The transport layer has several responsibilities. The primary responsibilities include the following: Tracking the individual communication streams between applications on the source and destination hosts Segmenting data at the source and reassembling the data at the destination Identifying the proper application for each communication stream through the use of port numbers
2. During a TCP session, a destination device sends an acknowledgment number to the source
device. What does the acknowledgment number represent?
A. The next byte that the destination expects to receive
B. One number more than the sequence number
C. The last sequence number that was sent by the source
D. The total number of bytes that have been received
The window size determines the number of bytes that will be sent before expecting an acknowledgement. The acknowledgement number is the number of the next expected byte. For example, if a host has received 3140 bytes, the host would respond with an acknowledgement number of 3141.
3. Which two services or protocols use the preferred UDP protocol for fast transmission and low
overhead? (Choose two)
Layer 4 port numbers identify the application or service which will handle the data.The source port number is added by the sending device and will be the destination port number when the requested information is returned. Layer 4 segments are encapsulated within IP packets. UDP, not TCP, is used when low overhead is needed. A source IP address, not a TCP source port number, identifies the sending host on the network. Destination port numbers are specific ports that a server application or service monitors for requests.
6. What is the purpose of the TCP sliding window?
A. To request that a source decrease the rate at which it transmits data
B. To end communication when data transmission is complete
C. To inform a source to retransmit data from a specific point forward
D. To ensure that segments arrive in order at the destination
The TCP sliding window allows a destination device to inform a source to slow down the rate of transmission. To do this, the destination device reduces the value contained in the window field of the segment. It is acknowledgment numbers that are used to specify retransmission from a specific point forward. It is sequence numbers that are used to ensure segments arrive in order. Finally, it is a FIN control bit that is used to end a communication session.
7. What is the purpose of the TCP sliding window?
A. The part of the FTP message that was lost is re-sent.
B. The message is lost because FTP does not use a reliable delivery method.
C. The FTP source host sends a query to the destination host.
Each application process running on the server is configured to use a port number, either by default or manually, by a system administrator. An individual server cannot have two services assigned to the same port number within the same transport layer services. A host running a web server application and a file transfer application cannot have both configured to use the same server port. There can be many ports open simultaneously on a server, one for each active server application.