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DESCRIPTION
3 Addressing Address spaces Flat Hierarchical Addressing Modes Unicast Multicast Broadcast Anycast
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1
Lecture, November 20, 2002
Message Delivery to ProcessesInternet AddressingAddress resolution protocol (ARP)Dynamic host reconfiguration protocol (DHCP)TunnelingMobile IP
Routing in Virtual Circuit Networks
2
Message delivery to processes
Host
Process
Network Network
Router Networkinterface Port
IP address = (NetworkId, HostId)
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Addressing
Address spacesFlatHierarchical
Addressing ModesUnicastMulticastBroadcastAnycast
4
Internet addressing
IPv4 address encoding – classes Problems and solutionsSubnettingClassless address encoding
Address resolution protocol (ARP)Dynamic host reconfiguration protocol (DHCP)TunnelingMobile IP
5
IPv4 packet format
32-bit destination IP address
options (if any)
32-bit source IP address
header checksum
packet length (bytes)
fragment identifier
Payload
12-bit fragment offset
ToS
upper layer prottime to live
flags
hlenversion
0 16 318
6
IPv4 address encoding
A
B
C
D
0 NetworkId
110 NetworkId
HostId
HostId
HostId
1110 Multicast address
10 NetworkId
0 8 16 31
E 1111 Reserved
24
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Problems with IPv4 address encoding
The size of the IP address space is: 232
Class C addresses not very useful…Class B addresses wasteful…We would like to group network addresses to reduce the size of forwarding tables.
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SubnettingDefine a subnet mask and a subnet number.Obtain the subnet number:
(IP address) AND (subnet mask)The whole idea is to allocate a single network number to a collection of networks.All hosts in a subnet have the same subnet number.Routing: given a destination IP address the router ANDs this address with the masks of all entries to determine the subnet number of the destination. Example.
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Subnetting
1111 1111 1111 1111 1111 1111 1000 0000
0 8 16 31
(a)
(b)
HostId0001 0111 0000 1110
NetworkId 1011 1000 0010 1100
HostId0000 1110
SubnetId0001 0111
(c)
NetworkId 1011 1000 0010 1100
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Subnet mask: 255.255.255.128Subnet Number: 184.44.23.128
SubnetNumber SubnetMask NextHop184.44.23.0 255.255.255.128 R1184.44.23.128 255.255.255.128 I0184.44.13.0 255.255.255.0 I1184.44.51.128 255.255.255.128 R3
Forwarding table of router R2
R10
1
R20
1
R30
1
H10
H2
0
H5
0
H40
Subnet mask: 255.255.255.128Subnet Number: 184.44.23.0
184.44.23.14
Subnet mask: 255.255.255.0Subnet Number: 184.44.13.0
Subnet mask: 255.255.255.128Subnet Number: 184.44.51.128
184.44.23.35
184.44.23.145
184.44.23.129
184.44.13.20
184.44.13.15184.44.13.19
184.44.51.136 184.44.51.129
184.44.23.133
184.44.23.137
H3
0
2
Internet
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Classless interdomain routing - CIDR
A block of class C addresses are aggregated to have a common prefix.Example:
195.2.32.xx 11000101 00000010 00100000 xxxxxxxx 195.2.63.yy 11000101 00000010 00111111 yyyyyyyyHave a common 18 bit prefix11000101 00000010 001
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Classless interdomain routing - CIDR
In this bloc we have 214 addresses (32-18=14).
If all potential 16,384 hosts in this block are
connected to LANs connected to the same router and
All routers know to use an 18 bit prefix for the lookup phase of forwarding
we are in business.
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Address Resolution Protocol
ARP response
Local Area Network
Source Hardware Address (bytes 0-3)
Source HardwareAddress (bytes 4-5)
Source IP Address(bytes (0-1)
Source IP Address(bytes 2-3)
Target HardwareAdress (bytes 0-1)
Target Hardware Address (bytes 2-5)
Target IP Address (bytes 0-3)
LAN type(e.g. Ethernet, FDDI)
Protocol Type(e.g. IP)
Hlen =48 Plen=32 Operation
(request/response)
0 8 16 31
ARP query
host B
host A
(a) (b)
Switch
Internet
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TunnelingInternetwork
IPheadersrc = 129.5.17.10dst =135.12.7.1
135.12.7.1
Destination NextHop 192.10.5 Inteface 0 195.4.50 Virtual Inteface default Interface 1
Tunnel
0
1
VI
Network 1192.10.5
192.10.5.14
192.10.5.2
R1
195.4.50.3
7129.5.17.10
Network 2195.4.50
2195.4.50.7
R2
IP payload
IPheadersrc = 192.10.5.14dst =195.4.50.3
IP payload
IPheadersrc = 192.10.5.14dst =195.4.50.3
IP payload
IPheadersrc = 192.10.5.14dst =195.4.50.3
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Dynamic host reconfiguration protocol - DHCP
DHCP responseunicast frame
Destination address:the physical address
of host interface
DHCP requestbroadcast frame
Local Area Network
DHCPserver
Laptop
DHCP relay DHCP responseUDP datagram for the
DHCP relay
DHCP requestUDP datagram for the
DHCP serverInternet
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Mobile IP
Internet
Home network 117.17
Tunnel
(1)
(2)
(3)
Sending Host
Router
Home Agent117.17.10.5
Router
Sender's networkRouter
Foreign network 192.6
Foreign Agent192.6.1.8
Mobile Host117.17.1..33
Tunnel
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IPv6flow label
payload length (bytes)
0 16 318
version priority
next header hop limit
128-bit source IP address
128-bit destination IP address
Payload
18
UDP
payload
0 16 318
source port
checksum length
destination port