The Need for a USB to Ethernet Adapter

The Ethernet adapter is far more reliable and much more efficient when compared to the USB while using the computer for internet surfing. Also since the connection is wireless, it makes more sense to have this adapter installed. The USB to Ethernet adapter is a modern way of integrating effectiveness with speed and provides low cost solution to desktops, laptops and notebook computers.

The main purpose is to allow for free access between machines and so for this purpose the Bridge driver needs to be installed in the CPU. In the latest machines, the driver will be automatically identified and the user will be prompted on whether or not he wishes to install the same. It is ideal to have it in the system as it allows for faster transfer of data and uninterrupted broadband services. This makes the system more reliable and perfect for environments where service needs to be uninterrupted and at a higher speed than usual. Easily available for Windows users, these might prove a bit of a hassle for those with systems running on MAC operating system. Even though the USB to Ethernet adapters are available easily at low cost, the drivers for MAC based systems are rather expensive. An alternative driver called Pegasus is available for them, which is economical and just as effective. When the USB cable is inserted it should throw up a screen that states that a new port has been added.



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What is a USB to Ethernet Adapter

While connecting an external device to the computer one makes use of the Universal Serial Bus (USB) ports available either in the front or rear side of the motherboard. Once the cable is put in place, it enables easy use of the local area network, or connection between two or more computers. Most of the external peripherals use a USB port for connection with the main computer. Since it is a plug and play system, it can be used for any kind of device as long as the related cable is put in place. The latest versions of USB supports up to 480 Mbps of data transfer which is phenomenally large when compared to the ones available earlier. In order to work faster and for the broadband connection to be fully utilized, USB to an Ethernet adapter needs to be installed. This requires special drives which first have to be put in place following which the user can enjoy unlimited internet access.


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EAP or Extensible Authentication Protocol

EAP was lately introduced as the newest PPP authentication protocol with MS CHAP V2 based features. During the authentication phase EAP is not in the picture! That's the biggest difference between EAP and other methods. EAP does not perform any sort of authentication, it in-fact only negotiates the actual EAP type and the user authentication is done by the Domain controller which hold the user database or a RADIUS (Remote Dial-in User Service) which works are an agent to get user credentials verified against a Domain Controller.

Until MS-CHAP V2, this authentication was happening only at the NAS server with the user database but with EAP, it's against a central user database holder or a Domain Controller only.

EAP is a new PPP authentication protocol that allows for an arbitrary authentication method. Once the user is connected over PPP, NAS server immediately collects the user credentials and sends them over to a RADIUS or Domain Controller for verification.


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MS-CHAP v2 or Microsoft Challenge Handshake Authentication Protocol Version 2

The newer version of MS-CHAP was introduced some after the older one giving it a name MS-CHAP V2. The encryption authentication mechanism was updated with much stronger security specifically when the username and password can now be exchanged along with determination of encryption keys. Initially the NAS server attempts to send the session ID and challenge to the remote client. The remote client uses the hash algorithm to reply back to NAS server's challenge string along with the supported encryption type, the session ID, its own peer challenge and the user password. In next step, the NAS server verifies client's information and responds with the another ID specifying the reason if this connection was a success or failure based upon the information like the negotiated encryption type, Peer challenge response, and decision on the NAS server challenge (the password client has provided).

The remote client verifies this information with the one it sent before and connects to the NAS server. If for some reason the authentication response was not correct, the remote client will terminate the connection. Therefore, it's a behavior where the both client and server authenticate each other mutually. Also, there are two type of encryption keys used, one of sending the data and the other one receiving the data.


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MS-CHAP or Microsoft Challenge-Handshake Authentication Protocol

MSCHAP is an encrypted authentication mechanism which works very similar to CHAP. We have seen in CHAP, where a NAS server sends a challenge to the client consisting of a Session ID and a hash challenge string. The remote client then, returns back the challenge with the session ID and MD4 based hashed answer. The introduction of MD4 gave an extra level of security where the clear-text was replaced with the hash passwords. MS-CHAP gave more attributes to the secure transmission of password over the wire by adding more error code aware attributes like, password expired code, next level of encryption between client and server allowing user to change there password while connected to the NAS server or during authentication process. The additional encryption between client and server is supported by using an encryption key to support data encryption by MPPE (Microsoft Point to Point Encryption).


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CHAP or Challenge-Handshake Authentication Protocol

CHAP is better than PAP as its uses encrypted authentication mechanism which would protect the username and password from being sent if the destination NAS server does not support this authentication method. Basically, the actual password will not be transmitted over the network, instead when the basic PPP connection is established, the NAS server sends a challenge phrase associated with a Session ID to the remote client. Then the remote client uses a specific MD5 (message digest version 4) hash algorithm to answer the challenge string with the username and an answer to the hash challenge with its username, network ID and password. The username will still be sent in plain text though.

CHAP is definitely a better choice than PAP where the password is sent in clear-text. But in CHAP the password is mixed up in hash form as an answer to the challenge string sent by the NAS server. Once the answer to the hash challenge is received the NAS server which already know the password, authenticates the user immediately. CHAP keeping sending challenges for the user to reply and verify its identity several times during the connection making it a more secure connection from any intrusion. The advantage CHAP carries over PAP is the way a user is authenticated over a dial-up or direct PPP connection.


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PPP NCP's

A PPP Network Control Protocol must be defined for each type of network packet which is to be encapsulated and transmitted across the PPP link.

Some of the defined PPP NCP's are:

• Internet Protocol Control Protocol
• OSI Network Layer Control Protocol
• Xerox NS IDP Control Protocol
• DECnet Phase IV Control Protocol
• Appletalk Control Protocol
• Novell IPX Control Protocol
• Bridging NCP
• Stream Protocol Control Protocol
• Banyan Vines Control Protocol
• Multi-Link Control Protocol
• NETBIOS Framing Control Protocol
• Cisco Systems Control Protocol
• Ascom Timeplex
• Fujitsu LBLB Control Protocol
• DCA Remote Lan Network Control Protocol (RLNCP)
• Serial Data Control Protocol (PPP-SDCP)
• SNA over 802.2 Control Protocol
• SNA Control Protocol
• IP6 Header Compression Control Protocol
• Stampede Bridging Control Protocol
• Compression on single link in multilink group control
• Compression Control Protocol


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PPP LCP

The PPP Link Control Protocol is responsible for establishing, configururing, managing, and terminating the point-to-point link.

LCP accomplishes these tasks through the use of simple control messages:
Link Configuration messages used to establish and configure a link:

• Configure-Request
• Configure-Ack
• Configure-Nak
• Configure-Reject

Link Termination messages used to terminate a link:

• Terminate-Request
• Terminate-Ack

Link Maintenance messages used to manage and debug a link:

• Code-Reject
• Protocol-Reject
• Echo-Request
• Echo-Reply
• Discard-Request


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What is PPP

PPP (Point-to-Point Protocol), is the most widely used method for transporting IP packets over a serial link between the user and the Internet Service Provider (ISP).
Although PPP is primarily used over dialup lines, variants such as PPoE (PPP over Ethernet) and PPoA (PPP over ATM) extend PPP to new data-link layer protocols.
PPP was designed to enable the transmission of different protocols over one point-to-point link by utilizing encapsulation. Encapsulation is the process of storing packets from the foreign protocol inside PPP frames.

In addition to this encapsulation function, PPP also provides:

• A Link Control Protocol (LCP) for establishing, configuring, and testing the data-link connection.
• A suite of Network Control Protocols (NCPs) for establishing and configuring different network-layer protocols.


