1. TCP/IP Networking (2:1) Joy Kuri, Haresh Dagale, T.V.Prabhakar

2. Grading Evaluation Evaluation –Class assignments5% –Class tests20% –Lab assignments17% –Lab tests 8% –Final50% Lab timings Lab timings –Friday: 2-00 PM to 5:00 PM

3. References Textbook Textbook –“TCP/IP Illustrated” vol. 1, W.Richard Stevens Additional reading Additional reading –“Data Networks”, D.P.Bertsekas and R.W.Gallager –“Interconnections”, R.Perlman Internet RFCs Internet RFCs –http://www.ietf.org

4. Course site drona.cedt.iisc.ernet.in/moodle drona.cedt.iisc.ernet.in/moodle –Individual accounts will be created

5. IP IP addresses usually refer to interfaces, not machines IP addresses usually refer to interfaces, not machines –Several interfaces: several IP addresses –Same interface: multiple addresses possible

6. IP Also possible to have several interfaces, but only one IP address Also possible to have several interfaces, but only one IP address IP addresses are logical entities IP addresses are logical entities IP provides unreliable and connectionless service IP provides unreliable and connectionless service –Connectionless: each datagram handled independently of others

7. IP addresses 32 bit addresses in IPv4 32 bit addresses in IPv4 Divided into netid and hostid Divided into netid and hostid –Otherwise: too many addresses must be kept track of by routers –A form of “aggregation”: a recurrent theme netid hostid

8. IP addresses Netid: allocated to organizations Netid: allocated to organizations Hostid: allocated by the organization Hostid: allocated by the organization How many bits for netid and hostid? How many bits for netid and hostid? –Large corporations: many hosts, so many hostid bits required –Small organizations: few hosts, few hostid bits Single partitioning scheme will not work Single partitioning scheme will not work

9. IP Addresses Possible scheme: find out the netid-hostid partition by looking at the IP address Possible scheme: find out the netid-hostid partition by looking at the IP address Requires Requires –Breaking up the IP address space into disjoint sets –Each set has a pre-defined number of bits allocated to netid

10. IP addresses IP address space Beginning with 0: Class A 10: Class B 110: Class C 1110: Class D

11. IP address classes 0 hostid (24 bits) 10 14 bits hostid (16 bits) 110 21 bits 1110 multicast group id A: B: C: D: 7 bits hostid 8 netid

12. IP datagram Header Data

13. IP Header Destination address Source address

14. A B C Dest addr: X Next hop: B Dest addr: X Next hop: C Dest addr: X Next hop: A XX X X

15. IP Header Destination address Source address TTL

16. IP Header: Multiplexing IP and lower layers Kernel User Entities using services of IP TCP Other UDP

17. IP Header Destination address Source address TTL Protocol

18. IP Header Destination address Source address TTL Protocol IdentificationFlags Offset With respect to fragmentation

19. IP Header Destination address Source address TTL Protocol IdentificationFlags Offset With respect to fragmentation Version Hdr length In 32 bit words ToS bits IP datagram length

20. Link layer encapsulation Header Data Header Data Hdr Trlr Link layer frame

21. Fragmentation Datagram Frag 1 Frag 2

22. Fragmentation Fragmentation and reassembly are done by the IP layer Fragmentation and reassembly are done by the IP layer Identification (16 bits) Identification (16 bits) –To identify fragments as pieces of the original (along with source and destination addresses, and “protocol” field) Flags (3 bits) Flags (3 bits) –“More” bit –“Don’t fragment” bit –Unused Offset (13 bits) Offset (13 bits) –Offset in 8-byte units from the beginning of the payload of the original