IP Routing - - PDF document

12 May, 2002 1

IP Routing

2 12 May, 2002 The Computer Communications Course

Subnetting: Subnet Addressing

• ✁✄✂

• ✧★✥✝☎☛✡✟☞✝✍✑✏✠☎✎✞✖✛✜✆✌✡✝✩✙✓✎☎✎✞

• ✮✜✯✠✰

• ✳✔✴✎✆✎✛✣✪✎✵

10

network id

subnet id host id 31

3 12 May, 2002 The Computer Communications Course

Subnets in Routing Tables

• ❆✟✂

• ❈✚✑✵

• ❈✚✑✵

• ❪✝✚✎✂✠❇❈✆✎✂✠✓❃✗

4 12 May, 2002 The Computer Communications Course

Forwarding Procedure

Let Let p p be incoming IP packet be incoming IP packet for each for each entry entry e e in the routing table: in the routing table: if if ( (p.dest_addr p.dest_addr & & e.subnet_mask e.subnet_mask == == e.network_address e.network_address) ) then then if if ( (e.next_hop e.next_hop == ==

direct

) then then use direct delivery use direct delivery else else forward the packet to forward the packet to e.next_hop e.next_hop

5 12 May, 2002 The Computer Communications Course

Example IP Network with Subnetworks

FDDI

Backbone 142.18.1.X

142.18.3.9 142.18.3.53 142.18.3.13 142.18.2.4 142.18.2.7 142.18.2.23 142.18.1.3 142.18.1.13 142.18.1.1

The INTERNET

Subnet 142.18.3.X Subnet 142.18.2.X

142.18.3.3 142.18.2.13

6 12 May, 2002 The Computer Communications Course

Supernetting

• ✧★✥✝☎☛✡✔✗

• ✧★✥✝☎☛✡✌✚✑✵

• ✧★✥✝☎✦✪✝✂

• ❈✚✑✵

• ❈✚✑✵

A B C

7 12 May, 2002 The Computer Communications Course

CIDR Address Allocation

• ✳✎✆✎✲✌✥✢✍✄✵

• ✳✎✆✎✲✌✥✢✍✄✵

• ✶❃✵

8 12 May, 2002 The Computer Communications Course

CIDR Address Allocation: Example

• ❁

• ❁

• ✹✔✻✑✻❈✭

• ☎✎✞✕✲✝✭

9 12 May, 2002 The Computer Communications Course

CIDR Address Allocation: Example (II)

194.0.0.0 194.255.255.255

194.24.0.0 194.24.7.255 194.24.8.0 194.24.11.255 194.24.16.0 194.24.31.255 2048 1024 1024 4096

C a m b r i d g e Edinburg Oxford 10 12 May, 2002 The Computer Communications Course

CIDR Address Representation: Example

• ✁✔✆✝✛✖✍✔✂✟✗

11 12 May, 2002 The Computer Communications Course

CIDR Routing Tables

• ⑨✑✚✝☞✌✞✟✗

• ⑨✑✚✝☞✌✞✟✗

• ❪✄✗

12 12 May, 2002 The Computer Communications Course

CIDR Forwarding Procedure

Let Let p p be incoming IP packet be incoming IP packet for each for each entry entry e e in the routing table: in the routing table: if if ( (p. p.dest dest_ _addr addr & & e.mask e.mask == == e.lowest_block_address e.lowest_block_address) ) then then if if ( (

longest match

) then then if if ( (e.next_hop e.next_hop == ==

direct

) then then use direct delivery use direct delivery else else forward the packet to forward the packet to e.next_hop e.next_hop

13 12 May, 2002 The Computer Communications Course

CIDR Forwarding Example

Great Britain France

Oxford

R1

R12 R11 R10

R101

194.0.0.0 255.0.0.0 R11 195.0.0.0 255.0.0.0 R12 194.24.16.0 255.255.240.0 R10

Routing table of R1:

14 12 May, 2002 The Computer Communications Course

CIDR Forwarding Example (II)

• ❆✕✆✝✲✝✩✠☎✔✞✒❇✜✗

15 12 May, 2002 The Computer Communications Course

IPv6: the Long-term Solution

• Addresses are 16 bytes (128 bits)

Addresses are 16 bytes (128 bits)

convention: 8000:0000:0000:0000:0123:4567:89AB:CDEF convention: 8000:0000:0000:0000:0123:4567:89AB:CDEF

::132.65.200.21 for IPv4 ::132.65.200.21 for IPv4

more than 1500 addresses for each m more than 1500 addresses for each m2

2 of surface area on the

• f surface area on the

planet (an address to every car, or even to every wheel planet (an address to every car, or even to every wheel… …) )

The IP header is doubled from 20 to 40 bytes The IP header is doubled from 20 to 40 bytes

• Three type of addresses:

Three type of addresses:

provider/geographically oriented provider/geographically oriented unicast unicast

anycast anycast: corresponds to more than one interface : corresponds to more than one interface

a packet sent to such address should be received by one of a packet sent to such address should be received by one of the interfaces sharing the address the interfaces sharing the address

multicast with support for multicast with support for scoping scoping

• Interoperability with IPv4

Interoperability with IPv4