1.3.2016 1 1 Internet Addressing ? dr Nenad Krajnović E-mail: [email protected] 2 What is an IP Address? • 32-bit number, defined by the Internet Protocol (IP) (RFC 791). • IP addresses must be unique within the network. • One IP address may point to: – one and only one destination on the Internet (unicast), or: – one and only one group of destinations (multicast). • IP addresses are 32-bit integers, oftenly written in 4-octet form: 147.91.8.6 • IP address distribution is coordinated in hierarchical manner. • End users receive their address space from their ISP! How many IP addresses exists? • Since 32-bits are used for IP addresses, maximum number of IP addresses is: 4.294.967.296 • Complete address range can not be used for host addressing!
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1.3.2016
1
1
Internet Addressing
?dr Nenad Krajnović
E-mail: [email protected]
2
What is an IP Address?
• 32-bit number, defined by the Internet Protocol (IP) (RFC 791).
• IP addresses must be unique within the network.
• One IP address may point to:
– one and only one destination on the Internet (unicast), or:
– one and only one group of destinations (multicast).
• IP addresses are 32-bit integers, oftenly written in 4-octet form:
147.91.8.6• IP address distribution is coordinated in hierarchical manner.
• End users receive their address space from their ISP!
How many IP addresses exists?
• Since 32-bits are used for IP addresses,
maximum number of IP addresses is:
4.294.967.296
• Complete address range can not be used for
host addressing!
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4
IP Address Structure
• IP address consists of two parts:
147.91.8.6
10010011 01011011 00001000 00000110
Network prefix
(m bits)
Host id
(32-m bits)
5
Network Address
• Addresses all hosts on a network segment:
147.91.8.0 /24
10010011 01011011 00001000 00000000
Network prefix
(m bits)
Host id
(32-m zeros)
/24 - denotes prefix length (m = 24)
6
Subnet mask
• Subnet mask - a way of keeping information about prefix length.
255.255.255.0
11111111 11111111 11111111 00000000
Network prefix
(m ones)
Host id
(32-m zeros)
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Broadcast Address
• Used by IP to broadcast data to all hosts on a given subnet.
147.91.8.255 /24
10010011 01011011 00001000 11111111
Network prefix
(m bits - network prefix)
Host id
(32-m ones)
/24 - denotes the prefix length (m = 24)
8
IP Address Structure - a Review (Repetitio mater studiorum est)
• IP adress:
10010011 01011011 00001000 00000110 147.91.8.6
10010011 01011011 00001000 00000000 147.91.8.0 /24
• Network address:
11111111 11111111 11111111 00000000 255.255.255.0
• Subnet mask:
10010011 01011011 00001000 11111111 147.91.8.255 /24
• Broadcast address:
9
Another Example ...
• Prefix length does notdoes not have to be on octet boundaries:
147.91.9.65 /26
10010011 01011011 00001001 01000001
Network prefix
(m=26 bits)
Host id
(6 bits)
/26 - denotes the prefix length (m = 26)
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Another Example - Review
• IP adress:
10010011 01011011 00001001 01000001 147.91.9.65 /26
10010011 01011011 00001001 01000000 147.91.9.64 /26
• Network address:
11111111 11111111 11111111 11000000 255.255.255.192
• Subnet mask:
10010011 01011011 00001001 01111111 147.91.9.127 /26
• Broadcast address:
Addressing in the LAN
147.91.9.64/26
147.91.9.66
147.91.9.67
147.91.9.68
147.91.9.69
147.91.9.70 147.91.9.71
147.91.9.65
147.91.9.126
147.91.9.72147.91.9.100 147.91.9.101
Addressing in the LAN (VLAN)
VLAN 1
10.10.5.0/24
VLAN 2
147.91.8.0/24
VLAN 8
147.91.9.0/24
VLAN 215
147.91.16.0/23
10.10.5.1
147.91.8.5
147.91.9.1
147.91.16.1
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Addressing in the WAN
21.15.4.1
21.15.4.2
18.240.6.1
18.240.6.2
18.240.6.0/30
21.15.4.6
21.15.4.521.15.4.9
21.15.4.10
21.15.4.13
21.15.4.14
Why we are using network addresses?
147.91.9.64/26
147.91.9.66
147.91.9.67
147.91.9.68
147.91.9.69
147.91.9.70 147.91.9.71
147.91.9.65
147.91.9.126
147.91.9.72147.91.9.100 147.91.9.101
eth0
147.91.9.64/26
147.91.9.66
147.91.9.67
147.91.9.68
147.91.9.69
147.91.9.70 147.91.9.71
147.91.9.65
147.91.9.126
147.91.9.72147.91.9.100 147.91.9.101
eth0
Routing table
147.91.9.65 -> eth0
147.91.9.66 -> eth0
147.91.9.67 -> eth0
147.91.9.68 -> eth0
147.91.9.69 -> eth0
147.91.9.70 -> eth0
147.91.9.71 -> eth0
147.91.9.72 -> eth0
147.91.9.73 -> eth0
147.91.9.74 -> eth0
…
Routing table
147.91.9.64/26 -> eth0
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IP Address Classification
• Total available address space: 0.0.0.0 0.0.0.0 -- 255.255.255.255255.255.255.255.
