ITEC851 Mobile Data Network Assignment
Added on - 29 Apr 2020
MOBILE DATA NETWORKQ.1: The following packets are transmitted in a SCTP session. The marked packet is lost. What arethe complete contents of the packet including the SACK chunk from Node 2?Ans.The data over the network is transmitted in the form of packets. The data is bind and providedover the network to be transmitted at another end. The packets move accordingly to the specified IPaddress. If any packet gets lost, it is due to the transmission error or various other factors i.e.network congestion, due to packet loss the reliability of network decreased as well as latency andthroughput get affected (Xinogalos, Psannis, and Sifaleras, 2012). It also affects the quality of service.Here the data is communicated between node 1 and node 2 and thus packets are transmitted overthe network medium. The various packets transmitted from node 1 are:- TSN 105, TSN 106, TSN 107,TSN 108, TSN 109, TSN 110 out of which acknowledgement is received only for 106 i.e. ACK 106 andthus it indicates that TSN 106 is received to the node 2. The packet TSN 107 gets lost in thetransmission medium and thus cannot be reached to node 2, the transmission medium might befilled with various packets or the network traffic might be more while transmitting the TSN 107.Similarly other packets are transmitted and thus another acknowledgement for the packets isreceived and that should be for the last send packet so the sender is aware about whether the datais reached to the respective authority.SCTP provides a secure, reliable and message-oriented transmission of data like TCP and UDP. It alsoprovides congestion control mechanism. It sends message in the form of chunks and thus provides asequence number to the streams of data so that the receiver can know the actual sequence of datatransmitted to provide easy implementation and processing of data and provide desired results(Khan, Othman, and Khan, 2013). The data transmission with the help of SCTP is shown in the figurebelow, various request are being made for the transmission of data. Chunks are the additional datastorage information that moves with SCTP protocol to provide the reliability of data.
The data is transmitted from SCTP A to SCTP Z and thus sender sends the actual amount of data thatother party wants and thus starts the communication. The SACK value is transmitted along with theactual data and by checking the available resources that are with the SACK at SCTP A the furtherSACK and DATA is transmitted that makes data executable. The SACK value can further be taken asthe acknowledgement of the available data files and resources.Q.2: Consider the topology shown below. Simulate the DSR protocol to establish a path from node1 to node 10. Find the paths found and the ratio of the number of Route Request packets sent outin the network.Ans.Table driven in routing helps to maintain consistent information regarding all the paths that areavailable and maintained to reach to a destination. The path is provided from each node to everyother node in the network. The Ad-hoc network is analysed and established with the help of tabledriven routing. Whenever a network topology changes the update message is propagated tomaintain simultaneous flow of data at different nodes. Each node maintains multiple routing tablesso that the information is reliable and consistent throughout the network (Khan, Kiah, Khan andMadani, 2013).DSDV (Destination Sequenced Distance Vector) is usually suitable for small networks. The criteriadepend on time complexity. The two basic disadvantages with this are that they have respectiveamount of data to be operated and they have slow reaction to every failures. Routing protocols arethere to show the available route with low weights to make data packets move efficiently.Q.3: The Ad Hoc network shown below (including node Q) is currently operating. The network isrunning the AODV routing protocol. Show the steps required to route a packet from node N tonode I. In particular, what state is maintained at each node in the network? What changes occur tothe route, and how are these determined if node Q drops out of the network?Ans.Ad-hoc on demand distance vector routing protocol is basically developed for wireless mobiledata communications. It is free to be operated on mobile Ad-hoc network. The AODV routingprotocol does not affect the global nodes, the local network affects only the local nodes that are tobe available within the area interface. They also make use of sequence number to indicate whichroute to be followed. Further, it helps for uncast and multicast communications (Palmer, 2008). TheAODV protocol has expiry date for particular route which expires if that route is not used. All theroutes are maintained but the one that used on regular basis are maintained periodically but theroute that are not in use they get expired and thus are not maintained for operation as they getdestroyed. The unused route is also called as STALE. The route table gives the entry of all theavailable routes and thus specifies the lifetime for which particular route is valid (Lorenzo,Constantinides, Geurts & Gómez, 2007).
The routes are decided depending upon the reverse and forward links of the nodes connected to theavailable source and destination unit medium and thus they are transmitted in actual data nodedistribution. The data is further broadcasted to provide the available data utility and thus helps togain access to the best route to get to the destination.Q.4: Consider the scenario wherein a mobile host (MH) is communicating with a fixed host (FH)through Mobility Support Router (MSR-1) using the Indirect TCP (I-TCP) protocol. The MSR sendsto the MH the packets P1, P2, P3, P4 and P5 in that order. Packet P3 is dropped but packet P4reaches the MH causing it to generate the first duplicate acknowledgement (DUPACK). Before thisDUPACK packet arrives at the MSR it has already sent out packet P5. Write down the sequence ofsteps that will be performed by the MSR and MH to bring the system to a consistent state. (5marks) The MH now moves from MSR-1 to another cell (MSR-2). Detail the sequence of steprequired to move the connection to the new MSR.Ans.The mobile host is movable thus the location of the user gets changed according to the distinctlocations. Due to advancement in internet, the task of processing at fixed location overcome withnew strategies. While mobility support router sends various packets to mobile host so it is possiblethat the host is moving from one place to another and thus, the network drop can take place anddisturbs the continuity of packets transmitted. Here, packets P1, P2 are successfully reached and thesender gets the acknowledgement regarding the same (Leitner, & Grechenig, 2009). Packet P3 getsdropped it might be because of the transmission error or network crowd in the transmissionchannel. Packet lost also results in discarding of information and if you did not have duplicate copyor backup of that data, the data gets lost permanently. Further, the packet P4 reaches the MH atspecified point and thus, the duplicate acknowledgement has to be generated to send back to thesender of the message to ensure them the message is successfully delivered. Before the DUPACKreaches to source, the MSR already sends out the packet P5. Now it might happens that packet P5get reached twice forming second copy of the received elements.