Download chap03

Chapter 3
Internetworking
Basics
E-Business Technologies
1
Objectives
In this chapter, you will learn to:
• Identify internetworking hardware, Internet
connections, and network addressing issues
• Describe the TCP/IP protocol suite, IP addresses,
and logical ports
• Explain domain names, the Domain Name
System, and Uniform Resource Locators
• Identify organizations that provide oversight for
the Internet and the World Wide Web
E-Business Technologies
2
Valued Gateway
Client:
Internetworking Hardware
• Special network devices, called switches and
routers, control data transmissions within and
between network segments
• A network segment is part of a network, usually
made up of computers that share a common
function
• These network devices ensure that data sent
between computers on the same segment are
transmitted only on that segment
E-Business Technologies
3
E-Business Technologies
4
Hubs
• Used to connect groups of computers, generally
fewer than 64 computers (inexpensive hubs
generally stop at 6 computer connections)
• Repeats a signal, passing transmissions to all
computers on a segment and the signal can be
'heard' by all computers connected via the hub
• Each computer connects to a hub using a separate
cable
• Hubs can interconnect to other hubs, switches, and
routers
E-Business Technologies
5
Switches
• An intelligent device that analyzes data packets to
determine how to route a data transmission to its
destination
• Reduces congestion by directing data
transmissions to specific ports used to connect
with each computer or device
• Switches can interconnect with hubs, switches,
and routers
E-Business Technologies
6
Routers
• Analyzes data packets to determine how to route a
data
• Specialized computers designed to manage data
transmissions over large LANs and WANs
• Relies on databases containing address
information to locate computers on network (these
'databases' can be maintained within the memory
of the router itself)
E-Business Technologies
7
Firewalls
• A security tool - stands between the outside
networks and the inside networks
• Specialized hardware or software or a
combination of both, that filters all incoming
and outgoing transmissions
• Blocks transmissions that do not meet
specific security criteria
why is this important for denial of
service attacks, spoofed e-mail, etc?
E-Business Technologies
8
Firewalls
• Placed between the public network and
private network
– Public network identifies the external
network connection or portion of the
Internet on the outside of a firewall
– Private network identifies a network or LAN
on the inside of a firewall, such as a
corporate LAN
E-Business Technologies
9
Packet Switching
• The practice of breaking data transmissions into packets
that can travel independently across a network
• Packets are assigned sequence numbers so they can be
reassembled in the correct order at the destination
• Routers direct packets across the network/Internet to their
assigned destination
E-Business Technologies
10
Internet Connections
• Internet connections can take place using many
different types of telecommunications media
– Access devices range from a standard phone line
and a modem to wireless satellite connections
– Individual consumers usually obtain Internet
access through an Internet service provider (ISP)
such as America Online (AOL)
– Businesses usually obtain Internet access using a
shared connection consisting of a router on a
corporate LAN and a telecommunications
connection between the router and the Internet
E-Business Technologies
11
Internet Connection Methods
• Dial-up router - 56Kbps
– Includes a modem that connects to the Internet
when it detects an office computer trying to
access the Internet
• Leased line/Frame relay
– A connection that is always on and much more
reliable than a dial-up connection
• Integrated Services Digital Network (ISDN) 128Kbps to 1.5Mbps (Table 3.1 in text is wrong)
– A dial-up connection about twice as fast as a
dial-up router
E-Business Technologies
12
Internet Connection Methods
• Digital Subscriber Line (DSL) - generally 32Mbps but
up to 52Mbps
– A connection that operates over a standard
phone line, but on a different set of
frequencies than voice conversations; much
faster than ISDN and usually less expensive
• T1 and T3 - 1.5Mbps and 43Mbps
– Communication lines leased from a common
carrier such as AT&T suitable for both voice
and data
E-Business Technologies
13
Network and Internetwork Addresses
• Physical addresses are used in communications
between computers on the same network
• MAC (physical) addresses are permanently set in
a device’s network interface card, such as:
52-54-50-21-D8-9B
• Virtual address, such as an IP address or Domain
Name, are used in communications between
computers over the Internet
E-Business Technologies
14
Internet Addressing
• Routers and other internetworking devices use
logical (virtual) addresses to identify devices or
applications on the Internet
• IP addresses are 32-bit number containing four 8bit octets that identifies a device connected to the
