Download Local Area Networks, 3rd Edition David A. Stamper

Local Area Networks, 3rd Edition
David A. Stamper
Part 5: Connecting to Other Systems
and Networks
Chapter 15
Internet Technology
© 2001 by Prentice Hall
14-1
Chapter Preview
In this chapter you will study:
• Describe the TCP/IP protocol
• Discuss Internet addressing
• Describe several protocols used on
the Internet
• Define a subnet and describe how
they are used
• List several components of the
TCP/IP protocol suite
© 2001 by Prentice Hall
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Internet Addresses
• Internet addresses are represented in a variety of
formats; however, all the formats are ultimately
resolved to a 32-bit number known as an IP
address.
• A 128-bit address is part of a new version of the
IP protocol.
• On the Internet, all network addresses must be
unique. Within a network, all subnet addresses
must be unique, and within a subnet all node
addresses must be unique.
• Currently there are four address classes, A
through D; Class E is defined but reserved for
future use.
© 2001 by Prentice Hall
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Internet Address Class Summary
Class
Subnets
Nodes
Comments
A
27 = 128
224 = 16 million
Address begins with a 0 bit
B
214 = 16,000
216 = 64,000
Address begins with bits 10
C
221 = 2 million
28 = 256
Address begins with bits 110
D
Address begins with bits 1110
© 2001 by Prentice Hall
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Subnet Addresses
• An Internet address is composed of three basic
parts: the class type identifier, the network
address, and the node addresses. An installation
that was fortunate to have a Class A address
space has the potential for approximately 16
million node addresses. It is unlikely that the
company would want all these nodes associated
with a single network address. Consequently, it is
possible for a company to divide the node
address range into two parts, a subnet address
and a node address within the subnet.
• This is accomplished by placing a subnet mask
over the local or node address part of the IP
address.
© 2001 by Prentice Hall
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Internet Node Addresses
• Static Addressing
– Static addressing means that a node is assigned a permanent IP address.
This is common for nodes that are continuously operating on the Internet or
network using TCP/IP.
• Dynamic Addressing
– In dynamic addressing, a node is assigned an Internet address when one is
needed. With dynamic addressing, a node will be given any address that is
not currently in use. The most common mechanism for dynamically
assigning Internet addresses is the dynamic host configuration protocol
(DHCP).
• Internet Addressing on LANs
– If a LAN node also has an IP address, an IP message can be delivered only if
the IP address is first translated into MAC address. The protocol that
performs this function is called the address resolution protocol (ARP).
© 2001 by Prentice Hall
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IP Routing
• Devices called routers are responsible for
internetwork message forwarding. Each router is
connected to two (or more) networks (some
routers have more than two ports), and each
router port has an address on the attached
subnet.
• Each router maintains a router table.
• Internet Naming Conventions
– For most Internet users, the four-octet address representation, called a
dotted decimal, is too cumbersome. Therefore, most users substitute a
naming convention called a uniform resource locator (URL). A URL uses
names and abbreviations that are easier to use and remember than the
dotted decimal representation.
– Domain names are a hierarchical word-oriented representation of an Internet
address.
© 2001 by Prentice Hall
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Root Level Domain Names
Com
edu
gov
mil
net
org
at
au
be
ca
de
es
fi
fr
it
jp
us
Commercial enterprise
education, for example, a university
U.S. government
U.S. military
network service
nonprofit organization
Austria
Australia
Belgium
Canada
Denmark
Spain
Finland
France
Italy
Japan
United States
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Domain Name Hierarchy
AF AU CA CN DE FR JP...US...ZW
COM EDU GOV MIL NET ORG
ABC Acme BGH….XYZ
grumpy doc sneezy… bashful
© 2001 by Prentice Hall
Countries
Most General
Organizational
Companies
Hosts
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Some URL Protocols
http
hypertext transfer protocol
ftp
file transfer protocol
file
file access
mailto
Send mail to a recipient.
news
Access a newsgroup or new article.
