Networking Standards

Networking Standards

All networking technologieshave standards associated with them. These are usually highly technical documents, and often presume that the reader has a fair bit of knowledge about networking. If you aren't an expert, you will probably have some difficulty understanding networking standards. (Some people seem to think I am an expert, but I too have trouble with most of the details in a typical networking standard.)

In fact, many technologies have quite a number of standards associated with them. A networking technology may have more than one standard for any or all of the following reasons:

* The original standard has been revised or updated;

* The technology is sufficiently complex that it needs to be described in more than one document;

* The technology borrows from or builds on documents used in related technologies;

* More than one organization has been involved in developing the technology.

Standards documents created in the United States are usually developed in English, but are also routinely translated into other languages. European standards are often published simultaneously in English, French and German, and perhaps other languages as well.

IEEE standards for Networking:

IEEE 802.11 is a set of standards carrying out wireless local area network (WLAN) computer communication in the 2.4, 3.6 and 5 GHz frequency bands. They are created and maintained by the IEEE LAN/MAN Standards Committee (IEEE 802).

There are several specifications in the 802.11 family:

* 802.11 — applies to wireless LANs and provides 1 or 2 Mbps transmission in the 2.4 GHz band using either frequency hopping spread spectrum (FHSS) or direct sequence spread spectrum (DSSS).
* 802.11a — an extension to 802.11 that applies to wireless LANs and provides up to 54-Mbps in the 5GHz band. 802.11a uses an orthogonal frequency division multiplexing encoding scheme rather than FHSS or DSSS.
* 802.11b (also referred to as 802.11 High Rate or Wi-Fi) — an extension to 802.11 that applies to wireless LANS and provides 11 Mbps transmission (with a fallback to 5.5, 2 and 1-Mbps) in the 2.4 GHz band. 802.11b uses only DSSS. 802.11b was a 1999 ratification to the original 802.11 standard, allowing wireless functionality comparable to Ethernet.
* 802.11e — a wireless draft standard that defines the Quality of Service (QoS) support for LANs, and is an enhancement to the 802.11a and 802.11b wireless LAN (WLAN) specifications. 802.11e adds QoS features and multimedia support to the existing IEEE 802.11b and IEEE 802.11a wireless standards, while maintaining full backward compatibility with these standards.
* 802.11g — applies to wireless LANs and is used for transmission over short distances at up to 54-Mbps in the 2.4 GHz bands.
* 802.11n — 802.11n builds upon previous 802.11 standards by adding multiple-input multiple-output (MIMO). The additional transmitter and receiver antennas allow for increased data throughput through spatial multiplexing and increased range by exploiting the spatial diversity through coding schemes like Alamouti coding. The real speed would be 100 Mbit/s (even 250 Mbit/s in PHY level), and so up to 4-5 times faster than 802.11g.
* 802.11r — 802.11r, also called Fast Basic Service Set (BSS) Transition, supports VoWi-Fi handoff between access points to enable VoIP roaming on a Wi-Fi network with 802.1X authentication.
* 802.1X — Not to be confused with 802.11x (which is the term used to describe the family of 802.11 standards) 802.1X is an IEEE standard for port-based Network Access Control that allows network administrators to restricted use of IEEE 802 LAN service access points to secure communication between authenticated and authorized devices.

WiFi Antennas

WiFi Antennas

If you are setting up a wireless home network, you should know that you can maximize your network's performance by replacing the WiFi antenna. While this is not necessary in the majority of cases, if you are having trouble getting access to the network throughout your home, or if you just can't strategically place your router or access point because no matter where you put it, the signal strength is weak in places, replacing the WiFi antenna may be the solution you've been looking for.

Built-In WiFi Antennas

Most access points and routers contain built-in omnidirectional antennas. These antennas send signals out equally well in all directions. This makes router or access point set up easy, since when it is placed in the center of the home, and wireless devices are located throughout the rooms, an omnidirectional antenna ensures that signals are sent to all corners of the house.

However, while the omnidirectional antenna built-in to your router or access point makes setup easy, it may not be the most effective antennas for your wireless home network. The built-in antenna may have trouble reaching all places in your house where network service is required.

Replacement Antennas

Built-in omnidirectional antennas can have trouble sending signals for long distances because power must be expended in all directions. This means there is less power left over for long distance coverage.

