TCP/IP Lecture Extra

1. TCP/IP Lecture Extra

2. TCP/IP • Developed by DARPA (Defense Advanced Research Projects) • TCP is a connection-oriented transport protocol that sends data as an unstructured stream of bytes. • By using sequence numbers and acknowledgment messages, TCP can provide a sending node with delivery information about packets transmitted to a destination node.

3. TCP/IP Continued • Where data has been lost in transit from source to destination, TCP can retransmit the data until either a timeout condition is reached or until successful delivery has been achieved. • TCP can also recognize duplicate messages and will discard them appropriately. • If the sending computer is transmitting too fast for the receiving computer, TCP can employ flow control mechanisms to slow data transfer. • TCP can also communicate delivery information to the upper-layer protocols and applications it supports.

4. TCP/IP versus OSI

5. TCP/IP Applications • SMTP (Simple Mail Transport Protocol) • FTP (File Transfer Protocol) • TELNET

6. Other things about TCP • Heaving processing burden on source and destination hosts • It adds to network traffic • Error correction of TCP adds to network delay

7. Internet Protocol • IP Basics • Connectionless • Unreliable • IP Datagrams • Hop by Hop • Traceroute example • http://www.visualware.com/visualroute/index.html

8. IP Addressing • Hierarchical Addressing • At the local computer level • At the gateway • Loopback address

9. IP Addressing Continued • Network Mask • Tells the router where to go • Subnet Part • Allows the message to be routed to the host computer • Subnet Mask • Generally listed as 255.255.255.0 but it can be manipulated to expand on the number of computers that can use one IP Address.

10. Other Facts about IP address • Rule 1: A prefix length of 0 matches anything • A prefix of 0.0.0.0/0, or 0/0, is the shortest possible IP address prefix and matches any IP address. We'll see later how this prefix can used to construct default routes to handle routing in cases where no other information is available. • Rule 2: A prefix length of 32 is an exact match • A prefix length of 32 bits, the width of a complete IP address, is the longest possible address prefix and matches one IP address exactly. 32 bit prefixes are used to construct host routes, which specify routing behavior for a single IP address. • Rule 3: Prefix lengths of 8, 16, and 24 match whole bytes • Any prefix length that's a multiple of 8 matches on byte boundaries. For example, a prefix of 172.30/16 matches any IP address that begins with 172.30 in the first two bytes, and ends with anything in the last two bytes. Similarly, an 8 bit prefix matches the first byte exactly and a 24 bit prefix matches the first three bytes exactly.

11. Routers • Source/Destination on the Same Subnet • Source/Destination Different Subnets • Router Forwarding to Another Router • Border Routers

12. Router Forwarding Tables • Next hop • Simple match • Masks – tell how long the match should be • Longest Match Selection • The longer the prefix the better the match • Metric-based selection • Used when two routers are tied when using longest match • Default Router • 0.0.0.0