Asynchronous Transfer Mode

Asynchronous Transfer Mode (ATM) is a switching technique for telecommunication networks. It uses asynchronous time-division multiplexing,^[1][2] and it encodes data into small, fixed-sized cells. This differs from networks such as the Internet or Ethernet LANs that use variable sized packets or frames. ATM provides data link layer services that run over OSI Layer 1 physical links. ATM has functional similarity with both circuit switched networking and small packet switched networking. This makes it a good choice for a network that must handle both traditional high-speed data traffic (e.g., file transfers), and real-time, low-latency content such as voice and video. ATM uses a connection-oriented model in which a virtual circuit must be established between two endpoints before the actual data exchange begins.^[2] ATM is a core protocol used over the SONET/SDH backbone of the Integrated Services Digital Network (ISDN).

CELL RELAY

In computer networking, cell relay refers to a method of statistically multiplexing small fixed-length packets, called "cells", to transport data between computers or kinds of network equipment. It is an unreliable, connection-oriented packet switched data communications protocol.
Cell relay transmission rates usually are between 56 kbit/s and several gigabits per second. ATM, a particularly popular form of cell relay, is most commonly used for home DSL connections, which often runs between 128 kbit/s and 1.544 Mbit/s (DS1), and for high-speed backbone connections (OC-3 and faster).

Circuit Switching vs. Packet Switching

Switching and routing

Switching and routing are technically two different things, but for the sake of simplicity, let us take switches and routers (which are devices that make switching and routing respectively) as devices doing one job: make a link in the connection and forward data from the source to the destination.

Paths or circuits

The important thing to look for in transmitting information over such a complex network is the path or circuit. The devices making up the path are called nodes. For instance, switches, routers and some other network devices, are nodes.

In circuit-switching, this path is decided upon before the data transmission starts. The system decides on which route to follow, based on a resource-optimizing algorithm, and transmission goes according to the path. For the whole length of the communication session between the two communicating bodies, the route is dedicated and exclusive, and released only when the session terminates. 

Packets

To be able to understand packet-switching, you need to know what a packet is. The Internet Protocol(IP), just like many other protocols, breaks data into chunks and wraps the chunks into structures called packets. Each packet contains, along with the data load, information about the IP address of the source and the destination nodes, sequence numbers and some other control information. A packet can also be called a segment or datagram. Once they reach their destination, the packets are reassembled to make up the original data again. It is therefore obvious that, to transmit data in packets, it has to be digital data.

In packet-switching, the packets are sent towards the destination irrespective of each other. Each packet has to find its own route to the destination. There is no predetermined path; the decision as to which node to hop to in the next step is taken only when a node is reached. Each packet finds its way using the information it carries, such as the source and destination IP addresses. 

The Golden Rules of Data Cabling

The Golden Rules of Data Cabling

Written by Julianus Yu

The Golden Rules of Data Cabling

One for sure that we usually forget the key part of data cabling system,
here some of the important part that we should keep in mind before we decide to setting up our data cabling system ;

• Networks never get smaller or less complicated.

• Build one cabling system that will accommodate voice and data.

• Always install more cabling than you currently require. Those extra outlets will come in handy someday.

• Use structured-cabling standards when building a new cabling system. Avoid anything proprietary!

 

• Quality counts! Use high-quality cabling and cabling components. Cabling is the foundation of your network; if the cabling fails, nothing else will matter. For a given grade or category of cabling, you’ll see a range of pricing, but the highest prices don’t necessarily mean the highest quality. Buy based on the manufacturer’s reputation and proven performance, not the price.

• Don’t scrimp on installation costs. Even quality components and cable must be installed correctly; poor workmanship has trashed more than one cabling installation.

• Plan for higher speed technologies than are commonly available today. Just because 1000Base-T Ethernet seems unnecessary today does not mean it won’t be a requirement in five years.

• Documentation, although dull, is a necessary evil that should be taken care of while you’re setting up the cabling system. If you wait, more pressing concerns may cause you to ignore it.

NETWORK

LAN (local area network)

A local area network (LAN) consists of two or more computers connected together in a building or home using software and hardware. A LAN is contrasted to a wide area network (WAN) such as the Internet, which covers a large geographic area. In a LAN, there is a main computer or server, and remote computers called clients. By creating a LAN in the home or office, computers on the LAN can share files, resources, and if desired, an Internet connection.
A lan can be one of two types: wired or wireless. A wired LAN requires Ethernet cable to physically connect all computers on the network to a main device called a switch. A wireless LAN uses radio waves to communicate, eliminating the need for wires. Therefore, the hardware used in a LAN should all be of either the wireless or wired type.WAN (wide area network)

A wide area network (WAN) is a computer network that covers a broad area (i.e., any network whose communications links cross metropolitan, regional, or national boundaries ^[1]). This is in contrast with personal area networks (PANs), local area networks (LANs), campus area networks (CANs), or metropolitan area networks (MANs) which are usually limited to a room, building, campus or specific metropolitan area

Network Protocols

Network protocols like HTTP, TCP/IP, and SMTP provide a foundation that much of the Internet is built on. Find out more about these protocols and how they work.

HTTP - the Hypertext Transfer Protocol - provides a standard for Web browsers and servers to communicate. The definition of HTTP is a technical specification of a network protocol that software must implement.
HTTP is an application layer network protocol built on top of TCP. HTTP clients (such as Web browsers) and servers communicate via HTTP request and response messages. The three main HTTP message types are GET, POST, and HEAD.
HTTP utilizes TCP port 80 by default, though other ports such as 8080 can alternatively be used.
Short for Transmission Control Protocol/Internet Protocol, the suite of communications protocols used to connect hosts on the Internet. TCP/IP uses several protocols, the two main ones being TCP and IP. TCP/IP is built into the UNIX operating system and is used by the Internet, making it the de facto standard for transmitting data over networks. Even network operating systems that have their own protocols, such as Netware, also support TCP/IP.

SMTP (Simple Mail Transfer Protocol) is a protocol for sending email messages across the Internet. It is used in conjunction with both POP3 and IMAP, protocols that enable you to download messages from a mail server to your computer. SMTP is used for outgoing mail while POP3 and IMAP are used for incoming mail.

If you want to use an email client such as Microsoft Outlook to send email messages, you will need to configure the client so that it connects to the correct SMTP mail server to send mail.