Network and Communications Assignment

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NETWORK AND COMMUNICATIONS1Network and CommunicationsNameCourseInstitutionDate of Submission
NETWORK AND COMMUNICATIONS2When communication and computing technologies are employed in the process oftransferring data from one place to another in a faster and secure way, it can be termed to be datacommunication. For a stable network to exist, there are technologies and techniques that have tobe put in place for success to be realized. For instance, technologies like computer networking,telecommunications, radio among others have to be there. The communication or transportationmedium has to be existing between the nodes that are in need of communication. Therefore, dataterminal equipment (DTE) and data communication equipment (DCE) is vital in a stable andrunning network.Question 1Packet Transmission for PC-1 and Subsequent NAT Router ActivitiesPackets from the Source IPThe IP address for PC-1 ( which is internal in this case is converted by theNAT device when a packet is transmitted from PC-1 to the external network. This being theaddress of the sender (packet header), it is therefore replaced with an IP address( which in this case is an external IP address belonging to NAT device meaningthat a port number that is available from its own pool is assigned to the connection.From the Router to the Destination ServerThis port number is inserted in the packet header also known as the source port field forthe packet to be forwarded to the external network. What follows is an entry being made by theNAT devise in a translation table(Park, Chung and Ahn, 2012). This entry is composed of thesource port that was original, the current source port that is translated, and the internal IP addressof the send packet. This means that all the succeeding packets that are originating from the sameconnection are therefore translated to the matching port number. Basing on the fact that the
NETWORK AND COMMUNICATIONS3address that is being transmitted to the remote server is being translated by the NAT device, aconnection to the IP and the port as definite in the transformed packet isestablished.The packet from the Destination Server Back to the Source Through a RouterWhen it is time for a packet to be transmitted from the external network back to PC-1,there is what is termed as mapping of that packet to the matching IP which in thiscase is the internal source IP address of the packet and the port number that was assigned by theNAT device in the translation table. This is usually the first step in determining the correctsource of the packet in the transmission mode.At the RouterThere is the replacement of an external IP of the NAT device ( togetherwith the port number contained in the arriving packet header’s port and IP address. There is atotal transformation of this packet form the IP address that it had while in the external networkback to its original internal one. At this point, the packet can be forwarded internally over theinternal network to the specific device.The Way in which a Router Keeps Track the Incoming PacketAn IP address and the port of the internal hosts or the source PC-1 are translated by theNAT devices for security purposes. This is to mean that, the valid endpoints of an internal hostthat expects the incoming packet are concealed on a private network(KumarGarg andP.C.Gupta, 2012, p.14). The data that is transmitted back from the destination server back to thesource PC-1 in the internal network is secure and directly delivered to the rightful owner of thatdata.Question 2
NETWORK AND COMMUNICATIONS4ICMPDue to problems that may arise in an event like a network blocking the transfer of an IPpacket, a router may adopt an error reporting protocol so that error messages are generated to theIP address that is the source of the packet. The message basically indicates that there is agateway obstruction to the internet. Despite the fact that ICMP does not do the same work like atransport protocol for sending packets amid systems, all devices connected to an IP network canprocess, receive or even send messages related to ICMP. The data in ICMP is encapsulated in anIP header allowing the message to be transmitted in a datagram format(Mariyammal, 2016). Forthe system to be able to determine the failed packet, the ICMP message is composed with thecomplete IP header of the message that is original.IP Routing and Frame ForwardingThe internet protocol is known to be a Network Layer Protocol whereby it borders theTransport Layer and the Network Layer. The ARP, on the other hand, is known to translate amida Network Layer and a Data Link Layer address. When PC-A pings PC-B (, there isa need for first determining the destined network. This is made possible with the help of theaddress resolution protocol which checks the subnet mask and the IP address of PC-A. For thepinged packet to be routed to the desired remote destination PC-B.Determining Whether PC-B is on a Local or Remote DestinationIP AI PC-A can easily determine come up with a conclusion whether PC-B is adestination that is local or remote through a mathematical calculation termed as an ANDoperation. This process is done internally by the sending host so that it can choose which modeto send the packets (direct to the host or through the router). ANDing can be done whereby all
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