To address this problem, some manufacturers sell external omnidirectional antennas that are significantly stronger than the built-in antennas. This increases the distance that the routers and access points can service. This will in turn increase network performance.

But there are also security concerns for wireless antennas that are too strong. The stronger your omnidirectional signal, the more likely it is to bleed outside the house, where signals can be snooped and exploited.

To deal with this concern, you can replace your omnidirectional antenna with a high gain directional antenna. This will send a strong signal in a particular direction of your choosing. Since the signal is focused, it can be better controlled by aiming it at the area of your home where wireless devices are located.

Many routers have an external antenna jack that allows you to connecting the new antenna. Consult the router product documentation for details.

Selecting a WiFi antenna

The single most important thing you can do to extend the range of your 802.11 system is to install an external antenna with some good gain and directional or omni-directional qualities. WiFi is simply a radio, which is used for computer. You can think of your antenna as the “speaker system” of your WiFi card. Get a bigger antenna; your WiFi will go a lot further. However, don't install a speaker on your wifi system or your range will be horrible!

Directional Antennas
Directional antennas are used for Point-to-Point or sometimes for Multi-Point systems depending on the setup. If you are trying to go from one location (say for instance your router), to another location, this is the type of antenna we recommend.

Omni-Directional
This is the common “Base” antenna used for Point-to-Multi-Point or can be an omni-directional antenna for your car. An Omni-Directional antenna would serve as your main antenna to distribute the signal to other computers or devices (such as wireless printers, PDAs, etc) in your workgroup. You can use 2 Omni-Directional antennas for a point to point system, but this is usually not recommended because there is no real point to distributing your signal all over the place when you only want to going from point A to point B.

Point-to-Point
Point-to-Point systems usually involve 2 different wireless points, or building to building wireless connections. But there are exceptions to every rule. If the access point is across a long valley and the owner of the system wishes to share the connection with multiple users on the other side of the valley. This would be a point to Multi-Point system but using directional antennas.

Home
Home antennas are always the easiest types of antennas to purchase and take the least amount of effort in choosing and installing. In most circumstances, only one antenna is needed on the remote computer. We recommend putting any external antenna on the remote computer, simply because if you install it on your router and don’t plan on setting up security, it will provide less signal strength outside of your home and your system will be less prone to hackers. If you have a multi-story home or a very large house, you may have to install antennas on every computer to get the range or bandwidth required. Every wall that you have to penetrate will decrease the signal strength of your system.

Office
Office antennas are pretty straight forward. If you want to run a network system inside of your office building and don’t want to run cables all over the place, first, purchase a good wireless card. However, this can get a little complex if the office is split between 2 different points or if the office is really large or on multiple stories of a building.

Mobile WiFi antennas
Why would anyone want WiFi in their car? Well, there are a lot of truck-stops and RV parks around the country now that offer wireless access. In fact, many public high speed wireless networks can be accessed directly from your car, truck, or RV. There is also something called WarDriving which is where bad people drive around neighborhoods and get their high-speed access for free.

Yagi Antennas
Yagi antennas were the design of two Japanese people, Hidetsugu Yagi and Shintaro Uda, and are sometimes referred to as Yagi-Uda antennas. They were originally designed for radio, but are now also used for 802.11 systems. These antennas are typically very directional and are used for point to point, or to extend the range of a point to multi-point system. We highly recommend using the RadioLabs 14 or 16 element weatherproof Yagi antenna if you want to install your system outside. They have excellent signal strength and in the right circumstances can communicate for miles!

Backfire antennas - The backfire is a small directional antenna with excellent gain. They look similar to a parabolic dish, but the gain isn't as high. We highly recommend Backfire antennas for point to point or point to multipoint systems because of the excellent gain and the good noise figures. We offer a backfire antenna with 15 dBi of Gain!! This is excellent considering the antenna is only 10 inches diameter. Almost invisible!!

Parabolic or dish antennas
This is where the real power is! Parabolic dish antennas put out tremendous gain but are a little hard to point and make a connection with. As the gain of an antenna increases, the antenna’s radiation pattern decreases until you have a very little window to point or aim your dish correctly. Dish antennas are almost always used for a point to point system for long haul systems. The Parabolic Dish antennas work by focusing the power to a central point and beaming the radio’s signal to a specific area, kind of like the adjustable reflector on a flashlight. These antennas are highly focused and are the perfect tool if you want to send your signal a very long distance.