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How a Router Works

When data packets are transmitted over a network (say the Internet), they move through many routers (because they pass through many networks) in their journey from the source machine to the destination machine. Routers work with IP packets, meaning that it works at the level of the IP protocol.

Each router keeps information about its neighbors (other routers in the same or other networks). This information includes the IP address and the cost, which is in terms of time, delay and other network considerations. This information is kept in a routing table, found in all routers.

When a packet of data arrives at a router, its header information is scrutinized by the router. Based on the destination and source IP addresses of the packet, the router decides which neighbor it will forward it to. It chooses the route with the least cost, and forwards the packet to the first router on that route.

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Routers for Home & Small Business

Not all routers are created equal since their job will differ slightly from network to network. Additionally, you may look at a piece of hardware and not even realize it is a router. What defines a router is not its shape, color, size or manufacturer, but its job function of routing data packets between computers. A cable modem which routes data between your PC and your ISP can be considered a router. In its most basic form, a router could simply be one of two computers running the Windows 98 (or higher) operating system connected together using ICS (Internet Connection Sharing). In this scenario, the computer that is connected to the Internet is acting as the router for the second computer to obtain its Internet connection.

Going a step up from ICS, we have a category of hardware routers that are used to perform the same basic task as ICS, albeit with more features and functions. Often called broadband or Internet connection sharing routers, these routers allow you to share one Internet connection between multiple computers.

Broadband or ICS routers will look a bit different depending on the manufacturer or brand, but wired routers are generally a small box-shaped hardware device with ports on the front or back into which you plug each computer, along with a port to plug in your broadband modem. These connection ports allow the router to do its job of routing the data packets between each of the the computers and the data going to and from the Internet.

Depending on the type of modem and Internet connection you have, you could also choose a router with phone or fax machine ports. A wired Ethernet broadband router will typically have a built-in Ethernet switch to allow for expansion. These routers also support NAT (network address translation), which allows all of your computers to share a single IP address on the Internet. Internet connection sharing routers will also provide users with much needed features such as an SPI firewall or serve as a a DHCP Server.

Wireless broadband routers look much the same as a wired router, with the obvious exception of the antenna on top, and the lack of cable running from the PCs to the router when it is all set up. Creating a wireless network adds a bit more security concerns as opposed to wired networks, but wireless broadband routers do have extra levels of embedded security. Along with the features found in wired routers, wireless routers also provide features relevant to wireless security such as Wi-Fi Protected Access (WPA) and wireless MAC address filtering. Additionally, most wireless routers can be configured for "invisible mode" so that your wireless network cannot be scanned by outside wireless clients. Wireless routers will often include ports for Ethernet connections as well. For those unfamiliar with WiFi and how it works, it is important to note that choosing a wireless router may mean you need to beef up your Wi-Fi knowledge-base. After a wireless network is established, you may possibly need to spend more time on monitoring and security than one would with a wired LAN.

Wired and wireless routers and the resulting network can claim pros and cons over each other, but they are somewhat equal overall in terms of function and performance. Both wired and wireless routers have high reliability and reasonably good security (without adding additional products). However —and this bears repeating — as we mentioned you may need to invest time in learning more about wireless security. Generally, going wired will be cheaper overall, but setting up the router and cabling in the computers is a bit more difficult than setting up the wireless network. Of course, mobility on a wired system is very limited while wireless offers outstanding mobility features.

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Why Would I Need a Router

For most home users, they may want to set-up a LAN (local Area Network) or WLAN (wireless LAN) and connect all computers to the Internet without having to pay a full broadband subscription service to their ISP for each computer on the network. In many instances, an ISP will allow you to use a router and connect multiple computers to a single Internet connection and pay a nominal fee for each additional computer sharing the connection. This is when home users will want to look at smaller routers, often called broadband routers that enable two or more computers to share an Internet connection. Within a business or organization, you may need to connect multiple computers to the Internet, but also want to connect multiple private networks — and these are the types of functions a router is designed for.

Router

A router is a device that forwards data packets along networks. A router is connected to at least two networks, commonly two LANs or WANs or a LAN and its ISP's network. Routers are located at gateways, the places where two or more networks connect, and are the critical device that keeps data flowing between networks and keeps the networks connected to the Internet. When data is sent between locations on one network or from one network to a second network the data is always seen and directed to the correct location by the router. They accomplish his by using headers and forwarding tables to determine the best path for forwarding the data packets, and they use protocols such as ICMP to communicate with each other and configure the best route between any two hosts.

The Internet itself is a global network connecting millions of computers and smaller networks — so you can see how crucial the role of a router is to our way of communicating and computing.


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What is ISDN

ISDN (Integrated Services Digital Network) is a system of digital phone connections that has been designed for sending voice, video, and data simultaneously over digital or ordinary phone lines, with a much faster speed and higher quality than an analog system can provide. ISDN is basically a set of protocol for making and breaking circuit switched connections as well as for advanced call features for the customers. ISDN is the international communication standard for data transmission along telephone lines and has transmission speeds up to 64 Kbps per channel.
ISDN uses two channels for communication which are the Bearer Channel or the B channel and the Delta Channel of the D Channel. The B channel is used for the data transmission and the D channel is used for signaling and control, though data can be transmitted through the D cannels as well. ISND has two access options, the Basic Rate Interface, also known as the BRI or the Basic Rate Access or BRA and Primary Rate Interface or Primary Rate Access. Basic Rate Interface is made up of two B channels with a bandwidth of 64 Kbit/s and a D channel with a bandwidth with 16 Kbit/s. The Basic Rate Interface is also known as 2B+D.

Primary Rate Interface has a greater number of B channels, which varies from nation to nation across the globe, and a D channel with a bandwidth of 64 Kbit/s. For example, in North America and Japan a PRI is represented as 23B+D (a total bit rate of 1.544 Mbit/s) while it is 30B+D in Australia and Europe (equivalent to a bit rate of 2.048 Mbit/s).

A technique called bipolar with eight-zero substitution technique is used to transfer calls through the data channels - the B channels - with the signaling channels (D channels) being exclusively used for call set up and management. Once the call had been set up, a 64 Kbit/s synchronous bidirectional B channel transfer the data between the ends, which lasts until the call ends. Theoretically, there can be as many calls as there are data channels, the choice of same or different end point not withstanding. Also, it is possible to multiplex a number of bearer channels (B channels) to produce a single higher bandwidth channel, using a process called B channel bonding.

ISDN has become a relatively old technology, but it isn't obsolete. ISDN is a technology that is often used behind the scenes as a component of more recent technology. Hopefully ISDN will continue to evolve so that it can continue to make an impact in the technological world.


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Broadband over Power Line Issues

Although the technology for Broadband over Power Lines is available, and companies have started offering the service in the US, it is facing opposition from ham operators and the Federal Emergency Management Administration (FEMA) who are concerned that Broadband over Power Lines technology will reduce the number of radio frequencies available for ham and short-wave radio operators and that RF transmission over unshielded medium-voltage lines will cause interference with already-assigned frequencies.

There are also no set transmission standards for Broadband over Power Lines technology. This is further hampering efforts to have the technology adapted by more Internet Service Providers.


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The Broadband over Power Lines Transmission Architecture

The key to broadband over power lines (Broadband over Power Lines) technology lies in a long established scientific fact: radio frequency (RF) energy can be bundled on the same line that carries electrical current. Since RF and electricity vibrate on different frequencies, there's not going to be any interference between the two. As such, data packets transmitted over RF frequencies are not overwhelmed or lost because of electrical current.