Internet
• Domain Names are text addresses that are
translated to IP addresses
• Port addresses identify the logical connection
between a server and a client application
E-Business Technologies
15
Transmission Control
Protocol/Internet Protocol
• The TCP/IP protocols operate within specific
layers of the OSI Model
OSI Model
Layer
Protocol
Description
Transport
TCP
Connects two computers,
transmits data packets,
verifies data delivery
UDP
Sends data in packets, no
data verification
SKIP SLIDE
E-Business Technologies
16
Transmission Control
Protocol/Internet Protocol
OSI Model
Layer
Protocol
Description
Network or
Internet
IP
Transmits data packets,
routes over intranet/Internet,
assembles at destination
ARP
Identifies host computer,
converts IP address to MAC
address
Reverse ARP
Converts MAC address to IP
address
SKIP SLIDE
ICMP
Reports transmission errors
to routers and host computers
E-Business Technologies
17
Transmission Control
Protocol/Internet Protocol
OSI Model
Layer
Protocol
Description
Application
HTTP
Controls delivery of Web
pages to Web browser
POP3
Provides storage and
forwarding of e-mail
SMTP
Sends e-mail between mail
servers on an IP network
IMAP4
Provides POP3 services, and
remote user access to mail
server
SKIP SLIDE
FTP
Enables file upload/download
between computers
E-Business Technologies
18
SKIP SLIDE
TCP Segments
• Data packets created at the Transport layer by TCP
• Requires an established connection between sending
and receiving computer before transmission
E-Business Technologies
19
TCP Segment Data
SKIP SLIDE
Data
Description
Source Port
Logical port address of the sending
computer
Destination Port
Logical port address of the destination
computer
Sequence Number Specifies the position of the packet in the
flow of data
Acknowledgement Contains receipt of data confirmation
Number
number
TCP Header
Length
Designates the TCP header length
E-Business Technologies
20
TCP Segment Data
SKIP SLIDE
Data
Description
Codes
Specifies any special condition, such
as “urgent”
Sliding-window
Size
Number of data blocks that the
destination computer can receive
Checksum
A value used to ensure data is
transmitted without error
Urgent Pointer
Identifies location of urgent data
Options
Specifies any special options
Padding
Ensures the TCP header is a multiple
of 32 bits
Data
Contains the sent data
E-Business Technologies
21
IP Datagram
• Created in the Network layer by the IP protocol
• Does not require a connection between sending
and destination computer
• Does not provide error-checking
• Does not guarantee data delivery
SKIP SLIDE
E-Business Technologies
22
SKIP SLIDE
IP Datagram
Data
Description
Version
Identifies the version of IP used for
packet formatting
Internet Header Defines the IP header length
Length
Type of Service Specifies the speed, priority, or
(ToS)
reliability of the data
Total Length
Total number of bytes in the IP
datagram
Identification
Specifies the datagram’s sequence
E-Business Technologies
23
SKIP SLIDE
IP Datagram
Data
Description
Flags
Specifics whether the datagram is part
of a fragmented sequence
Fragment Offset
Reports the relative position of the
datagram in a fragmented sequence
Time to Live
Delay time before a datagram is
discarded as undeliverable
Protocol
Identifies the protocol which receives
the datagram (TCP or UDP)
Header
Checksum
A value used to ensure the Header is
transmitted without error
E-Business Technologies
24
SKIP SLIDE
IP Datagram
Data
Description
Source IP
address
IP address of the sending computer
Destination IP
address
IP address of the destination
computer
Options
Contains special processing
instructions
Padding
Ensures the IP header is a multiple of
32 bits
Data
Contains the sent data
E-Business Technologies
25
E-Mail Subprotocols
• Sending and receiving e-mail requires a
mail server and mail client (application)
• A mail server is a computer that supports
both storage and forwarding of e-mail
• A mail client is an application that can
access a mail server to retrieve and send
e-mail
• TCP/IP supports the e-mail subprotocols
— SMTP, POP3, and IMAP4
E-Business Technologies
26
SMTP
• Simple Mail Transfer Protocol is standard e-mail
protocol on the Internet
• It defines the message format and the message
transfer agent (MTA), which stores and forwards
the mail to SMTP, POP3, and IMAP4 servers
• Supports MIME (multipurpose Internet mail
extensions) and other encoding methods to
enable program and multimedia files to be
attached to e-mail messages
E-Business Technologies
27
POP3
• Post Office Protocol 3 mail server is
commonly used on the Internet
• Provides message storage for incoming email until users log on to download
• A simple system with little selectivity, all
pending messages and attachments are
downloaded at the same time
• POP3 servers use the SMTP messaging
protocol
E-Business Technologies
28
IMAP4
• Internet Messaging Access Protocol
is more sophisticated than POP3
• Messages can be archived in folders
• Mailboxes can be shared
• Users can access multiple mail
servers