Gain Considerations
The gain you will require for each individual WiFi antenna system will dependant on any direct objects in your path, the distance you must cover and the individual wifi cards. These all must be taken into consideration before choosing the proper antenna system. If our calculator is too difficult to use, please feel free to contact us for information.

Interference
As with all radio systems, interference is always a problem. If you are listening to an AM radio and you hear static, this is interference. The same thing applies to WiFi systems, however not to such a large degree. Things that cause interference with WiFi systems are Microwave ovens, certain lighting systems, other 802.11 access points or systems, microwave transmitters, even high speed processors for computers can cause interference for 802.11 systems. All these problems must be isolated before you can expect any significant range out of your system. If you need help, please don't be afraid to ask us. Afterall, WiFi is our business.

Virtual Private Network(VPN)

A VPN (Virtual Private Network) is a virtual computer network that exists over the top of an existing network. The purpose of a VPN is to allow communications between systems connected to the VPN using an existing shared network infrastructure as the transport, without the VPN network being aware of the existence of the underlying network backbone or without the VPN interfering with other network traffic on the backbone. A VPN between two networks is often referred to as a VPN Tunnel.

Most VPN technologies can be separated into two broad categories, Secure VPNs and Trusted VPNs.

Secure VPNs are designed to provide information security features such as authentication and confidentiality and are often used to secure traffic travelling over the Internet. Secure VPNs may be implemented by organizations wishing to provide remote access facilities to their employees or by organizations wishing to connect multiple networks together securely using the Internet to carry the traffic. A common use for Secure VPNs is in remote access scenarios, where VPN client software on an end user system is used to connect to a remote office network securely.

Trusted VPNs are commonly created by carriers and large organizations and are used for traffic segmentation on large core networks. They often provide quality of service guarantees and other carrier-grade features. Trusted VPNs may be implemented by network carriers wishing to multiplex multiple customer connections transparently over an existing core network or by large organizations wishing to segregate traffic flows from each other in the network.

Trusted VPNs differ from Secure VPNs in that they do not provide security features such as data confidentiality through encryption. Secure VPNs however do not offer the level of control of the data flows that a Trusted VPN can provide such as bandwidth guarantees or routing.

Some other types of VPN may not fit neatly within these two categories. For example, an end-user managed GRE tunnel may not necessarily use encryption to protect the tunnel contents. L2TP can also be used to tunnel traffic from a network access server to another location without enforcing encryption.

Clients and Servers

A VPN server is a piece of hardware or software that can acts as a gateway into a whole network or a single computer. It is generally ‘always on’ and listening for VPN clients to connect to it.

A VPN Client is most often a piece of software but can be hardware too. A client initiates a ‘call’ to the server and logs on. Then the client computer can server network can communicate. They are on the same ‘virtual’ network. Many broadband routers can 'pass' one or more VPN sessions from your LAN to the Internet. Each router handles this differently.

VPN Software

VPN ‘server’ software is rather rare. Windows Server level operating systems like ‘Windows 2000 Server’ have a ‘VPN server’ built in. I know if no software products priced for home or small business that allows you to set up a VPN server.

VPN ‘client’ software is much more common. When loaded on your computer, this software allows you create a secure VPN tunnel across the Internet and into another network fronted by a VPN server.

VPN Languages

There are two major 'languages' or protocols that VPN's speak. Microsoft uses PPTP or Point to Point Tunneling Protocol and most everyone else uses IPSec - Internet Protocol Security. Most broadband routers can pass PPTP traffic by forwarding port 1723 but IPSec is more complex. If your router does not explicitly support IPSEC pass through, then even placing your computer in the DMZ might not work.

PPTP has 'good' encryption and also features 'authentication' for verifying a user ID and password. IPSec is pureley an encryption model and is mutch safer but does not include authentication routines. A third standard, L2TP is IPSec with authentication built in.

Broadband Routers with VPN Servers

Until recently, VPN server hardware was VERY expensive. As home networks become more sophisticated, the demand for home level VPN’s increase. At the end of 2001, the home network industry responded by adding VPN servers into some broadband routers. These products are often priced at under $300 (us) and some are as inexpensive as $170.