The Broadband over Power Lines system does not utilize the complete power grid. Electricity from power generating plants proceeds to transmission substations which distribute the current using high-voltage transmission lines carrying between 155,000 to 765,000 volts. These high-voltage lines are not suitable for data or RF transmission.

The Broadband over Power Lines solution is to bypass the substations and high-voltage wires and focus on the medium-voltage transmission lines (carrying around 7,200 volts) and the transformers that convert the electrical current to 240 volts - the electrical current used in households.

In other words, standard fiber optic lines specifically designed for Internet transmissions are going to be used to carry data. These fiber optic lines will be connected to medium-voltage lines. Repeaters are installed at these junction points to 'repeat' the data and boost the strength of the transmission. Couplers or specialized devices are also going to be installed at the transformers to provide a data link around these. After that, the digital data will be carried down the 240-volt line that connects to the residential or office buildings' electrical outlets which become the final distribution point for the data.

At this point, the residents and the office administrators have two options for Internet connectivity. They can get wireless transmitters that will wirelessly receive the signal and send the data on to computer stations or they can get Broadband over Power Lines modems for data filtering -the Broadband over Power Lines modem will screen out power line noise and let only data through - then send the data onwards to the stations. The wireless transmitter or the Broadband over Power Lines modem can transmit the signal to end-users or computer stations wirelessly (which necessitate WLAN-capable devices) or through wires (which require computers connected to the data transmitter or Broadband over Power Lines modem through Ethernet cables).


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What is Broadband over Power Lines

Broadband over Power Lines, or BPL, refers to the transmission (sending and receiving) of digital data through existing power cables and electricity distribution infrastructures. This can be viewed as a mere variation on using television cables; instead of using television cables, though, power transmission lines are going to be used.


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Conclusion

The oversimplified version of this information is newer cable technology permits you to both receive and transmit over cable at the same time. This allows you to watch your favorite television shows while downloading your email and paying bills online. This is done using the same cable, but using separate receiver and modem. It's a good example of a technology previously thought to be useful in only one application being fully exploited to advance new technologies and expand previously unknown possibilities. Success has been the byproduct of this brave new move.


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Transfer Rates

Most DOCSIS cable modem service providers implement caps on upload and download rates to suit their different configurations. For example, Comcast, the largest cable TV network in the U.S. caps the download bandwidth at 6 Mbps and upstream bandwidth at 384 Kbps. The caps are set by sending a configuration file to the modem via TFTP, at the instance when the modem establishes a connection to the provider server for the first time. The caps vary with different players. Most companies offer higher download rates, but you can expect to pay more for this service.


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Global DOCSIS Standards

Because frequency allocation plans differ between European and US counterparts, a separate European DOCSIS has been developed exclusively for European countries under the name 'EuroDOCSIS'. The main difference between the two standards is in the TV channel bandwidths. For example, European TV channels confirm to PAL TV standards while American ones confirm to NTSC standards. In comparison, the wider bandwidth of EuroDOCSIS is advantageous to Internet users because it has more bandwidth that can be allocated towards downstream data path.

Japan has developed its own version of DOCSIS that is further distinguished from either of the existing services in either Europe or the US.


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DOCSIS Types

DOCSIS 1.0 debuted in March 1997 and is what most consumers typically link with high speed cable Internet access . This version facilitates a downstream traffic transfer rates of 27-36 Mbps over a radio frequency (RF) path in the 50 MHz to 750+ MHz range, and upstream traffic transfer rates between 320 Kbps-10 Mbps (average 5 Mbps) over a RF path between 5 and 42 MHz. In layman's terms when more people who use DOCSIS 1.0 are using the Internet the slower the overall speed will be for customers.

DOCSIS 1.1 can coexist with DOCSIS 1.0, but features an increased upstream data transmission and improved security. This version facilitates multiple services such as voice and streaming. The end result is faster transmission and reception with a greater inventory of features.

DOCSIS 2.0 has an added capacity for symmetric services by operating at 64 QAM, backed by a new 6.4 MHz wide channel. Enhanced modulation and improved error correction ensures that this standard offers an increased bandwidth for IP traffic. The upstream traffic DOCSIS 2.0 is above 30 Mbps which is 3 times better than DOCSIS 1.1 and 6 times faster than DOCSIS 1.0. DOCSIS 2.0 is interoperable and backward compatible with DOCSIS 1.x. Long story short - this version works with both of the others but remains much faster and exhibits fewer errors.

The latest development in cable Internet connection is Embedded DOCSIS (eDOCSIS). eDOCSIS is designed to provide subordinate services at the core chip level to the host device. Its purpose includes end device management (including traffic management), configuration and security issues to significantly reduce cost in the service operation and to enhance speed and quality of end customer services. This evolution of service provides greater overall speed, reduced costs, and is less problematic for your service provider.


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DOCSIS Architecture

The DOCSIS architecture consists of two primary components. 1) A cable modem located with the customer and, 2) the cable modem termination system operated by cable service providers. The second function is to perform as a Hi Speed way station for multiple cable modems and then communicate with the system network. DOCSIS defines protocol for bi-directional signal exchange between these two components through the use of cable.


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What is DOCSIS

Data Over Cable Service Interface Specification (DOCSIS) defines the interface standards for cable modems and supporting equipment involved in high speed data transfer and distribution over cable television system networks. It permits additional high-speed data transfer over an existing cable TV system and is widely used by television operators to offer Internet access through an already existing hybrid fiber coaxial infrastructure. Other devices that recognize and support DOCSIS include HDTV's and Web-enabled set-top boxes for televisions. In other words, the same cable that brings you CSI can also allow you to send email and receive Internet news.

CableLabs developed DOCSIS and this technology has been approved as a standard for cable modems by ITU.


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Which is Faster: DSL or Satellite Internet

For those looking for an answer to this question, you will be happy to know that there is a clear-cut answer. DSL is in almost every case the faster broadband Internet technology available.

DSL broadband Internet technology can usually deliver speeds to a home from between 2Mbps to 8Mbps. On the other hand, satellite Internet usually delivers anywhere from 512 Kbps to 2Mbps. DSL broadband internet is also much cheaper than satellite internet. For instance, you should expect to pay about 3 times as much for comparable bandwidth and the modem and other equipment can cost you hundreds, if not thousands of dollars.***( Not so. My Verizon DSL is 54mbps. Even when busy, it yields 36 mbps.)

While satellite Internet does offer those in rural areas a great way to connect to the Internet at a decent enough speed, there really isn't any challenge when comparing whether satellite is faster than DSL.

Another Note: HughesNet would take issue with these claims of DSL being faster.


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Is DSL Faster than Satellite Internet

DSL, also called digital subscriber line, is a technology that delivers broadband Internet to many people's homes via their conventional telephone landline. DSL is one of two popular broadband Internet technologies used for the home market, the other being cable broadband which uses existing cable TV lines to deliver broadband Internet.

Another growing technology for delivering broadband internet to homes is Satellite Internet technology. While nowhere near as popular yet, satellite internet technology is gaining popularity in rural areas where landlines or cable TV lines are not available. In addition, satellite Internet technology is also a possibility for those homes that have satellite TV. The only thing usually required is a clear view of the satellite.


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What is the Difference Between ISDN and DSL

Definitions

Integrated Services Digital Network (ISDN): ISDN is a digital transmission system, which is used to transmit voice and data through copper telephone wires. In other words, it's a circuit-switched data transmission system that is used for voice and data transmission over the wire.

