IP Routing And Frame Forwarding For Network Communications

Sender Activities

In network communications, major components required for communication to be complete are sender, medium of communication, receiver and protocol required in communication process (Alani & M., 2014). The following are the list of activities that take place at the sender (named PC-1):

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  1. Message to be send starts its journey at the application layer (for instance email, browser etc.) and it traces its way downwards.
  2. The packet will proceed to TCP layer. This protocol assigns the packet port number. Port number assignment is important because a number of programs use TCP stack during the sending of messages. The assignment enables unique identification the program whose port is being listened to. For instance, in our case, the packet is assigned 1020 as the port number(Sriramoju, 2017).
  • Once the packet passes through the TCP protocol, it enters into IP layer. IP layer assigns destination address. For example, a packet going out of PC-1 heading to remote server will be assigned remote server’s address as the destination IP address. Once the packet has been assigned both IP address and port number, it is ready to be send out over the Internet. The packet is turned into electronic waves by the physical and datalink layers and it is forwarded to the WAN(White, 2015).
  1. On the receiving end of the WAN link, ISP’s router will perform routing activities. It determine destination address and forward the packet to the right end device.
  2. In the final stage, the packet reaches the remote server. This packet is received at the lower end of TCP stack. It will have to walk uphill(Goransson & Black, 2014).
  3. During the process of going up, the routing information attached to the packet is removed.
  • When the packets reaches the TCP stack top, the packets are assembled into the initial message.

The router uses the following procedures to keep track incoming and outgoing traffic:

When a packet arrives at the router from the switch, it removes layer 2 header info (for instance MAC address) available in the packet and it determines destination IP address from the packet. The router then finds a route for the destination prefix. If the prefix matches, it will assign its interface as the exit MAC address to appear as source address. The packet is then forwarded to exit interface. If there is no route found in the routing table, the packet in transit will be dropped (Grimes, 22 Apr 2016). The routing table for our case study will be as shown below:

Source IP address

Next hop IP address

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Destination IP address

Source  Physical address

Next hop MAC address

Destination MAC address


Remote server IP address

PC-1 MAC address

Router’s Fa0/0 mac address

Router’s Fa0/0 mac address

ISP’s receiving interface

Remote server IP address

Router’s exit interface MAC address

ISP’s receiving interface MAC address

ISP’s receiving interface MAC address

 ISP’s IP address

 Remote’s server’s default gateway 

Remote server IP address

 ISP’s exit interface MAC address

 Remote server’s interface that has default gateway

Remote server’s MAC address.

Question Two

IP routing and frame forwarding process that delivers ICMP. This process takes the following steps:

  1. PC-A sends out a ping request to
  2. Address Resolution Protocol works in conjunction with IP to make a decision which ping request will be forwarded to. This is achieved by determining the  IP address and give out the mask of workstation PC-A. The packet is then forwarded to the router for it to direct it to the right remote network workstation (Lammle & Swartz, 2013).
  • Once PC-A has issued out packet to router, it has to know the MAC address of interface of the router that is directly connected to the network.
  1. The router has to recognize the sent IP address and has to reply to it. The router then sends back a reply to PC-A. It takes some time for ARP to deliver the info and enquire the receiving device to respond. At one point, TTL decrements to zero interpreting that ping request has expired(Carrell, et al., 2013).
  2. Router will reply with its physical address of interface which connects to network segment. The PC will have complete information it requires to send outside the local router. Network layer assigns the packet to datalink layer. At this point, a packet containing ICMP request is created. This packet consists of destination address and source IP and ping ECHO request(Pyles, et al., 2016).
  3. PC-A’s datalink layer creates a frame. The frame will consist of destination and source MAC addresses. Cyclic Redundancy Check will be attached to ensure that  the destination workstation drops the frame if it is destroyed.
  • Physical layer receives the frame from datalink layer. The physical layer converts the frame to zeros and ones. This is digital signal which leaves from the physical layer.
  • The router’s physical layer receives the frame. It then checks if there exists errors in the frame.
  1. Since the destination physical address of received frame has been established, the router will submit the packet to Internet Protocol. PC-A’s MAC address will be stored in the router’s memory routing table.
  2. The IP looks for destination IP address to make a decision if the packet belongs to the destination router.
  3. The router will be required to construct a frame which it forwards to PC-B, ie the destination.
  • The destination device will respond with its physical address together with the ARP response. The router has acquired all it necessitates to respond.
  • The destination PC-B collects the frame. The PC performs CRC checks to check whether there exists any kind of errors. Once the frame matches with PC-B’s frame indicating absence of errors, the protocol now decides the next of the packet.
  • The destination PC-B generates a new reply PING response packet. The reply echo will contain source IP address and destination IP address. The protocol starts the journey all the way to the other end(Bosworth, et al., 2012).

