IST 228\Ch3\IP Addressing1 TCP/IP and DoD Model (TCP/IP Model)

IST 228\Ch3\IP Addressing2 Process/Application Layer Defines protocols node-to-node application communication such as –DCHP, LPD, SNMP, DNS, NFS, Telnet, FTP, SMTP, TFTP Controls user-interface specifications

IST 228\Ch3\IP Addressing3 Process/Application Layer Protocols Telnet- terminal emulation File Transfer Protocol (FTP) Network File System: allows to different types of file systems operate. Simple Mail Transfer Protocol (SMTP) Line Printer Daemon (LDP): facilitates printer sharing HTTP Simple Network Management Protocol (SNMP) X Windows

IST 228\Ch3\IP Addressing4 Resolves host names into IP addresses. –Discussion: Why do we need this? –  Use nslookup, dig, and host to find the IP addresses for psu.edu and mit.edu The DNS system is divided into nonoverlapping zones. Each zones have one or more DNS servers. Domain Name Service (DNS) edu name server psu.edu bk.psu.edu yale.edu cs.yale.edu ist.bk.psu.edu is looking for the IP address for linda.cs.yale.edu

IST 228\Ch3\IP Addressing5 Dynamic Host Configuration Protocol (DHCP) Gives IP addresses to hosts, and more –IP address –Subnet mask –Domain name –Default gateway (routers) –DNS

IST 228\Ch3\IP Addressing6 The Host-to-Host Layer Functions –Reliable end-to-end communication –Ensuring error free delivery of data –Prepares the data for delivery Protocols –Transmission Control Protocol (TCP) –User Datagram Protocol (UDP)

IST 228\Ch3\IP Addressing7 Ports TCP and UDP use port numbers to communicate with the upper layers. Ports help to keep track of different conversations over the network simultaneously –The Well Known Ports are those from 0 through –The Registered Ports are those from 1024 through –The Dynamic and/or Private Ports are those from through  Visit for well-known port numbershttp://  You can see LINUX ports /etc/services (type cat /etc/services |more)  Use nmap to scan open ports of a machine.

IST 228\Ch3\IP Addressing8 Be familiar with these ports –TCP port 20 – FTP data transfer –TCP port 21 – FTP control port –TCP port 23 – Telnet –TCP port 25 – SMTP –TCP & UDP port 53 – DNS –TCP (port 80) – HTTP Web services –TCP & UDP port 123 – Network Time Protocol (NTP) –TCP port 110 – Post Office Protocol version 3 (POP3) –TCP port 119 – Network News Transport Protocol (NNTP) –UDP port 69 – TFTP –UDP port 161 – SNMP How does it work? AB Destination port =23. I better send the packet to my Telnet application. SP DP Telnet Z SP DP I got a packet. Destination port is Currently, my Telnet application is using this port, send it to the Telnet application.

IST 228\Ch3\IP Addressing9 TCP FunctionDefinition Ordered data transfer and segmentation Continuous stream of bytes from upper-layer process that is segmented, numbered, and sequenced for transmission Establish and terminate a connection Process used to initialize port numbers and sequence and acknowledgement fields Flow control using windowing Process that uses window sizes to protect buffer space and routing devices Error recovery (reliability) Process of numbering and acknowledging data with sequence and acknowledgment header fields MultiplexingMultiplexing Function that allows receiving hosts to decide the correct application for which the data is destined, based on the port number Three-way hand shake

IST 228\Ch3\IP Addressing10 TCP Segment Format TCP creates a lot of overhead. Discussion: Why do we need that much overhead?

IST 228\Ch3\IP Addressing11 User Datagram Protocol Used transporting information that does not require reliable delivery Does not sequence the segments Sends the segments off and forgets about them Does not create a virtual circuit Connectionless protocol

IST 228\Ch3\IP Addressing12 The Internet Layer Protocols Functions –Routing –Provide single network interface to upper layers Protocols –Internet Protocol (IP) –Internet Control Message Protocol (ICMP) –Address Resolution Protocol (ARP) –Reverse Address Resolution Protocol (RARP)

IST 228\Ch3\IP Addressing13 Internet Protocol IP sees the picture Functions: –Receives segment from Host-to-Host Layer, fragment them into packets, using routing tables, routes them over the network, and then reassembles them into segments on the receiving end.

IST 228\Ch3\IP Addressing14 IP Header

IST 228\Ch3\IP Addressing15 Internet Control Message Protocol (ICMP) Provides message control and error- reporting services between two TCP/IP host and between a host server and gateway to the Internet Routes periodically sends following messages –Destination unreachable –Buffer full –Hops –Pings –Traceroute

IST 228\Ch3\IP Addressing16 Address Resolution Protocol (ARP) finds the hardware address of a host from a known IP address How does it work? –First look at the ARP cache (ARP table). –If IP to MAC mapping is not in the cache, broadcast a ARP request to hosts on the local segment –If the device in the local network, it returns a ARP reply. –.. Discussions: –How does the source know the IP of the destination? –What would happen if no ARP reply is received? –What happens when an ARP reply is received? –Why is it not a good idea to use static ARP cache in the local network?

IST 228\Ch3\IP Addressing17 Reverse Address Resolution Protocol (RARP) Discovers the identity of the IP address for diskless machines.

IST 228\Ch3\IP Addressing18 Routers on the network

IST 228\Ch3\IP Addressing19 Putting Things Together IP Routing 1. ICMP creates an echo pay load 2. ICMP hands the pay load to IP, which creates a packet. What is the information loaded in the IP header? 3. IP works with ARP to determine the destination is on the local network or not 4. No the destination is not on the local network, the packet needs to be sent to the default gateway. Look for the address of the local gateway.

IST 228\Ch3\IP Addressing20 5.The default gateway address is (the IP address of interface E0). MAC address must be known for this interface. Why? 6.Check the ARP cache for the MAC address corresponding MAC address is known now. Hand packet down to Data Link Layer. A frame is generated. 8.The frame is handed down to the Physical Layer to be put on the medium. 9.Every device on the collision domain receives the bits. They run CRC and check FCS field. The interface E0 matches the FCS field. Look what type of Network layer protocol is used. 10.The packet is pulled out from the frame, and the frame is discarded. 11.IP receives the packet and checks the destination IP address. 12.The routing table must have an entity for , or the packet is discarded. 13.The router finds an entity for The router forwards the packet to the E1 buffer 15.The E1 buffer must know the hardware address of the destination host. Why?

IST 228\Ch3\IP Addressing21 16.The router sends an ARP request for Host B responds with its MAC address. 18.The Data Link Layer (in router) creates a frame. The frame is handed down to the Physical Layer to be sent out on the physical medium. 19. Host B receives the frame and runs a CRC. It is a match. 20.At the network layer, IP receives the packet. The protocol field is checked to find the owner of the payload. 21. It is for ICMP. The payload is handed to ICMP. 22.Happy Ending