Digital Subscriber Line (DSL): DSL is also a digital transmission system and utilizes already installed copper wires to send voice and data packets.

Differences

As far as the differences between ISDN and DSL transmission system are concerned, there are several differences one can find:

Speed

In terms of speed, DSL is faster than ISDN. DSL sends data packets with speeds ranging from 128Kbps – 1.5Mbps. On the other hand, ISDN comes in two different speeds i.e., 64Kbps and 128Kbps.

Price

In terms of price, ISDN is somewhat more expensive than DSL. The main reason is that DSL utilizes wires that are already installed into homes or businesses, and there is no special line installation needed. However, ISDN lines need to be installed and connection charges vary depending upon the connection you choose. In case of dedicated or, "always on" connections – you will have to pay more as some ISDN packages are charged on per minute basis. A special dial-up package, on the other hand, will cost less and might be an easy option where a DSL connection is still not available.

Technology

ISDN is a dial-up service and transmits voice and data through a single line. There are two types of ISDN: Basic Rate Interface (BRI) and Primary Rate Interface (PRI). BRI is used mostly for residential homes and comes with three channels. On the other hand, Primary Rate Interface (PRI) ISDN is a business version and comes with 24 channels. In this case, 23 B channels are used to transmit voice, data and video – all through the same wire. A D channel carries low speed data and signaling. This signaling is used to generate alarm signals and provide support for non-voice functions. ISDN does not transmit data through analog lines.
DSL connections are often referred to as "always on" connections, so don't do not need to dial up a number. In DSL, there is only a single route for carrying voice, data and video. Two types of DSL connections are widely: Symmetric DSL (SDSL) and Asymmetric DSL (ADSL). These two types of DSL connections differ in their data carrying capacities i.e., upload and download. For more downloading, ADSL is a better choice.

ISDN and DSL are both distance sensitive. To get either service, your place should not be more than 18,000 feet away from the central office.


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Review of Cable and DSL Speeds

The most important thing to do is to compare the different connections of cable and DSL speeds. The cable modem offers bandwidths up to 30 Mbps while broadband DSL speeds are a maximum 10 Mbps. However, there is a type of DSL technology called VDSL that does have speeds comparable to the cable modem, but is rarely offered to customers due to financial and technical reasons.

There are some aspects of the cable modem that affect its advantage over DSL. As mentioned earlier, the cable modem bandwidth may be lowered when many subscribers are connected to the Internet at any one time. Also, Internet service providers may implement a bandwidth cap that affects Internet speeds for subscribes as well. Other issues that affect Internet speed regardless of a cable modem or DSL include technical glitches in the network, spyware, home network problems and wireless routers that are not configured correctly.

Most domestic cable modem Internet connections do not have the advantage of the possible 30 mbps bandwidth because most service providers offer a bandwidth of 1-6 mbps for downloads and an even lower bandwidth of 768 kbps for uploads. The reason service providers do this is to accommodate more customers with the existing bandwidth and provide an equal share of bandwidth to all customers when possible. Another aspect is that ISPs frequently cap the speed of the Internet connection in order to create several price points. This means subscribers can choose a faster connection if they want to pay more. This is really a scheme by ISPs to make more money.

When it comes to DSL connections the Internet speed depends upon the telephone line quality, how far the subscriber's home is from the telephone hub, and the technical reliability of the service provider among other things.

If you are looking for a great Internet connection and are choosing between a cable modem and DSL it is up to you to determine which provider will best suit your needs. There are advantages and disadvantages to both types of Internet service providers and you will be able to make a decision by comparing reliability, cost, customer support and other aspects in regard to your personal needs. Once this is done you will easily see which connection works best for you and can then proceed with installation and getting online!


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DSL Broadband

DSL broadband is a bit different because it relies on residential telephone lines to provide web access. The speed of the Internet is sometimes faster than the speed provided by a cable modem especially when multiple users are accessing the web. However, the biggest disadvantage with the DSL broadband connections is that the further one lives from the service provider the speed of data transfer decreases significantly. So, if you live far from the service provider your Internet connection speed will be slower and vice versa.

When comparing the cable modem to DSL broadband it is obvious that the cable modem is faster than broadband DSL when bandwidth sharing is balanced. However, in the real world there are some instances where the advantage of the cable modem is eliminated because of technical reasons.


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Cable Modem

Generally the cable modem is used domestically in homes. This is because of the convenience and affordability factors due to the fact that the cable modem transfers the Internet data along he same cable as television programming. This technology is due to separate wires within the cable that are dedicated either to cable television programming or Internet data transfer.

This design is profitable to the service provider because there are no additional set up costs and the unused bandwidth is utilized for Internet transfer. Another aspect of the cable modem is that individuals within an area rely on the same cable for access to the World Wide Web. As a result, the sharing of bandwidth among so many subscribers within a similar area might result in slower connections and downloads/uploads when multiple users are trying to access the net simultaneously.
Also, with cable modem Internet access the distance of the customer's home from the service provider does not have an impact on the Internet speed. This is not the case with broadband DSL users.


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DSL vs Cable Modem

Two of the most popular technologies that offer speedy access to the World Wide Web are DSL broadband and the cable modem. There are several reasons why this is the case and the first one is that both of these Internet connections are considerably faster than the standard dialup connections. However, when you compare the speed of data transfer between DSL and a cable modem there is a bit of variance depending on various technical aspects. Because of these variances DSL and the cable modem might have the advantage at different times. An overview of both technologies will clearly show the advantages and disadvantages of both.


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What is a DSL Filter and How DSL Filters Work

A DSL filter is an analog device that improves a DSL connection by minimizing telephone signal interference with the DSL system. When installed, it acts as a barrier to prevent low frequency telephone signals to interfere with the high frequency ADSL system and vice versa.

How DSL Filters Work

Telephone signals usually range from 300 to 3400 hertz, while ADSL systems use frequencies between 25 KHz and 1.1 MHz to carry fast data traffic. Both signals are present and they pass through the same copper wire. With both signals working at the same time in the same line, interference is possible causing problems for ADSL (low speed) and telephone (line noise) connections.

A DSL filter is usually just a small plastic box with a plug which goes to your phone socket. It has two outputs, one for your DSL modem and another for the telephone. By filtering and sending the right frequencies to the appropriate sockets, a DSL filter reduces interference problems. It also maximizes the 1.1 MHz frequency capacity of the copper line by attenuating the tendencies of the two signals interfering with each other.

Installing DSL filters does not require a technician's help. More often than not, most companies send the micro-filters with the DSL modem directly to the end user. To install a DSL filter, you have to take the steps listed below.
1. Plug your phone and modem into the RJ11 jack.
2. Switch on the DSL modem and see if your computer will connect to the Internet.
3. Check your phone for a dial tone.
The methods for installing more than one DSL filter are listed below:
1. Unplug other phones in your house before installing the DSL filters.
2. Immediately check for a dial tone on each phone after installing the filters.



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What is Symmetric DSL

Symmetric DSL, more commonly known as SDSL, is one kind of Digital Subscriber Line (DSL).

SDSL provides bandwidth between 72kb/s and 2,320kb/s.
Symmetric DSL is called "symmetrical" because the upstream and downstream connections have the same bandwidth.

SDSL requires only one pair of wired copper line to support a connection. These wires may reach as long as 3 kilometers.

Unlike Asymmetric DSL, Symmetric DSL uses the entire available bandwidth of the two copper wires. This means that regular analog telephone service through the PSTN is not possible over the same wires.

