Switching Techniques Circuit Switching Packet Switching The Network
- Slides: 19
Switching Techniques Circuit Switching Packet Switching
The Network Core • The fundamental question: how is data transferred through net? • Circuit switching: dedicated circuit per call: telephone net • Packet-switching: data sent thru net in discrete “chunks”
Basic of Switching • In large networks there might be multiple paths linking sender and receiver. Information may be switched as it travels through various communication channels. There are two typical switching techniques available for digital traffic. • Circuit Switching • Packet Switching
Circuit Switching • Circuit switching is a technique that directly connects the sender and the receiver in an unbroken path. • Telephone switching equipment, for example, establishes a path that connects the caller's telephone to the receiver's telephone by making a physical connection. • With this type of switching technique, once a connection is established, a dedicated path exists between both ends until the connection is terminated. • Routing decisions must be made when the circuit is first established, but there are no decisions made after that time
Packet Switching Each end-end data stream divided into packets Bandwidth division into “pieces” • User A, B packets share network resources Dedicated allocation • Each packet uses full link bandwidth Resource reservation • Resources used as needed, • There are two methods of packet switching: Datagram and virtual circuit.
Packet Switching • In both packet switching methods, a message is broken into small parts, called packets. • Each packet is tagged with appropriate source and destination addresses. • Since packets have a strictly defined maximum length, they can be stored in main memory instead of disk, therefore access delay and cost are minimized. • With current technology, packets are generally accepted onto the network on a first-come, first-served basis. If the network becomes overloaded, packets are delayed or discarded (``dropped'').
What is Unicast? • Unicast is a type of communication where data is sent from one computer to another computer. • In Unicast type of communication, there is only one sender, and one receiver. • Example: • 1) Browsing a website. (Webserver is the sender and your computer is the receiver. ) • 2) Downloading a file from a FTP Server. (FTP Server is the sender and your computer is the receiver. )
What is Multicast? • Multicast is a type of communication where multicast traffic addressed for a group of devices on the network. IP multicast traffic are sent to a group and only members of that group receive and/or process the Multicast traffic. • Devices which are interested in a particular Multicast traffic must join to that Multicast group to receive the traffic. IP Multicast Groups are identified by Multicast IP Addresses (IPv 4 Class D Addresses) • In Multicast, the sender transmit only one copy of data and it is delivered and/or processed to many devices (Not as delivered and processed by all devices as in Broadcast) who are interested in that traffic. • Example : Multicast Windows Deployment Services (WDS) OS deployment traffic, IP TV etc
What is Broadcast? • Broadcast is a type of communication where data is sent from one computer once and a copy of that data will be forwarded to all the devices. • In Broadcast, there is only one sender and the data is sent only once. But the Broadcast data is delivered to all connected devices. • Switches by design will forward the broadcast traffic and Routers by design will drop the broadcast traffic. In other words, Routers will not allow a broadcast from one LAN to cross the Router and reach another Network Segment. The primary function of a Router is to divide a big Broadcast domain to Multiple smaller Broadcast domain. • Example: ARP Request message, DHCP DISCOVER Message
Anycast • Anycast is a network addressing and routing method in which datagrams from a single sender are routed to the topologically nearest node in a group of potential receivers, though it may be sent to several nodes, all identified by the same destination address. • Anycast is networking technique where the same IP prefix is advertised from multiple locations. The network then decides which location to route a user request to, based on routing protocol costs and possibly the 'health' of the advertising servers. • Anycast addressing uses a one-to-nearest association; datagrams are routed to a single member of a group of potential receivers that are all identified by the same destination address.
Routing Algorithm • The Main function of the network layer is to route packets from the source machine to the destination machine • The routing algorithm the part of the network layer’s software responsible for deciding which path should be chosen to reach the destination • The network layer maintains a routing table that contains all the routes to the destination • The routing process may be either static (non-adaptive) or dynamic • Static : The Network administrator maintains a routing table for routing the packets to the destination. Routes change slowly over time and it has to be update manually. For eg. Shortest path routing, flooding • Dynamic: The System maintains the routing table. Routes changes more quickly this is monitored and updated automatically. For eg. Link state and distance vector
Routing Algorithm • Fixed Path Routing • Shortest path routing • Flooding • Distance vector routing • Link state Routing
Link State Routing Algorithm • Dijkstra’s Algorithm • Discover its neighbors, learn their network address, HELLO • OSPF and ISIS are link state routing protocols
Distance Vector Routing Algorithm • Bellman-Ford Algorithm • Rip (Routing Information Protocol)