1) comparing the Star topology to other topologies, Star provides better performance and signals may not necessary to get them to all stations if we are using a Switch in place of a hub. The signal reaches the required destination in not more than 3-4 devices and 2-3 links. The entire capacity of the network dependent upon the central hub. ("logical vs. physical topology Definition from PC Magazine Encyclopedia", 2017)
2) adding newer devices to the network is quite easy and doesn’t affect the rest of the network and its other components. Similarly, the components can be removed as well quite easily.
3) the management of the network is totally centralized and monitoring needs to be done at single station itself. ("logical vs. physical topology Definition from PC Magazine Encyclopedia", 2017)
4) failure of one of the node doesn’t affect the rest of the network and in case of failure it is quite easy to detect and troubleshoot.
Disadvantages of Star Topology
1) the dependency on the central node is quite high and it has its own drawbacks. If it fails the entire network goes down.
2) Smarter the central devices costlier the overall cost of the network.
3) the performance and capacity to cater the number of devices is totally dependent over the central device.
Advantages of Bus Topology
- It is easy to connect the in a linear peripheral device.
- Less cables are needed as compared to the star topology.
Disadvantages of Bus Topology
- Entire network goes down if there is break in the cable.
- Terminators are needed at both the ends. ("What is Physical Topology? - Definition from Techopedia", 2017)
- It is difficult to manage and troubleshoot in case of breakage in cable.
- Cannot be used as standalone solution for the system.
Advantages
- Any broken link would not hinder with the transmission of data in the entire mesh network. Every node in the network is connected to several other nodes in the network. The broken node would then disconnect with the node and look out for another node. ("logical vs. physical topology Definition from PC Magazine Encyclopedia", 2017)
- Adding newer devices doesn’t affect the network of mesh, it in turn provides the alternative paths for the network making it more robust in nature. ("What is Physical Topology? - Definition from Techopedia", 2017)
- The mesh topology can handle very large amount of data and traffic over its connection. Thereby better network management and lesser congestion all the times.
Disadvantages
- Maintaining the mesh network is costly and cumbersome. It requires constant supervision of the network for proper functioning. Highly skilled network administrator is needed to manage the mesh network. ("Diagram Physical Topologies | Network Diagram Software Physical Network Diagram | Network Topologies | Diagram Physical Topologies", 2017)
2. Encapsulation is the process in which the data is wrapped up into a capsulated form and protected from any outside interference or misuse and also simplifying the overall use by the system of the same data packet. It also helps in transforming the data packets from one network to another.
Encapsulation happens when a packet from the higher layer goes down to the lower layer and encapsulated in the form that is understandable by the protocol of that particular layer. The encapsulation into the data the form of an identity that without any major checks can be determined to which layer the packet belongs to. The header information added to the system allows the layer to interact properly. A simple example of the mail delivery system is that of an envelope which has a marked address with postage stamp. The letter should have an identity to get to its destination like address we have provided. The Address and Stamp act as header for the envelop to reach the required destination. ("Diagram Physical Topologies | Network Diagram Software Physical Network Diagram | Network Topologies | Diagram Physical Topologies", 2017)
Decapsulation is just a reverse of the encapsulation process, it is the process in which each of the header of the respective layer is read and passed to the layer above, the decapsulation process starts from the physical layer to the Application Layer. ("logical vs. physical topology Definition from PC Magazine Encyclopedia", 2017)
3. Calculate the approximate bit rate and signal level(s) for a 6.8 MHz bandwidth system with a signal to noise ratio of 132. (5 Marks)
C = B log2(1+SNR) = 6.8 log(1+132) = 6.8 * 2.12 = 14.442 Mbps
This is the upper limit of the channel for easier calculations we use 10 Mbps as capacity
2 * B * log L = 10
2 * 6.8 * log L = 10
log L = 0.735
L = 1.66 (Channels)
4. The OSI layer is better than TCP/IP can be said as in one’s perspective, the idea behind the OSI was to simply the layer architecture and provide the open layer architecture for all the devices, which can help anyone to develop the communicating device that is compatible to any other device it wants to communicate. This feature was not available in the TCP/IP model, the devices were hard bounded to TCP and UDP protocols and protocols that were not flexible enough for the development or enhancement of the protocol. ("Diagram Physical Topologies | Network Diagram Software Physical Network Diagram | Network Topologies | Diagram Physical Topologies", 2017)
The reason for OSI didn’t become popular because the timing of the launch was very bad, the technology developed till that date was bad and due to bad politics by the hardware development companies. The timing was bad due to the fact that it tool way too long to finish and very large amount of money was invested in the TCP/IP till then. It was bad due to the fact that the layers of presentation and session were almost empty and the datalink layer was over crowded. Early implementation of the OSI was very buggy and thus it became the synonymous for the poor quality, with the implementation of TCP/IP based products coming as more reliable. Finally, the politics came into picture that TCP/IP was more so towards the Unix hence it was more popular among the academia people and research organizations but the OSI has no such association. (System, 2017) ("What is the difference between TCP/IP model and OSI model?", 2017)
Advantages of OSI:
- Provides number of choices of implementation
- Independent of system or specific computers
- Interprets the product and its functionality at each stage for better understanding.
- It encrypts the data for security reasons
- Multiple network models can be added and worked upon easily.
Disadvantages of OSI:
- Application that do not need the data integrity is an added burden in OSI layer for them
- Complex in nature to implement
- Not adapted to all the telecommunication applications.
Advantages of TCP/IP:
- Can be used to build communication between different types of systems
- It is independent of the OS
- Support number of routing protocols
- Internetworking of devices and organization is done through ease
- Scalable client server architecture.
Disadvantages of TCP/IP:
- Complex to setup initially and manage
- IPX
- The overhead is higher.
5.
Propagation time = distance / propagation speed
= 1900 Km /2.2 x 108 m/s = 8.63 ms
Transmission time = Message size / Bandwidth
= 5 x 106 bits/ 8 Mbps = .625 s = 6250 ms
Queuing time = 10 routers * 3.5 us = 35 us
Processing Delay = 10 routers * 1.8 us = 1.8 us
Total delay (latency) = 8.63 + 6250 + 0.035 + .0018 = 6258.6668 ms = 0.62586 sec
6.
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References:
Diagram Physical Topologies | Network Diagram Software Physical Network Diagram | Network Topologies | Diagram Physical Topologies. (2017). https://www.conceptdraw.com. Retrieved 2 May 2017, from https://www.conceptdraw.com/examples/diagram-physical-topologies
logical vs. physical topology Definition from PC Magazine Encyclopedia. (2017). Pcmag.com. Retrieved 2 May 2017, from https://www.pcmag.com/encyclopedia/term/46301/logical-vs-physical-topology
Physical & Logical Topology: Definition & Characteristics | Study.com. (2017). Study.com. Retrieved 2 May 2017, from https://study.com/academy/lesson/physical-logical-topology-definition-characteristics.html
System, O. (2017). Difference Between TCP/IP and OSI Model (with Comparison Chart) - Tech Differences. Tech Differences. Retrieved 2 May 2017, from https://techdifferences.com/difference-between-tcp-ip-and-osi-model.html
What is Physical Topology? - Definition from Techopedia. (2017). Techopedia.com. Retrieved 2 May 2017, from https://www.techopedia.com/definition/4794/physical-topology
What is the difference between TCP/IP model and OSI model?. (2017). SearchNetworking. Retrieved 2 May 2017, from https://searchnetworking.techtarget.com/answer/What-is-the-difference-between-OSI-model-and-TCP-IP-other-than-the-number-of-layers
