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IP Basics - Computer Networks - Lecture Slides, Slides of Computer Networks

During the first semester of our degree program, we study Computer Networks Fundamentals. These lecture slides are very informative for me. The major points which are core of course are:Ip Basics, Internet Network Layer, Router, Network Layer Functions, Protocol, Error Reporting, Datagram Format, Addressing Conventions, Packet Handling Conventions, Path Selection

Typology: Slides

2012/2013

Uploaded on 04/25/2013

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4: Network Layer 4a-1
10: IP Basics
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Download IP Basics - Computer Networks - Lecture Slides and more Slides Computer Networks in PDF only on Docsity!

4: Network Layer 4a-

10: IP Basics

4: Network Layer 4a-

The Internet Network layer

This image cannot currently be displayed.

routing

table

Host, router network layer functions:

Routing protocols

  • path selection
  • RIP, OSPF, BGP

IP protocol

  • addressing conventions
  • datagram format
  • packet handling conventions

ICMP protocol

  • error reporting
  • router ā€œsignalingā€

Transport layer: TCP, UDP

Link layer

physical layer

Network

layer

4: Network Layer 4a-

Protocol stack:

packet forwarding

HTTP

TCP

IP

ethernet

Host A

IP

ethernet

Router R

link

HTTP

TCP

IP

ethernet

Router W

Host B

IP

link ethernet

4: Network Layer 4a-

IP Addressing

 IP address:

 32 bits

 network part (high order bits)

 host part (low order bits)

 Defined by class of IP address?

 Defined by subnet mask?

4: Network Layer 4a-

IP Addressing

How to find the

networks?

 device interfaces with same network part of IP address?

 can physically reach each other without intervening router?

223.1.1.

Interconnected

system consisting

of six ā€œnetworksā€

or one network

4: Network Layer 4a-

IP Addresses (Classes)

0 network^ host

10 network^ host

110 network^ host

1110 multicast address

A

B

C

D

class

1.0.0.0 to

128.0.0.0 to

192.0.0.0 to

224.0.0.0 to

32 bits

given notion of ā€œnetworkā€, let’s re-examine IP addresses:

ā€œclass-fullā€ addressing

Unicast

Multicast

E 1111 reserved

240.0.0.0 to

Reserved

4: Network Layer 4a-

IP Address Space Allocation

CAIDA 1998

4: Network Layer 4a-

Current Allocation

 Interesting to examine current IP address

space allocation (who has class A’s? Etc)

 Who has A’s?

 Computer companies around during initial

allocation (IBM, Apple)

 Universities (Stanford, MIT)

 Have A and still use other IP address blocks?

 CAIDA has info on complete allocation

4: Network Layer 4a-

Recall: How to get an IP

Address?

 Answer 1: Normally, answer is get an IP address

from your upstream provider

 This is essential to maintain efficient routing!

 Answer 2: If you need lots of IP addresses then

you can acquire your own block of them.

 IP address space is a scarce resource - must prove you have fully utilized a small block before can ask for a larger one and pay $$ (Jan 2002 - $2250/year for / and $18000/year for a /14)

4: Network Layer 4a-

How to get lots of IP

Addresses? Internet Registries

RIPE NCC (Riseaux IP Europiens Network

Coordination Centre) for Europe, Middle-East,

Africa

APNIC (Asia Pacific Network Information Centre )

for Asia and Pacific

ARIN (American Registry for Internet Numbers) for

the Americas, the Caribbean, sub-saharan Africa

LACNIC (Latin America and the Caribbean)

Note: Once again regional distribution is important

for efficient routing!

Can also get Autonomous System Numbers (ASNs)

from these registries

4: Network Layer 4a-

How to get a block of IP

addresses?From upstream provider

Network (network portion):

 get allocated portion of ISP’s address space:

ISP's block 11001000 00010111 00010000 00000000 200.23.16.0/

Organization 0 11001000 00010111 00010000 00000000 200.23.16.0/

Organization 1 11001000 00010111 00010010 00000000 200.23.18.0/

Organization 2 11001000 00010111 00010100 00000000 200.23.20.0/

... ….. …. ….

Organization 7 11001000 00010111 00011110 00000000 200.23.30.0/

4: Network Layer 4a-

Hierarchical addressing: route aggregation

ā€œSend me anything with addresses beginning 200.23.16.0/20ā€

Fly-By-Night-ISP

Organization 0

Organization 7

Internet

Organization 1

ISPs-R-Us ā€œSend me anything with addresses beginning 199.31.0.0/16ā€

Organization 2

. . .

. . .

Hierarchical addressing allows efficient advertisement of routing

information:

4: Network Layer 4a-

IP Address Allocation

 CIDR is great but must work around existing

allocations of IP address space

 Company 1 has a /20 allocation and has given out sub portions of it to

other companies

 University has a full class B address

 Company 2 has a /23 allocation from some other class B

 ALL use the same upstream ISP – that ISP must advertise routes to all

these blocks that cannot be described with a simple CIDR network ID and

mask!

 Estimated reduction in routing table size with CIDR

 If IP addresses reallocated, CIDR applied to all, IP addresses reallocated

based on geographic and service provider divisions that current routing

tables with 10000+ entries could be reduced to 200 entries [Ford,

Rekhter and Brown 1993]

 How stable would that be though? Leases for all?

4: Network Layer 4a-

IP addresses: how to get one?

One more time 

 Hard-coded by system admin in a file

 Long with subnet mask, default gateway and DNS

server

 DHCP: Dynamic Host Configuration Protocol:

dynamically get network identity and neighborhood

info dynamically, ā€œplug-and-playā€