Symmetric DSL is a type of DSL technology which focuses on rate adaptation.
SDSL is usually more expensive than ADSL, but less expensive than a T1/E1 leased line. SDSL outperforms ADSL for dedicated data connections where upstream and downstream traffic is similar.

Symmetric DSL is slowly being replaced with G.SHDSL (Single-Pair High-speed Digital Subscriber Line).


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What is an ADSL Router

Definition

An ADSL router is also known as a DSL modem. The router is used to connect the computer to the DSL phone line for using the ADSL service. Some countries also use the term NTBBA, which stands for Network Termination BroadBand Access. There are some ADSL routers that are also capable of sharing a single Internet connection with a group of computers on a network. This system is also known as the residential gateway.

The ATU-R

Every ADSL router has a functional block called ADSL Terminal Unit-Remote, or the ATU-R (transceiver). The ATU-R is responsible for functions like demodulation, modulation, and framing. There are other functional blocks as well that perform specific functions like IP routing and bridging. The interfaces for the ADSL router are either Ethernet or USB. The ADSL modem might have been assigned an IP address from the beginning for management purposes, though an ADSL router that works as a bridge does not need an IP address.

Router Placement

The ADSL router in most cases is not placed inside the computer. It is connected to the computer's port, like the USB port or Ethernet. Voiceband modems, on the other hand, are placed inside the computer. The Windows operating systems, as well as other operating systems, do not recognize the ADSL router. There is no property sheet or an internal method to manage them. The reason is that the computer and the transceiver are separate nodes in the LAN. The transceiver (ADSL modem) is not controlled by the computer, unlike the keyboard and mouse.

Configuration

The ADSL router can be configured manually by opening a Web page in the browser. Some routers require no configuration because they are incorporated into the physical layer of the network. The frequencies of the router range between 25 kHz and 1 MHz. Hence, it does not interfere with the voice service, whose bandwidth ranges between 0 and 4 KHz. Hence, you can talk on the phone even if you have powered on the router and are using the Internet. Voiceband modems, on the other hand, work on the same frequency as the telephone; hence, they might interfere with the voice service.

Speed

The speed of the ADSL router varies and depends on the plan you have purchased from your ISP. Speeds vary from hundreds of kilobits per second to megabits per second. The ADSL router exchanges data with the wired DSLAM that is connected to the Internet. The router is configured for particular protocols only and might not work even on another line in the same house or company.

Hardware Components

The hardware components of the ADSL router are a transformer and a data connection such as Ethernet or USB. Also required are the digital data pump, a line driver, a filter, and a micro controller.


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How ADSL works

ADSL makes use of your existing telephone line. It splits the line into two distinct channels, one for data connection and the other for voice. The ADSL signal requires 2 special modems. One is used at your end while the other is used in the telephone exchange. Each modem is geared to a different frequency. Your telephone line is prepared for ADSL by opening up the copper pair to high frequencies and then routing the digital data in these frequencies to a Digital Subscriber Line Access Multiplexer (DSLAM) which converts this signal to ATM packets. The signal is then sent back to the servers and the server then forwards the request and assigns an IP address to the client.

ADSL modulation exists in two schemes. One is Carrierless Amplitude (CAP) and the other is Discrete Multi-Tone (DMT). These modulation schemes allow data transmission over high frequencies thus increasing internet access speed. The two schemes are used for both upstream and downstream data transmission. However, most modern installations are based on the DMT modulation scheme. The idea behind DMT is to split the bandwidth into a large number of sub channels and allocate data so that the throughput of every single sub channel is maximized.

Advantages of ADSL

1. Unlike traditional dial up connection where one session could only be used by one user, ADSL allows several users to share one account meaning the cost can be split between multiple users.
2. ADSL uses standard telephone lines for digital transmission thus setting the analog transmission signals apart from the digital. This allows normal usage of the telephone facility even as you are browsing the internet.
3. Allows for high speed internet access without the cost of ISDN.
4. ADSL 2 and ADSL 2+ have the advantage that they offer several improvements to ADSL. Some of these improvements include faster data transmission of up to 20 Mbps, dynamic data rate adaptation, standby power saver, better resistance to noise etc.
5. ADSL transfers data digitally and digital data has a higher noise tolerance than analog data.


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What is ADSL

ADSL is the acronym for Asymmetric Digital Subscriber Line. ADSL is a loose set of protocols that allows for high speed internet access over normal copper telephone lines or what is more commonly known as POTS (Plain Old Telephone Service). This is possible because the signals are sent digitally instead of through analog waves. ADSL is known as asymmetric because the download and upload speeds are not symmetrical with download speeds being averagely faster than upload speeds. Upstream data speeds are lower because requests for web pages normally do not require a lot of bandwidth.
ADSL provides internet access that is constantly on unlike dial up phone access. That way, your computer remains connected to the internet when it is powered on unless the cable is manually disconnected. ADSL allows for the simultaneous use of normal telephone services (voice), Integrated Service Digital Network (ISDN) and high speed data transmission such as video. ADSL provides much higher bandwidth than traditional dial up connections. Speeds can range from 512Kbps to 9 Mbps.


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What is a VLAN

The Basic Definition

The acronym VLAN expands to Virtual Local Area Network. A VLAN is a logical local area network (or LAN) that extends beyond a single traditional LAN to a group of LAN segments, given specific configurations. Because a VLAN is a logical entity, its creation and configuration is done completely in software.

How Is a VLAN Identified

Since a VLAN is a software concept, identifiers and configurations for a VLAN must be properly prepared for it to function as expected. Frame coloring is the process used to ensure that VLAN members or groups are properly identified and handled. With frame coloring, packets are given the proper VLAN ID at their origin so that they may be properly processed as they pass through the network. The VLAN ID is then used to enable switching and routing engines to make the appropriate decisions as defined in the VLAN configuration.

Why Use VLANs

Traditional network designs use routers to create broadcast domains and limit broadcasts between multiple subnets. This prevents broadcast floods in larger networks from consuming resources, or causing unintentional denials of service unnecessarily. Unfortunately, the traditional network design methodology has some flaws in design

• Geographic Focus - Traditional network designs focus on physical locations of equipment and personnel for addressing and LAN segment placement. Because of this there are a few significant drawbacks:
• Network segments for physically disjointed organizations cannot be part of the same address space. Each physical location must be addressed independently, and be part of its own broadcast domain. This can force personnel to be located in a central location, or to have additional latency or connectivity shortfalls.
• Relocations of personnel and departments can become difficult, especially if the original location retains its network segments. Relocated equipment will have to be reconfigured based on the new network configuration.

A VLAN solution can alleviate both of these drawbacks by permitting the same broadcast domain to extend beyond a single segment.

• Additional Bandwidth Usage - Traditional network designs require additional bandwidth because packets have to pass through multiple levels of network connectivity because the network is segmented.

A proper VLAN design can ensure that only devices that have that VLAN defined on it will receive and forward packets intended as source or destination of the network flow.

Types of VLAN

There are only two types of VLAN possible today, cell-based VLANs and frame-based VLANs.

• Cell-based VLANs are used in ATM switched networks with LAN Emulation (or LANE). LANE is used to allow hosts on legacy LAN segments to communicate using ATM networks without having to use special hardware or software modification.
• Frame-based VLANs are used in ethernet networks with frame tagging. The two primary types of frame tagging are IEEE 802.10 and ISL (Inter Switch Link is a Cisco proprietary frame-tagging). Keep in mind that the 802.10 standard makes it possible to deploy VLANs with 802.3 (Ethernet), 802.5 (Token-Ring), and FDDI, but ethernet is most common.