VPN functionality is very processor intensive and most broadband routers have somewhat slow processors in them. Broadband router based VPN servers are often limited in throughput because of their microprocessors. Most have a maximum VPN throughput of around .6Mbps or 600Kbps.

Network Switches

Like a hub, a switch is a device that connects individual devices on an Ethernet network so that
they can communicate with one another. But a switch also has an additional capability; it
momentarily connects the sending and receiving devices so that they can use the entire bandwidth
of the network without interference. If you use switches properly, they can improve the
performance of your network by reducing network interference.

Switches have two benefits: (1) they provide each pair of communicating devices with a fast
connection; and (2) they segregate the communication so that it does not enter other portions of
the network. (Hubs, in contrast, broadcast all data on the network to every other device on the
network.)

Different models of network switches support differing numbers of connected devices. Most consumer-grade network switches provide either four or eight connections for Ethernet devices. Switches can be connected to each other, a so-called daisy chaining method to add progressively larger number of devices to a LAN.

Function:

The network switch, packet switch (or just switch) plays an integral part in most Ethernet Local Area Networks or LANs. Mid-to-large sized LANs contain a number of linked managed switches. Small office/home office (SOHO) applications typically use a single switch, or an all-purpose converged device such as gateway access to small office/home broadband services such as DSL router or cable Wi-Fi router. In most of these cases, the end user device contains a router and components that interface to the particular physical broadband technology, as in the Linksys 8-port and 48-port devices. User devices may also include a telephone interface to VOIP.

In the context of a standard 10/100 Ethernet switch, a switch operates at the data-link layer of the OSI model to create a different collision domain per switch port. If you have 4 computers A/B/C/D on 4 switch ports, then A and B can transfer data between them as well as C and D at the same time, and they will never interfere with each others' conversations. In the case of a "hub" then they would all have to share the bandwidth, run in Half Duplex and there would be collisions and retransmissions. Using a switch is called micro-segmentation. It allows you to have dedicated bandwidth on point to point connections with every computer and to therefore run in Full duplex with no collisions.

Role of switches in networks:

Switches may operate at one or more OSI layers, including physical, data lin, network or transport. A device that operates simultaneously at more than one of these layers is known as a multilayer switch.

In switches intended for commercial use, built-in or modular interfaces make it possible to connect different types of networks, including Ethernet, fibre channel , ATM and 802.11 . This connectivity can be at any of the layers mentioned. While Layer 2 functionality is adequate for speed-shifting within one technology, interconnecting technologies such as Ethernet and token ring are easier at Layer 3.

Interconnection of different Layer 3 networks is done by routers. If there are any features that characterize "Layer-3 switches" as opposed to general-purpose routers, it tends to be that they are optimized, in larger switches, for high-density Ethernet connectivity.

In some service provider and other environments where there is a need for a great deal of analysis of network performance and security, switches may be connected between WAN routers as places for analytic modules. Some vendors provide firewall network intrusion detection and performance analysis modules that can plug into switch ports. Some of these functions may be on combined modules.

In other cases, the switch is used to create a mirror image of data that can go to an external device. Since most switch port mirroring provides only one mirrored stream, network hubs can be useful for fanning out data to several read-only analyzers, such as intrusion detection systems and packet sniffers.

Purchase Considerations

When you purchase and install a switch, you should review and
apply the following criteria:

• Your switches must be compatible with your physical and data link
level protocols. If you are running a 10BaseT Ethernet network, then
you must purchase a 10BaseT switch.
• Some switches can accommodate more than one physical or data link
level protocol. For example, modern switches accommodate both
10BaseT and 100BaseTX protocols. It is wise to purchase a switch
with at least one 100BaseTX port, since you can interconnect your
switches via their high speed ports to improve network performance
(even if the remainder of your network uses 10BaseT).
• If you purchase a switch that accommodates more than one protocol,
then make sure that it automatically senses which protocol is being
used on each port. Autosensing switches ensure that you can connect
any part of the network to any switch port. (Older switches required
that you attach each segment of the network to a port compatible
with its physical and data link level protocol. Keeping the segments
and ports straight presents a management headache.)
• Purchase switches from a known manufacturer whose support you
trust. Make sure the manufacturer provides a competitive warranty.
• Install your switches in a room that is cool and free of dust, if
possible. Additionally, plug your switches into an uninterruptible
power supply (UPS) to ensure that they receive clean power.

