1. Networks I Internet Protocol Instituto Tecnológico y de Estudios Superiores de Monterrey Campus Estado de México Prof. MSc. Ivan A. Escobar Broitman TC1007

2. Introduction Many networks exist in the world, often with different hardware and software. People connected to one network want to communicate with people attached to a different one. This desire requires connecting together different, and frequently incompatible networks, sometimes by using machines called gateways to make the connection and provide the necessary translation, both in the terms of hardware and software. A collection of interconnected networks is called an inter-network or just Internet ___________ Tananebaum pg16.

3. Network Arquitecture How are networks interconnected? Red 1 GW Red 2 Red 1 GW1 Red 2 GW2 Red3

4. Network Arquitecture Internet Protocol: It is the glue that holds together the Internet. It treats all the networks in the same way, for example a LAN like Ethernet or Token Ring, a Wan like ARPANET and even a point to point link between two computers. Designed with internetworking in mind.

5. Network Arquitecture: IP

6. IP in the OSI MODEL Aplications Trustworthy Transport Service Best Effort no Connection Transfer of Packets L7 L4 TCP L3 IP

7. Ethernet Frames: Data Link Layer a) DIX Ethernet Frame b)IEEE 802.3 Frame

8. Frame Demultiplexing in Ethernet IP Module ARP Mod.RARP Mod. Demux Based on Frame Type Frame Arrival 0X800 0X835 0X806

9. The Internet Protocol (IP) Provides mechanisms to transport units called IP datagrams. IP is a best effort protocol. Delivery of datagrams is not guaranteed by this protocol. IP is made up of 5 parts: Datagram Format. Datagram Routing. Error Control. Fragmentation IP Options. DATAIP HEADER The fundamental part of the internet services are the delivery of packets.

10. IP Frame Format 04816192431

11. IPv4 Frame Fields Version (4 bits): Version of the protocol, currently IPv4. Assures compatibility during transition. IHL (4 bits): Tells us how long is the header. Default Value = 5, no options, header 20 bytes. Max value is 15 which limits header to 60 bytes. Type of Service (8 bits): Specifies the way to process a datagram. Precedence UnusedRTD – Precedence: priority from 0 (normal) to 7. – Three flag bits allow the hosts to specify what they care most about the set (Delay, Throughput, Reliability)

12. IPv4 Frame Fields Total Length (16 bits): Includes the length of data and header. Maximum theoretical length 64Kbytes. Identification (16 bits): Frame identification. Unused bit. DF (1 bit): Dont Fragment. Avoid small packet networks. MF (1 bit): More fragments. Used to acknowledge when the last fragment has arrived. All fragments except the last one have it set. Fragment Offset (13 bits): Tells us where in the current datagram the fragment is. Maximum fragments per datagram > 8192.

13. IPv4 Frame Fields Time To live (TTL 8 bits): Theoretically marks the maximum lifetime in seconds of a packet. In practice it counts hops. Initialised to 255, decremented by one at each hop. Prevents packets from wondering around the net forever. Protocol (8 bits): Tells us which protocol to use to interpret the information in the data area. (TCP,ARP,etc.) Analogous to the Type Field in Ethernet. Header Checksum (16 bits): Used to verify the header of a packet. Source and Destination Address (32 bits): Indicate network and host numbers.

14. Analogy between Type and Protocol When Protocol field is initialized to: 1 it indicates that in the datagram area we have encapsulated the ICMP protocol 17 it indicates that in the datagram area we have encapsulated the UPD protocol 6 it indicates that in the datagram area we have encapsulated the TCP protocol

15. Frame Encapsulation Datagram Header Data Header Frame

16. IPv4 Frame Fields Options Field (0 40 bytes): Used to include information not present in the original design. Information for network test. Rarely used. Variable in length.

17. IPv4 Frame Fields Some of the IP Options

18. IPv4 Frame Fields: Options Security: How secret the information might be. Military applications. Monitor specific data. Strict Source Routing: Establishes complete path to follow from source to destination. Useful for emergency packets. Loose Source Routing: Specifies certain routers the packet must travel from source to destination. Allows packets to choose other routers on the way. Application, send routers through a certain type of route.

19. IPv4 Frame Fields: Options Record route: Each router along the path from source to destination writes down its IP address in the options field. Managers can track down bugs in routing algorithm. Used to debug and to modify existing routing algorithms. Ex: packet from ITESM to UNAM. Timestamp: Similar to record route option. Routers record both a 32 bit IP address and a 32 bit timestamp. Used mainly for debugging and algorithm creation. Are 40 bytes enough?

20. IP: Options. Options are included to: Test and Depure the network. IP OPTIONS FIELD : 08162431 0 1 2 3 4 5 6 7 CODE LENGTH POINTER PADDING COPY OPTION CLASS OPTION NUMBER

21. IP Options Class Num OpLongDescription 03varLoose source routing 07varRecord route 09varStrict source routing 24varInternet timestamp

22. IP Addresses IP address formats.

23. IP Addresses NIC: Network Information Center. Assigns only netid portion of the IP address. Host id is the responsibility of the Network Administrator. Examples: Lans. Websites.

24. IP Addresses Special IP addresses.