Basics of Ethernet

Ethernet 

Ethernet is the Media access method in a network where all the device or hosts, that share data or share the bandwidth in between them. Its popular due to its scalability property.

Types: Ethernet , Fast Ethernet , Gigabit Ethernet

Basically Ethernet Uses the multiple access technique of CSMA/CD (Carrier Sense Multiple Access with Collision Detection).

Collision Domain:

Under one physical domain, when two devices transmit packet/ signal / data at a same time, a interference may happen due to the collision on the transmission medium (wire).

Output of a Collision:-

• A signal Jam
• Delay in transmission
• Traffic Congestion
• Low Throughput

Note:- Ethernet works in both Physical and Datalink Layer of the OSI Model.

CSMA/CD :-

CSMA defines by its name as Accessing the Carrier or medium by sensing . CSMA/CD works when a device wants to transmit data in a network it first checks if any other signal is presence in that medium . And if any form of signal present then it detects and waits for clearance to avoid collision of data and hence to avoid traffic jam like condition which results transmission failure or delay.

* Ethernet at the Data-link layer have the main role of Ethernet addressing or MAC addressing . Also it is responsible for framing the data or packet it receives. There are four different type of Ethernet framing used as:-

                              1. Ethernet II

                              2. 802.3

                              3. 802.2

                              4.SNAP

Ethernet Frame

Ethernet Framing consists of packet like in the given figure :-

• Preamble is the header file of the frame, a pattern of  1/ 0 which gives 5 MHz clock at the start of each packet for lock the incoming bit stream of the receiving device.
• DA is the Destination Address contains 48 bits or 6 bytes.
• SA is the Source Address also contains 48 bits or 6 bytes.
• Type is used to recognize the network layer protocol contain of  2 bytes.
• Data is then the actual data sent which contains approx 50-1500 bytes.
• FCS is Frame check Sequence at the end of the frame to monitor the CRC.(Cyclic Redundancy Check).
• Ethernet at the Physical Layer are three different types according to as :-

1. 10base2
2. 10base5
3. 10baseT

 IEEE802.3 standardized as-

10base2:10mbps up to 186 meter in length supports 30 Hosts.

10base5: 10mbps up to 500 meter in length.

10baseT: 10mbps using cat3 twisted pair cabling per 1 Host supports up to 100 meter in length.

100baseTX: 100mbps using cat5/6/7 two pair cabling per 1 Host.

100baseFX: Uses fiber cabling 62.5/125 micron multimode fiber and point to point supports 400meter.

Ethernet cabling :-

Ethernet cabling can be done three types based on the requirement as :

1. Straight-through Cable

2. Crossover Cable

3. Rollover Cable.

All cabling structures has been described at section basics of cabling in this blog .

-DR

Basics about CIDR and VLSM

CIDR

Classless Inter-Domain Routing (CIDR) known as subnet mask or can be used as super netting where, all the IP address and its associated routing prefix is presented. It is noted as “/” such as /0, /10 etc/. It is an appropriate method of designating a subnet mask. It improves the efficiency of the address distribution which was followed in older class based IP address system. It is based on variable length subnet masking (VLSM). 

The earlier classfull address were as below

Class A: over 16 million host identifiers.

Class B: 65535 hosts

Class C: 254 host identifiers.

CIDR Block

A CIDR block is nothing a group of IP addresses that share the same prefix and contain the same number of bits. Super netting occurs when multiple CIDR blocks are connected together to structure a larger network. A prefix’s length determines the size of a CIDR block.

Subnet Mask and their CIDR value

255.0.0.0 : /8

255.128.0.0: /9

255.192.0.0: /10

255.224.0.0: /11

255.240.0.0: /12

255.248.0.0: /13

255.252.0.0: /14

255.254.0.0: /15

255.255.0.0: /16

Similarly, it will continue up to 255.255.255.252 having the CIDR value /30.

For example

If one Class A IP address have default subnet mask is 255.0.0.0, this means the first byte of the subnet mask is all ones (1s). As mentioned below, having CIDR value /8:

11111111.0.0.0 

VLSM

VLSM enables network administrators to divide IP address in to hierarchy of subnets of different sizes. 

For example

If an IP address is 127.10.50.34 and with a subnet mask 255.0.0.0 (8 network bits) then it will be noted as 127.10.50.34/8

There are many sub netting concepts that we can cover later. 

If you have any suggestions, please feel free to post below.

-DR

Basics of KVM Switch

KVM Switch

KVM is a hardware device in computer world and is stands for Keyboard, Video (monitor) and Mouse. It allows to use multiple computers or systems or servers in one keyboard, video, and mouse to control and switch between them. The KVM is also called as Console.

Normally this is used where there lots of servers available such as data centre or large infrastructure, WAN environment. The KVM switch then allows data center personnel to connect to any server in the rack.

A KVM allows for switching with the correct signals every time through the use of signal emulation technology. 

As per study high performance KVM solutions offer maximum security, flexibility and reliability for your network. From a single screen, keyboard and mouse, you can access all your computers no matter where they are located whether in another room or building. You can switch promptly between applications and carry out several functions in quick sequence with no delay. Traditional switching configurations range from 2 to 64 possible computers attached to a single device. 

There are two types of KVM available such as local remote KVM and KVM over IP.

Local remote KVM device allows users to control computer equipment up to approximate 1,000 feet away from the user consoles (keyboard, monitor and mouse). It includes standard cat5 cables and usb cables for connectivity.

KVM over IP delivers better content faster for a range of applications, including broadcasting and control rooms. It uses a dedicated micro-controller and specialized video capture hardware to capture the video, keyboard, and mouse signals. The it compresses and converts them into packets, and sends them over an Ethernet link to a remote console application.

Below are advantages to consider using KVM.

• Multiple computer or server control in a network.
• Not required to invest in extra computer equipment and that helps save money.
• It helps to keep your space less use.
• Some KVM switches support USB peripherals, for example, eliminating the need for separate USB hub.
• Remotely access and control computers and servers.
• Gain network flexibility.

So, a KVM switch is to reduce the pain, complexity, vulnerability and cost of IT environments.

-DR