All About Repeater

Definition: Network repeaters regenerate incoming electrical, wireless or optical signals. With physical media like Ethernet or Wi-Fi, data transmissions can only span a limited distance before the quality of the signal degrades. Repeaters attempt to preserve signal integrity and extend the distance over which data can safely travel.

Actual network devices that serve as repeaters usually have some other name. Active hubs, for example, are repeaters. Active hubs are sometimes also called "multiport repeaters," but more commonly they are just "hubs." Other types of "passive hubs" are not repeaters. In Wi-Fi, access points function as repeaters only when operating in so-called "repeater mode."

Higher-level devices in the OSI model like switches and routers generally do not incorporate the functions of a repeater. All repeaters are technically OSI physical layer devices.

Usage

Repeaters are often used in trans-continental and submarine communication cables, because the attenuation(signal loss) over such distances would be unacceptable without them. Repeaters are used in both copper-wire cables carrying electrical signals, and in fibre optics carrying light.

Repeaters are used in radio communication services. Radio repeaters often transmit and receive on different frequencies. A special subgroup of those repeaters is those used in amateur radio.

Repeaters are also used extensively in broadcasting, where they are known as translators, boosters or TV relay transmitters.

When providing a point-to-point telecom link using radio beyond line of sight, one uses repeaters in a microwave radio relay. A reflector, often on a mountaintop, that relays such signals around an obstacle, is called a passive repeaer or Passive Radio Link Deflection. A microwave repeater in a communications sattelite is called a transponder.

In optical communications the term repeater is used to describe a piece of equipment that receives an optical signal, converts that signal into an electrical one, regenerates it, and then retransmits an optical signal. Since such a device converts the optical signal into an electrical one, and then back to an optical signal, they are often known as Optical-Electrical-Optical (OEO) repeaters.

Before the invention of electronic amplifiers, mechanically coupled carbon microphones were used as amplifiers in telephone repeaters. The invention of the audion tube made transcontinental telephony practical. In the 1930s vaccum tube repeaters using hybrid coils became commonplace, allowing the use of thinner wires.

Bridges(Networking)

A bridge is a device that connects two or more local area networks, or two or more segments of
the same network. For example, suppose that your network includes both 10BaseT Ethernet and localTalk connections. You can use a bridge to connect these two networks so that they can
share information with each other.
In addition to connecting networks, bridges perform an additional, important function. They filter information so that network traffic intended for one portion of the network does not congest the rest of the network.

Bridges operate at the data link layer (Layer 2) of the OSI model. Bridges inspect incoming traffic and decide whether to forward or discard it. An Ethernet bridge, for example, inspects each incoming Ethernet frame - including the source and destination MAC addresses, and sometimes the frame size - in making individual forwarding decisions. Bridges serve a similar function as switches, that also operate at Layer 2. Traditional bridges, though, support one network boundary, whereas switches usually offer four or more hardware ports. Switches are sometimes called "multi-port bridges" for this reason.

