1 CSCI 233 Internet Protocols Class 2 Dave Roberts

More on Course Mechanics 50 word limit on homework answers and exam answers “Which is better?”--trick question! Usually there is no “better”, there are tradeoffs 2

3 Good Citizen Principle In a crisis, when resources are short, we tend to hoard resources The hoarding creates shortages What if, in a crisis, each of us reduced our use of scarce resources? The Internet operates on the Good Citizen Principle

Good Citizen Principle When a resource is scarce, instead of trying to claim as much of it as possible, reduce your use of that resource until the scarcity passes 4 This is an important Internet design principle. We will see it again and again.

Important Internet Principles 1.Good Citizen Principle—when a resource is scarce, reduce your demand for it 5

6 Tonight Review of networking technologies Internetworking Protocol Layering Internet addresses

Early Ethernet 7 Stiff wire, hard to bend Vampire connectors reduce performance Hard to change when offices are rearranged

Modern Ethernet 8

Ethernet Frame 9 HeaderPayload

Internetworking How to interconnect networks? –Application level –Network Level Users attach to a local network Internetworking software hides details of networks, forwards information among them 10

Internet Architecture 11

The User’s View 12 ThisLooks Like This

Protocol Layering Internet protocols are organized into levels, called “layers” Each layer deals with certain topics Layers make protocols easier to understand 13

Just Think of Problems Hardware failure Network congestion Packet loss Data corruption Data duplication Data arriving out of sequence 14

Layering and Problems Layering allows a problem to be solved in just one layer Especially, applications do not have to deal with network problems 15

Layers 16

Layering Models OSI 7-layer model –Developed for Open System Interconnect protocol family –International standard developed over years by ISO –Failed TCP/IP 5-layer model –Developed by US DARPA for military use –Widely adopted, basis for the Internet 17

OSI Model We may have an exercise or two The course is about Internet protocols You will never be examined on the OSI model 18

TCP-IP 5-Layer Reference Model 19 VERY IMPORTANT!!!!

Important Boundaries 20

In Reality 21

How It Works 22

What’s Happening 1.Sender hands message to transport layer, which packages message and hands it to Internet layer 2.Internet layer packages message as an IP datagram, with IP addresses, then hands it to network layer 3.Network interface puts message into an Ethernet frame, with Ethernet addresses, and sends through network adapter 23

Encapsulation 24

IP Demultiplexing 25

INTERNET ADDRESSING 26

The Internet Is it a physical or virtual network? It’s a virtual network, defined by protocols that run on hosts and routers. Internet protocols make the Internet look like a world-wide uniform network, although it encompasses many networks that are very different from each other. 27

Internet Addresses Each host connection on the Internet has a unique Internet address The addresses are designed to make forwarding of Internet packets simple An IP address has two parts: a prefix that identifies a network and a suffix that identifies a host on the network 28

Need for Control To avoid conflicts in address use, some sort of authority is needed It makes sense to assign addresses in blocks, not one at a time ICANN (Internet Corporation for Assigned names and Numbers) oversees IP address assignment Originally assigned in blocks of Class A, B and C addresses 29

IPv6 Addressing Each address is 128 bits Enough addresses for every person on earth to have an internet with three times the addresses of the present Internet! addresses per square meter of the earth’s surface 30

IPv6 Address Assignments 31

IPv4 to IPv6 Transition 32

IPv6 Address Split 33

Question How many Internet addresses can one host have? As many as it has network adapters 34

IP Addresses 35

Functions of Internet Addresses Provide a unique identification for a particular interface between a device and the network so that a datagram can be delivered to the correct recipient Enable a path to be found across the Internet to reach the recipient, a process called routing 36

IP and Ethernet Addresses Is the IP address the same as the Ethernet address? –No! What is the role of each? –Ethernet: delivery on the local area network –IP: forwarding across the Internet 37

38 IPv4 Address 32-bit integer, unique for each host on the network, used in all communication with the host ::= –Netid: identifier of a network –Hostid: identifier of a host on the network

39 Dotted Decimal Notation 32-bit Internet address Is written

40 Classes of IPv4 Addresses “Classful” addresses—types A, B and C below first 2 bits distinguish 3 primary classes Design of these classes is for efficient routing There have been other refinements—to discuss later

Class Determination Algorithm 41

Address Class Characteristics 42

Host Capacities 43

IP Address Split 44

Advantages of Classful Addressing Simplicity and clarity—addresses and their setup are very easy to understand Flexibility to accommodate different sizes of networks Ease of separating host address for routing Allows for reservation of some addresses for special purposes 45

Classless IPv4 Addressing Temporary addressing scheme that does away with class A, B, C addresses Network prefix can be any specified length Forwarding techniques expanded to account for this: called Classless Inter-Domain Routing (CIDR) 46

47 Special IP Addresses

IP and Ethernet Addresses Physical transmissions are all made using Ethernet addresses across a local area network IP addresses give destinations across the Internet When a router gets an IP datagram, it decides whether to send it on to another router or deliver it locally 48

Address Resolution If the router decides to deliver locally, then it must find out the local network’s Ethernet address that corresponds to the IP address in the datagram We’ll talk about address resolution next week!! 49