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Internet Protocols

by: Miracle Jaskolski

Internet Protocols ECE 573

Miracle Jaskolski
GPA 3.75


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Class Notes
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This 7 page Class Notes was uploaded by Miracle Jaskolski on Thursday October 15, 2015. The Class Notes belongs to ECE 573 at North Carolina State University taught by Staff in Fall. Since its upload, it has received 9 views. For similar materials see /class/223904/ece-573-north-carolina-state-university in ELECTRICAL AND COMPUTER ENGINEERING at North Carolina State University.

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Date Created: 10/15/15
Today s Lecture The TCP State Machine Diagram TCP Timers TCP Lecture 2 Interactive ie low rate data transfer Internet Protocols IV Flow control Window size advertisements CSCECE 573 Fall 2005 Project Part posted N 039 State unwary HW3 will be posted today Project Choices Implement TCP at the application layer Implement the routing protocol RIP at the the application layer IsrrlrglceaeIrRtIa new protocol from either Infocom or TH E TCP STATE MACH I N E Implement interplanetary TCP Implement a DNS server Implement IPSec Authentication Header Implement basic VoIP Implement another Internet protocol Interpreting State Machine Diagrams States of a TCP Connection Each shows the TCP state machine for one K Themmwmemon endpoint of a connection other endpoint may be In a different state a The transitions between states arcs are labeled t with m m the input event that causes the transition SENS 05quot NSC059 Wm the output signal or message that will be sent to the imbemme39m a other endpoint sr li g w Sada m Recv st sand sw Ac transferred Qty gt0 uAnnFc39iusa or am ZMSLlimeuul occurs sand nmnmm lime Appll aliun cluse Sen W gt sand nulhi Dara being transferred M w Sand ACK Dara being transferred Tnneour grubems l W W a Re K sand Dining M W s and ACK ZMSLlimeuul occurs sand nmnrnm Appliu liun cluse sand in sand nuinrna en Ien All Together Now CL ENT SERVER esets Simultaneous Active Opens A connects with B B connects with A at same time pass each other in the network only one connection will be established compare with simultaneous telephone calls Stare svnis EN r st ch ESTAEUSHED Simultaneous Close A sends FIN to B B sends FIN to A at same time pass each other in the network still 4 messages but less time gm TCP TIMERS wwij 3 FW FiNyvAiU CLOSlNG CLOSlNG TlMEivalT TlMEivalT Keepalive Timer After agreeing with the other side to close a It is possible for TCP connections to be idle for a connection TCP enters the TIMEWAIT state Iong t39me starts a timer that runs for twice the maximum packet EX client opens a connection to a server and then lifetime makes a request once every 30 minutes the connection is closed after the timer expires allowing EX client opens a connection to a server but never port number to be reused makes a reque Ensures all packets and their ACKs have been Connections never closed unless explicit delivered or discarded before reusing the termination by the application or other endpoint connection Problem consumes resources memory on the helps prevent the overlapping connections problem server Keepalive Timer cont d Timer Implementation Details Keepaive timer maintained by some To reduce overhead timeout conditions are often implemen a 39 evaluated on halfsecond 500 ms boundaries or not part ofTCP standard somewhat controversial CIOCK OKs example timer interval 2 hours Le a timeout scheduled forx seconds in the future will be processed at X 5 it tick in the future which is in the timer Is restarted every time a segment Is received the interval x 5x When timer expires check if other side is still SEttlmEuuthErE Timeuut uncurs connected fur is in future here an clack m send probe packet 10 times at 75 second intervals if there is no response the connection is terminated a sun W 1m 2m 2m mm my man 45m Sana 55m man details of probe packet omitted 5 sec Characterby Character Transfer Telnet INTERACTIVE DATA TRANSFER Ach echo or 39o ACK echo or a Performance Improvement 1 Delayed AC Ks Each data packet has 1 character Purpose by waiting there may be more data to 40 bytes of overhead PTCP 1 byte of payload send ie ACK can be piggybacked with data Some TCP segments are Just ACKs 40 bytes of meme no payload Maximum amount of time to wait is implementation dependent Improvements possible Does it matter Shorterbetter Longer better ex Linux min of 40ms max of 200ms Good reduces overhead any drawbacks Delayed ACK Example mprovement ag e s goritm RFC 896 Idea accumulate data before sending a data ent Send d segm MW 60W When application generates data slowly send the first byte and bufferthe rest until 9 1a maximum sized segment is lled or 2 an ACK is received or 2 0Wquot 3 halfthe current window size is lled ACK 5 echo 5 2 ACK echo or a Send 39239 1 Nagle s Algorithm cont d Benefits a selfclocking algorithm ie no timers needed useful for paths with long roundtrip times Effect on throughput for low data rate applications for high data rate applications Any drawbacks FLOW CONTROL AND OPTIMAL WINDOW SIZES Sliding Vl ndow Again Send 39c39 Accumulate a Accumulate 39t39 Accumulate 9 ACK echo of 39c39 Send a 2 e Flow Control in TCP Flow control making sure the sender doesn t overrun the receivers buffer buffer contains data accepted from TCP not yet processed by application Each ACK from receiver carries a window advertisement Window Size of additional bytes the sender is authorized to send be ore it must wait for an acknowle gment Sliding Nndow Again cont39d R allows 3 bytes to be sent 5 sends bytes 1 1 3 R Acks bytes up through 2 allows 3 bytes beyond that tEI be sent 5 sends bytes 45 R Acks bytes up through 3 allows 5 bytes beyond that tEI be sent 5 sendsbytes 6 7 R Acks bytes up through at allows 5 bytes beyond that to be sent 5 sends bytes 8 at in R Acks bytes up through B allows 7 bytes beyurid l3 that to be sent 5 sends bytes 11 12 l Rules for Sliding Window The left edge is shifted to right by acknowledgments if right edgequot doesn t move means window gets smaller The right edge is shifted to the right by window advertisements if le edgequot doesn t move means window gets larger Should never see le edgequot moving to le why not right edgequot moving to le why not How Big Should the V ndow Be Example the receiver can process data at ie it s bandwidth is a maximum rate of 100000 bitss the roundtrip time 39om S to R and back is 4 s very highbandwidth 1 Gbs or greater network ideal solution sender sends at exactly the rate the receiver can receive How Big Should the V ndow Be oont d Just right 40000 bit window 5000 bytes 8 sends 40000 bits waits 45 sends 40000 bits rate 40000 bits45 100000 bitss Send1024 bytes Send 7024 bytes Is Applcenbn removed ms 1024 M95170quot butter removed 12 abdication Send 7024 bytes t I mp received quot11024 Mes but Duffel m r How Big Sh uld the V ndow Be cont d Too small 10000 bit window 1250 bytes 8 sends 10000 bits waits 45 sends 10000 bits rate 10000 bits45 25000 bitss Too large 100000 bit window 12500 bytes 8 sends 100000 bits waits 45 sends 100000 bits rate 100000 bits45 250000 bitss How Big Should the V ndow Be oont d The optimum window size receiver bandwidth roundtrip time this is called the bandwidthdelay product eg 4 10000040000 bits Challenges how determine the maximum receiver rate how determine the roundtrip time what if either or both changes frequently Other Examples whine state diagram captures all the behavior of connection state af ne 2MSL timer and long sequence numbers help avoid confusion between independent connections Delayed ACKs and Nagle s algorithm improve the efficiency of lowdatarate highRTT transfers Summary cont39d Next Lecture 4 The receiver limits the sending rate through TCP lecture 3 ts window advertisemen gt the sliding window size can change over time 5 the optimal window size is based on the network delayreceiver bandwidth product


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