Wide Area Network (WAN)

Types and Characteristics of WANs

What is a WAN?

There are two prevailing definitions of a Wide Area Network (WAN). The book definition of a WAN is a network that spans large geographical locations, usually to interconnect multiple Local Area Networks (LANs). The practical definition of a WAN is a network that traverses a public network or commercial carrier, using one of several WAN technologies

What are its Main Components?

The main components for a WAN are routers, switches and modems. These components are described below in the hardware section.

CPE – Devices on the subscriber premises are called customer premises equipment (CPE).

The subscriber owns the CPE or leases the CPE from the service provider. A copper or fiber cable connects the CPE to the service provider’s nearest exchange or central office. This cabling is often called the local loop, or “last-mile”.

DTE/DCE – Devices that put data on the local loop are called data circuit-terminating equipment, or data communications equipment (DCE). The customer devices that pass the data to the DCE are called data terminal equipment (DTE). The DCE primarily provides an interface for the DTE into the communication link on the WAN cloud.

Hardware

In a WAN you will need various types of hardware components for it to function. The typical items of hardware that you will need in a WAN are:

Router – An electronic device that connects a local area network (LAN) to a wide area network (WAN) and handles the task of routing messages between the two networks. Operates at layer 3, and makes decisions using IP addresses.

Switch – A switch is a network device that selects a path or circuit for sending a unit of data to its next destination. Operates at layer 2, and uses MAC addresses to send data to correct destination.

Modem – Short for modulator/demodulator, a modem enables a computer to communicate with other computers over telephone lines. Operates at layer 1, where signals are converted from digital to analogue and vice versa for transmission and receiving.

Wan Standards

WANs operate within the OSI model using layer 1 and layer 2 levels. The data link layer and the physical layer. The physical layer protocols describe how to provide electrical, mechanical and functional connections to the services provided by the ISP. The data link layer defines how data is encapsulated for transmission to remote sites.

Encapsulation

Encapsulation is the wrapping of data in a particular protocol header. Remember that WANs operate at the physical layer and the data link layer of the osi model and that higher layer protocols such as IP are encapsulated when sent across the WAN link. Serial interfaces support a wide range of WAN encapsulation types, which must be manually specified. These types include SDLC, PPP, Frame delay etc. Regardless of WAN encapsulation used it must be identical on both sides of the point to point link.

Packet and Circuit Switching

Circuit switching and packet switching are both used in high-capacity networks.

The majority of switched networks today get data across the network

through packet switching.

Circuit-switching is more reliable than packet-switching. Circuit switching is old and expensive, packet switching is more modern.

General Routing Issues

What is a Routing Protocol?

A routing protocol is a protocol that specifies how routers communicate and exchange information on a network. Each router has prior knowledge of its immediate neighbours and knows the structure of the network topology. The routers know this because the routing protocol shares this information.

Protocol

RIP (Routing Information Protocol) was one of the most commonly uses protocols on internal networks. Routers use RIP to dynamically adapt changes to the network connections and communicate information about which networks routers can reach and the distance between them. RIP is sometimes said to stand for Rest in Pieces in reference to the reputation that RIP has for breaking unexpectedly and rendering a network unable to function.

Routing Algorithms

Distance Vector

This type of routing protocol requires that each router simply inform its neighbours of its routing table. The distance vector protocol is also known as the bellman-ford algorithm.

Link State

This type of routing protocol requires that each router maintain a partial map of the network. The link state algorithm is also know as Dijkstra’s algorithm.

IGRP

IGRP is a type of distance vector routing protocol invented by cisco used to exchange routing data in a autonomous system. Distance vector protocols measure distances and compare routes. Routers that use distance vector must send all or a portion of their routing table in a routing update message at regular intervals to each neighbour router.

Addressing and Routing

What does routing mean?

Routing is the process of deciding how to move packets from one network to another.

The directions also known as routes can be learned by a router using a routing protocol then the information is passed from router to router along the route of the destination.

IP Address’s

Every machine connected to the internet is assigned an IP address. An example of an IP address would be 192.168.0.1. IP addresses are displayed in decimal format to make it easier for humans to understand but computers communicate in binary form. The four numbers that separate an IP address are called Octets. Each position consists of eight bits. When added to together you get 32 bit address. The purpose of each octet in an IP address is to create classes of IP addresses that can be assigned within a network. There are three main classes that we deal with Class A, B and C. The octets of an IP address are split into two parts Network and Host. In a class A address the first octet is the network portion, this determines which network the computer belongs to, the last octets of the address are the hosts that belong to the network.

