Data Communication and Network Comps Assignment 1 Khoa Le - s3103004 Question 1.
a) Why is the transport layer not present inside the core network? Marks 3
● Core Network is the internetworking of routers. ● Transport layer deals with communication between applications. ● The transport layer is not present because it provides additional functions to the core network to compensate for the limitation of the core network layer. ○ In the case of TCP/IP protocol, the Transport Layer provide more complex services such as flow control or connectionoriented data stream transfer to increase the reliability of the data as it is sent through the network. ● By keeping these layers separate, the transport layer is able to provide a uniform networking interface where the actual topology of the underlying network can be hidden. This allows services such as flowcontrol, error detection/correction and connection protocols such as TCP to exist. b) While transport layer provides reliable processtoprocess message delivery and error recovery, error control is also offered in the data link layer. Suppose the transmission channels become virtually errorfree. Is the data link layer still needed? Marks 3
● If the transmission channel becomes virtually errorfree, the error control service in the data link layer is still needed because: ○ Data Link Layer detect errors in frames between devices within the same Local Area Network while Transport layer deals with error control and detection for application processes on the host computer. ○ Transport layer deals with packets while Data Link layer deals with frames which is a digital data transmission unit. Both layer provide error detection independent of each other. ● In terms of error control, Data Link Layer only detects corrupted frames and once found, it will be immediately discard that frame. This saves network resources by preventing known damaged frame from propagating across the network....
Links: ● ● ● ● ● ● http://en.kioskea.net/faq/2093introductiontomtu http://sd.wareonearth.com/~phil/net/overhead/ https://learningnetwork.cisco.com/thread/31702 https://learningnetwork.cisco.com/thread/31702?start=15&tstart=0 Lecture Notes Data Computer Communications 8th William Stallings
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