions: • Wireless transmissions consume radio frequency spectrum in the network area. • Mobility: • In infrastructure-based wireless networks, each mobile user is associated with a fixed base station for transmitting and receiving data. • Energy Efficiency: • Mobile nodes are usually powered by the batteries they carry. • In infrastructure-based wireless networks, when a node dies, there is no significant impact on the network topology.

  12. Multiple access schemes • Polling: • A polling system is a special types of queuing system with one server and m stations. • Each customer requests service from the server and departs the system when its service is completed. • Any customer that arrives when the buffer is full is dropped. • When the server finishes serving a station, it may decide which station to serve next. • ALOHA and Slotted ALOHA

  13. Multiple access schemes(Continued..) • With pure ALOHA, a station transmits a packet whenever it wants to. • Pure ALOHA is a very simple multiple access protocol, but its throughput is very low. • The exact scheduling of ALOHA is complicated and hard to analyze. • Slotted ALOHA is an extension of pure ALOHA for improved throughput. • Time is divided into slots, and the length of one time slot is equal to the packet transmission time.

  14. Congestion control in wireless networks • Congestion control is a key function of the transport layer. • A router buffer is shared by multiple independent sessions in a store-and-forward communication network. • When the instantaneous arrival rate is higher than the output rate, the router buffer occupancy grows. • Congestion occurs when the buffer is overflow, resulting in packet loss.

  15. conclusion • Networks are becoming a strategic cornerstone for organizations in every industry. • As companies explore new global marketplaces and virtual organizations, they really increasingly on electronic communication. • Access to networks becomes a crucial component of business maneuvers in today’s business environment.

  16. references References: • Cognitive Radio Communications and Networks: Principles and Practice by Alexander M. Wyglinski, Maziar Nekovee, Thomas Hou • Local control of cognitive radio networks: Christian Doerr · Dirk Grunwald · Douglas C. Sicker • Communication Network http://www.samson.de/pdf_en/l155en.pdf

  17. THANK YOU

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