Sub netting

Sub netting allows you to create multiple networks within a class A, B or C address. The subnet address is the address used by your LAN. In a Class C network address you would have a subnet mask of 255.255.255.0. A subnet mask identifies which portion is network and which is host. For example 192.168.6.15 the first octet three octets are the Network address and the last octet being the host(Workstation). It is important to subnet a network because gateways need to forward packets to other LANS. By giving each NIC on the gateway an IP address and a Subnet mask it allows the gateways to route packets from LAN to LAN. Once the packet arrives at its destination, the gateway then uses the bits of the subnet portion of the IP address to decide which LAN to send the packets.

Circuit Switched Leased Lines

A circuit switched network is one that establishes a dedicated circuit (or channel) between nodes and terminals before the users may communicate. Here are some terminologies associated with a Circuit switched network.

Frame relay is a telecommunication service designed for cost-efficient data transmission between local area networks (LANs)

Basic rate interference is a service used by small business for internet connectivity. An ISDN BRI provides two 64 Kbps digital channels to the user.

Primary rate interface (PRI) is a telecommunications standard for carrying voice and data transmissions between two locations

All data and voice channels are ISDN and operate at 64kbit/s

Packet Switching

http://www.raduniversity.com/networks/2004/PacketSwitching/main.htm – _Toc80455261

Packet switching refers to protocols in which messages are broken up into small packets before they are sent. Each packet is then transmitted over the Internet. At the destination the packets are reassembled into the original message. Packet switching main difference from Circuit Switching is that that the communication lines are not dedicated to passing messages from the source to the destination. In Packet Switching, different messages can use the same network resources within the same time period.

http://en.wikipedia.org/wiki/Asynchronous_Transfer_Mode

Asynchronous Transfer Mode (ATM) is a cell relay, packet switching network and protocolwhich encodes data into small fixed-sized cells.

ISDN is used to carry voice, data, video and images across a telephone network. ISDN stands for integrated services Digital Network. Isdn also provides users with a 128kbps bandwidth. This is done through frame relay. Frame relay complements and provides a service between ISDN, which offers bandwidth at 128 Kbps and Asynchronous Transfer Mode which operates in somewhat similar fashion to frame relay but at speeds from 155.520 Mbps or 622.080 Mbps. Frame relay is based on the older X.25 packet switching technology and is used to transmit analogue signals such as telephone conversations.

PSDN stands for packet switched data network and is a data communication network. Packet switched networks do not establish a physical communication signal like the public telephone does (circuit switched network) Packets are sent on a fixed length basis and assigned with a source and a destination address. The packets then rely on the routers to read the address and route the packets through the network.

Mobile and Broadband Services

Digital Subscriber line(DSL) is mainly used to bring high bandwidth connections to homes and small business’s over a copper wire telephone line. This is can only be achieved if you stay within the range of the telephone exchange. DSL offers download rates of up to 6mbps allowing continuous transmission of video, audio and 3D effects. DSL is set to replace ISDN and compete with the cable modem in providing multimedia to homes. DSL works by connecting your telephone line to the telephone office over copper wires that are twisted together.

Asymmetric Digital Subscribers Line is most commonly used for home users. It provides a high download speed but a lower upload speed. Using ADSL, up to 6.1 megabits per second of data can be sent downstream and up to 640 Kbps upstream.

http://en.wikipedia.org/wiki/Symmetric_Digital_Subscriber_Line

Symmetric Digital Subscriber Line is a digital subcriber line which runs over one pair of copper wires. The main difference between ADSL and SDSL is the difference in upload and download speeds. SDSL allows the same upstream data rate and downstream data rate as ADSL upstream can be very slow.

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HDSL High bit-rate Digital Subscriber Line, one of the earliest forms of DSL, is used for wideband digital transmission within a corporate site and between the telephone company and a customer. The main characteristic of HDSL is that provides equal bandwidth in both directions.

IDSL is a system in which data is transmitted at 128 Kbps on a regular copper telephone line from a user to a destination using digital transmission.

