Technology Articles Blog
Below is an example check list for Linux server hardening – All ports except SSH, http is blocked. On some of the servers, DNS and SMTP ports are open for name resolution and mail sending purposes. We have hardened the kernel to disable all the unnecessary services. This has been done at the kernel level…
One of the fastest growth rates in the telecommunications industry anywhere in the world is that of mobile radio communication devices. The basic architecture of such a mobile communication network is shown below – Radio telephones or cell phones provide a switched two-way channel between two conversing parties like a conventional telephone. Telephones may…
Olden form of phone systems involved manual exchanges which involved a great task in switching and routing of calls to various subscribers that increased network traffic and longer setup times. Also, fault checking and identification was very difficult. With the introduction of electronic exchanges which used a stored program concept of switching and routing of…
It’s helpful for data communication and IT students to understand the evolution of Data communication systems. The first phase in the evolution of data communication systems was Telegraph Systems. Later, with developments in the telephone systems, it was then possible to interconnect various computer terminals for data communication. With the advancements in network computing and the…
Data Communications is the function of transferring a digital signal from one digital device to another. Data transmission and data communications mean two different things. Data communication has a much wider meaning which embraces not just electrical transmission but, any other factors involved in controlling, checking and handling the movement in a communication-based computer system….
Suppose machine A wants to send its message packets to B which has the IP address 1B. A only knows B’s IP address and thus as a first step, sends an ARP request to B to get machine B’S hardware address. Now, before sending the ARP request, A checks up in its ARP cache whether…
ARP or Address Resolution Protocol is used to map Internet addresses to physical addresses. Address resolution is the process of mapping Internet IP addresses into physical addresses. Two machines in the internet cannot communicate with each other without knowing each others actual physical address i.e address of its hardware interface, for e.g. the network interface…
Below are couple major weaknesses of IP addresses – A machine cannot be assigned a permanent IP address i.e. it should change when the machine is connected to different physical networks When class C networks grow beyond 255 hosts, they should be changed to class B networks. Such changes in IP addresses requires high labor,…
An IP address with all 0’s in the host id, refers to this particular and the IP addresses with all 0’s in the network id refers to this particular network. This network addressing is useful in cases when a host wants to communicate with a network whose network address the host sends the ‘this’ type…
Network and Broadcast address are derived from the general IP addresses and are used for specific or reserved applications. Network address refers to the IP addresses with all the bits in the host address 0s. The network address refers to the network itself. For e.g, a class A address 96.0.0.0 refers to the same class…
Internet address refers to the unique identification or address assigned to each machine in the physical network. The basic need for assigning Internet address is to identify every machine in the network. Internet address is defined as the 32-bit (or 64 bit) address assigned to each machine on the internet so as to identify that…
As shown above, the Internet consists of various physical networks (Net1 … Netn) connected together as a single large network. Each network may have host machines connected or other networks connected within it. G1 .. Gn represents the Gateways or routers that connects two networks. Gateways or routers routes data packets from a host in…
Internetworking is the technology that makes it possible to interconnect many disparate physical networks with diverse underlying hardware technologies and make them function as a coordinated unit. The internetworking / Internet technology hides the details of network hardware and permits computers to communicate independent of their physical network connections. When we speak of interworking technology, we…
ARPANET (Advanced research project agency network) is the oldest wide area packet switched network build by the DARPA (Defense advanced research project agency). Physically ARPANET consisted of about 50 BBN corp’s C30 and C300 minicomputers called the PSNs (packet switching nodes) that were scattered over US and Europe. Each PSN was a dedicated packet switching…
ProNET variation as star topology is as shown below – The 3 hosts are connected logically by a ring connection and physically by a start connection via a wire center. The wire center consists of relays R1, R2, R3, R4 so that the relays connects the corresponding host to the wire center via the interface….