Gopher
Use the Gopher text-oriented access.
finger
Use utility to access information about a user.
© 2001 by Prentice Hall
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IP Routing Algorithm
•
•
•
•
•
•
•
•
•
•
Source node obtains the destination node’s IP address.
IP protocol builds the IP header and affixes it to the packet
Send packet to router.
Determine the network address of the destination node.
If the network address is this network, use local delivery
method and skip remaining steps.
Router consults routing table for network address.
Router sends message out on port addressed to next router
Receiving router decrements time-to-live field.
If time-to-live field is 0, packet is discarded.
Return to step 3.
© 2001 by Prentice Hall
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Internet Tools
• Finger
– Finger is a utility that allows a user to gather information about other
network users. For security reasons, some systems do not allow the use of
this utility.
• Tracert
– Tracert allows a user to trace the round trip between the user’s node and
another node on the network.
• Ping
– Ping allows a user to determine if a given system is active on the network.
Some versions of Ping also give performance information like number of
hops to the system and speed of the links if the system is available.
• Talk and Internet Relay Chat (IRC)
– Talk is a UNIX utility that allows on user to communicate interactively with
another user. Through the talk utility, characters typed at one station are
immediately displayed on the other participant’s monitor.
© 2001 by Prentice Hall
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Key Upgrades in IPv6
• Expanded Address Space
– Currently, the length of Internet addresses is 32 bits. This gives an address space of
approximately 4 billion; however, the actual number of addresses available is less
than that because some addresses are reserved and because some address ina class
may not be used. IPv6 increases the size of the address field to 128 bits; this will allow
an address space from 0 to 3x1038.
• Quality of Service
– To accommodate time-sensitive transmissions like audio and video, IPv6 will institute
service categories to prioritize the flow of data. Transmissions declared as real-time
will be provided with improved performance.
• IP Header Changes
– Changes will be necessary to provide for the larger address space and quality of
service.
• Security and Privacy
– IPv6 will allow extensions to the header to provide security capabilities. The
extensions will allow a variety of authentication algorithms and allow detection or
elimination of known techniques for one node to impersonate another node for
sending or receiving packets.
© 2001 by Prentice Hall
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Ipv6 Header Format
Field
Size in Bits
Comments
Version
4
Contains protocol version 6 for Ipv6
Priority
4
Message priority
Flow control
24
Quality-of-service identifier
Payload length
16
Size in octets of packet following the header
Next header
8
Type of header extension, if any
Hop limit
8
Number of hops allowed before datagram is
discarded
Source address
128
Sender’s IP address
Destination address
128
Recipient’s IP address
© 2001 by Prentice Hall
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A Generic Firewall
LAN
The Internet
Generic
Firewall
Protected Systems
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A Gateway Firewall
The Internet
Private Network
Gateway
Firewall
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A Screened Subnet Firewall
The Internet
Traffic Not Allowed
Traffic Allowed
Private Network
Traffic Allowed
Screened Subnet
(Private)
© 2001 by Prentice Hall
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Information Superhighway Uses
• A business might use the information superhighway to
conduct a conference among employees in different
locations.
• A software company might use the information
superhighway to distribute software directly to customers.
• A publishing company might distribute books or magazines
directly to readers or perhaps to a local outlet for ondemand printing.
• Movies and games may be available on demand.
• Education classes at all levels may be available and allow
people to learn new skills at their home or office.
• Electronic mail and video images may be exchanged.
Interactive use of such technologies may give rise to online
discussion groups and conferencing.
© 2001 by Prentice Hall
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Potential Information
Superhighway Implementation
Backbone
Network
Fiber Optic
Cable
Fiber Optic
Cable
Large Business
Local Distribution
Point
Coaxial Cable
or Twisted-Pair Wires
Homes or
Small Businesses
© 2001 by Prentice Hall
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