The Local Loop enables operators to connect directly to the consumer via copper local loops and then add their own equipment to offer broadband and other services. This process involves operators accessing local exchange buildings to connect to a network of copper lines which connect them to homes and businesses. BT is an Example of a Local Exchange. The local loop connecting the telephone exchange to most subscribers is capable of carrying frequencies well beyond the 3.4 kHz upper limit.

Benefits of using DSL

DSL can provide virtually instantaneous transmission of voice, data and video over ordinary copper phone lines. A DSL connection can eliminate delays when waiting to download information and graphics from the Internet. It provides users with a cost effective high speed Internet connection. Another benefit is that a DSL connection is always on-line (like a LAN connection) with no waiting time for dialling or connecting.

There are now more than 10 million broadband connections in the UK. By December 2005 there were 9.792 million broadband connections in the UK and the average broadband take up rate during the three months to December was more than 70,000 per week.

Dog Health Concerns and Common Diseases

Dogs are truly man’s best friend. These loyal, loving, protective and playful creatures have served beside man for thousands of years with an undying and relentless devotion. It’s hard to repay such a service of love, commitment and duty. When put to the basics, we provide our dogs with shelter, healthy nutrition, exercise and friendship. However, a dog’s health and well-being sometimes goes beyond the basics, requiring an owner with an eye for disease risks and proper veterinary care.

If you’re a dog owner, you should make sure your animal sees a qualified veterinarian on a regular basis. The range of diseases, parasites and genetic conditions that dogs can succumb to is vast, so it’s important to keep up your pet’s vaccines, stick to regular check-ups and also know what to look for.

Keep reading to learn about some of the most dangerous and fatal diseases that can afflict your beloved pet along with effective prevention methods.

1. Canine Distemper Virus (CDV)

CDV attacks the respiratory, gastrointestinal and central nervous systems. The disease is contracted through contact with other infected dogs and can be fatal to both young and old dogs. Symptoms include vomiting, diarrhea, fever, shivering, redness around the eyes, loss of appetite, weight loss, seizures, thickened footpads, cough and a discharge from the nose. There is no specific treatment, but sometimes antibiotics can be effective. However, a vaccine exists and should always be administered.

2. Canine Adenovirus or Infectious Canine Hepatitis (ICH)

Infectious Canine Hepatitis (ICH) is an acute liver disease, and highly contagious. The virus is transmitted through bodily fluids like urine, eye or nose secretions. Young and old dogs can be affected by ICH, but puppies are at a higher risk. Symptoms include fever, loss of appetite, vomiting, jaundice and corneal edema, though a blood test is needed to make a final diagnosis. Many dogs recover, but it’s best to prevent ICH through a simple vaccination.

3. Para Influenza or Tracheobronchitis (aka Kennel Cough)

The common name for Tracheobronchitis is Kennel Cough because of its propensity for spreading in close quarters, such as in a boarding kennel. It’s highly contagious and attacks the dog’s upper respiratory system. Like bronchitis in humans, the symptoms are coughing, snorting, hacking and sometimes fever. Kennel Cough can be treated with antibiotics or prevented through vaccination.

4. Rabies

Rabies is not just a dog disease; it will affect all mammals that are not vaccinated against the disease. Rabies directly attacks the brain and the prognosis is often deadly. This common disease can be easily prevented through vaccination. In many states, vaccination for domestic pets is absolutely mandatory.

In short, keep your dog healthy by making sure it gets regular vaccinations. Almost all diseases are preventable.

What You Really Need to Know About a MPLS Network

MPLS… or Multi-Protocol Label Switching…. seems to be the buzzword for connecting company data networks these days. But MPLS is really nothing new. It’s been around awhile actually. Maybe now it’s just gaining more popularity and thus noticeable public acceptance and notoriety. Rightfully so too. MPLS offers lots of advantages over traditional T1 point-to-point WAN architectures.

But….. to decide if MPLS is really a good fit for your network requirements….. there’s some things you need to understand first.

There’s no one “MPLS Service”. A lot of what you get will depend how the service provider has Engineered and built their core network. Bear in mind that many carriers don’t own the whole network, but will piece together a service from other carriers networks, or will interconnect with other carriers to extend their reach.