When bridges were introduced in the 1980’s, they typically joined two homogeneous networks
(for example, two kinds of Ethernet networks). More recently it has become possible for bridges
to connect networks with different physical and data link level protocols. For example, you can
use a bridge to connect a LocalTalk network to an Ethernet network, or an Ethernet network to a TokenRing network.
Like switches, bridges learn the MAC addresses of all connected clients, servers, and peripherals,
and associate each address with a bridge port (network connection). When a bridge (or switch)
receives an incoming frame, it opens and reads its destination MAC address. If the port that will
receive the frame is different from the port connected to the sender, then the bridge forwards the frame to the destination port. If the port that will receive the frame is the same as the port
connected to the sender, the bridge drops the frame. (Since the bridge is by definition at the end
of the network segment, the receiving computer presumably intercepted a copy of the frame on its way to the bridge.) If the bridge cannot determine which port is associated with a destination
address, it passes the frame along to all ports.
Traditional bridges connect a single workgroup to another workgroup. More recently, however, manufacturers have produced multiport bridges. Multiport bridges allow network managers to connect more than two network segments to each other. Additionally, you can reconfigure or expand networks because simply by replacing one network interface card inside the multiport bridge with another (for example, adding a LocalTalk interface to a multiport Ethernet bridge).
Bridges generally inspect data link level information within a network signal—information like
the Ethernet or LocalTalk (MAC) destination address. They do not attend to network routing or
transport protocol information such as that carried within the TCP/IP, IPX/SPX, or AppleTalk
portions of the signal. However, bridges can be fitted with custom filters that enable them to read this information—including network routing or transport source address, packet size, or type of protocol—and reject or forward information based on it. Custom filters enable network managers to isolate particular areas of the network and control which protocols enter or leave each area.
For example, custom filters might allow requests from the Internet (outside the school district) not to enter certain areas of the network.
Bridges are relatively simple and efficient traffic regulators. However, in some networks they
have been replaced by their more powerful cousins—hubs, switches, and routers. Each of these
traffic regulators brings a unique set of strengths and weaknesses to its work:
• Hubs, switches, bridges, and routers can interconnect two different kinds of networks such as
10BaseT Ethernet and 100BaseTX.
• Hubs (unlike switches, bridges, and routers) do not filter traffic between the two networks.
• Switches have the unique capability to enable communicating devices momentarily to utilize
the full bandwidth (data carrying capacity) of the network.
• However, switches (and hubs) cannot accommodate the variety of protocols and cabling types
that bridges can.
• Routers are much more expensive and much more difficult to install and manage than hubs,
switches, or bridges, but they can filter and route information much more precisely. (We
discuss routers in more detail later in this chapter.)
When you purchase equipment, make sure you understand how each of these details affects your
network. Then work with your technical staff or network integrator to choose the best equipment
for each situation.
Because bridges (like switches) generally depend upon MAC addresses, we say in the parlance of
the OSI model that bridges are level 2 devices. You must purchase a bridge that is compatible
with your physical network and your data link protocols.

Purchase Considerations
When you consider purchase of a bridge, you should follow
these guidelines:

• Before you decide on your purchase, take a moment to clarify what
you wish to achieve (connecting a Macintosh LocalTalk lab to
Ethernet? connecting two Ethernet segments?). Then work with your
technical staff, or with manufacturers and consultants, to determine
your options. You can often use a hub, switch, or router in the same
places that you can use a bridge. Each device brings its unique set of
strengths and weaknesses to the job.
• Make sure that the bridge is compatible with your physical and data
link protocols.
• Purchase bridges from a known manufacturer whose support you
trust. Make sure the manufacturer provides a competitive warranty.
• Install your bridges in a room that is cool and free of dust, if
possible. Additionally, plug your bridges into an uninterruptible
power supply (UPS) to ensure that they receive clean power

Advantages of network bridges:

• Self-configuring
• Simple bridges are inexpensive
• Isolate collision domain
• Reduce the size of collision domain by microsegmentation in non-switched networks
• Transparent to protocols above the MAC layer
• Allows the introduction of management/performance information and access control
• LANs interconnected are separate, and physical constraints such as number of stations, repeaters and segment length don't apply
• Helps minimize bandwidth usage.

Disadvantages of network bridges:

• Does not limit the scope of broadcasts
• Does not scale to extremely large networks
• Buffering and processing introduces delays
• Bridges are more expensive than repeaters or hubs
• A complex network topology can pose a problem for transparent bridges. For example, multiple paths between transparent bridges and LANs can result in bridge loops. The spanning tree protocol helps to reduce problems with complex topologies.

Three types of bridges are used in networks:

• Transparent bridge Derives its name from the fact that the devices on the network are unaware of its existence. A transparent bridge does nothing except block or forward data based on the MAC address.

• Source route bridge Used in Token Ring networks. The source route bridge derives its name from the fact that the entire path that the packet is to take through the network is embedded within the packet.

• Translational bridge Used to convert one networking data format to another; for example, from Token Ring to Ethernet and vice versa.

ROUTERS

A router is a device in computer networking that forwards data packets to their destinations, based on their addresses. The work a router does it called routing, which is somewhat like switching, but a router is different from a switch. The latter is simply a device to connect machines to form a LAN.

Routing is the process during which data packets are forwarded from one machine or device (technically referred to as a node) to another on a network until they reach their destinations.

Routing is the same as switching (with some very technical differences, which I will spare you from). IP routing uses IP addresses to forward IP packets from their sources to their destinations. IP adopts packet switching.

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.