• We can classify addresses according to the following criteria:
–– Classes:Classes:
– A, B, C, D, E class networks. Classes are now obsoleted!
–– Usage:Usage:
– Public IP addresses (globally routeable, unique and non-reusable).
– Private IP addresses (routeable in private networks only).
– Special IP addresses (reserved, broadcast, multicast etc. networks).
–– Validity:Validity:
– Provider aggregatable (valid until the ISP-User agreement is valid).
– Provider independent (valid until initial criteria for their assignment
are met).
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Network Prefix Length - m
• Prefix length may be determined:– Automatically, depending on the address class - A, B, C, D, E (classful).
– Arbitary, depending on the ISP and customer network topology (CIDR).
• It defines the maximum number of addresses available to the user:
6553665536 //1616 65536 addresses
256256 //2424 256 addresses
6464 /26/26 64 addresses
16 bits
24 bits
26 bits
• Assigned network prefix length may be expanded (subnetting)
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Classful Addressing
• Today mostly obsoleted, used only by some routing protocols.
• Classful addressing was created in the past to ease allocations.
• IP adress space is divided to 5 IP adress classes - A, B, C, D i E:
0 remaining 31 bits 0.0.0.0 - 127.255.255.255A
10 remaining 30 bits 128.0.0.0 - 191.255.255.255B
110 remaining 29 bits 192.0.0.0 - 223.255.255.255C
1110 remaining 28 bits 224.0.0.0 - 239.255.255.255D
1111 remaining 28 bits 240.0.0.0 - 255.255.255.255E
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Prefix Length and Classes
Class IP range Start IP address m Subnet mask
A 0/1 0.0.0.0 8 255.0.0.0
B 128/2 128.0.0.0 16 255.255.0.0
C 192/3 192.0.0.0 24 255.255.255.0
D 224/4 224.0.0.0 - -
E 240/4 240.0.0.0 - -
• Older routing protocols determined prefix length (m) by the class.
• Newer routing protocols explicitly transmit prefix length.
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Classless Addressing(CIDR)
• Basis for classless inter-domain routing (CIDR).
• A customer is assigned an IP network on arbitary boundaries, e.g.:
1319 195195..9191..160160..00 //1919 (81928192 hosts)
• The customer might expand the network prefix length, e.g.:
819 /24/245 3232 subnets, 254254 hosts/subnet
• Subnet number of all 0’s and all 1’s is allowed by default.
• At the time of introduction of classless routing, it was necessary to additionally configure routers to support it.
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Example Network Topology
Ethernet
Ethernet
Ethernet
Repeater
Access
server
Embedded
router
Router Router
Dial-in x 10
Total of 200
hosts
100
hosts
50 PCs
50 PCs
40 PCs
35 PCs
30 PCs
20 PCs
PPP (unnumbered)
1
2
3
4
5
6
7
8
9
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Fixed-length Subnet Masks
Ethernet
Ethernet
Ethernet
Repeater
Access
server
Embedded
router
Router Router
10.0.0.3 10.0.0.12
10.0.0.50 10.0.0.0/24
10.0.0.0/24
Dial-in x 10
10.0.9.0 /24
10.0.0.77
10.0.1.77 10.0.1.2110.0.1.0/24
10.0.1.78 10.0.1.7950 PCs - 10.0.2.0/24
50 PCs - 10.0.3.0/24
40 PCs - 10.0.4.0/24
35 PCs - 10.0.5.0/24
30 PCs - 10.0.6.0/24
20 PCs - 10.0.7.0/24
PPP (unnumbered)
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Addressing Plan - FLSM
i hosts Max addr Start address Prefix Subnet mask Broadcast
1 200 254 10.0.0.0 /24 255.255.255.0 10.0.0.255
2 100 254 10.0.1.0 /24 255.255.255.0 10.0.1.255
3 50 254 10.0.2.0 /24 255.255.255.0 10.0.2.255
4 50 254 10.0.3.0 /24 255.255.255.0 10.0.3.255
5 40 254 10.0.4.0 /24 255.255.255.0 10.0.4.255
6 35 254 10.0.5.0 /24 255.255.255.0 10.0.5.255
7 30 254 10.0.6.0 /24 255.255.255.0 10.0.6.255
8 20 254 10.0.7.0 /24 255.255.255.0 10.0.7.255
9 10 254 10.0.8.0 /24 255.255.255.0 10.0.8.255
Network address and broadcast address can Network address and broadcast address can NOTNOT be used for host be used for host
addressing!addressing!