Cell-mode MPLS was mentioned: basically this is ATM which has been retro-fitted with MPLS. Be careful with this for VoIP applications because it can use bandwidth very inefficiently.

MPLS can support QoS, but many services aren’t engineered with this, or only with very basic prioritization. Also the services are very often structured to reduce the potential complexity and to ensure the network can cope. Bear in mind a typical MPLS router can only carry a percentage of “high-priority, real time” traffic. If everyone sends all their data as high priority then the benefit is lost, and the network may suffer. Usually QoS is provided as a small number of service classes, typically 3 or 4.

The biggest bottleneck in any such service is normally the tail circuit to each of your premises. If you move from a T1 mesh to a MPLS service then you will likely find that some sites need more bandwidth than others. Tracking the requirement for this bandwidth is usually your problem, although the service provides may give you some reporting tools to assist with this. I would avoid service providers who cannot offer this as it will make it very difficult for you to manage your bandwidths.

If you factor in multiple service classes then your management of these tail circuits gets more complex as you no only have to work out how much bandwidth is required for each tail circuit, but how much of it should be reserved for each service class.

Regarding resilience, within the service providers core, the service is normally highly resilient to failures. However, when failures do occur, very often (depending on how the service is engineered) the rerouting can take a second or two. During this network re-convergence you will lose packets. Depending on the protocol your traffic uses this can be unimportant or devastating. For instance, some VPN and VoIP services don’t survive this well.

Normally resilience is not automatically provided all the way to the customer. Typically you will have one tail circuit and one router at each site. If either fails (or if the Service provider’s PE router has problems) you will lose service to the site, totally.

If this is an issue, you need to factor in dual connections. There’s multiple ways of doing this, and different service providers will offer different options. Make sure you get your Network Engineer involved as the devil is in the detail here, and some options which sound like they provide a fantastic level of resilience may not be as good as they sound, depending on how your internal network is configured.

And, of course, the key to all of this is SLAs: what do they offer? What happens if they break them? How do they report them to you?

Generally speaking, MPLS services are a great way to run a multi-site data network including VoIP services. I have seen many carriers and their customers doing this successfully for years.

Strictly speaking MPLS does not provide QoS. QoS is done by prioritizing traffic, and most IP routers, even those on the backbone of the Internet, can do this. The difference is whether they are configured to do this or not. In an MPLS network MPLS is provided by standard router features. MPLS technology (specifically Traffic Engineering) gives the carrier better control over how this traffic is prioritized and routed (and restored in case of network fault). All this does is give them the confidence to support SLAs.

As I mentioned, “QoS” is provided as a set of “service classes”. Typically these are things like “real-time”, “high-priority” and “everything else”. Mapping actual traffic into these classes can be done in a few different ways, but this is largely up to you to control. For instance, you could quite easily put web-browsing traffic into “real time” although this would normally be a dumb thing to do.

I would suggest the case for MPLS in terms of performance, cost and continuity against ‘traditional’ or ‘legacy’ data networks is now pretty robust, i.e. MPLS provides significant advantages in all 3 areas.

The key considerations when migrating include provider selection, access media (e.g. using Ethernet rather than SDH/SONET), the decision on procuring a managed or unmanaged service (often called wires-only) and the providers ability to map their CoS/QoS to the applications you need to support. This is especially important if you are operating any proprietary applications.

There is also an increasing trend to use WAN Optimization/application management solutions either as a value added service from the provider or from an alternative integrator or indeed doing it in house. This is important say for voice or applications such as CITRIX.

MPLS providers also now offer a whole suite of value added services such as integrated internet, managed network based firewalls and remote user support. If these are important to you make sure the providers demonstrate how this is achieved.

In selecting your provider ensure they have good geographic coverage in your areas and experience within your market segment. I always recommend requesting up to 3 references. Equally I think it is wise to understand how important a client you will be to the provider. It’s all well and good using the market leader (say according to Gartner)….. but you’ll often get a better service from a provider who values and really wants your business.

Need help designing the right MPLS configuration for your network? There’s a ton of resources….. free and fee….. listed and discussed at Broadband Nation.

