Hey, Hope I got help with this research question ... 1. What is the goal of the
ID: 3621398 • Letter: H
Question
Hey, Hope I got help with this research question ...
1. What is the goal of the Urgent Pointer field and the URG flag in the
TCP header? [SOLVED]
2. What is the goal of the PSH flag in the TCP header? [SOLVED]
3. There are well known variations of the TCP congestion control algorithm
named TCP Tahoe, TCP Reno, and TCP Vegas. Describe the differences
between them in handling congestions. [SOLVED]
4. Describe the way the time-out period computed in TCP. [SOLVED]
5. Give some examples of a TCP options header values.
6. What is the goal of the HTTP protocol Keep-alive header field?
Note: It is important to show all the used references for each question
separately.
Thanks in advance
Explanation / Answer
Dear, 1) Urgent Pointer – Points to urgent data in the TCP data field. This Urgent pointer field is 16-bit field, indicates to the receiver that the value is an offset that must be added to the sequence number field to produce the sequence number of the last byte or urgent data. It can use only URG flag is set. The receiver is notified of the urgent data in the data stream and receiver decides what to do when notification received. URG = Urgent pointer field in use This flag is used to send out-of-band data without waiting for the receiver to process octets already in stream. When it is set then only Urgent pointer valid. 2) PSH flag: Here TCP to immediately deliver data for this message to the upper-layer process.PSH is independent of segment boundaries, it act as record marker. The transmitter should collapse PSH bits when it packetizes data to send the largest possible segment. An application program is logically required to set the PSH flag in a send call whenever it needs to force delivery of data to avoid a communication dead-lock. PSH can be used to avoid unnecessary wake-up calls to the application process; it is good performance measure for large time-sharing hosts. 3) Vegas Vs Tahoe Vs Reno: Vegas to cause are much stronger in the face of lost packets. It can perceive and retransmit lost packet much sooner than timeouts in Tahoe. It also has fewer re-transmissions since it doesn’t empty the whole pipe whenever it loses packets. It is better at congestion avoidance and its modified congestion avoidance and slow start algorithms measure incipient congestion and very precisely measures the available bandwidth available and therefore uses network resources cleverly and don’t contribute to congestion. More than half of the coarse-grained timeouts of Reno are prevented by Vegas as it detects and re-transmits more than one lost packet before timeout occurs. It doesn’t have to always wait for 3 duplicate packets so it can retransmit sooner and it doesn’t reduce the congestion window too much prematurely. The advantages that it has in congestion avoidance and bandwidth utilization over Tahoe exist here as well compare to Reno and Vegas. TCP Vegas is different from all the other implementation in its behavior during congestion avoidance. It does not use the loss of segment to signal that there is congestion. It determines congestion by a decrease in sending rate as compared to the expected rate, as result of large queues building up in the routers. Thus it is clear that TCP Vegas is definitely better than Tahoe and Reno. 5)TCP options header value A TCP must implement all options. Currently defined options include (kind indicated in octal): Kind Length Meaning ---- ------ ------- 0 - End of option list. 1 - No-Operation. 2 4 Maximum Segment Size. 6) Goal of keep-alive header field where a connection could be reused for more than one request.