EE450-U10-TransportLayer-Nazarian-Summer11

EE450-U10-TransportLayer-Nazarian-Summer11 - EE450 Computer...

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EE450 Computer Networks Transport Layer Shahin Nazarian Summer 2011
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Shahin Nazarian/EE450/Summer 2011 Layer Relations 2
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Shahin Nazarian/EE450/Summer 2011 Transport Layer 3
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Shahin Nazarian/EE450/Summer 2011 Transport Layer Protocols 4
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Shahin Nazarian/EE450/Summer 2011 Transport Layer Protocols (Cont.) 5
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Shahin Nazarian/EE450/Summer 2011 Port Numbers IP layer provides for header error checking and the data part may still be erroneous when it gets to Transport layer. UDP and TCP error checking provides for error checking on that When we write an application program we create a process Transport layer uses port numbers to distinguish btn processes The port numbers on the server site are well-known port numbers, whereas the one on the client site are chosen _______ by the NOS Local host can be client or server 6
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Shahin Nazarian/EE450/Summer 2011 IP Addresses versus Port Numbers Well-known port numbers range between 0 and 1023 Note that routers do not see the port number. To a router a port number is nothing but a part of the IP packet 7
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Shahin Nazarian/EE450/Summer 2011 Process Aggregation We saw TDM and FDM multiplexing in Physical layer that aggregate traffic from several sources into a single link TCP or UDP do multiplexing by combining different applications into a single _________ 8
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Shahin Nazarian/EE450/Summer 2011 Well-known Port Numbers Used by UDP 9
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Shahin Nazarian/EE450/Summer 2011 A Note on DNS DNS primarily uses User Datagram Protocol (UDP) on port number 53 to serve requests DNS queries consist of a single UDP request from the client followed by a single UDP reply from the server However, DNS uses ______ when the response data size exceeds 512 bytes, or for some of its tasks Some operating systems, such as HP-UX (HP-Unix) are known to have resolver implementations that use TCP for all queries, even when UDP would suffice 10
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Shahin Nazarian/EE450/Summer 2011 User Datagram Protocol (UDP) 11
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Shahin Nazarian/EE450/Summer 2011 UDP (Cont.) 12
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Shahin Nazarian/EE450/Summer 2011 UDP Datagram Format Total length of the datagram is defined by ___ bits. _______ is fixed, but ________ is variable, because the data is variable Question: Is the source port number the well-known port number? ____________ Checksum is the field for the end-to-end checking. The check is for the entire _________ (remember that in layer 3, IP header checksum was for the header part only) 13
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Shahin Nazarian/EE450/Summer 2011 UDP Datagram Format (Cont.) Also keep in mind that the IP is inside the network, and packet is going through routers in the network and we do not want the routers to be slowed down to check the entire packet, alternatively, we would like the routers to check only for the header because the destination address is in the header and we leave error checking to layer 4 We can have up to 2 __ port addresses 14
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Shahin Nazarian/EE450/Summer 2011 Well-known Port Numbers Used by TCP Read the notes on DNS (the page with UPD-based well-known port numbers 15
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This note was uploaded on 08/27/2011 for the course EE 450 taught by Professor Zahid during the Summer '06 term at USC.

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EE450-U10-TransportLayer-Nazarian-Summer11 - EE450 Computer...

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