VLAN modes

There are three different modes in which a VLAN can be configured. These modes are covered below:
• VLAN Switching Mode - The VLAN forms a switching bridge in which frames are forwarded unmodified.
• VLAN Translation Mode - VLAN translation mode is used when the frame tagging method is changed in the network path, or if the frame traverses from a VLAN group to a legacy or native interface which is not configured in a VLAN. When the packet is to pass into a native interface, the VLAN tag is removed so that the packet can properly enter the native interface.
• VLAN Routing Mode - When a packet is routed from one VLAN to a different VLAN, you use VLAN routing mode. The packet is modified, usually by a router, which places its own MAC address as the source, and then changes the VLAN ID of the packet.

VLAN configurations

Different terminology is used between different hardware manufacturers when it comes to VLANs. Because of this there is often confusion at implementation time. Following are a few details, and some examples to assist you in defining your VLANs so confusion is not an issue.

Cisco VLAN terminology

You need a few details to define a VLAN on most Cisco equipment. Unfortunately, because Cisco sometimes acquires the technologies they use to fill their switching, routing and security product lines, naming conventions are not always consistent. For this article, we are focusing only one Cisco switching and routing product lines running Cisco IOS.

• VLAN ID - The VLAN ID is a unique value you assign to each VLAN on a single device. With a Cisco routing or switching device running IOS, your range is from 1-4096. When you define a VLAN you usually use the syntax "vlan x" where x is the number you would like to assign to the VLAN ID. VLAN 1 is reserved as an administrative VLAN. If VLAN technologies are enabled, all ports are a member of VLAN 1 by default.
• VLAN Name - The VLAN name is an text based name you use to identify your VLAN, perhaps to help technical staff in understanding its function. The string you use can be between 1 and 32 characters in length.
• Private VLAN - You also define if the VLAN is to be a private vlan in the VLAN definition, and what other VLAN might be associated with it in the definition section. When you configure a Cisco VLAN as a private-vlan, this means that ports that are members of the VLAN cannot communicate directly with each other by default. Normally all ports which are members of a VLAN can communicate directly with each other just as they would be able to would they have been a member of a standard network segment. Private vlans are created to enhance the security on a network where hosts coexisting on the network cannot or should not trust each other. This is a common practice to use on web farms or in other high risk environments where communication between hosts on the same subnet are not necessary. Check your Cisco documentation if you have questions about how to configure and deploy private VLANs.
• VLAN modes - in Cisco IOS, there are only two modes an interface can operate in, "mode access" and "mode trunk". Access mode is for end devices or devices that will not require multiple VLANs. Trunk mode is used for passing multiple VLANs to other network devices, or for end devices that need to have membership to multiple VLANs at once. If you are wondering what mode to use, the mode is probably "mode access".

Cisco VLAN implementations

VLAN Definition

To define a VLAN on a cisco device, you need a VLAN ID, a VLAN name, ports you would like to participate in the VLAN, and the type of membership the port will have with the VLAN.
• Step 1 - Log into the router or switch in question and get into enable mode.
• Step 2 - Get into configuration mode using "conf t".
• Step 3 - Create your VLAN by entering "vlan X" where X is the ID you would like to assign the VLAN.
• Step 4 - Name your VLAN by entering "name ". Replace with the string you would like to identify your VLAN by.
• Step 5 - If you want your new VLAN to be a private-vlan, you now enter "private-vlan primary" and "private-vlan association Y" where Y is the secondary VLAN you want to associate with the primary vlan. If you would like the private VLAN to be community based, you enter "private-vlan community" instead.
• Step 6 - Exit configuration mode by entering "end".
• Step 7 - Save your configuration to memory by entering "wr mem" and to the network if you have need using "wr net". You may have to supply additional information to write configurations to the network depending on your device configuration.

You have now created a vlan by assigning it an ID, and giving it a name. At this point, the VLAN has no special configuration to handle IP traffic, nor are there any ports that are members of the VLAN. The next section describes how you complete your vlan configuration.

VLAN Configuration

A VLAN isn't much use if you haven't assigned it an IP Address, the subnet netmask, and port membership. In normal network segment configurations on routers, individual interfaces or groups of interfaces (called channels) are assigned IP addresses . When you use VLANs, individual interfaces are members of VLANs and do not have individual IP addresses, and generally don't have access lists applied to them. Those features are usually reserved for the VLAN interfaces. The following steps detail one method of creating and configuring your VLAN interface. NOTE: These steps have already assumed that you have logged into the router, gotten into enable mode, and entered configuration mode. These specific examples are based on the Cisco 6500 series devices.

• Step 1 - Enter "Interface VlanX" where X is the VLAN ID you used in the VLAN definition above.
• Step 2 - This step is optional. Enter "description " where VLAN description details what the VLAN is going to be used for. You can just simply re-use the VLAN name you used above if you like.
• Step 3 - Enter "ip address

" where

is the address you want to assign this device in the VLAN, and is the network mask for the subnet you have assigned the VLAN.
• Step 4 - The step is optional
• Create and apply an access list to the VLAN for inbound and outbound access controls. For a standard access list enter "access-group XXX in" and "access-group YYY out" where XXX and YYY corresponds to access-lists you have previously configured. Remember that the terms are taken in respect to the specific subnet or interface, so "in" means from the VLAN INTO the router, and "out" means from the router OUT to the VLAN.
• Step 5 - This step is optional. Enter the private VLAN mapping you would like to use if the port is part of a private VLAN. This should be the same secondary VLAN you associated with the primary VLAN in VLAN definition above. Enter "private-vlan mapping XX" where XX is the VLAN ID of the secondary VLAN you would like to associate with this VLAN.
• Step 6 - This step is optional. Configure HSRP and any other basic interface configurations you would normally use for your Cisco device.
• Step 7 - Exit configuration mode by entering "end".
• Step 8 - Save your configuration to memory by entering "wr mem" and to the network if you have need using "wr net". You may have to supply additional information to write configurations to the network depending on your device configuration.

Now you have your vlan defined and configured, but no physical ports are a member of the VLAN, so the VLAN still isn't of much use. Next port membership in the VLAN is described. IOS devices describe interfaces based on a technology and a port number, as with "FastEthernet3/1" or "GigabitEthernet8/16". Once you have determined which physical ports you want to be members of the VLAN you can use the following steps to configure it. NOTE: These steps have already assumed that you have logged into the router, gotten into enable mode, and entered configuration mode.