ProNET 10 token recovery is essential to handle situations of loss of token when the host want to transmit. Such token loses occur due to malfunction or electronic interference that damages the token. To recover the token, we implement two timers at each station – flag timers and token timers. The flag timer is reset…
ProNET Token ring technology is an alternative to ethernet technology and it also works fairly good speeds. It uses token ring technology- Token ring network as shown above consists of hosts connected as a ring via wires that comes out of each host and connected to the other host. Each host in the network engage…
Ethernet technology started with using the costly coaxial cables. Now it is possible to carry ethernet frames over cost-effective and cheaper twisted pair cables supporting greater speeds. Another variation of ethernet is to use cable like that of cable TV. This variation of Ethernet is called thin wire ethernet which is expensive but cover only…
Ethernet bridge is a fast computer with two Ethernet interfaces and a fixed program that improve upon the functions of repeaters by replicating the packets, instead of amplifying them. Bridges, thus do not amplify the noise, errors or malformed frames like the repeaters, but only reproduces a completely valid frame. Ethernet bridges supports CSMA/CD mode…
Ethernet Addresses refers to the unique physical/hardware address assigned or hardcoded on to the Ethernet interface card in 48 bits machine readable form. Physical ethernet addresses are meant to be different for each interface card and moving the hardware to a new machine or replacing the existing card with a new one will change the…
Ethernet data transmission enabled by TCP/IP is a best-effort delivery method. i.e the sender is given no information about whether the data packets were received by the receiver or not. The hosts in the Ethernet participate in data communication over the common Ethernet bus by a process of carrier sense multiple access with collision detection…
A cross section of a Ethernet cable is as shown below – Ethernet is typically a 10Mbps local area packet switched network technology. The cross section of an Ethernet cable is as shown above. The Ethernet coaxial cable is of 1/2 inch in diameter and is extendable upto 500-1500 meters. The outer insulating jacket and…
WAN (Wide Area Network) connects machines over widely separated geographical locations. A WAN usually consists of various packet switches installed at various points on the network to carry the signals to long distances. LAN (Local Area Network) span shorter distances usually with an enterprise or within the enterprise department. Since LAN cover shorter distances, they…
TCP/IP internet services and other internetworking services can be compared on the basis of following features of TCP/IP internet – Network Topology Independence While TCP/IP is based on conventional packet switching technology that defined datagram as the unit of data transmission, it is independent of any particular vendor’s hardware or other underlying network technologies. …
Internetworking is the technology that makes it possible to interconnect many disparate physical networks with diverse underlying hardware technologies and make them function as a coordinated unit. The internetworking/internet technology hides the details of network hardware and permits computers to communicate independent of their physical network connections. When we speak of internetworking technology, we speak of…
ISDN, though not popular in US, it is still one of the most popular data communication networks in UK, India and many other European countries. ISDN evolved from the IDN (Integrated Digital Network) in which both the transmission media and switches employs digital techniques. In this system, speech signals are converted to digital signal at…
One of the fastest growing telecommunication industry is obviously mobile radio communication. Below figure shows a basic architecture of such a mobile communication network – Radio telephones or cellphone, as they are generally called, provides a switched two way channel between two conversing parties like a conventional telephone. Telephones may be in vehicles which can…
In the past, we had manual exchanges which involved a great task in switching and routing of calls to various subscribers that increased network traffic and longer setup times. Also fault checking and identification was very difficult. Now, with the introduction of electronic exchanges which uses a stored program concept for switching of calls and…
Almost all of the Data communication systems across the world evolved from Telegraph systems. Later with developments in the telephone systems, it was now possible to interconnect various computer terminals for data communication. With the advancements in the network computing and the digitization of telephone networks, it was now possible to setup an efficient data…
Data communication is the function of transporting digital signal from one digital device to another. Data transmission and data communications means two different things. Data communications has a much wider meaning which embraces not just electrical transmission but many other factors involved in controlling, checking and handling the movement of information in a communication-based computer…
Here is a simple light weight HTTP analyzer written in PHP. I wrote this to brush up my skills writing schedulers for a typical LAMP stack. Nothing fancy, there are more things to implement on detecting malicious requests, but this will get you started – <?php /** //Simple http log parser and report generation script…
If you are not one of the people who have had the bad experience of having your email account being subjected to a bulk spam attack, you are lucky. But what to do if you are? Don’t panic. I recently faced this situation and I will explain how to solve this. Follow through the points…
Parallel execution has been one of the core techniques of programming languages that enables and stabilizes the heavy orchestrated flow of information across information management systems. All Object Oriented Programming languages provides couple different ways to implement this to function smoothly under heavy and stressful load 🙂 A better way was introduced in C# which…
Software Project Size is of great importance since it determines the level of management controls and the types of tools and technologies required for a software project. Accordingly, software projects are classified into 6 major categories as follows (this basic yard stick is used in all of the diversified software development and project management methodologies)…
Software Engineering is and will be the backbone and driving force behind the technological advancements that we enjoy and that will lead us to greater realms of information and knowledge management. Its good for us to refresh our basics and foundations. Software Engineering is a discipline which was conceptualized, developed and is constantly reviewed for…
Design patterns in general helps you to implement standardized and efficient solutions to software design and programming problems. Design patterns are not pure inventions like a light bulb or a car. They are derived patterns that software engineers and architects found that could be standardized to be used to solve similar problems categorized across 3…