23
Variable-length Subnet Masks
(VLSM)
Ethernet
Ethernet
Ethernet
Repeater
Access
server
Embedded
router
Router Router
10.0.0.3 10.0.0.12
10.0.0.50 10.0.0.0/24
10.0.0.0/24
Dial-in x 10
10.0.2.192/28
10.0.0.77
10.0.1.77 10.0.1.2110.0.1.0/25
10.0.1.78 10.0.1.7950 PCs - 10.0.1.128/26
50 PCs - 10.0.1.192/26
40 PCs - 10.0.2.0/26
35 PCs - 10.0.2.64/26
30 PCs - 10.0.2.128/27
20 PCs - 10.0.2.160/27
PPP (unnumbered)
24
Addressing Plan - VLSM
i hosts Max addr Start address Prefix Subnet mask Broadcast
1 200 254 10.0.0.0 /24 255.255.255.0 10.0.0.255
2 100 126 10.0.1.0 /25 255.255.255.128 10.0.1.127
3 50 62 10.0.1.128 /26 255.255.255.192 10.0.1.191
4 50 62 10.0.1.192 /26 255.255.255.192 10.0.1.255
5 40 62 10.0.2.0 /26 255.255.255.192 10.0.2.63
6 35 62 10.0.2.64 /26 255.255.255.192 10.0.2.127
7 30 30 10.0.2.128 /27 255.255.255.224 10.0.2.159
8 20 30 10.0.2.160 /27 255.255.255.224 10.0.2.191
9 10 14 10.0.2.192 /28 255.255.255.240 10.0.2.207
Network address and broadcast address can Network address and broadcast address can NOTNOT be used for host be used for host
addressing!addressing!
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IP Address Distribution
ISP ISP
ISP ISPISP ISP ISPISP
IANA
Assignments
Allocations
RIPE NCC ARIN APNIC LACNIC AfriNIC
Internet Registries
27
Address Distribution - Example
ISP
ISP
RIPE NCC
IANA
ISP
193193//88
193.1.32.0 /19193.1.32.0 /19
193193..22..00..0 0 //1616
193.1.128.0 /18193.1.128.0 /18
193.2.20.32 /27193.2.20.32 /27 193.2.20.0 /24193.2.20.0 /24
193.2.8.0 /21193.2.8.0 /21
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Information about address
distribution?
• Every Internet Registry is maintaining
public database about address assignment
• www.ripe.net - RIPE
• www.arin.net - ARIN
• www.lacnic.net - LACNIC
• www.apnic.net - APNIC
• www.afrinic.net - AfriNIC
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Address Categories
Public IP numbers:
• Globally unique - one IP address points to one and only one destination.
• Non-reusable - once used, the same IP address must not be used elsewhere!
• Routable - theoretically “visible” from anywhere in the Internet.
• Need global coordinated allocation/assignment process (IANA, RIRs, ISPs …).
• Agreggatable - routes to 6262..22..1616//2121 and i 6262..22..2424//2121 give 6262..22..1616//2020!
• Limited resource, like a radio-frequency spectrum! They need careful planning!
Private IP numbers:
• Defined by the RFC 1918 (networks 10/810/8, 172.16/12172.16/12 and 192.168/16192.168/16).
• Basic application - intranets, networks behind firewalls or NATs or networks
which won’t connect to the Internet at all!
• They must not be routed on the public networks!
• Need coordination withing the private network where they are used.
32
Special IP Addresses
• Used internally by various networking protocols.
• They must notmust not be used for host/network addressing.
IP network m Abbreviated IP network usage
0.0.0.0 /0 0/0 Default gateway
127.0.0.0 /8 127/8 Loopback network
224.0.0.0 /4 224/2 Multicast addresses (class D)
240.0.0.0 /4 240/4 Class E (reserved by IANA)
• Special addresses are also: network address, subnet mask, broadcast address.
33
Address Validity(RFC 2050)
Provider aggregatable (PA) address space:
• Assigned by the ISPs, for the need of their end users.
• Valid until the agreement between the ISP and the customer is valid.
• Upon provider change, the user must renumbermust renumber their network!
• Provider guarantees global uniqueness and visibility of the assigned addresses.
• Most of assignments, being done today, are provider aggregatable.
Provider independent (PI) address space:
• Address space, formerly assigned directly by InterNIC, RIPE NCC, APNIC.
• InterNIC, RIPE NCC, APNIC do notdo not assign addresses to end users any more!
• The ISP reserves the right to refuse to route them, or to extra charge the cost for
their routing.
• Necessary for multihomed networks!
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