Underground Electric Dog Fence

An underground electric dog fence is a great way to keep your dog safe from the street or roaming into uninvited areas like your neighbor’s yard. They come in a variety of sizes to fit all dogs: underground fences for little dogs of under 12 lbs, average sized dogs and even large dogs as well as extra wire for larger acres of land. The electric fence can be buried underground, stapled above ground or attached along an existing fence. These fences give precise and consistent correction and some are specifically made for the stubborn dog with strong retriever tendencies or low sensitivity and in need of beeps and stronger vibration for them to get the message.

These underground wired fences work on slopes or in hilly areas, treed lots, in water and acres of land. Their precision and consistent correction capabilities allow for good reliability near busy streets. The variety of collars that are interchangeable make them great for small dogs, like a Chihuahua or a large dog like a Great Dane.

A small indentation or groove made in the pavement is big enough for the wire to be brought beyond the driveway to the extended yard making the dog fence very practical, just backfill the driveway with outdoor sealant. If you don’t want to buy wire get the staples and run the wire above ground. Zip ties can help you secure the wire along an existing fence.

Correction depends upon the dog receiving the   transmission . Therefore, you need to make sure that the receiver collar is the right size for your dog. It should not be smaller than the space of your two fingers between the collar and his neck (we don’t want to choke poor “Pooch”!), but the prongs need to touch the skin of your dog in order for the shock to be felt. Remember, it’s a harmless shock that is meant to catch your dog’s attention and change his current behavior. Long or medium haired dogs may need a scissor cut around the neck area so the prongs will contact the skin. If necessary, there are long pronged collars available for the long haired dog as well.

We love our dogs but, let’s face it, nothing is certain with them for dogs are naturally impulsive. Therefore, even with the underground electric dog fence training is imperative if you want a great chance of solid obedience. We highly recommend training the dog before actually using any system. Flags are available for training the dog to learn the boundary. Take 2-3 weeks, depending on your dog, to walk around the boundary with the flags so “Pooch” can see where the boundary is. Then place the collar on him and walk around with him guiding him to retreat when the signal on the collar transmits a warning. Before you know it, your dog will readily stay within the boundary of the underground electric dog fence without your presence because he won’t know that he can run through it!

Have You Ever Heard of Viral Marketing?

Viral Marketing is the spread of a word from one person to many others on a quick basis similar to a virus by an infected patient to other people surrounding him/her. It’s a new form of informal advertising by passing along a message or making other people aware about a product or a service just by talking about it.

The name viral is derived from the image of a person being infected with the marketing message, then spreading it to friends like a virus. The major difference, however, is that the customer voluntarily sends the message to others.

Viral Marketing messages include ads for goods and services, hyperlinked promotions that take someone immediately to a website, online newsletters and various games. Statistics indicate that 81 percent of recipients who receive a viral marketing message pass it along to another person. Almost 50 percent pass it along to two or more people.

The marketing message can be more deliberate such as when an individual recommends something to a friend. It can also be transmitted passively, when the message is simply attached to an email. Viral Marketing allows a firm to gain rapid product awareness at a low cost.

The main advantage of implementing viral marketing technique is getting fast and effective results by using this technique widely on the Internet. This gives a better exposure to the website as well as its owner and make other people aware of its existence. It also helps in conveying the desired message to a larger audience therefore building a good reputation for both the company/website and the owner.

Another benefit is that the more popularity the website gain, the bigger number of webmasters it will attract who will be willing either in exchanging links or just placing inbound links. This will definitely increase the value of the website by having external links which will ultimately result in improving its page rank with search engines.

The number of visitors to the website will also rise on a regular basis as it gains popularity and search engine ranking. The website owner will really benefit from the high volume targeted traffic that is going to blow his or her website fame and shoot up his or her revenue. Therefore, I can not emphasize more on the importance of viral marketing in boosting the Internet Marketing industry these days.

Blue Marble, a viral marketing company, created a program for Scope mouth wash. Consumers were able to send a customized, animated e-mail – kiss – to their friends. The attached marketing message reinforced the brand message that Scope brings people – kissably close. People who received the e-mail kiss could then forward the message to someone else. Scope’s tracking technology indicated most did forward the message.

The term – viral – may connote the negative image of a computer virus. Consequently, More concern should be shown when offering this program to a certain company. Company leaders may want to find some other term to describe the technique to the general public so that no undue suspicion or fear arises.