Transcript TCP/IP Model - PlanetLinks.com

Communications Protocol
• All communications between devices require that the
devices agree on the format of the data. The set of rules
defining a format is called a protocol. At the very least, a
communications protocol must define the following:
• rate of transmission (in baud or bps)
• whether transmission is to be synchronous or
asynchronous
• whether data is to be transmitted in half-duplex or fullduplex mode
• In addition, protocols can include sophisticated
techniques for detecting and recovering from
transmission errors and for encoding and decoding data.
TCP/IP Model
1-25-06
Layer
Name
Common
Components
OSI
Reference
Application
HTTP, SMTP, POP3
FTP, DNS
Application
Presentation
Session
Transport
TCP, UDP
Transport
Network
IP, ICMP
Network
Physical
Ethernet, FDDI
Data Link
Physical
TCP/IP Protocols
• Hypertext Transfer Protocol (HTTP)
– Web servers implement this protocol. Short
for HyperText Transfer Protocol, the
underlying protocol used by the World Wide
Web. HTTP defines how messages are
formatted and transmitted, and what actions
Web servers and browsers should take in
response to various commands. For example,
when you enter a URL in your browser, this
actually sends an HTTP command to the Web
server directing it to fetch and transmit the
requested Web page.
TCP/IP Protocols
• Simple Mail Transfer Protocol (SMTP)
– Used by e-mail servers (and sometimes Web servers)
to send e-mail. Short for Simple Mail Transfer
Protocol, a protocol for sending e-mail messages
between servers. Most e-mail systems that send mail
over the Internet use SMTP to send messages from
one server to another; the messages can then be
retrieved with an e-mail client using either POP or
IMAP. In addition, SMTP is generally used to send
messages from a mail client to a mail server. This is
why you need to specify both the POP or IMAP server
and the SMTP server when you configure your e-mail
application.
TCP/IP Protocols
• Post Office Protocol Version 3 (POP3)
– A protocol used to retrieve e-mail from a mail server.
Most e-mail applications (sometimes called an e-mail
client) use the POP protocol, although some can use
the newer IMAP (Internet Message Access Protocol).
– There are two versions of POP. The first, called
POP2, became a standard in the mid-80's and
requires SMTP to send messages. The newer
version, POP3, can be used with or without SMTP.
TCP/IP Protocols
• IMAP - Short for Internet Message Access
Protocol, a protocol for retrieving e-mail
messages. The latest version, IMAP4, is similar
to POP3 but supports some additional features.
For example, with IMAP4, you can search
through your e-mail messages for keywords
while the messages are still on mail server. You
can then choose which messages to download
to your machine.
• IMAP was developed at Stanford University in
1986.
TCP/IP Protocols
• File Transfer Protocol (FTP)
– The protocol for exchanging files over the Internet.
FTP works in the same way as HTTP for transferring
Web pages from a server to a user's browser and
SMTP for transferring electronic mail across the
Internet in that, like these technologies, FTP uses the
Internet's TCP/IP protocols to enable data transfer.
– FTP is most commonly used to download a file from a
server using the Internet or to upload a file to a server
(e.g., uploading a Web page file to a server).
TCP/IP Protocols
• DNS
– Short for Domain Name System (or Service or
Server), an Internet service that translates domain
names into IP addresses. Because domain names
are alphabetic, they're easier to remember. The
Internet however, is really based on IP addresses.
Every time you use a domain name, therefore, a DNS
service must translate the name into the
corresponding IP address. For example, the domain
name www.example.com might translate to
198.105.232.4.
– The DNS system is, in fact, its own network. If one
DNS server doesn't know how to translate a particular
domain name, it asks another one, and so on, until
the correct IP address is returned.
TCP/IP Protocols
Transmission Control Protocol (TCP)
– Creates a reliable connection between two
computers. TCP is one of the main protocols
in TCP/IP networks. Whereas the IP protocol
deals only with packets, TCP enables two
hosts to establish a connection and exchange
streams of data. TCP guarantees delivery of
data and also guarantees that packets will be
delivered in the same order in which they
were sent.