• Step 1 - Enter "Interface " where is the name Cisco has assigned the interface you would like to associate with the VLAN.
• Step 2 - This step is optional. Enter "description " where is text describing the system connected to the interface in question. It is usually helpful to provide DNS hostname, IP Address, which port on the remote system is connected, and its function.
• Step 3 - This step depends on your equipment and IOS version, and requirements. Enter "switchport" if you need the interface to act as a switch port. Some hardware does not support switchport mode, and can only be used as a router port. Check your documentation if you don't know the difference between a router port and a switch port.
• Step 4 - Only use this step if you used step 3 above. Enter "switchport access vlan X" where X is the VLAN ID of the VLAN you want the port to be a member of.
• Step 5 - Only use this step if you used step 3 above. Enter "switchport mode access" to tell the port that you want it to be used as an access port.
• Step 6 - Exit configuration mode by entering "end".
• Step 7 - Save your configuration to memory by entering "wr mem" and to the network if you have need using "wr net". You may have to supply additional information to write configurations to the network depending on your device configuration.
• Step 1 - Enter "Interface " where is the name Cisco has assigned the interface you would like to associate with the VLAN.
• Step 2 - This step is optional. Enter "description " where is text describing the system connected to the interface in question. It is usually helpful to provide DNS hostname, IP Address, which port on the remote system is connected, and its function.
• Step 3 - This step depends on your equipment and IOS version, and requirements. Enter "switchport" if you need the interface to act as a switch port. Some hardware does not support switchport mode, and can only be used as a router port. Check your documentation if you don't know the difference between a router port and a switch port.
• Step 4 - Only use this step if you used step 3 above. Enter "switchport trunk encapsulation dot1q". This tells the VLAN to use dot1q encapsulation for the VLAN, which is the industry standard encapsulation for trunking. There are other encapsulation options, but your equipment may not operate with non Cisco equipment if you use them.
• Step 5 - Only use this step if you used step 3 above. Enter "switchport trunk allowed vlan XX, YY, ZZ" where XX, YY, and ZZ are VLANs you want the trunk to include. You can define one or more VLANs to be allowed in the trunk.
• Step 6 - Only use this step if you used step 3 above. Enter "switchport mode trunk" to tell the port to operate as a VLAN trunk, and not as an access port.
• Step 7 - Exit configuration mode by entering "end".
• Step 8 - Save your configuration to memory by entering "wr mem" and to the

network if you have need using "wr net". You may have to supply additional information to write configurations to the network depending on your device configuration.

• Step 1 - Enter "Interface " where is the name Cisco has assigned the interface you would like to associate with the VLAN.
• Step 2 - This step is optional. Enter "description " where is text describing the system connected to the interface in question. It is usually helpful to provide DNS hostname, IP Address, which port on the remote system is connected, and its function.
• Step 3 - This step depends on your equipment and IOS version, and requirements. Enter "switchport" if you need the interface to act as a switch port. Some hardware does not support switchport mode, and can only be used as a router port. Check your documentation if you don't know the difference between a router port and a switch port.
• Step 4 - Enter "switchport private-vlan host association XX YY" where XX is the primary VLAN you want to assign, YY is the secondary VLAN you want to associate with it.
• Step 5 - Enter "switchport mode private-vlan host" to force the port to operate as a private-vlan in host mode.
• Step 6 - Exit configuration mode by entering "end".
• Step 7 - Save your configuration to memory by entering "wr mem" and to the network if you have need using "wr net". You may have to supply additional information to write configurations to the network depending on your device configuration.

You should now have your VLAN properly implemented on a Cisco IOS device.

HP VLAN terminology

HP's Procurve line of switchgear is becoming more and more prevalent in enterprise and other business environments. Because of this, it isn't uncommon to have to get Cisco and Procurve hardware to integrate, and because of terminology this can be a challenge. Below some of the VLAN terminology is defined so there is less opportunity for confusion.

• VLAN ID - Fortunately, VLAN id's are pretty much the same everywhere, the only significant differences are the range of IDs that can be used. With Procurve devices, the number of VLANs is defined in the configuration. The default maximum VLANs supported on a Procurve device differs between models and firmware revisions, but is commonly set to 8. Newer Procurve hardware supports 4,096 VLAN ids, but only 256 concurrently defined VLANs on a single device. VLAN ID 1 is reserved for the "DEFAULT_VLAN" or the default administrative VLAN.
• VLAN names - VLAN names are text fields that assist technicians to identify VLANs. Procurve allows names up to 32 characters, but if you want it to properly display in menu configuration mode, you should probably limit the name to 12 characters.
• VLAN modes - Procurve has three modes of operation for VLANs on the chassis, Untagged, Tagged, and No. Untagged mode is cisco's access mode. This mode is used for ports that connect to end nodes, or devices that will not be passing VLAN traffic forward. Tagged mode is the same as Cisco's trunk mode. This mode is used for ports that are connecting to devices that will be passing VLAN traffic forward, or for trunking multiple VLANs. No mode means that the port in question has no association whatsoever with that VLAN.
• Special note on "trunk" - Lots of confusion surrounds the word "trunk" when you go between vendor equipment. In Cisco's case, trunking is only used with VLANs. If you want to group multiple ethernet ports into a single logical ethernet group, they call it a channel-group. This is regardless of whether FEC or LACP is used for the channel properties. Procurve uses "trunk" to define a group of ethernet ports when using the HP trunking protocol, and the term "Tagged" for what Cisco calls a VLAN trunk. Of course, these two technologies have nothing to do with each other, but because of naming conventions, confusion arises.

HP Procurve VLAN implementations

VLAN Definition

Most modern Procurve switches enable VLAN use by default, but if, for some reason, you have an older model, log into the switch, get into manager mode, go to the switch configuration menu (usually item 2), then the VLAN menu (usually item 8), then the VLAN support item (usually item 1), and make sure VLANs are enabled. If you change this setting, you will need to reboot the switch to get it to activate properly. The configuration menu is useful for these kinds of activities, troubleshooting, and other things, but is a little more difficult for configuring multiple switches or for using configuration templates, so the rest of the HP Procurve configuration details will be provided for the console configuration mode. Aside for enabling VLAN support as a whole, VLAN definitions and configuration are created in the same place, so the rest of the configuration examples will be provided under the VLAN configuration topic.

VLAN Configuration

Configuring VLANs on a modern Procurve is pretty simple, you must first define the VLAN, set its properties, and then set up membership for ports and the VLAN mode they will support. The following list should help you accomplish these tasks. NOTE: HP has defined its interface ports by using a module/port convention. If you have a non-modular chassis (such as the 3448cl) then ports are numbered only using numbers, such as 1 or 36. If the chassis is modular (such as the 5308) then the ports number is prepended with the module slot, such as A1 or H6. No reference to the type of switch port (ethernet, fast ethernet, gigabit ethernet) is used for port reference.
• Step 1 - Log into the switch and get into manager mode. If, after logging in, you are in the configuration menu, exit the configuration menu by selecting item 5 (in most cases) or by using the arrow keys on your keyboard to highlight the "Command Line (CLI)" item.
• Step 2 - Enter "conf t" to get into terminal configuration mode.
• Step 3 - Enter "vlan X" where X is the VLAN id of the VLAN you would like to create.
• Step 4 - Name your VLAN by entering "name """ where is a text string from 1 to 32 characters (12 characters if you care about the configuration menu display). You should use quotes when naming the VLAN.
• Step 5 - Give the VLAN an IP address by entering "ip address " where is the IP address you want to assign this switch in that subnet, and is the network mask for the subnet assigned.
• Step 6 - This step is optional. If you want to assign some end node ports to the VLAN enter "untagged " where is a list of ports either comma delimited if they are non-sequential, or using a dash between list beginning and end if they are. An example of this is "untagged 1,3,5,7-16". This would configure ports 1, 3, 5, and 7 through 16 to be untagged on that VLAN.
• Step 7 - This step is optional. If you want to assign some VLAN trunk ports to the VLAN enter "tagged " where is a list of ports either comma delimited if they are non-sequential, or using a dash between list beginning and end if they are. An example of this is "untagged 1,3,5,7-16". This would configure ports 1, 3, 5, and 7 through 16 to be untagged on that VLAN.
• Step 8 - Enter "exit" to leave VLAN configuration mode.
• Step 9 - Exit configuration mode by entering "exit" again.
• Step 10 - Save your configuration by entering "wr memory".
You have now successfully configured your HP Procurve VLAN

Vendor Summary

If you are going to integrate Cisco and HP Procurve hardware on the same network, and you intend to use VLANs there are only a few things you need to remember:
• For end nodes - Cisco uses "mode access", HP uses "untagged" mode.
• For VLAN dot1q trunks - Cisco uses "mode trunk", HP uses "tagged" mode.
• For no VLAN association - Cisco uses no notation at all, HP uses "no" mode in the configuration menu, or you have VLAN support turned off.
Next time you have to integrate the two with VLANs, this simple list should help keep you out of trouble.


