Data communications system Essay

1.Message. 2.Sender 3.Receiver. 4.Transmission medium. 5.Protocol. Q1-11) Why are protocols needed? To achieve end-to-end delivery of data. Q-17) Explain the difference between an Internet draft and a proposed standard? – An Internet draft is a working document (a work inprogress) with no official status and a six- month lifetime. – A proposed standard is elevated to draft standard status after atleast two successful independent and interoperable implementations. Q2-5) A host communicates with another host using the TCP/IP protocol suite. What is the unit of data sent or received at each of the following layers? a. application layer:Message b. network layer:Datagram c. data-link layer:Frame Q2-12) When we say that the transport layer multiplexes and demultiplexes application layer messages, do we mean that a transport-layer protocol can combine several messages from the application layer in one packet? Explain. The TCP/IP protocol suite uses several protocols at some layers, we can say that we have multiplexing at the source and demultiplexing at the destination. Multiplexing in this case means that a protocol at a layer can encapsulate a packet from several next-higher layer protocols (one at a time); demultiplexing means that a protocol can decapsulate and deliver a packet to several next-higher layer protocols (one at a time). To be able to multiplex and demultiplex, a protocol needs to have a field in its header to identify to which protocol the encapsulated packets belong. At the transport layer, either UDP or TCP can accept a message from several application-layerprotocols. At the network layer, IP can accept a segment from TCP or a user datagram from UDP. IP can also accept a packet from other protocols such as ICMP, IGMP, and so on. At the data-link layer, a frame may carry the payload coming from IP or other protocols such as ARP. P1-4) For each of the following four networks, discuss the consequences if a  connection fails. a. Five devices arranged in a mesh topology. It Will not failed b. Five devices arranged in a star topology (not counting the hub). It Will not failed c. Five devices arranged in a bus topology. It will failed d. Five devices arranged in a ring topology. It will failed P2-11) Protocol layering can be found in many aspects of our lives such as air travelling. Imagine you make a round-trip to spend some time on vacation at a resort. You need to go through some processes at your city airport before flying.You also need to go through some processes when you arrive at the resort airport. Show the protocol layering for the round trip using some layers such as baggage checking/claiming, boarding/unboarding, takeoff/landing. 1-Print your boarding pass and check your luggage. 2-Head to security. 3-Find your gate/terminal. 4- Hang out and wait for your plane. 5-Wait for the announcement to board. 6-Get your boarding pass checked. 7-Enter the aircraft. 8-Stow your carry-on items. 9- Get settled in.