This problem is about the TCP “silly window syndrome”. (a) Fill in the blank: Si

Question

This problem is about the TCP “silly window syndrome”. (a) Fill in the blank: Silly windows can happen when the sender only has very small data packets to send or when the receiver advertises a very small, but nonzero . (b) What is the official name of the solution to this problem? (c) Why is it important to some video games to disable this feature of TCP? (d) All the headers of a TCP/IP packet total 64 bytes in length. Suppose one end of a connection is constantly sending packets that have only 1 byte of actual data (in addition to the header). What percentage of the connection’s bandwidth is being used for actual data? (e) Compare with the percentage when the sender is sending full segments of 1460 bytes of data

(a) Suppose TCP slow start is active. A sender has sent a total of 8 packets and has received 8 ACKs in reply. What is the maximum number of segments the sender is allowed to send? (b) In slow start the number of segments a receiver is allowed to send effectively doubles every round trip time, going 1, 2, 4, 8, . . . . However, this applies only if the receiver sends an individual ACK for each segment they receiver. TCP has a feature where sometimes if a receiver gets multiple segments at once, they will only ACK every second segment instead of every segment. In this case, instead of 1, 2, 4, 8, what will the first four values be? Assume that if a receiver gets n segments, they will send back dn/2e ACKs.

7. If you send a random TCP packet to www.google.com at port 80 with the ACK bit set and you haven’t already established a connection via the three-way handshake, Google’s servers will likely send you back a packet with what TCP flag (besides ACK) set?

(a) TCP sequence numbers can range from 0 up to what value? (b) Suppose you are on a 1 Tbps (terabits per second) connection, maxing out the connection with data. How long will it take until the TCP sequence numbers wrap around? (c) Explain why this extremely quick wraparound is a problem. (d) The solution to this fast wraparound is something called PAWS. Explain how PAWS uses a particular TCP option to mitigate the problem of quick sequence wraparound

Explanation / Answer

To use UDP, an application passes it a distinct block of data that is usually fairly short.

To use a protocol like UDP, many applications would be forced to artificially divide their data into messages of a size that has no inherent meaning to them. This would immediately introduce new problems requiring more work for the application. It would have to keep track of what data is in what message, and replace any that were lost.

TCP is said to treat data coming from an application as a stream; thus, the description of TCP as stream-oriented. Each application sends the data it wishes to transmit as a steady stream of octets (bytes). It doesn't need to carve them into blocks, or worry about how lengthy streams will get across the internetwork. It just “pumps bytes” to TCP. Increasing the Flexibility of Application Data Handling

TCP is designed to have applications send data to it as a stream of bytes, rather than requiring fixed-size messages to be used. This provide maximum flexibility for a wide variety of uses, because applications don’t need to worry about data packaging, and can send files or messages of any size. TCP takes care of packaging these bytes into messages called segments.

So basically applications using TCP do not have to consider how to create data block encapsulated by TCP, while applications using UDP do. applications send data to TCP as a stream of bytes and not prepackaged messages.

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TCP Segment
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