TCP/IP Protocols
• Internet Protocol (IP)
– Provides addressing scheme.. IP specifies the format of packets,
also called datagrams, and the addressing scheme. Most
networks combine IP with a higher-level protocol called
Transmission Control Protocol (TCP), which establishes a virtual
connection between a destination and a source.
– IP by itself is something like the postal system. It allows you to
address a package and drop it in the system, but there's no
direct link between you and the recipient. TCP/IP, on the other
hand, establishes a connection between two hosts so that they
can send messages back and forth for a period of time.
– The current version of IP is IPv4. A new version, called IPv6 or
IPng, is under development.
TCP/IP Protocols
• Internet Control Message Protocol (ICMP)
– Provides error messages. an extension to the Internet
Protocol (IP) defined by RFC 792. ICMP supports
packets containing error, control, and informational
messages. The PING command, for example, uses
ICMP to test an Internet connection.
– RFC - Short for Request for Comments, a series of
notes about the Internet, started in 1969.An Internet
Document can be submitted to the IETF by anyone,
but the IETF decides if the document becomes an
RFC. Eventually, if it gains enough interest, it may
evolve into an Internet standard.
TCP/IP Protocols
• User Datagram Protocol (UDP)
– Does not establish a connection, just sends
messages.
– a connectionless protocol that, like TCP, runs on
top of IP networks. Unlike TCP/IP, UDP/IP
provides very few error recovery services,
offering instead a direct way to send and receive
datagrams over an IP network. It's used primarily
for broadcasting messages over a network.
Connecting Your LAN to the
Internet
• Your ISP connects to the Internet
• A WAN connection is used between your
building and the ISP
• A T-Carrier connection is often used
– A digital connection for voice and data
Common T-Carrier Connections
Other ways to Connect to the
Internet
• Integrated services digital network (ISDN)
– Dial-up access
– Basic Rate Interface (BRI) up to 128 Kbps
– Primary Rate Interface (PRI) up to 1.544 Mbps
• Digital Subscriber Line (DSL)
– Often differing speeds for uploads and downloads
– Depending on type, up to 6.1 Mbps for downloads
and 1.544 Mbps for uploads
• Cable Modem
– Shared access cable provided by cable TV company
With the addition of users in the area transfer speeds
will be reduced.
Web Hosting Solutions
• Standard hosting
– Your site resides on the same computer with many
other sites
– Cheapest solution
• Dedicated server
– You have a server that only you use
• Co-location
– Your own server is physically located at the company
that does your Web hosting
Web Browsers
Browser Wars
• A software application used to locate and
display Web pages. The two most popular
browsers are Netscape Navigator and
Microsoft Internet Explorer. Both of these
are graphical browsers, which means that
they can display graphics as well as text.
In addition, most modern browsers can
present multimedia information, including
sound and video, though they require
plug-ins for some formats.
Web Browsers
Netscape
• The creation
• Netscape Navigator was developed by the team
who had created the Mosaic web browser at the
National Center for Supercomputing
Applications. The company they created was
initially named "Mosaic Communications
Corporation" and their web browser "Mosaic",
but a legal challenge from NCSA over the rights
to the name resulted in the company and the
product being renamed. The name "Netscape"
was invented by sales representative Greg
Sands.
Web Browsers
Mosaic Netscape 0.9
Web Browsers
Netscape
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Release history
Mosaic Netscape 0.9 – October 13, 1994
Netscape Navigator 1.0 – December 15, 1994
Netscape Navigator 1.1
Netscape Navigator 1.22
Netscape Navigator 2.0 – September 18, 1995
Netscape Navigator 2.01
Netscape Navigator 2.02
Netscape Navigator 3.0 – August 19, 1996
Netscape Navigator 3.01
Netscape Navigator 3.02
Netscape Navigator 3.03
Netscape Navigator 3.04 – October 4, 1997
Netscape Navigator 4.0 – June 1997
Web Browsers
Netscape
The rise of Netscape
• When the consumer internet revolution arrived in
the mid to late 1990s, Netscape was well
positioned to take advantage of it. With a good
mix of features and an attractive licensing
scheme that allowed free use for noncommercial purposes, the Netscape browser
soon became the de facto standard, particularly
on the Windows platform.
