Author: Neftaly Malatjie

1. Packet switching is a method for sending data whereby the data is divided in packets. Each packet is given a header containing information of the destination. Each packet is forwarded through the network to the destination using this information. At the destination the data has to be reassembled from the received packages.

   Packet switching is the approach used by some computer network protocols to deliver data across a local or long distance connection. Examples of packet switching protocols are Frame Relay, IP, and X.25.

1. A message is a logical unit ofinformation and can be of any length.
2. In message switching, if a station wishes to send a message to another station, it first adds the destination address to the message.
3. Message switching does not establish a dedicated path between the two communicating devicese. no direct link is established between sender and receiver.
4. Each message is treated as an independent unit.
5. In message switching, each complete message is then transmitted from device to device through the internetworke. message is transmitted from the source node to intermediate node.
6. The intermediate node stores the complete message temporarily, inspects it for errors and transmits the message to the next node based on an available free channel and its routing information. Because of this reason message switched networks are called store and forward network as shown in fig.
7. The actual path taken by the message to its destination is dynamic as the path is established as it travels along.
8. When the message reaches a node, the channel on which it came is released for use by another message.
9. As shown in Figure message Ml is transmitted from A to D and M2 is transmitted C to B. Message Ml follows the route A –> I –> II –> III –> D and M2 follows the route C –> IV –> II –> B depending upon the availability of free path at that particular moment.
10. The first electromechanical telecommunication system used message switching for telegrams. The message was punched on paper tape off-line at the sending office and then read in and transmitted over a communication line to the next office along the way, where it was punched out on paper tape. An operator there tore the tape off and read it in on tape readers.

Message switching is a network switching technique in which data is routed in its entirety from the source node to the destination node, one hope at a time. During message routing, every intermediate switch in the network stores the whole message. If the entire network’s resources are engaged or the network becomes blocked, the message-switched network stores and delays the message until ample resources become available for effective transmission of the message.

Before the advancements in packet switching, message switching acted as an efficient substitute for circuit switching. It was initially employed in data communications such as telex networks and paper tape relay systems. Message switching has largely been replaced by packet switching, but the technique is still employed in ad hoc sensor networks, military networks and satellite communications networks.

1. • Unit Standard:	US 114074
     Course:	Demonstrate an understanding of different computer network architectures and standards
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1. • Network managers concerned with the user experience face their biggest challenges over the wide area. LAN-like performance is the goal for users at home or branch offices, but many network managers have a hard time keeping application service levels up to par on their local networks, never mind across distributed offices supported by varying levels of connectivity.

     Let us look at some of the key issues.

     1. Insufficient bandwidth.

     Techniques that optimize bandwidth include data compression and reduction. It can reduce the data it stores and sends over wans through deduplication (to remove redundancies) and caching (which leverages a stored version of recently requested data). Wan optimization controllers (wocs) are the primary technology supporting compression and reduction. Web security gateways include some of these capabilities as well.

     2. Poorly performing applications.

     Application misfires can be addressed by deploying an adc near the application server. Other options include leveraging wocs that include optimization features and instituting web layer controls using web application firewalls.

     3. Application contention.

     When applications compete for network resources, the resulting contention slows performance. Addressing this requires traffic prioritization, using qos tools and wocs, as well as better bandwidth allocation. Next-generation firewalls incorporate basic bandwidth management and prioritization.

     4. Network reliability.

     To improve reliability by reducing link downtime, organizations may deploy multiple links at various network points and then attempt dynamic routing and link balancing. Most use combination router/vpn devices or edge firewalls built on routing protocols.

     5. Application reliability.

     It shops tackle reliability through load balancing. Local load balancing takes advantage of a layer 2 or layer 3 adc device that forwards requests based on a
     set algorithm. Global load balancing, designed to provide balance across data centres, is more complicated and generally less effective.

     6. Security concerns.

     Wan security solutions include access control tools, anti-malware, intrusion prevention, web security gateways and proxy servers. Leveraging their position on the edge, next-generation branch firewall devices include some
     of these security features, allowing it to get additional return from their firewall investments. Web security gateways and proxy servers include limited web-oriented wan security.