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 Window 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 Firewallor serve as a DHCP Server.

Wired and Wireless Routers

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.

1. Static routers - Are configured manually and route data packets based on information in a router table.
2. Dynamic routers - Use dynamic routing algorithms. There are two types of algorithms:
   • Distance vector - Based on hop count, and periodically broadcasts the routing table to other routers which takes more network bandwidth especially with more routers. RIP uses distance vectoring. Does not work on WANs as well as it does on LANs.
   • Link state - Routing tables are broadcast at startup and then only when they change. The open shortest path first (OSPF) protocol uses the link state routing method to configure routes or distance vector algorithm (DVA).

Common routing protocols include:

• IS-IS -Intermediate system to intermediate system which is a routing protocol for the OSI suite of protocols.
• IPX - Internet Packet Exchange. Used on Netware systems.
• NLSP - Netware Link Services protocol - Uses OSPF algorithm and is replacing IPX to provide internet capability.
• RIP - Routing information protocol uses a distance vector algorithm.

There is a device called a brouter which will function similar to a bridge for network transport protocols that are not routable, and will function as a router for routable protocols. It functions at the network and data link layers of the OSI network model.

Internet Protocol

Internet Protocol

The Internet Protocol (IP) is a protocol used for communicating data across a packet-switced internetwork using the Internet Protocol Suite, also referred to as TCP/IP.

IP is the primary protocol in the Internet Layer of the Internet Protocol Suite and has the task of delivering distinguished protocol datagrams (packets) from the source host to the destination host solely based on their addresses. For this purpose the Internet Protocol defines addressing methods and structures for datagram encapsulation. The first major version of addressing structure, now referred to as Internet Protocol Version 4(IPv4) is still the dominant protocol of the Internet, although the successor, Internet Protocol Version 6(IPv6) is being deployed actively worldwide.

IP (Internet Protocol) is the primary network protocol used on the Internet, developed in the 1970s. On the Internet and many other networks, IP is often used together with the Transport Control Protocol (TCP) and referred to interchangeably as TCP/IP.

IP supports unique addressing for computers on a network. Most networks use the Internet Protocol version 4 (IPv4) standard that features IP addresses four bytes (32 bits) in length. The newer Internet Protocol version 6 (IPv6) standard features addresses 16 bytes (128 bits) in length.

Data on an Internet Protocol network is organized into packets. Each IP packet includes both a header (that specifies source, destination, and other information about the data) and the message data itself.

IP functions at layer 3 of the OSI model. It can therefore run on top of different data link interfaces including Ethernet and Wi-Fi.

IP encapsulation

Data from an upper layer protocol is encapsulated as packets/datagrams(the terms are basically synonymous in IP). Circuit setup is not needed before a host may send packets to another host that it has previously not communicated with (a characteristic of packet switched networks), thus IP is a connectionless protocol. This is in contrast to public switched telephone networks that require the setup of a circuit for each phone call (connection-oriented protocol).

Services provided by IP

Because of the abstraction provided by encapsulation, IP can be used over a heterogeneous network, i.e., a network connecting computers may consist of a combination of Ethernet, ATM, FDDI,Wi-Fi or others. Each link layer implementation may have its own method of addressing (or possibly the complete lack of it), with a corresponding need to resolve IP addresses to data link addresses.

Internet Protocol Service (IPS) is a dedicated Internet access service that rides on Level 3’s continuously upgradeable IP, transport, and physical networks. IPS, which is delivered using the Level 3 IP platform, provides a broad range of IP transit and network interconnection solutions tailored to meet the varied needs of Government agencies. Level 3’s IPS provides dedicated Internet access connectivity to the public Internet via the Level 3 Multi-Protocol Label Switching (MPLS)-based IP network. Access to locations on the public Internet that do not reside on the Level 3 Network is achieved via peering relationships between Level 3 and other Tier 1 providers. Level 3’s IPS provides a variety of port interfaces to accommodate customer Internet access requirements. The following types of port interfaces are available options for our IPS service:

• DS-1 (1.54 Mbs)
• Fractional T3
• DS-3 (45 Mbps)
• OC-3 (155 Mbps)
• OC-12 (622 Mbps)
• OC-48 (2.5 Gbps)
• OC-192 (10 Gbps)
• 100BT/Fast Ethernet (100 Mbps)
• 1000SX/GigabitEthernet (1000 Mbps)
• 10 Gigabit Ethernet