Web Browsers
Netscape
The fall of Netscape
• Microsoft saw Netscape's success as a clear
threat to the dominant status of the Microsoft
Windows operating system. It began a widereaching campaign to establish control over the
browser market. Browser market share, it was
reasoned, leads to control over internet
standards, and that in turn would provide the
opportunity to sell software and services.
Microsoft licensed the Mosaic source code from
Spyglass, Inc., an offshoot of the University of
Illinois, and turned it into Internet Explorer.
Web Browsers
Netscape
• The resulting battle between the two companies
became known as the browser wars. Versions of
IE were markedly inferior to contemporary
versions of Netscape Navigator; IE 3.0 (1996)
began to catch up to its competition; IE 4.0
(1997) was the first version that looked to have
Netscape beaten, and IE 5.0 (1998) with many
bug fixes and stability improvements saw
Navigator's marketshare plummet below IE for
the first time.
Web Browsers
Netscape
• In March 1998, Netscape released most of the code base for
Communicator under an open source license. The product named
Netscape 5, which was intended to be the result, was never
released, as managers decided that the code needed a complete
rewrite. This product, taking growing contributions from the opensource community, was dubbed Mozilla, once the codename of the
original Netscape Navigator. Netscape programmers gave Mozilla a
different GUI and released it as Netscape 6 and later Netscape 7.
After a lengthy public beta, Mozilla 1.0 was released on June 5,
2002. The same code base, most notably the Gecko layout engine,
became the basis of several standalone applications, including
Firefox and Thunderbird.
• These products, however, came too late for Netscape as a business.
Eventually Microsoft emerged victorious in the browser wars, and
Netscape was acquired in 1999 by AOL.
Web Browsers
Internet Explorer
• Internet Explorer 3 was the first major
browser with Cascading Style Sheets
(CSS) support released in August, 1996
and it could handle the PICS system for
content metadata. The improvements
were significant, compared to its main
competitor at the time, Netscape
Navigator.
Web Browsers
Internet Explorer
• The browser was not widely used until
version 4, which was released in October
1997 and was integrated with the
Windows 98 operating system. This
integration, however, was subject to
numerous criticisms (see United States v.
Microsoft). Version 5, released in
September 1998, was another significant
release that supported bi-directional text,
ruby characters, XML and XSL.
Web Browsers
Internet Explorer
• Version 6 was released on August 27, 2001, a
few weeks before Windows XP. This version
included DHTML enhancements, content
restricted inline frames, and better support of
CSS level 1, DOM level 1 and SMIL 2.0. The
MSXML engine was also updated to version 3.0.
Other new features included a new version of
the IEAK, Media bar, Windows Messenger
integration, fault collection, automatic image
resizing, P3P, and a new look-and-feel that is in
line with the style of Windows XP
Web Browsers
Internet Explorer
• For version 7.0 of Internet Explorer, set to ship with
Windows Vista and as a separate download for Windows
XP with Service Pack 2, large amounts of the
architecture, including the security framework, have
been completely overhauled. Partly as a result of these
security enhancements, the browser will be a standalone application, rather than integrated with the
Windows shell, and it will no longer be capable of acting
as a file browser. The "beta 1" (build 5112) and "beta 2
preview" (build 5299) pre-releases both operate in this
new stand-alone manner.
Web Browsers
Developing Web sites For
• Browsers have been criticized for implementing non-standard HTML
markup extensions such as the BLINK tag, which is sometimes
referred to as a symbol for Netscape's urge to develop extensions
not standardized by the W3C, and even mentioned in the fictional
Book of Mozilla. Both IE and Netscape have also been criticized for
following actual web standards poorly, often lagging behind or
supporting them very poorly or even incorrectly. This criticism wasn't
very loud during the days of its popularity as web masters then often
simply developed for Netscape Navigator, but came to be an
increasing annoyance to webmasters who wish to provide backward
and cross-browser compatibility. Today, many web masters still
struggle with cross-browser compatibility do not choose to support
old versions, due to their poor and invalid web standard
implementations.