A globally accepted method of identifying computers.
To provide a universal communication service.
TCP/IP universal host identifiers - are standard compact binary addresses used for efficient computation in routing
and identification.
Scheme is analogous to physical network addressing where:
Each host on the internet is assigned an integer address (IP address) of 32-bits.
That address is represented in "dotted-decimal"
notation.
Each address is a conceptual pair of (netid, hostid)
netid: identifies a network
hostid: identifies a host on that network.
Internet Address Classification:
IP Addresses (version 4)
Five classes (A,B,C,D,E)
They are distinguished by their first 5 bits.
Addresses are 32-bits.
Later versions of the Internet Protocol may have more
classes and use a different number of bits to represent an
address.
IPv6 (proposed) uses 64-bits.
Class E - (11110) - Reserved for future use.
Class D - (1110) - Multicast addressing.
Currently being used with applications that use selective broadcasting in communication:
Video-conferencing.
MBONE
Audio-conferencing.
The three highest-order bits are used to determine the
three Primary Classes:
Class A - (0) - used for a handful of networks which
have more than 65,536 (216) hosts attached to each.
Netid = 7 bits
Hostid = 24 bits
Ex. (10.0.0.1) - ARPANET
Class B - (10) - used for intermediate size networks that have between 256 (28) and 65,536 (216) hosts attached to each.
Netid = 14 bits
Hostid = 16 bits
Ex. (128.235.251.11) - Hertz.njit.edu
Class C - (110) smallest configuration for hosts. Allows for less than 256 (28) hosts attached to each.
Netid = 21 bits
Hostid = 8 bits
Ex. (195.213.49.3) - Local area networks
Addresses are designed to allow extraction of either id quickly which makes gateway routing more efficient.
Network and Host ID Ranges:
Address
Network Range
Host Range
Class A
0.0.0.0 - 127.0.0.0
0.0.0 - 255.255.255
Class B
128.0.0.0 - 191.255.0.0
0.0 - 255.255
Class C
192.0.0.0 - 223.255.255.0
0 - 255
Class D
224.0.0.0 - 239.255.255.255
N/A
Addresses Specify Network Connections:
Gateways connect two or more physical networks. Each
connection requires its own IP address.
Conventional computers that have two or more physical
connections are called multi-homed hosts and require multiple IP addresses.
IP addresses specify both a network and a host on that
network (not an individual machine, but its connection to
the network).
Network and Broadcast Addresses:
Hostid = 0 (128.235.0.0) : names/addresses the network
as a whole. (Ex. NJIT network)
Hostid = All 1's (128.235.255.255) : directed broadcast address which refers to every host on that network. (Ex.
Hertz.njit.edu)
Netid & Hostid = All 1's (255.255.255.255) : limited
broadcast address provides broadcast address independent of
assigned Netid.
Directed broadcast addresses require knowledge of the network address, limited broadcast addresses do not.
Limited broadcast addresses provide a broadcast address for local networks, independent of the assigned Netid.
Network and Broadcast Addresses:
Notations
1's => 'All'
0's => 'This'
Netid = 0 => 'This network'
Multicast Addresses:
Multicast addresses - provide multi-point delivery of packets.
Also known as selective broadcasting, multicast
addressing is a subset of normal broadcasting.
Multicast addresses can be hardware or software
addresses.
See Lesson 17(Multicast IP and the MBONE) for further information.
Weaknesses in IP Addresses:
If a host moves to a different network, it must change
it's IP address.
If the number of hosts grows more than 255 (Class
C):
The addressing scheme must be changed to a Class B.
Extremely time consuming administration changes must also be made to enable the address change.
Routing:
Multiple IP addresses for a single host may be routed entirely different from each other.
The route chosen depends upon the address chosen (in
some cases).
Knowing only one IP address for a single host may
sometimes NOT be enough.
Availability:
The number of available IP addresses is rapidly reducing, forcing temporary extensions of the IP addressing scheme,
until a more scaleable scheme can be put in place.
If a stable replacement for the current IP addressing scheme is not in place within 5-10 years, all IP addresses will be completely exhausted. (IPv6)
Common Representation of Addresses:
Dotted Decimal Notation - a common way of representing an IP address by using four decimal integers separated by decimal
points to ease in reading.
Each integer represents the value of the binary numbers
contained within that octet of the address.
Reserved for loopback on any local machine to test the communication system and for inter-process communication (IPC) on that machine.
Network 127 addresses should never appear on any network, be routed or propagated beyond the network interface card (NIC).
Commonly used as local IP addresses when configuring PCs for pseudo-SLIP connectivity.
Obtaining an IP Address:
Network Information Center (NIC) is the central authority which ensures that all Internet addresses are unique. It does so by managing the approval and assignment of all IP network addresses.
When requesting an IP address, you should choose a type which fits the current and anticipated future sizes of your company.
Sample size networks and appropriate address classes:
Local Area Networks: Class C
Campus-wide Networks: Class B
Large Companies: Class B
International Networks: Class A
Applying for IP addresses is only needed if your network is going to be connected to the Internet on a permanent basis.
Currently there is a long waiting list for companies
and organizations to obtain IP addresses.
The NIC may soon charge for IP addresses because of the increased demand and lack of available addresses.
When should an organization apply for an IP address?
Any organization that connects to the Internet has no option, they must obtain a registered number.
If an organization communicates with it’s subsidiaries using the Internet, it too must request a registered number.
Advantages and Disadvantages of Registering:
Advantage:
Ensuring that your address and naming conventions are protected (njit.edu).
Disadvantage:
When you connect to the Internet, your use of a registered
address is recorded in the Assigned Numbers RFC along with a
contact names of administrators and policy personnel..
Choosing a network number without official registration:
Avoid Class A addresses.
Do not copy examples given in a configuration handbook
or textbook.
Avoid well-known addresses that are published.
Use high-end Class B or C addresses at random.
Contacting the Network Information Center:
Contacting the NIC:
Snail Mail:
Government Systems Inc,
Attn: Network Information Center
14200 Park Meadow Drive
Suite 200
Chantilly, VA 22021
Voice:
1-703-802-4535
1-800-365-DNIC
Fax:
1-703-802-8376
E-Mail:
NIC@NIC.DDN.MIL
Network Byte Ordering:
Little Endian - lowest memory address contains low-order byte of integer.
Big Endian - lowest memory address holds the high-order byte of the integer.
Direct copying may change the value of data from machine to machine.
TCP/IP protocols define Network Standard Byte Order - most signification byte first (Big Endian)
Mapping Names to IP Addresses:
Most users do not directly use IP addresses when using network services, they use Domain Names which map to IP addresses.
When connecting to a server at NJIT, you use the domain name (hertz.njit.edu) and not it's IP address
(128.235.251.11).
Domain names are not IP addresses, but mapped to them for readability by the Domain Naming System[Lesson 13].