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ATM History and Developments

When ATM was originally conceived in the 1990s, many people saw it as the 'next best thing' in networking technologies since it could handle both LAN and WAN technologies, allowing users to 'jump' between LAN and WAN without difficulty, in other words, it would have become a single integrated system combining both.

Unfortunately, ATM never became a "magic" end-to-end solution integrating LAN and WAN technologies. ATM adapters for LAN-based desktops were expensive, and the standards for interconnecting networks using the ATM cell system were often confused and delayed. Telephone companies, ISPs and large corporations made use of ATM for their WAN architecture and critical backbones because of the QoS it could assure.


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Key Elements of ATM Technology

One of the major innovations in ATM is the use of 53-byte fixed-length cells, unlike conventional TCP/IP which uses variable-sized packets. This allows ATM users to build very fast circuits, simply because it is easier to process known data packet sizes rather than to have circuits trying to pinpoint the start and end of data packets. The small ATM packet (composed of a five-byte header and a 48-byte data 'container') also guarantees that voice and video can be slotted into the data stream frequently enough for real-time transmission.

Constant Bit Rate, which guarantees sufficient bandwidth for voice and video transmissions in real time, Unspecified Bit Rate, providing 'best effort' service for non-critical data such as file transfers, Available Bit Rate (ABR) which fine-tunes bandwidth according to LAN traffic congestion levels and Realtime variableBit Rate (rt-VBR) can support multimedia applications that require minimal delays

Another innovation in ATM technology is its ability to interconnect LAN and WAN protocols, allowing for a seamless transfer between WAN and LAN. One mode is called MPOA (Multi Protocol Over ATM) can be used to route TCP/IP protocols and IPX while maintaining ATM's quality of service.

LANE (LAN Emulation) modes allows it to interconnect between rival Ethernet and Token Ring, summarizing their frames or data packets in LANE packets and then converting these into ATM 53-byte cells. MPOA or traditional servers can be used to interconnect differing LAN segments, with the ATM communications protocols handling data transfers.


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What is ATM

ATM (Asynchronous Transfer Mode) is a technological system developed for both local and wide area networks (LAN and WAN), and designed to handle data as well as video and voice traffic in real time, all at the same time. The system architecture makes use of switches that set up logical circuits at both ends of the data stream, which ensures unprecedented quality of service (QoS).

Unlike conventional telephone switches that sets up dedicated end-to-end circuits, unused bandwidth in Asynchronous Transfer Mode (ATM) can be used for other purposes if needed. For example, idle or unused bandwidth in a video conferencing meeting can be used to transfer data along the same line.

Large carrier networks (telcos) and large enterprises have made use of ATM technology but it has never been picked up for LAN use.


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Understanding EtherCAT

EtherCAT is, in a sense, a synergy of several distinct technologies and developmental efforts, starting with the "fieldbus."

"Fieldbus" is a broad, non-specific term which describes an updated digital communications system in an industrial setting. An industrial system that makes extensive use of automation - for example, a modern automobile assembly line which uses robots for assembly, welding, painting and other repetitive tasks - requires a highly organized, multi-level structure of controllers to function efficiently.

This usually requires a top-level unit called a Human Machine Interface where a human operator monitors and controls the system; followed by a middle-level comprised by a number of Programmable Logic Controllers (PLCs) which are linkedto the upper-level HMIs by a communications system; and finally, the "fieldbus" which links the PLCs to the actual operational components such as motors, actuators, sensors, etc.

In a human organization, one can think of the HMI as the top-level manager (or Chief Operating Officer) who oversees and directs the company's operations; the PLC is the equivalent of the company's 'middle managers' who head up separate divisions dealing with specific areas of company operations; and the 'operators' - or the people working under the middle managers who handle specific, day-to-day operations or activities: field agents, mechanics, drivers, support personnel, etc.

The 'fieldbus' is the communications system which links the field personnel to the middle managers, providing status reports, implementation data, etc. which are processed and forwarded to the COO.

Although the communication linkages between the different levels may appear to be simple, this can become increasingly complex if one considers the multitude of actions and activities that take place at the 'field' level - many of which have to be coordinated with each other, requiring an exchange of information at that level and going upwards to 'middle managers' which, in turn, have to interact and communicate with each other, and so on.



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Ethernet

Ethernet is the established (and favored) communications standard for local area networks, originally designed to connect different computers to each other for sharing information and data. Ethernet technologies have gone through several phases of development and these have all been for the purposes of simplifying the connections between computers and users as well as increasing the size of the pipeline (through which information will flow) to establish maximum efficiency in resource allocation.
One of the major contributions of Ethernet development are the concepts of information 'packets' - bundles of information or instructions which are then streamed to every computer in the network - and traffic control systems - this mechanism ensures that information packets are sent to the correct recipients. There are also procedures in place to ensure that recipients can still receive the packets even if the computers are 'busy'.


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What is EtherCAT

EtherCAT stands for "Ethernet for Control Automation Technology." It is an open-source, high performance system that aims to use Ethernet protocols (the favored system for Local Area Networks) in an industrial environment, especially for factories and other manufacturing concerns which make use of robots and other assembly-line technologies.


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How Collisions Occur under CSMA/CD

Imagine a very simple Ethernet network with only two nodes.
Each node, independently, decides to send an Ethernet frame to the other node.
Both nodes listen to the Ethernet wire and sense that no carrier is present.
Both nodes transmit simultaneously, causing a collision.

Both nodes detect the collision and each node waits a random amount of time before transmitting again.

Collisions are normal on an Ethernet network. A small amount of collisions are expected in the protocol design.

If too many nodes are transmitting on an Ethernet network the number of collisions can rise to an unacceptable level. This can reduce the amount of available bandwidth on an Ethernet network because so much bandwidth is lost in retransmission.

Ethernet switches greatly reduce the already minor difficulties experienced with the CSMA/CD protocol.


Posted by: Wasim Javed

What is CSMA/CD

CSMA/CD (Carrier Sense Multiple Access / Collision Detection) is the protocol used in Ethernet networks to ensure that only one network node is transmitting on the network wire at any one time.

Carrier Sense means that every Ethernet device listens to the Ethernet wire before it attempts to transmit. If the Ethernet device senses that another device is transmitting, it will wait to transmit.

Multiple Access means that more than one Ethernet device can be sensing (listening and waiting to transmit) at a time.

Collision Detection means that when multiple Ethernet devices accidentally transmit at the same time, they are able to detect this error.


Posted by: Wasim Javed

Features of PoE

The main reason behind the invention of Power over Ethernet system was to run various Wireless Access Point (WAP) devices, embedded systems, surveillance cameras and IP telephone sets.

Since the power supply is centralized, Power over Ethernet reduces the likelihood of downtime due to power shortages and surges. It ensures that there is a continuous and uniform flow of current to all systems. Power over Ethernet is usually linked to a good battery or UPS, which is common in homes and large offices.


Posted by: Wasim Javed