1. ECE4605: Advanced Internetworking
Raghupathy Sivakumar

2. Administrative Information
Office: 5164 Centergy
Phone:
URL:

3. Announcements 2 students per group
Same group for both project and paper presentations
Either both should be undergraduate students, or both should be graduate students
Please send me preferences for teams by midnight today!!

4. Announcements First four teams will make presentations next week!
I will send out details on the first four groups before next class
First four papers already online
Sample presentation outline online (prepare for 30 minute presentations)

5. Puzzle 1 You have a chain consisting of 63 inter-linked gold links
You have to stay at a motel where the charge per day is 1 gold link
You do not trust the motel manager and neither does he trust you
What is the minimum number of links you need to break in order to stay for 63 days?
Clue: The manager will not sell the links till you check out

6. Overview of TCP/IP

7. TCP/IP Protocol Suite Differences between OSI and TCP/IP? 5 layers:
Physical
Data link/MAC (ARP, SLIP)
Network (IP, ICMP, IGMP)
Transport (TCP, UDP)
Application (http, ftp, telnet, smtp)

8. Medium Access Control
When multiple stations share a common channel, the protocol that determines which station gets access to the shared channel
Key characteristics based on which MAC protocols are evaluated: utilization and fairness

9. MAC Protocols
ALOHA
Slotted-ALOHA
CSMA
CSMA/CD

10. Other MAC Schemes Collision free protocols
Bit map protocol
Binary countdown protocol
Limited contention protocols
Adaptive tree walk protocol

11. TCP/IP Protocol Suite Physical layer Data-link layer – ARP, RARP, SLIP
Network layer – IP, ICMP, IGMP, BootP
Transport layer _ TCP, UDP, RTP
Application layer – http, smtp, ftp

12. Internet Protocol (IP)
Addressing
Routing
Fragmentation and Reassembly
Quality of Service
Multiplexing and Demultiplexing

13. Addressing
Need unique identifier for every host in the Internet (analogous to postal address)
IP addresses are 32 bits long
Hierarchical addressing scheme
Why?
Conceptually …
IPaddress =(NetworkAddress,HostAddress)

14. Address Classes Class A Class B Class C 0 netId hostId
7 bits 24 bits
netId hostId
14 bits 16 bits
netId hostId
21 bits 8 bits

15. IP Address Classes (contd.)
Two more classes
1110 : multicast addressing
1111 : reserved
Significance of address classes?
Why this conceptual form?

16. Addresses and Hosts
Since netId is encoded into IP address, each host will have a unique IP address for each of its network connections
Hence, IP addresses refer to network connections and not hosts
Why will hosts have multiple network connections?

17. Special Addresses hostId of 0 : network address
hostId of all 1’s: directed broadcast
All 1’s : limited broadcast
netId of 0 : this network
Loopback :
Dotted decimal notation: IP addresses are written as four
decimal integers separated by decimal points, where each
integer gives the value of one octet of the IP address.

18. Exceptions to Addressing
Subnetting
Splitting hostId into subnetId and hostId
Achieved using subnet masks
Useful for?
Supernetting (Classless Inter-domain Routing or CIDR)
Combining multiple lower class address ranges into one range
Achieved using 32 bit masks and max prefix routing

19. Weaknesses Mobility Switching address classes
Notion of host vs. IP address

20. IP Routing Direct Indirect
If source and destination hosts are connected directly
Still need to perform IP address to physical address translation. Why?
Indirect
Table driven routing
Each entry: (NetId, RouterId)
Default router
Host-specific routes

21. IP Routing Algorithm RouteDatagram(Datagram, RoutingTable)
Extract destination IP address, D, from the datagram and compute the netID N
If N matches any directly connected network address deliver datagram to destination D over that network
Else if the table contains a host-specific route for D, send datagram to next-hop specified in table
Else if the table contains a route for network N send datagram to next-hop specified in table
Else if the table contains a default route send datagram to the default router specified in table
Else declare a routing error

22. Routing Protocols Interior Gateway Protocol (IGP)
Within an autonomous domain
RIP (distance vector protocol), OSPF (link state protocol)
Exterior Gateway Protocol (EGP)
Across autonomous domains
BGP (border gateway protocol)

23. IP Fragmentation
The physical network layers of different networks in the Internet might have different maximum transmission units
The IP layer performs fragmentation when the next network has a smaller MTU than the current network
MTU = MTU=500
IP fragmentation

24. IP Reassembly Fragmented packets need to be put together
Where does reassembly occur?
What are the trade-offs?

25. Multiplexing Web Email MP3 Web Email MP3 TCP UDP TCP UDP IP IP
IP datagrams
IP datagrams

26. IP Header Used for conveying information to peer IP layers Source
Destn
Application
Application
Transport
Router
Router
Transport IP IP IP IP
DataLink
DataLink
DataLink
DataLink
Physical
Physical
Physical
Physical

27. IP Header (contd.) 4 bit version 4 bit hdr length 16 bit total length
TOS
16 bit identification
3 bit
flags
13 bit fragment offset
8 bit TTL
8 bit protocol
16 bit header checksum
32 bit source IP address
32 bit destination IP address
Options (if any) (maximum 40 bytes)
data

28. Puzzle
Two threads. Each thread will burn completely in 1 hour when lit from an end.
Rate of burn variable and non-uniform (e.g. a thread cut in half will not burn in 30 minutes)
How will you time 45 minutes?