Basics of Signal Duplexing

Signal Duplex

A duplex communication scheme is a point-to-point system composed of two or more connected devices that can communicate with one another in both directions.

Duplex systems are employed in many communications networks, either to allow for concurrent communication in both directions between two connected parties or to provide a reverse path for the monitoring and remote adjustment of equipment in the field.

There are two types of duplex communication systems: full-duplex (FDX) and half-duplex (HDX).

A full-duplex (FDX) system, allows communication in both directions, and, unlike half-duplex, allows this to happen simultaneously.

Land-line telephone networks are full-duplex since they allow both callers to speak and be heard at the same time, with the transition from four to two wires being achieved by a hybrid coil in a telephone hybrid. Modern cell phones are also full-duplex.

The Duplex Scheme Available for the Mobile Wimax are , FDD, TDD, H-FDD [Half Duplex FDD].

For the duplexing scheme FDD, TDD, H-FDD are available options in case of mobile wimax. 

• TDD: It has same frequency band for UL/DL.2. Frame is divided in to DL subframe & UL subframe in the time domain. 
• FDD: Different frequency band,2. UL/DL subframes are overlapped in the time domain. 
• H-FDD: Two different frequency bands for DLand UL .2. DL/UL subframes dont overlap in the time domain.

-DR

Basics of MAC Address

MAC Address

Media Access Control is a Physical Address of a System like the IP addresses. They are always represented by decimal value and is a 48 bit value.

A Sample MAC Address looks like: 00-02-A3-B2-67-68

Every piece of hardware on your local network has a MAC address in addition to the IP address assigned to it by the local router, switch or server.

An address system is required to uniquely identify computers and interfaces to allow for local delivery of frames on the Ethernet. Ethernet uses MAC addresses that are 48 bits in length and expressed as 12 hexadecimal digits. The first six hexadecimal digits, which are administered by the IEEE, identify the manufacturer or vendor. This portion of the MAC address is known as the Organizational Unique Identifier (OUI). The remaining six hexadecimal digits represent the interface serial number or another value administered by the manufacturer. MAC addresses are sometimes referred to as burned-in MAC addresses (BIAs) because they are burned into ROM and are copied into RAM when the NIC initializes. 

At the data link layer MAC headers and trailers are added to upper layer data. The header and trailer contain control information intended for the data link layer in the destination system. The data from upper layers is encapsulated within the data link frame, between the header and trailer, and then sent out on the network.

The NIC uses the MAC address to determine if a message should be passed on to the upper layers of the OSI model. The NIC does not use CPU processing time to make this assessment. This enables better communication times on an Ethernet network.

When a device sends data on an Ethernet network, it can use the destination MAC address to open a communication pathway to the other device. The source device attaches a header with the MAC address of the intended destination and sends data through the network. As this data travels along the network media the NIC in each device checks to see if the MAC address matches the physical destination address carried by the data frame. If there is no match, the NIC discards the data frame. When the data reaches the destination node, the NIC makes a copy and passes the frame up the OSI layers. On an Ethernet network, all nodes must examine the MAC header.

All devices that are connected to the Ethernet LAN have MAC addressed interfaces. This includes workstations, printers, routers, and switches.

Network cards each have a unique MAC address. Packets that are sent on the ethernet are always coming from a MAC address and sent to a MAC address. If a network adapter is receiving a packet, it is comparing the packet’s destination MAC address to the adapter’s own MAC address. If the addresses match, the packet is processed, otherwise it is discarded.

MAC Address of any network Card is 6 bytes and 48 bits long. 

Network switches store a list of MAC addresses seen at every port and only forward packets to the ports that need to see the packet.

DHCP servers use the MAC address to identify devices and give some devices fixed IP addresses.

Wanna Check?

Go to command prompt type: 

Start > Run > cmd 

ipconfig/all Enter

 

The network card is responsible for the determining whether the data is intended for it or for another network card. Each network card is given a set of rules that it follows.

 

 -DR

Basics of Network and Internet

01

Welcome to my First Blog!

Hello Readers! 

As I have started my career from this domain, so just wished to share the knowledge for understanding on basics of this domain. Hope it will help everyone to learn the domain. I have tried to keep all the relevant information in this entire blog. Please go to each post and read them. If you have any suggestions and comments on any section, please provide your valuable feedback or suggestion for improvement. 

Secondly this blog can be helpful for anyone who wanted to start a career in network domain, IT domain, Cyber security and Information Security domain. Because all the content were intended to cover those areas only. 

Lets start;

A Basic Computer Network 

A computer network is a group of computers connected together through wired or wireless medium. 

A basic network allows devices to share information or communicate with each other.

How they communicate ?

Language: Binary i.e. 0 and 1

Interface: Physical (Ports) / Wireless 

Medium: Cable / Wifi / Bluetooth / RF

Computers are generally connected from their Ethernet Port (RJ45 Interface/ Network Interface Card) via ethernet cable (UTP Cat cable/ Patch cord) to a LAN port (RJ45 interface) designated at table/wall or direct at Switch device port. 

 

In case of wireless connectivity they are connected through wireless NIC card. 

Basically there are three types of a computer network.

LAN: Local Area Network

MAN: Metropolitan Area Network

WAN: Wide Area Network

There are networks in other way as;

WLAN: Wireless Local Area Network

SAN: Storage Area Network

We will cover each sections in our coming next blogs. 

A computer network is used for following tasks to be performed.

• File Sharing and Transfer
• Browsing Internet and other stuffs.
• Allow user to access information. 

There are different designs of connectivity used such as;

Peer to peer and Client/ Server 

Peer to peer means one to one connectivity. Such as Switch to PC.

Client Server architecture means there is a primary server to which one or multiple PC can be connected through LAN or WAN. For example centralized Database Management Server, One Web application Server, etc. 

Topology: 

The term Network Topology is the logical arrangement of computer networking devices to the way in which the various nodes or hosts or computers of a network are linked together.

So, multiple devices connected with each other physically and logically with each other in various ways as mentioned below; 

• Mesh Topology
• Star Topology
• Bus Topology
• Ring Topology
• Tree Topology
• Hybrid Topology

To know how the network works or behaves, a topology is must required. There are many commercial software available in the market, who represent the network architecture or topology in graphical interface or dashboard for easy identification. 

There are many available tools and software for simulation of network such as Cisco Packet Tracer. It allows students and teachers to design, build, configure, and troubleshoot complex networks using virtual equipment.

Network Interface Card (NIC)/ LAN Card

A NIC (network interface card/ Network interface controller) is designed to connect over a computer network through Ethernet cable or wireless (In case of WNIC). A NIC card can transmit signals at the physical layer and deliver data packets at the network layer, it acts as a middleman between a computer/server and a data network. 

 

Internet

Internet, a system architecture that has modernized communications and methods of information exchange by allowing various computer networks around the world to interconnect. Sometimes known as a “network of networks”. 

It was first created by the Advanced Research Projects Agency (ARPA) of the U.S. Department of Defense. ARPANET was one of the first general-purpose computer networks. It connected time-sharing computers at government-supported research sites, largely universities in United States using packet switching. Then it became a critical section of infrastructure for the computer science research community in the United States.

Bandwidth:

Bandwidth is calculated as the amount of data that can be transferred from one point to another within a network in a definite amount of time. It is expressed as a bitrate and measured in bits per second (bps). Similarly in today’s technology we are more familiar with higher values which are measured as Kbps, Mbps, Gbps, etc,.

The more bandwidth, the more data can be communicated or transferred. 

So this is just a basic and first writeup. Will update and come with new information in my next posts. Stay tuned. 

Thanks!

-DR