addressing in tcp/ip
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Addressing in TCP/IP. LESSON 6 (September 22, 1995) Daniel Z. Tabor Jr. New Jersey Institute of Technology. A Need for Identification Internet Address Classification Network and Host ID Ranges Addresses Specify Network Connections Network and Broadcast Addresses Multicast Addresses. - PowerPoint PPT PresentationTRANSCRIPT
Lesson 6 - (1 of 37)
Addressing in TCP/IPAddressing in TCP/IP
LESSON 6(September 22, 1995)
Daniel Z. Tabor Jr.
New Jersey Institute of Technology
Lesson 6 - (2 of 37)
Outline:Addressing in TCP/IP
• A Need for Identification
• Internet Address Classification
• Network and Host ID Ranges
• Addresses Specify Network Connections
• Network and Broadcast Addresses
• Multicast Addresses
• Weaknesses in IP Addresses
• Common Representation of Addresses
• Loopback Addresses
• Obtaining an IP Address
• Contacting the NIC
• Network Byte Ordering
• Mapping Names to IP Addresses
Lesson 6 - (3 of 37)
A Need for Identification:
• There is a need to establish:– A globally accepted method of identifying
computers.– To provide a universal communication service.
Lesson 6 - (4 of 37)
A Need for Identification:
• 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.
Lesson 6 - (5 of 37)
A Need for Identification:
– Each address is a conceptual pair of (netid, hostid)• netid: identifies a network• hostid: identifies a host on that
network.
Lesson 6 - (6 of 37)
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.
Lesson 6 - (7 of 37)
Internet Address Classification:
• 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.
Lesson 6 - (8 of 37)
Internet Address Classification:
• 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
Lesson 6 - (9 of 37)
Internet Address Classification:
• 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
Lesson 6 - (10 of 37)
Internet Address Classification:
• 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.
Lesson 6 - (11 of 37)
0 1
1
4 2 3 8 24 16 31
0
1
1
1
1 1
1 1 1 1
0
0
0
0
netid
netid
netid
hostid
hostid
hostid
multicast address
reserved for future use
Class A
Class B
Class C
Class D
Class E
IPv4 Address Types:
Lesson 6 - (12 of 37)
Network and Host IDRanges:
Address Network Range Host Range
Class A 0.0.0.0 - 127.0.0.0 0.0.0 - 255.255.255Class B 128.0.0.0 - 191.255.0.0 0.0 - 255.255Class C 192.0.0.0 - 223.255.255.0 0 - 255Class D 224.0.0.0 - 239.255.255.255 N/A
Lesson 6 - (13 of 37)
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).
Lesson 6 - (14 of 37)
Network and BroadcastAddresses:
• 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.
Lesson 6 - (15 of 37)
Network and BroadcastAddresses:
• 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.
Lesson 6 - (16 of 37)
Network and BroadcastAddresses: Notations
• 1’s => ‘All’• 0’s => ‘This’• Netid = 0 => ‘This network’
Lesson 6 - (17 of 37)
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 MBONEMulticast IP and the MBONE) for further information.
Lesson 6 - (18 of 37)
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.
Lesson 6 - (19 of 37)
Weaknesses in IP Addresses:
• 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.
Lesson 6 - (20 of 37)
Weaknesses in IP Addresses:
• 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)
Lesson 6 - (21 of 37)
Common Representationof 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.
• Example: 10000000 00001010 00000010 00011110 = 128.10.2.30
Lesson 6 - (22 of 37)
Loopback Addresses:
• Class A address 127.0.0.0– 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.
Lesson 6 - (23 of 37)
all 0s
all 0s
all 1s
all 1s
host
net
127 anything (often 1)
This host
Host on this net
Limited broadcast(local net)
Directed broadcastfor net
Loopback
Summary of Addresses:
Lesson 6 - (24 of 37)
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.
Lesson 6 - (25 of 37)
Obtaining an IP Address:
• 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
Lesson 6 - (26 of 37)
Image source: Internetworking with TCP/IP vol I (1995 Prentice Hall, Douglas Comer)
Lesson 6 - (27 of 37)
Obtaining an IP Address:
• 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.
Lesson 6 - (28 of 37)
Obtaining an IP Address:
• 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.
Lesson 6 - (29 of 37)
Obtaining an IP Address:
• 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..
Lesson 6 - (30 of 37)
Obtaining an IP Address:
• 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.
Lesson 6 - (31 of 37)
Contacting the NetworkInformation Center:
• Contacting the NIC:– Snail Mail:
Government Systems Inc,
Attn: Network Information Center
14200 Park Meadow Drive
Suite 200
Chantilly, VA 22021
Lesson 6 - (32 of 37)
Contacting the NetworkInformation Center (continued):
– Voice:• 1-703-802-4535• 1-800-365-DNIC
– Fax:• 1-703-802-8376
– E-Mail:• [email protected]
Lesson 6 - (33 of 37)
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)
Lesson 6 - (34 of 37)
Mapping Names toIP 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 Domain Naming System System (Lesson 13).
Lesson 6 - (35 of 37)
ETHERNET 128.10.0.0
MERLIN(multi-homed
host)
GUENEVERE(Ethernet
host)
LANCELOT(Ethernet
host)
128.10.2.3 128.10.2.8 128.10.2.26
192.5.48.3
128.10.2.70
192.4.48.7 192.5.48.6 10.0.0.37TOKEN
RING192.5.48.0
ARTHUR (token ring host)
GLATISANT(router)
TALIESYN(router)
192.5.48.1
To ARPANET
Image source: Internetworking with
TCP/IP vol I (1995 Prentice Hall,
Douglas Comer)
Lesson 6 - (36 of 37)
QuestionsAddressing in TCP/IP
• What range of addresses should never appear on a network?
• If billions of different IP addresses can be created from 32-bits, why is there a shortage?
• If we can identify computers using hardware addresses, why use IP addresses?
• What are the differences between the IP addressing scheme and the U.S. telephone numbering scheme?
• Why have a network standard byte order?
Lesson 6 - (37 of 37)
Reference MaterialsAddressing in TCP/IP
• IP Address to Latitude/Longitude -(http://cello.cs.uiuc.edu/cgi-bin/slamm/ip2ll/)
• Network Information Center (NIC) - (http://ds.internic.net/)
• DNS Resources Directory - (http://www.dns.net/dnsrd/)
• Internetworking w/ TCP/IP Vol I, Douglas Comer.• Internet Standards - RFCs
(ftp://nic.merit.edu/documents/std/)