[ ANSWER ] What is Firewalls

Firewalls

Introduction

This lecture discusses about security mechanisms in the Internet namely Firewall . In brief, It's a configuration of routers and networks placed between an organization's internal internet and a connection to an external internet to provide security. In other words, Firewall is a mechanism to provide limited access to machines either from the outside world to internal internet or from internal world to outside world. By, providing these security mechanisms, we are increasing the processing time before one can access a machine. So, there is a trade-off between security and ease of use. A firewall partitions an internet into two regions, referred to informally as the inside and outside.                                                                                    __
                                                                                   |   | _________  Firewall
                  ______________________                     |   |             ____________________
                 |                                           |                     |   |             |                                      |
                 |                                           |                     |   |             |                                      |
                 |      Rest of Internet          |________     |   |_____   |      Intranet                   |
                 |                                           |                    |   |             |                                       |
                 |_____________________ |                    |   |             |___________________| 
                                                                                  |_|
                            Outside                                                                        Inside
 
Security Lapses

• Vulnerable Services    - NFS :  A user should not be allowed to export certain files to the outside world and from the outside world also, someone should not be allowed to export our files.
• Routing based attacks :  Some kind of ICMP message should not be allowed to enter my network. e.g.. Source routing and change route ICMP's.
• Controlled access to our systems :  e.g.. Mail server and web pages should be accessible from outside but our individual PC's should not be accessible from the outside world.
• Authentication : Encryption can be used between hosts on different networks.
• Enhanced Privacy : Some applications should be blocked. e.g..  finger  ...
• PING & SYN attack : Since these messages are send very frequently, therefore you won't be able to do anything except reply to these messages. So, I should not allow these messages to enter my network.

[ ANSWER ] What is a Socket ?

 click here complete Lecture Notes: Computer Networks

What is a Socket ?

In unix, whenever there is a need for inter process communication within the same machine, we use mechanism like signals or pipes(named or unnamed). Similarly, when we desire a communication between two applications possibly running on different machines, we need sockets. Sockets are treated as another entry in the unix open file table. So all the system calls which can be used for any IO in unix can be used on socket. The server and client applications use various system calls to conenct which use the basic construct called socket. A socket is one end of the communication channel between two applications running on different machines.

if u lik

 click here complete Lecture Notes: Computer Networks

e the post just say thank u in comment box.

LTE

LTE
Long Term Evolution or LTE is the first step towards true 4G technologies. To be a truly 4G technology, download speeds of 100 Mb/s and 1Gb/s should be available from moving (i.e. in a car) or pedestrian points respectively. It was however widely decided across the world that companies could market LTE as "4G LTE" due to some having already taken that step and to avoid further consumer confusion with the terms 3.5G or 3.9G that were starting to surface.
LTE offers maximum download speeds of 299.6 Mb/s although there has been controversy over the speeds some operators running LTE networks are providing, sometimes being lower than the supposedly 'inferior' HSPA (plus) technology. Commercially available speeds vary wildly and using the (at the time of writing) recently launched UK LTE network, tests have shown anywhere in between 8-50 Mb/s in available areas. LTE requires brand new network technology and masts / radios. This also means that the devices that support LTE will also need to have a compatible receiver.
Much like the available 3G technologies, connection to an LTE signal will cause an extra strain on your device's battery and it is recommended to manage your connections.
LTE frequency bands vary quite a lot across the world and as a result it is very possible that an LTE compatible device may work in one territory but not another. Due to the difference in frequency bands this could even happen within territories (with different network providers supporting different bands) and is possibly more likely than with previous GSM based technologies where frequency issues existed but were less likely to cause a problem unless you travelled internationally.

GSM / GPRS / EDGE/ 3G / HSDPA / HSPA (plus) and LTE

GSM / GPRS / EDGE/ 3G / HSDPA / HSPA (plus) and LTE

                It can be confusing trying to understand the differences between the various mobile connectivity options listed in the specifications of smartphones and touted by the mobile networks as the best way to connect to the internet. In this guide we will try to summaries these technologies and point out the advantages and disadvantages of each technology.
GSM
  GSM (Global system for mobile communications) is the standard by which the vast majority of mobile handsets work in Europe and is becoming dominant in other parts of the world with over 2 billion people currently using the system. When you purchase a mobile or smartphone it is important to understand what frequencies are used by each technology because manufacturers and networks have a tendency to quote these figures with little explanation as to what they mean.
The majority of GSM networks use 900MHz and 1800MHz but in the US the 850MHz and 1900Mhz are prominent. If these are quoted the phone will be classed as a tri-band phone and can be used in Europe, the US and many other territories (provided your SIM is enabled). If you require mobile access in the Far East and areas such as Scandanavia you will need to check with your mobile provider because at the minimum a quad-band phone will be required and in some areas only a phone purchased in the country will work.
Most GSM phones are primarily used for voice but can be used for mobile internet access via the GPRS Core Network.