Access Methods

Level 3 IPS offering includes a variety of access methods, including dial up, private line, broadband, and UNI connections with existing frame relay and ATM networks:

• Analog Dial-up
• Private Line/ SONETS
• Ethernet

Peering Arrangements

Level 3 has established peering relationships worldwide. These include both public and private peering. Relative to the shared switched fabric connecting networks in public exchanges, private peering provides improved performance and scalability. Level 3’s private peering connections are OC-48, OC-192 or 10 GigE. Approximately 95% of Level 3’s interconnection traffic runs through private interconnections. Private interconnects provide the best possible performance between Level 3 and other Tier 1 backbones.

IP Addresses and Domain Names

Level 3 IPS supports IP address assignment and domain name service. IP network numbers are globally governed by the Internet Assigned Numbers Authority (IANA). IANA in turn delegates authority for some parts of the IP address space to regional Internet registries. Although assigned to the customer for the duration of its service contract with Level 3, all Level 3-assigned IP network numbers remain an integral part of Level 3’s contiguous range of addresses and must be relinquished by the customer when service expires or is terminated. Customers who require or desire IP address portability must apply for IP network numbers directly from the appropriate registry. For customers who have legally assigned IP network numbers that they wish Level 3 to route as part of IPS, Level 3 will accept routing of those IP network numbers on behalf of these customers. For customers requesting that Level 3 route IP network numbers belonging to another ISP’s address space, Level 3 requires written permission from that ISP to route those network numbers on the customer’s behalf. For broadband access, the Level 3 Team offers both Dynamic Host Configuration Protocol (DHCP) and static IP options. Some DSL services may be a point-to-point Protocol over Ethernet (PPPoE) variant of DHCP. Sometimes it may not be possible, or desirable, to install a PPPoE software stack on an end user’s PC. In these cases, the Team will deploy secondary CPE (router and/or hub) for purposes of authenticating a PPPoE session.

Domain Name Service

Domain name registration service includes the administrative tasks of originating unique domain names with an ICANN-accredited registrar. Level 3 will assist the customer with submission of the appropriate information to register chosen domain names. However, the customer is responsible for actual submissions to the registrar, all registration fees, ongoing maintenance charges, and modifications to the domain names. These are the direct responsibility of the customer, as dictated by the domain registrar. Level 3 provides primary name server support for its customers. In this service, Level 3 establishes and manages primary zone records for the customer’s domains on one of Level 3’s name servers. Once established, Level 3 performs zone record changes during normal business hours and limits these changes to one per week (on average). Level 3 attempts to implement customer change requests within one business day. Level 3’s name servers are located at physically separate facilities within the United States and are connected to Level 3’s backbone at different points. Level 3 also provides secondary name server support for its customers. In this service, Level 3 establishes and manages zone transfers with the primary name server keeping the master zone records. Zone transfers will not occur more frequently than once per hour. Customers can elect for Level 3 to support secondary name services or both primary and secondary name services.

Border Gateway Protocol (BGP) Support

Static routing is the standard configuration for those customers with a single Internet connection. BGP4 routing is supported for customers with connections to multiple Level 3 Gateways or customers with connections to both Level 3’s and other ISPs’ networks. Customers may provide their own registered Autonomous System (AS) Number or may use a Level-3-provided, private AS when the customer is multi-homed only to Level 3.

Benefits

Many companies attempt to integrate multiple legacy systems to create one complete network. These “patchwork” systems create many difficulties when problems must be controlled or when the source of a problem must be located. Level 3 is unencumbered by legacy networks and is able to more easily and more rapidly scale our network. This provides for a faster deployment of new technologies. The Level 3 IPS consistently provides outstanding performance, including best-in-class latency, outstanding availability, very low packet loss, and fast service restoration. Level 3 repeatedly receives top marks in reputation and quality from both our customers and third-party analysts. Level 3 built its entire IP Core North American network from the ground up. Optronics and optical fiber are uniform throughout. We maintain complete operations and management control over the network. The result is fewer variables when troubleshooting, which enables us to provide to the Government highly reliable and available IP-based services.

Alternative Services:

• SONETS
• CHS
• NBIP-VPNS

Restrictions:

• None