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13 Cards in this Set
- Front
- Back
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What is the window/buffer size of Selected Repeat Protocol? |
Window = 2^(m-1) Buffer = 2^m |
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How does the sender/receiver keep track of packets? |
Use different symbols to represent different attributes of the packet. i.e. the sender will have a symbol for sent w/o ACK and sent w/ACK receiver will have symbols for out of order |
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What does an ACK number mean in SRP? |
Means that the numbered packet has been received (as opposed to Go-back-N where the number was the next expected packet) |
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How does SRP handle duplicates? |
Drops them, same as the others. Re-sends ACK for those packets. |
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When does the receiver push to the application layer? |
When it has a consecutive sequence within the window note: this is also when the window moves down |
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Piggybacking |
two buffers, two windows when TCP establishes a connection, this is what it sets up |
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Checksum in UDP |
optional, defaults to off |
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UDP Header format |
8 bytes and then the payload (data) hex 1,2 = Sender port # 2,3 = Destination port # 3,4 = Length of message (bytes) 5,6 = Check-sum Each of these are 2 bytes each |
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What is the sequence number of a packet in TCP? |
It is the first byte number in that packet |
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What is the ACK number of a packet in TCP? |
It is the last byte number in the packet + 1 |
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How large is the TCP header? |
20-60 bytes 20 base, 40 for extras |
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TCP format |
Source port number (16 bits) Destination port number (16 bits) Sequence number (32 bits) ACK number (32 bits) HLEN - header length (4 bits, rep. # of words) reserved (6 bits) URG - urgent flag (1 bit) ACK flag (1 bit) PSH push to application once you get (1 bit) RST - reset, abort connection (1 bit) SYN - handshaking (1 bit) FIN - terminate connection (1 bit) window size (16 bits) checksum (16 bits) urgent ptr (16 bits, points to urgent data as offset into payload) options (up to 40 bytes) |
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To study: Split the header into 4 sections |
source/dest port numbers sequence and ACK number HLEN, reserved, flags, window size checksum, urgent ptr, options |
