Networking and OSI Model Based on your understanding of the topics covered durin
ID: 3675454 • Letter: N
Question
Networking and OSI Model
Based on your understanding of the topics covered during the week, answer the following, citing relevant examples wherever possible:
Describe how error checking is handled in the data link layer. Define a check sum and describe how Transport layer protocols implement them to ensure data integrity. Define and describe sequencing.
Describe a network address including its addressing scheme, formats, and alternate names. Define and describe the two parts of a MAC address. Compare Ethernet and Token Ring frames in terms of their operation on a network.
Describe a drawback of analog signals. Describe two benefits of digital signaling that make it worthwhile even though extra signaling pulses are involved. Explain how half-duplex transmissions work.
Describe what frequency division multiplexing (FDM) is and how it works.
Describe variables that may influence the final cost of implementing a certain type of media. Explain the makeup of coaxial cable. Explain the makeup of twisted pair wire and describe the advantages of twisted pair wiring. Explain the makeup of fiber-optic cable and describe the benefits of fiber-optic cabling over copper cabling.
Describe the advantages and disadvantages of using traditional peer-to-peer networks. Describe the advantages client/server networks offer over peer-to-peer networks. Define a network operating system (NOS) and describe the tasks it performs. Describe license tracking in networks.
Explanation / Answer
Please find the anwers below :
1)
Data link layer performs the error check using the Frame Check Sequence in the trailer and discards the frame if an error is detected. It then looks at the addresses to see if it needs to process the rest of the frame itself or whether to pass it on to another host.
To ensure data integrity, connection-oriented protocols like TCP use a checksum. A checksum is a unique character string that allows the receiving node to determine if an arriving dataunit exactly matches the data unit sent by the source. Checksums are added to data at the source andverified at the destination. If at the destination a checksum doesn’t match what the source predicted,the destination’s Transport layer protocols ask the source to retransmit the data.
Sequencing is a method of identifying segments that belong to the same group of subdivided data.Sequencing also indicates where a unit of data begins, as well as the order in which groups of datawere issued and, therefore, should be interpreted. While establishing a connection, the Transport layerprotocols from two devices agree on certain parameters of their communication, including asequencing scheme. For sequencing to work properly, the Transport layer protocols of two nodes mustsynchronize their timing and agree on a starting point for the transmission
2)
Network addresses follow a hierarchical addressing scheme and can be assigned through operatingsystem software. They are hierarchical because they contain subsets of data that incrementally narrowdown the location of a node, just as your home address is hierarchical because it provides a country,state, zip code, city, street, house number, and person’s name. Network layer address formats differdepending on which Network layer protocol the network uses. Network addresses are also calledNetwork layer addresses, logical addresses, or virtual addresses.
MAC addresses contain two parts: a block ID and a device ID. The block ID is a six-charactersequence unique to each vendor. IEEE manages which block IDs each manufacturer can use. Forexample, a series of Ethernet NICs manufactured by the 3Com Corporation begins with the six-character sequence “00608C,” while a series of Ethernet NICs manufactured by Intel begins with“00AA00.” Some manufacturers have several different block IDs. The remaining six characters in theMAC address are added at the factory, based on the NIC’s model and manufacture date, andcollectively form the device ID. An example of a device ID assigned by a manufacturer might be005499. The combination of the block ID and device ID result in a unique, 12-character MAC addressof 00608C005499. MAC addresses are also frequently depicted in their hexadecimal format - forexample, 00:60:8C:00:54:99.
Ethernet frames are different from token ring frames, and the two will not interact with each other on anetwork. In fact, most LANs do not support more than one frame type, because devices cannot supportmore than one frame type per physical interface, or NIC. (NICs can, however, support multipleprotocols.) Although you can conceivably transmit both token ring and Ethernet frames on a network,Ethernet interfaces cannot interpret token ring frames, and vice versa. Normally, LANs use eitherEthernet or token ring, and almost all contemporary LANs use Ethernet
3)
One drawback to analog signals is that their voltage is varied and imprecise. Thus, analog transmissionis more susceptible to transmission flaws such as noise, or any type of interference that may degrade asignal, than digital signals.
Because digital transmission involves sending and receiving only a pattern of 1s and 0s, represented byprecise pulses, it is more reliable than analog transmission, which relies on variable waves. In addition,noise affects digital transmission less severely.
In half-duplex transmission, signals may travel in both directions over a medium but in only one direc-tion at a time. Half-duplex systems contain only one channel for communication, and that channelmust be shared for multiple nodes to exchange information.
4)
FDM (frequency division multiplexing) is a type of multiplexing that assigns a unique frequency bandto each communications subchannel. Signals are modulated with different carrier frequencies, thenmultiplexed to simultaneously travel over a single channel. The first use of FDM was in the early 20thcentury when telephone companies discovered they could send multiple voice signals over a singlecable. That meant that rather than stringing separate lines for each residence (and adding to the urbantangle of wires), they could send as many as 24 multiplexed signals over a single neighborhood line.Each signal was then demultiplexed before being brought into the home