• Better integration with MIME
E-Business Technologies
29
E-Mail Clients
• Client e-mail programs, such as Eudora or
Outlook, are mail user agents (MUA or UA)
• MUAs submit e-mail messages to SMTP servers
and receives messages from either POP3 or
IMAP4 servers
• MUAs retrieve/submit e-mail from/to the
message store (MS) on a mail server
• The MS holds the mail until it is selectively
retrieved and deleted
E-Business Technologies
30
E-Business Technologies
31
Internet Protocol (IP) Addresses
• Logical address for identifying
computers and devices on the Internet
• 32-bit number composed of four 8-bit
octets:
255.255.255.255
E-Business Technologies
32
Categories of IP addresses
• Public IP addresses can be accessed from
the Internet
• Private IP addresses (such as a LAN behind a
firewall) cannot be accessed from the Internet
• Static IP addresses are assigned to a specific
host and remain unchanged
• Dynamic IP addresses are assigned when a
computer logs on to a network and expires at
log off
E-Business Technologies
33
Logical Port Addressing
•
•
Client/Server applications use logical port addressing to
connect with specific applications across an IP network
There are 65,536 logical ports available on an IP network
E-Business Technologies
34
Well-Known Port Addresses
• Protocol port number that is widely used for a
certain type of data on the network
–
–
–
–
–
Port 21: File Transfer Protocol
Port 25: Outgoing e-mail (SMTP)
Port 80: Web pages (HTTP services)
Port 110: Incoming e-mail (POP3)
Port 443: Encrypted Web pages
E-Business Technologies
35
Domain Names
• Text-based addressing scheme to locate
data on the Internet
• Domain name addresses correspond to a
specific IP address:
ICANN.ORG
192.0.34.65
E-Business Technologies
36
Organizing Domains
•
•
•
Top-level domains
identify major domains
(such as “.com”, “.org”.
“.gov”)
Subdomains identify
computers by
organization function
(such as “baba.org”)
Subdomains are divided
by function (such as
“mail.baba.org”
E-Business Technologies
37
The Domain Name System
• Uses name servers that contain databases
of domain names and their equivalent IP
addresses
• Translates domain names into IP
addresses, also called “resolving a
domain name”
E-Business Technologies
38
Domain Name System
• 13 root servers contain the top level domains
(TLDs)
• IP address downloaded regularly to thousands of
Domain name resolvers
• Name servers at ISP resolves addresses upon
receipt of a request from a Web client
E-Business Technologies
39
E-Business Technologies
40
Registering a Domain Name
• Internet Corporation for Assigned Names and
Numbers (ICANN) manages Domain Name
registration
• Domains can be registered through ICANN or
through a Shared Registration System (SRS)
partner, such as Register.com or VeriSign
E-Business Technologies
41
Registration process
1. Contact ICANN or an accredited registrar
2. Search the database of registered domains to
determine the availability of the desired domain
name
3. Select the domain name, and record the required
accounting information
4. Provide the IP address of host ISP’s primary and
secondary domain name servers
5. Pay the fee
E-Business Technologies
42
Uniform Resource Locators (URLs)
• A URL is a short text address used with a Web browser to
retrieve a Web page and its related files
• A URL includes the TCP/IP subprotocol, host name, domain
name, and the path to the Web page file including any
subfolders and the filename
E-Business Technologies
43
Internet Corporation for Assigned
Names and Numbers
• Internet Corporation for Assigned Names and
Numbers (ICANN) manages Domain Name
registration
• Assigns and tracks IP addresses
• Polices bad Internet practices, such as
cybersquatting
E-Business Technologies
44
World Intellectual Property
Organization (WIPO)
• Operates under United Nations mandate
• Provides global enforcement for copyrights and
trademarks
• WIPO plays an increasing role in resolving
international domain name disputes
E-Business Technologies
45
Internet Society (ISOC)
• ISOC supports the development of Internet standards and
protocols through member groups such as the Internet
Engineering Task Force (IETF) and the Internet
Architecture Board (IAB)
• Membership includes more than 150 organizations and
over 6,000 individual members
E-Business Technologies
46
World Wide Web Consortium (W3C)
• W3C promotes standardization and
interoperability on the Web to assure that Web
languages such as HTML and XML and protocols
such as HTTP are compatible with any hardware
and software used to access the Web
E-Business Technologies
47
Request for Comment
(Setting the Standards)
• An RFC is a tool used by Internet scientists to
help publicize or improve an idea for a new
system or function
• Scientist develops the proposed function, and
then submits an RFC document to the
appropriate standards body
• The RFC is then assigned a unique number and
posted for review and comment
• RFC is refined, reviewed, refined again, and
reviewed again, until agreement is reached on a
new or revised Internet standard
E-Business Technologies
48