SPDY : Let's Make the Web Faster

Here is a brief description of what SPDY is ?

SPDY is an Experimental Application layer protocol which augments HTTP protocol with new features and best practices. HTTP and TCP are the standard protocols used for the web today. There is not much we can optimize at the transport level (TCP) so the HTTP protocol at the application layer was rethought. HTTP protocol at the application layer has a lot of drawbacks. Thus SPDY was designed to overcome these drawbacks of HTTP and help load the web Pages faster. 

SPDY introduces some of features such as Multiplexing of Streams, Request Prioritization, Server initiated streams and HTTP Header Compression. It has been experimentally determined that page loads are 50% faster in SPDY than in HTTP. There are both client and server level support for SPDY protocol. SPDY is easier to deploy and is also server efficient. SPDY with SSL is also implemented for secure transmission of data over SPDY protocol.

 Important goals of SPDY include faster page loads and improved web security. SPDY also supports Bidirectional streams. Most of the client end Browsers such as Firefox, Silk and Chrome now fully support SPDY protocol. At the server side, Servers such as Apache, Jetty etc. are now supporting SPDY. Most of Google Web sites now have completely implemented SPDY protocol.

Server : The King in a Network

Everything you do on the internet from Social networking, Emailing to watching videos make use of the server. All the applications you use on the internet are actually hosted in some remote computer called server.

What is a Server ?

A Computer on the network which serves other computers is called a server.

In simple sense, it is a computer on the network which basically serves the requests of the client computers on the network. The request from client may be request for some resource such as some file or some web page,these are all taken care by the server. A client simply has to connect to a server on the network and request for resources, if the client is  authorized for that resource than definitely the client is served by the server.

Server Operating Systems :

Since a server serves some thousands of clients at any time,the server OS should be Robust, Stable and Secure to meet the demands of the clients connected to it.

There are these special purpose server operating systems which are designed and built specifically to make the server robust,stable,secure and scalable.

A server operating system is not packaged with lots of GUI and flashy applications as seen on normal desktop OS, this is to avoid security vulnerabilities in the server systems.

In server OS you will be given a command prompt,using which required software packages such as Apache Web server, Filezilla, MySQL should be configured and installed.

Some of the well known server operating systems are :-

Ubuntu Linux server.

Red Hat Linux Enterprise Edition.

OpenSuSE Linux Enterprise Edition.

Windows 2008 Server. etc 

Server Hardware :

A Server should be up and running 24 hours a day , 7 days a week . Usually the server is booted once or twice in 2-3 months. So, you definitely need special purpose hardware to build such robust,reliable and persistent systems.

• Server Processors : Intel XEON processors are used which are robust and reliable.

• Redundant Power Supplies : Usually servers are provided with 2-3 power cables , to make sure that even if one power cable fails the server is still up and running.You can Hotswap these power modules which basically means that you can remove the faulty power cable and replace with another power cable without rebooting the system.

•  RAID ( Redundant array of Inexpensive disks ) : Raid is used to make multiple physical hard disks to fall into a single logical disk. RAID is basically an array of Hard disks which are Hotswappable . Once the hard disks change in the RAID they are configured accordingly to fit in the new hard disk .

• ECC RAM : Since servers need a lot sophisticated RAM which does not get corrupted easily, a special purpose RAM known as ECC RAM is used which does error checking and corrections.

Server Functions :

Servers provide varied functionality to all its clients depending on the request.

Servers are configured with the following software packages to serve clients :

1. Apache Web Server : Is a software installed on the server which is used to fetch web pages to the client. IIS is used in-case of Windows 2008 Server.
2. FTP Server : Software which serves the clients with files.
3. Mail Servers : Which help to send and receive electronic mails.
4. Active Directory Service

and much more..

Authentication :

Server resources are protected to prevent illegal access to the data.So usually a client is given permissions to access only specified regions of data on server.So client sends the username and password to the server and then server validates the information and sends back the access token which is used further to access the authorized resources on the server. 

Servers are indeed the king of networks in the sense they fulfill all the demands of there clients . Analogy being servers to be the king and clients to be the people in the kingdom ruled by the king. 

 Provide your feedback and valuable comments on the article....

Firewall

According to Wikipedia 

"A firewall is a device or set of devices designed to permit or deny network transmissions based upon a set of rules and is frequently used to protect networks from unauthorized access while permitting legitimate communications to pass. "

Firewall acts as a filter between the Home /private network and the Internet allowing only specified packets to enter into or exit the private/home network.

There are basically two types of firewalls :

1 : Hardware firewalls.

2 : Software firewalls.

Hardware firewalls :

Hardware firewalls are physical devices with ports. These devices are extensively used in Large and medium sized IT firms to control the traffic flow.The device is configured to allow/deny only certain packets to enter or exit through certain ports.

Ex :Cisco ASA 5500 series etc.

Software firewalls :

Software firewall is a software which is used to configure the rules of the firewall. It is configured to allow/deny the traffic only through certain pre-configured ports.

Ex : Antivirus programs,UFW in Ubuntu, SuSEfirewall2 in OpenSuSE etc.

Usually Servers in a firm are configured with firewalls to prevent access to the server by any anonymous user on the internet. Instead they allow users on the internet to access their server only through some of the standard ports such as 80 (HTTP). All the packets are dropped by the firewall except packets to port no 80.In this way,the packet traffic is filtered.

In a similar way,we can restrict access to some of the websites on the internet using firewalls.Thus firewall can act as a parental control system not letting access to some websites on the internet.

  

UFW firewall Configuration on Ubuntu :

UFW is a software firewall in Ubuntu which is used to configure the packet flow.

