IP (Internet Protocol) –the network level protocol in the Internet. –Philosophy – minimum functionality in IP, smartness at the end system. –What does IP do? Addressing and fragementation (Internetworking). Routing provided by other protocols –What IP does not do: congestion control error control resource management (under extensive development recently)

–IP Service an unreliable, best-effort, connectionless packet delivery service. –Addressing ip address: 4 bytes, xxx.xxx.xxx.xxx example: ip address for diablo logically Five types (classes) A, B, C, D, E. class A 0 7 bits network number 24 bits host number class B bits network number 16 bits host number class C bits network number 8 bits host number class D bits multicast address class E reserved

IP address for a computer in a class A network: – to How many class A, B, C networks around? How many computers can a class A network have at most? Usually all machines in the same organization have the same network number obtained from NIC (Network Information Center). special addresses: – this host –network number = 0, hostnumber a host on this network – broadcast on local network –network number, hostnumber = broadcast on remote network – , loopback

Subnets –Written as or /24. –Each organization typically have one network number. –Using the subnet mask to allow the three-tie structure, sufficient for most organizations. Using the bitwise AND operation on the IP address and the subnet mask produces the subnet number. –E.g: machine subnet mask: ==> subnet number: –All hosts on the same subnet share the same subnet mask –Example: FSU xxx.yyy, subnet mask , FSU CS xxx xxx.

Question: Can a machine (router) have more than one IP address? Version IHL Type of Service Total length identification DF MF Fragment offset Time to live protocol header checksum source address destination address Options/Padding Version: Current 4, Next Generation 6, IPv6 IHL: 4 bits, header length, 16 * 32 bits Type of service: Quality of Service requirement (not used before) Total length: 16 bits, 65,535 Bytes (64K), including header

–Identification: unique for each IP (1) source increments a counter (2) gateway copies. All fragments of a datagram contain the same Identification number. –Flags: three bits (unused DF MF), DF if 1, means do not fragment, MF if 1, means more fragment (not end of packet. –Fragment Offset: offset in the original datagram in unit of 8 octets. »Why 8 octets? –Time to Live: was intended to count time. Now use to count hops. –Portocol: number of higher number protocols »ICMP : 1, TCP 6, UDP 17 –Question: is the header in an ip packet fixed throughout it journey?

–Routing: two type of routers: –border router: next hop –internal router: maintain routing table nexthop Intradomain routing in TCP/IP networks. –Routing Information Protocol (RIP, RFC 1058) »distance vector, hop count as metric »maximum hop count = 15, limited size »routing tables maintained by application level processes (daemons) (routed in unix) exchanging distance vector information using UDP port 520

–Routing: new intradomain routing: –Open Shortest Path First (OSPF, RFC 1247) »link state routing using dijkstra algorithm »use reliable broadcast for flooding LS packets »two level hierarchy: backbone/area »Link state routing within each area/backbone Interdomain routing: BGP (border gateway protocol) -- dealing more with the politics issues.

–Some control protocols used by IP ICMP: Internet Control Message Protocol –control messages »source quench, too many packets (choke packet) »time exceeded: TTL zero,(wandering for too long) »destination unreachable »fragmentation required: MTU too small. »parameter problem: header invalid –for information messages: »echo request/reply »timestamp request/reply –Two programs that use the ICMP protocol: »ping and traceroute – IP invokes ICMP to report errors, ICMP encapsulates messages in IP for transmission: protocol number 1

–Some control protocols used by IP ARP: address resolution protocol –find out the ethernet address for an IP address –a host broadcast to everyone asking “who owns IP address xxx.xxx.xxx.xxx” –The host with that IP address response with its Ethernet address. RARP: reverse address resolution protocol. –Find out a host’s IP address. –The host broadcast to everyone asking “My Ethernet address is ?????????, who knows my IP address?” –The RARP server looks up the configuration file and reply with its IP address.

CIDR - Classless InterDomain Routing Problem? We are running out of IP addresses. CIDR is the temporary solution for this problem. –Many IP address are wasted due to the two levels structure. (Half of the class B networks have less than 50 machines, nobody wants class C networks). –Allocating the remaining Class C network address space without enforcing the logical structure -- otherwise the routing table may be too big. –Routing table contains an addition mask field (network address, mask, nexthop). –In routing: if (IP address AND mask == network address) then forward it the nexthop

IPv6 –compatible with TCP, UDP, ICMP,…… –main problem: IPv4 is running out of address space –16 bytes address space –less header fields -- more efficient to process –more hierarchy levels -- reduce routing table size –QoS(Quality of Service) –multicasting –mobile IP –security