A Uniform Resource Locator (URL) specifies the location of an electronic resource and follows a general syntax of <scheme>:<scheme-dependent information>. The URL components include the scheme (such as http), machine/domain name (such as www.example.com), and path to identify the specific resource. URLs allow both humans and software to directly access resources over the internet or local networks. Common issues that can prevent accessing a URL include typing mistakes, the site being unavailable, or files being moved to a new location.

1. URL
&
protocols

2. URL
A Uniform Resource Locator (URL) is a standard
way developed to specify the location of a
resource available electronically.
RFC 1738

3. URL
What are URLs?
• URLs make it possible to direct both people
and software.
• A URL is like your complete mailing
address:
• In short, a URL is a very convenient way to
direct people to a file or other electronic
resource.
• URLs assist your exploration of the Internet.
John Brown
12 Stoke Road
Stoke-on-Trent
ST4 2DG
• Uniform Resource Locators (URLs)
• http://news.bbc.co.uk/1/hi/education/5341426.stm

4. URL
General URL syntax
<scheme>:<scheme-dependent-information>
Scheme examples:
– http (hyper text transfer protocol)
– ftp (file transfer protocol)
– news (news protocol)

5. URL
Scheme Dependent Information
<scheme>:<scheme-dependent-information>
– The information is detailed with each scheme
– Machine is used for making the file available
– "Path" provides the information
– Example (for HTTP):
http://www.7sport.net/7sport/index.htm
Machine Path
Scheme

6. URL
URL Example (explained)
http://www.7sport.net/7sport/index.htm
Machine Path
Scheme
• http is the scheme
hyper text transfer protocol
• two slashes (//) separate the scheme from the
machine/domain name
• www.7sport.net is the machine/domain name
• single slash (/) separates the name from the path
• Finally 7sport/index.htm is the path.

7. URL
HTTP URL Example (explained)
http://www.w3schools.com/html/html_forms.asp
Machine/Domain Name Path
Scheme
• http is the scheme
hyper text transfer protocol
• two slashes (//) separate the scheme from the
machine/domain name
• www.w3schools.com is the machine/domain name
• single slash (/) separates the name from the path
• Finally html/html_forms.asp is the path.

8. URL
Troubleshooting URLs
Reasons for not being able to access URLs:
– the remote machine refuses the
connection
– the site is very busy (e.g. peak hours of
use)
– you have misspelled the URL
– the file was moved

9. Protocol
In computing, a protocol is a convention or
standard that controls or enables the
connection, communication, and data transfer
between computing endpoints.

10. IP
Internet Protocol is a protocol which is
responsible for addressing and packet
routing between networks.

11. TCP
Transmission Control Protocol basically ensures
that the packets get to their destination in the
current sequence and without error.

12. FTP
File Transfer Protocol is a network protocol used
to exchange and manipulate files over a TCP
computer network, such as the Internet.

13. POP3
Post Office Protocol version 3 is an application-layer
Internet standard protocol used by local e-mail clients to
retrieve e-mail from a remote server over a TCP/IP
connection.

14. SMTP
Simple Mail Transfer Protocol is an internet
standard for e-mail transmission across internet
protocol (IP) networks.

15. PPP
Point-to-Point Protocol, or PPP, is a data link protocol
commonly used to establish a direct connection
between two networking nodes. It can provide
connection authentication, transmission encryption
privacy, and compression.

16. Telnet
Telecommunication network is a network protocol used
on the internet or local area networks. It provides access
to a command-line interface on a remote machine.

17. HTTP
Hypertext Transfer Protocol is an application-level
protocol for distributed, collaborative, hypermedia
information systems. Its used for retrieving inter-linked
resources led to the establishment of the world wide
web (www).