1.3. IP Service Model

“IP provide deliberately simple, dumb, minimal service”

I. Network Layer:

is responsible send IP datagram to the other end: IP Datagram = IP Data + IP Header

IP(Internet Protocol) is only one protocol must used by Network Layer

II. IP Service’s Property

1. Datagram: self-contained, individual hop-by-hop routing

2. Unreliable: no promise delivered to destination, that is it is not registered mail

3. Best effort: only makes errors, certain conditions happened

4. Connectionless: communication doesn’t start by establishing connection to end

III. IP Service is simple and minimal: WHY?

1. To keep network simple:

packet delivered quickly at low cost maintenance

2. End-to-End principle:

network can become easier to evolve if complicated feature implemented at end host(software). Not in hardware of the Internet

3. Allow a reliable / unreliable choice on top layer

let application choose the reliability(i.e. TCP / UDP) for performance reasons

4. Can work over any link layer:

IP makes a very little expectation of the link layer below. So any of link layer technologies(i.e. wired, wireless) can be implemented

IV. Other services provided by IP

1. TTL(Times To Live: Hop Count): prevent packet looping forever

2. Fragment packets if they are too long to send as itself:

each link layer has maximum bandwidth to send a frame at a time

3. Use header checksum to reduce chance of wrong destination on delivery

4. Allow compatible with new version of IP: IPv6

5. Allow new fields added to datagram header:

pros: new service can be added using new fields

cons: break the goal of simple and minimal design of IP

V. IP Datagram Detail…



Unit 1. The Internet and IP

1.0. The Internet and IP

1.1. A day in the list of an application

1.2. The 4 layer Internet model

1.3. The IP service model

1.4. A day in the life of a packet

1.5. The principle of Packet Switching

1.6. The principle of Layering

1.7. The principle of Encapsulation

1.8. The Byte order and Packet formats

1.9. IPv4 addresses and CIDR

1.10. Longest Prefix Match: LPM

1.11. Address Resolution Protocol

1.12. The Internet and IP(recap)

1.13. SIP — Jon Peterson