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6.033 Lecture 12 – TCP details & Intro to Internet Routing

http://mit.edu/6.033/www/assignments/lec12.ppt (or .pdf). 6.033 Lecture 12 – TCP details & Intro to Internet Routing. Key ideas: slow start reordering buffer path vector routing. Samuel Madden. Hands-on 3 due tomorrow; DP1 due Thursday. Congestion collapse. Basic TCP Protocol.

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6.033 Lecture 12 – TCP details & Intro to Internet Routing

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  1. http://mit.edu/6.033/www/assignments/lec12.ppt (or .pdf) 6.033 Lecture 12 – TCP details & Intro to Internet Routing Key ideas: slow start reordering buffer path vector routing Samuel Madden Hands-on 3 due tomorrow; DP1 due Thursday

  2. Congestion collapse

  3. Basic TCP Protocol timeout= b * RTT (or RTT + b * stddev) wsize = 1 //window size in # outstanding TCP segments on ack: wsize = min(wsize + 1/wsize, receiver window) timeout = b * RTT on retry timer timeout: timeout = timeout * 2 wsize = max(1, wsize/2) Note that the algorithm presented in class (and previous version of these slides) omitted the /wsize erroneously.

  4. TCP with Slow Start timeout= b * RTT wsize = 1 starting = true on ack: if (starting) wsize = min(wsize + 1, receiver window) else wsize = min(wsize +1/wsize , receiver window) timeout = b * RTT on retry timer timeout: timeout = timeout * 2 wsize = max(1, wsize/2) starting = false Note that the algorithm presented in class (and previous version of these slides) omitted the /wsize erroneously. Receiver can also control rate of sender

  5. Reordering head : sno of last delivered packet size: length of reordering queue slot: position to insert new packet recv(p): slot = p.sno – head if (slot > head + size): drop else: new = isempty(slot) if (new) add p to slot ack p if (slot == head and new) deliver prefix to app head = head+ len(prefix) Application head= 1 head+ size PREFIX head= 3 P2 P4 P5 size = 5 P1 Reordering Buffer P6?

  6. Reordering head : sno of last delivered packet size: length of reordering queue slot: position to insert new packet recv(p): slot = p.sno – head if (slot > head + size): drop else: new = isempty(slot) if (new) add p to slot ack p if (slot == head and new) deliver prefix to app head = head+ len(prefix) head= 3 head+ size P4 P5 size = 5 Reordering Buffer

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