Uploaded by Eshan Herath

WDD aid

Communication protocols are formal descriptions of digital message formats and rules.
They are required to exchange messages in or between computing systems and are
required in telecommunications.
Communications protocols cover authentication, error detection and correction, and
signaling. They can also describe the syntax, semantics, and synchronization of analog
and digital communications. Communications protocols are implemented in hardware
and software. There are thousands of communications protocols that are used
everywhere in analog and digital communications. Computer networks cannot exist
without them.
Communications devices have to agree on many physical aspects of the data to
be exchanged before successful transmission can take place. Rules defining
transmissions are called protocols.
There are many properties of a transmission that a protocol can define. Common
ones include: packet size, transmission speed, error correction types,
handshaking and synchronization techniques, address mapping,
acknowledgement processes, flow control, packet sequence controls, routing,
address formatting
Popular protocols include: File Transfer Protocol (FTP), TCP/IP, User Datagram
Protocol (UDP), Hypertext Transfer Protocol (HTTP), Post Office Protocol
(POP3), Internet Message Access Protocol (IMAP), Simple Mail Transfer
Protocol (SMTP).
Servers are computers designed to wait for any requests from users or
other computers and then act on that request. Their main purpose is to
be there for you, to share data and perform tasks to keep your workflow
smooth and productivity elevated.
A web server is server software, or hardware dedicated to running said software, that can
satisfy World Wide Web client requests. A web server can, in general, contain one or more websites.
A web server processes incoming network requests over HTTP and several other related protocols.
The primary function of a web server is to store, process and deliver web pages to clients.[1] The
communication between client and server takes place using the Hypertext Transfer Protocol (HTTP)
Commonly used Web server programs
– Apache HTTP Server, Microsoft Internet Information Server (IIS), Sun Java System Web Server
Netcraft networking consulting company Web survey
– Measures Web server software’s relative popularity
∗ Stabilizing in recent years
Web server performance differences
– Workload, operating system, Web pages served
∗ Critical: choose right server for each business need
Apache HTTP Server
– 994: Rob McCool developed Apache
– Original core system with lots of patches
∗ Known as“a patchy”server
– Ongoing group software development effort
– Dominated Web since 1996
∗ Free, performs efficiently
– In IBM WebSphereapplication server package
–Z eus based on Apache open-source code
– Most widely installed Web server software package
– Runs on many operating systems, hardware
Microsoft Internet Information Server
– Bundled with Microsoft Windows Server operating systems
∗ Runs on Windows server operating system (by design)
– Used on many corporate intranets
∗ Adopted Microsoft products as standard products
– ASP, ActiveX Data Objects, SQL database queries
– Microsoft FrontPage Web site development tool, reporting tools
– HTML pages, ActiveX components, scripts can be combined to produce dynamic Web pages
Sun Java System Web Server (Sun ONE,iPlanet, Netscape)
– Original NCSA Web server program descendent
– Former names: Sun ONE, Netscape Enterprise Server,iPlanetEnterprise Server
– AOL-Sun Microsystems partnership called iPlanet
∗ Agreement expired March 2002
∗ iPlanetbecame part of Sun
– Not free: reasonable licensing fee
– Runs on many operating systems
– Web server use
∗ One percent of all Web servers
∗ Busiest and best-known Internet sites: BMW, Dilbert, E*TRADE, Excite, Lycos, Schwab
∗ More than 30 percent of all public Web sites
∗ More than half of top 100 enterprise Web sites
– Supports dynamic application development
– Provides connectivity to database products
The Domain Name System (DNS) is the phonebook of the Internet. Humans access information
online through domain names, like nytimes.com or espn.com. Web browsers interact through
Internet Protocol (IP) addresses. DNS translates domain names to IP addresses so browsers can
load Internet resources.
Each device connected to the Internet has a unique IP address which other machines use to find
the device. DNS servers eliminate the need for humans to memorize IP addresses such as (in IPv4), or more complex newer alphanumeric IP addresses such as
2400:cb00:2048:1::c629:d7a2 (in IPv6).
DNS recursor - The recursor can be thought of as a librarian who is asked to go find a particular
book somewhere in a library. The DNS recursor is a server designed to receive queries from
client machines through applications such as web browsers. Typically the recursor is then
responsible for making additional requests in order to satisfy the client’s DNS query.
Root nameserver - The root server is the first step in translating (resolving) human readable
host names into IP addresses. It can be thought of like an index in a library that points to
different racks of books - typically it serves as a reference to other more specific locations.
TLD nameserver - The top level domain server (TLD) can be thought of as a specific rack of books
in a library. This nameserver is the next step in the search for a specific IP address, and it hosts
the last portion of a hostname (In example.com, the TLD server is “com”).
Authoritative nameserver - This final nameserver can be thought of as a dictionary on a rack of
books, in which a specific name can be translated into its definition. The authoritative
nameserver is the last stop in the nameserver query. If the authoritative name server has access
to the requested record, it will return the IP address for the requested hostname back to the
DNS Recursor (the librarian) that made the initial request.
The Structure of a Domain Name
Every domain consists of at least two parts: the actual domain name and the TLD or Top Level
Domain. In our domain.me example, “.ME” is the TLD of Montenegro and the “domain” part is
a domain name or domain label we chose for our site. You’ve surely heard of some other toplevel domains like .COM, .NET, .ORG, .INFO, .US etc.
Domains are under the jurisdiction of ICANN, the Internet Corporation for Assigned Names and
Numbers which is responsible for creating new and maintaining current top-level domains.
On the other hand, you can choose your domain name and register it with a domain name
registry. So, if you want to register this-is.me, go right ahead!
Now you know that a domain name consists of an actual name and the TLD suffix. There is also
something called a subdomain, which is the third-level of a domain. If you own john.thisis.me domain, “.ME” is top-level domain, “this-is” is the level 2 domain name and “john” is the
subdomain of “this-is” domain. It’s really not that complicated; just follow the hierarchy from
right to left.
How are search engine rankings established?
There are hundreds of factors involved in search engine rankings, and Google is in the habit of
updating and tweaking their algorithm to more closely reflect real human contact. What might
have worked several months ago could end up working against you in the long run, so it pays to
stay on top of your SEO, continually improve your site, and keep your content updated.
Good Content
I’ve talked about the connection between content and ranking, and hopefully you’ve taken that
into consideration when building your site. Most users want the sense that there are real people
behind the scenes of a company and their website, and Google rewards the websites that use
this sort of content with a higher ranking on the search results page.
The use of keywords in your content can help your overall performance in search results,
provided you use these keywords in a realistic, humanly readable way. Content that’s crammed
with keywords will work against you. Be strategic in your choice of keywords and create content
that is useful and focused on the topic(s) that are presented on your website. Be useful!
Here again, relevant links to and from your site will help the search engines determine that your
site is filled with useful content, while an overabundance of links could indicate a site that’s
spammy and not useful.
Site design/user experience
Outdated website design, even with great content, can work against you. Certain design
elements have had their day in the sun, and if your site is still using these elements, your ranking
may not be what you hoped it would be. Make sure your site uses current web
design techniques, loads quickly, and presents your content well.