$ sudo ufw status 

Shows the current status of the firewall,displays all the rules already laid.

$sudo ufw default allow

By default allows all the traffic through all the ports

$sudo ufw default deny

By default blocks all the traffic through all the ports coming in or going out of the private/home network.

$ufw enable             

Loads all the rules laid and configured.

$ufw disable

Unload all the rules configured.

$ufw allow 80

Allow traffic through port no 80.

$ufw deny 80

Disable packet flow through port no 80. 

$ufw delete allow 80

Deleting the rule set.

$ufw allow from 207.81.88.91

Allow person with 207.81.88.91 IP address to connect to the server and block all others.

$ufw deny from 10.0.0.1

Deny this IP address to connect to server.

Similarly on OpenSuSE we have tool called SuSEfirewall2 which is used to configure firewall on OpenSuSE Linux.

For any queries or clarifications , Leave a comment.

Suggestions for Topics to be included for future posts are welcome.

mail me @ : rajeevrvis@gmail.com

Hubs, Switches and Routers

Hubs, Switches and Routers form an important part of inter-networking. These play a very important role in forwarding of packets from a source to its destination.

Hubs, Switches and Routers can be considered the building blocks of a network.

In this article we will discuss the working and mechanism of operation of each of these entities.

HUB :

1. Hub works at Layer1 (Physical layer) of the OSI model.
2. The Hub undertakes the forwarding decisions based on the bits which arrive into the hub.
3. The bits of information coming in through some port of hub is transmitted across all other ports of the hub regardless of the information.
4. It consists of a giant collision domain and a broadcast domain.
5. Collisions are more.

SWITCH :

1. Switch works at Layer2 ( Data link Layer) of the OSI model.
2. Forwarding decision is based on the MAC addresses.
3. Basically the Switch learns the hosts connected to it and there respective MAC addresses and builds a MAC table which is looked up for future forwarding of packets.
4. Switch is capable of simultaneous routing of many packets across different ports without collisions.
5. It provides a dedicated route and bandwidth for each packet to be routed to its respective destination.
6. If there are n ports then there are 'n' collision domains. 

ROUTERS :

1. Routers work at Layer3 (Network Layer) of the OSI Model.
2. Routers take forwarding decisions based on the Logical addresses provided to a network.
3. Routers maintain a routing table which consists of information which is used to route the packet to its destination.
4. There is no broadcast propagation through routers.
5. Routers are smarter than switches and hubs . They take their routing decisions based on numerous intelligent routing protocols.

If you liked the article , Do provide your feedback.

Do leave a comment on the topics you would love to see on this blog.

mail me at : rajeevrvis@gmail.com

How Email Works ?

Email stands for Electronic mail. Email has become the basic means of communication of information on the web. Through Email, one can send and receive text messages with attached files. 

In this article , we deal with the general Working of an Email

Email is composed usually using two methods :

1 : Through Browser .

2 : By Using Email Client such as Outlook , Thunderbird , Evolution etc.

Email through Browser :

User composes his mail in the browser by visiting the Email service providers websites such as gmail ,Ymail, hotmail etc and also provides the email-id of the receiver. Whenever he/she compiles the message and sends it . The message is sent to the Email server of respective Email service provider using SMTP (Simple Message transport protocol) protocol using port no 25. This email message is further routed across several email servers before it reaches the receivers email server. The receiver then connects to this email server and pulls the message from the email server using POP (Post Office Protocol) through port no 110. In a similar manner whenever receiver replies back the sender with a message ,the email is sent using SMTP and received using POP protocol.

Email through Email Clients :

The working of an email is same with Email Clients as that with Browsers except that the message is pulled and stored locally by the email client for browsing the messages offline.

Sometimes IMAP(Internet Message access protocol) is also used for pulling messages from the email server.

Leave comments regarding the articles  you want to see in the future posts.

Article subjects : mail me at rajeevrvis@gmail.com

Ping Engineering

Ping is networking command available both in Windows and Linux operating systems which is used basically to check the status of the server  or host on the IP network.

According to Wikipedia :
"Ping is a computer network administration utility used to test the reachability of a host on an Internet Protocol (IP) network and to measure the round-trip time for messages sent from the originating host to a destination computer ".


In simple terms , it is used to check for the availability of the host on an IP (Internet Protocol) network which means to check whether a particular host identified by the IP addresss is up and ready to accept connections or not.
Ping was authored by Mike Muuss . 
Ping uses ICMP (Internet Control Message protocol) echo request packets for pinging the host in the network.
These echo request packets sent are echoed by the particular host pinged. 

Domain Name Server ( DNS )

What is Domain name server ?

Domain name server is a server which converts the human readable domain-names into numeric IP addresses .

There exists basically two namespaces in Domain name system :

1 . The Human readable domain names . Ex : www.google.com

2 . The Numeric IP addresses which is used to locate the computer in the network. 

     Ex : 209.85.231.104

Netstat in Unix

Unix Commands are the most robust to use and easier to implement and understand. Unix is provided with some of the unique and the best networking commands which are used for varied activities from packet sniffing to packet analysis. In this tutorial we will discussing about netstat command which is widely used for statistically analysing the network .

Netstat : Is basically used for displaying the network statistics which include routing tables, network and interface connections .

Usage : netstat [options]

Browse Internet through your Mobile Bluetooth in Linux ( 10 Easy steps) :

To Browse the Internet in Linux through your Mobile Bluetooth ( With Net activated in your Mobile )  follow the steps provided as under :
1 ) Enter into your terminal , Switch to the super user mode by using sudo command .

2 ) Connect your Mobile to the system by adding your Mobile device in Network Settings.