Fall 2004FSU CIS 5930 Internet Protocols1 Second phase of the project Please check some networking textbooks for details on TCP and OSPF

Fall 2004FSU CIS 5930 Internet Protocols2 TCP Emphasizing on the followings: –Connection management –Flow control and congestion control –Reliable transmission (packet retransmission)

Fall 2004FSU CIS 5930 Internet Protocols3 Connection management Connection establishment –Three-way handshaking SYN/ACK –Window size (buffer that you have) Connection release –FIN/ACK –Preparing to receive data before ACKed Preparing for packet loss –Timer for SYN packet –You can close your connection without receiving ACK, but after a certain amount of time

Fall 2004FSU CIS 5930 Internet Protocols4 Flow control and congestion control Three parameters: –Receiver window size (rwnd), –congestion window size (cwnd), –slow-start threshold (ssthresh) At any time –Sendingdata <= min(rwnd, cwnd)

Fall 2004FSU CIS 5930 Internet Protocols5 Slow start and congestion avoidance At beginning –cwnd = one segment –ssthresh = 64K While cwnd <= ssthresh –Double cwnd after each window round –(increasing cwnd by one (packet) every time packet ACKed) After cwnd > ssthresh –Linear increasing –Increasing cwnd by one after each window round –(cwnd += 1/cwnd)

Fall 2004FSU CIS 5930 Internet Protocols6 Reliable transmission (conceptually) a timer for each unAcked packet When timer goes off, retransmit packet At receiver side –A modified Go-back-N –Buffering out-of-order packets –Acking maximum continually received packet

Fall 2004FSU CIS 5930 Internet Protocols7 Reliable transmission How to set time-out interval? Estimating RTT RTT = alpha RTT + (1-alpha) new_sample Time-out = beta RTT

Fall 2004FSU CIS 5930 Internet Protocols8 Open Shortest Path First (OSPF) We use a simplified version OSPF has two phases –Learning phase, when an OSPF router first starts –Maintenance phase, thereafter

Fall 2004FSU CIS 5930 Internet Protocols9 Learning phase (5 steps) Learning neighbors –Neighbors are ones on the same subnet Exchanging connectivity info with neighbors Flooding learned info Computing shortest path to all routers Computing shortest path to all subnets

Fall 2004FSU CIS 5930 Internet Protocols10 OSPF message types OSPF_TYPE_HELLO –To probe other routers OSPF_TYPE_HELLOACK –To respond to hello messages OSPF_TYPE_LSA_UPDATE –To advertise updates (connectivity info)

Fall 2004FSU CIS 5930 Internet Protocols11 When an OSPF router starts It probes others After a certain amount of time (say 10 seconds), it assumes it has all topology info Computing shortest paths by applying Dijkstra algorithm –You get shortest paths to all other routers Computing shortest paths to all subnets

Fall 2004FSU CIS 5930 Internet Protocols12 Maintenance phase It probes others with a larger interval –Say 1 probe per 10 seconds If it does not hear from a neighbor for several probe intervals, it assumes the neighbor is dead –Say 3 probes, (I.e., 30 seconds) Propagating this loss of neighbor Recomputing shortest-paths

Fall 2004FSU CIS 5930 Internet Protocols13 Grading policy (100 points) 1.Emulation of packet loss: 5 points 2.TCP connection management 3.TCP congestion management 1.Slow start, congestion avoidance, TCP Tahoe or Reno 4.TCP retransmission (go back N or selective repeat) 5.FTP application

Fall 2004FSU CIS 5930 Internet Protocols14 Second phase (Cont’d) OSPF learning neighbors: 5 points OSPF exchanging connectivity OSPF flooding OSPF computing shortest path to all routers OSPF computing shortest path to all subnets Code readability: 5 points Report: 5 points

Fall 2004FSU CIS 5930 Internet Protocols15 A new command ip –ip loss –ip ospfd –ip sh route Showing the content of the routing table –ip rm route Deleting all content of the routing table

Fall 2004FSU CIS 5930 Internet Protocols16 Project—UDP and TCP To configure a local host –APPL [UDP|TCP] port_number type –Type: MSG: for short messages FTP: for file transfer

Fall 2004FSU CIS 5930 Internet Protocols17 UDP and TCP For two hosts to communicate –MSG [UDP|TCP] source_port, dst, dst_port message –FTP source_port dst dst_port file_name For file transfer –A simple file transfer protocol: Client specifies the name of the file he wants to download from the server.