Question Three

  1. EIGRP, OSPF and RIP.
  2. IGRP and RIPv1
  • Demonstration: EIGRP, OSPF and RIP deploys classes addressing. In a classless routing, subnet masks of a network are send with its updates. This allows VLSM masks. In our network case scenario, network segment A and B are interlinked, their masks are provided as, right? Now, in case a classful routing protocol was adopted, these network segments will take their default subnet masks of while the other will take 255.0.0. Subnet mask. This interprets that incorrect information will be routed. During the use of a classful network protocol, it is recommended that the subnet mask should remain consistent all through the network.
  1. The network address would be in the WAN interface and on the Fa0/0 interface of the router on left hand side and on the right hand side.
  2. Convergence parameter is key during routing, in our mentioned case scenario, OSPF will converge faster as compared to other routing protocols. This is as a result of a feature of OSPF that allows small areas to group as individuals and their groupings treated as a network on their own (Clarke, 2012).

Question Four

Data acknowledgement exchange of information

Stop and wait working together with Automatic repeat enquiry refers to control process integrated stop and wait control flow protocol. If an error is experienced by the receiving end, it will discard and send a NAK enquiring the sending end to resend.

In case the does not arrive at the recipient, the sending end will always sets a timer (Oriyano, 2014). Any time a frame is send, a timer clock is set, if no acknowledgement is nor NAK is received, the frame is resend again. However, the time introduces a challenge. For example, the sending end may do a retransmission yet the recipient did receive the frame. This interprets a duplicate on the receiving end. To avoid this kind of scenario, frames and acknowledgements are put into groupings i.e. Acknowledgement 1 for frame 0 and Acknowledgement 0 for frame 1 (VISWANATHAN & BHATNAGAR, 2014). 


Alani & M., M., 2014. End-to-End Dataflow. In: Guide to OSI and TCP/IP Models. New York City: Springer, pp. 15-17.

Bosworth, S., Kabay, M. E. & Eric, 2012. Internet Control Message Protocol. In: Computer Security Handbook, Set. Hoboken: John Wiley & Sons, pp. 23-25.

Carrell, J. L., Chappell, L. & Tittel, ‎., 2013. Internet Control Message Protocol. In: Guide to TCP/IP. Boston: Cengage learning, pp. 293-295.

Clarke, G. E., 2012. CompTIA Network+ Certification Study Guide, 5th Edition (Exam N10-005). New York: McGraw Hill Professional.

Goransson, P. & Black, C., 2014. Software Defined Networks: A Comprehensive Approach. Edinburgh: Elsevier.

Grimes, B., 22 Apr 2016. CTS-D Certified Technology Specialist-Design Exam Guide. Pennsylvania Plaza New York City: McGraw Hill Professional.

Lammle, T. & Swartz, J., 2013. CCNA Data Center – Introducing Cisco Data Center Networking Study Guide. Hoboken: John Wiley & Sons.

Oriyano, 2014. Dissecting the TCP/IP Suite. In: CEH: Certified Ethical Hacker Version 8 Study Guide. Hoboken: John Wiley & Sons, pp. 33-34.

Pyles, J., Carrell, J. L. & Tittel, E., 2016. Testing and Troubleshooting Sequences for ICMP. In: Guide to TCP/IP: IPv6 and IPv4. Boston: Cengage Learning, p. 286.

Sriramoju, S. B., 2017. Basic Dataflow. In: NTRODUCTION TO BIG DATA: INFRASTRUCTURE AND NETWORKING CONSIDERATIONS. s.l.:Horizon Books ( A Division of Ignited Minds Edutech P Ltd, pp. 72-74.

VISWANATHAN, H. & BHATNAGAR, M., 2014. Telecommunication Switching Systems and Networks. In: TELECOMMUNICATION SWITCHING SYSTEMS AND NETWORKS. s.l.:PHI Learning Pvt. Ltd, pp. 433-436.

White, C., 2015. Data Communications and Computer Networks: A Business User’s Approach. Belmont: Cengage Learning.