Network topology is the layout pattern of interconnections of the various elements (links, nodes, etc.) of a computer[1][2] or biological network.[3] Network topologies may be physical or logical. Physical topology refers to the physical design of a network including the devices, location and cable installation. Logical topology refers to how data is actually transferred in a network as opposed to its physical design. In general physical topology relates to a core network whereas logical topology relates to basic network. Topology can be understood as the shape or structure of a network. This shape does not necessarily correspond to the actual physical design of the devices on the computer network. The computers on a home network can be arranged in a circle but it does not necessarily mean that it represents a ring topology. Any particular network topology is determined only by the graphical mapping of the configuration of physical and/or logical connections between nodes. The study of network topology uses graph theory. Distances between nodes, physical interconnections, transmission rates, and/or signal types may differ in two networks and yet their topologies may be identical. A local area network (LAN) is one example of a network that exhibits both a physical topology and a logical topology. Any given node in the LAN has one or more links to one or more nodes in the network and the mapping of these links and nodes in a graph results in a geometric shape that may be used to describe the physical topology of the network. Likewise, the mapping of the data flow between the nodes in the network determines the logical topology of the network. The physical and logical topologies may or may not be identical in any particular network. Topology There are two basic categories of network topologies: [4] 1 Physical topologies 2 Logical topologies The shape of the cabling layout used to link devices is called the physical topology of the network. This refers to the layout of cabling, the locations of nodes, and the interconnections between the nodes and the cabling. [1] The physical topology of a network is determined by the capabilities of the network access devices and media, the level of control or fault tolerance desired, and the cost associated with cabling or telecommunications circuits. The logical topology, in contrast, is the way that the signals act on the network media, or the way that the data passes through the network from one device to the next without regard to the physical interconnection of the devices. A network's logical topology is not necessarily the same as its physical topology. For example, the original twisted pair Ethernet using repeater hubs was a logical bus topology with a physical star topology layout. Token Ring is a logical ring topology, but is wired a physical star from the Media Access Unit. The logical classification of network topologies generally follows the same classifications as those in the physical classifications of network topologies but describes the path that the data takes between nodes being used as opposed to the actual physical connections between nodes. The logical topologies are generally determined by network protocols as opposed to being determined by the physical layout of cables, wires, and network devices or by the flow of the electrical signals, although in many cases the paths that the electrical signals take between nodes may closely match the logical flow of data, hence the convention of using the terms logical topology and signal topology interchangeably. Logical topologies are often closely associated with Media Access Control methods and protocols. Logical topologies are able to be dynamically reconfigured by special types of equipment such as routers and switches. The study of network topology recognizes eight basic topologies: [5] •

Point-to-point

Bus

Star

Ring or circular

Mesh

Tree

Hybrid

Daisy chain

Point-to-point The simplest topology is a permanent link between two endpoints. Switched point-to-point topologies are the basic model of conventional telephony. The value of a permanent point-to-point network is unimpeded communications between the two endpoints. The value of an on-demand point-to-point connection is proportional to the number of potential pairs of subscribers, and has been expressed as Metcalfe's Law. Permanent (dedicated) Easiest to understand, of the variations of point-to-point topology, is a point-to-point communications channel that appears, to the user, to be permanently associated with the two endpoints. A children's tin can telephone is one example of a physical dedicated channel. Within many switched telecommunications systems, it is possible to establish a permanent circuit. One example might be a telephone in the lobby of a public building, which is programmed to ring only the number of a telephone dispatcher. "Nailing down" a switched connection saves the cost of running a physical circuit between the two points. The resources in such a connection can be released when no longer needed, for example, a television circuit from a parade route back to the studio. Switched: Using circuit-switching or packet-switching technologies, a point-to-point circuit can be set up dynamically, and dropped when no longer needed. This is the basic mode of conventional telephony. Bus Main article: Bus network

Bus network topology In local area networks where bus topology is used, each node is connected to a single cable. Each computer or server is connected to the single bus cable. A signal from the source travels in both directions to all machines connected on the bus cable until it finds the intended recipient. If the machine address does not match the intended address for the data, the machine ignores the data. Alternatively, if the data matches the machine address, the data is accepted. Since the bus topology consists of only one wire, it is rather inexpensive to implement when compared to other topologies. However, the low cost of implementing the technology is offset by the high cost of managing the network. Additionally, since only one cable is utilized, it can be the single point of failure. If the network cable is terminated on both ends and when without termination data transfer stop and when cable breaks, the entire network will be down. Linear bus

The type of network topology in which all of the nodes of the network are connected to a common transmission medium which has exactly two endpoints (this is the 'bus', which is also commonly referred to as the backbone, or trunk) – all data that is transmitted between nodes in the network is transmitted over this common transmission medium and is able to be received by all nodes in the network simultaneously.[1] Note: The two endpoints of the common transmission medium are normally terminated with a device called a terminator that exhibits the characteristic impedance of the transmission medium and which dissipates or absorbs the energy that remains in the signal to prevent the signal from being reflected or propagated back onto the transmission medium in the opposite direction, which would cause interference with and degradation of the signals on the transmission medium. Distributed bus The type of network topology in which all of the nodes of the network are connected to a common transmission medium which has more than two endpoints that are created by adding branches to the main section of the transmission medium – the physical distributed bus topology functions in exactly the same fashion as the physical linear bus topology (i.e., all nodes share a common transmission medium). Notes: 1. All of the endpoints of the common transmission medium are normally terminated using 50 ohm resistor. 2. The linear bus topology is sometimes considered to be a special case of the distributed bus topology – i.e., a distributed bus with no branching segments. 3. The physical distributed bus topology is sometimes incorrectly referred to as a physical tree topology – however, although the physical distributed bus topology resembles the physical tree topology, it differs from the physical tree topology in that there is no central node to which any other nodes are connected, since this hierarchical functionality is replaced by the common bus. Star: Main article: Star network

Star network topology In local area networks with a star topology, each network host is connected to a central hub with a pointto-point connection. The network does not necessarily have to resemble a star to be classified as a star network, but all of the nodes on the network must be connected to one central device. All traffic that traverses the network passes through the central hub. The hub acts as a signal repeater. The star topology is considered the easiest topology to design and implement. An advantage of the star topology is the simplicity of adding additional nodes. The primary disadvantage of the star topology is that the hub

represents a single point of failure. However, according to O'Brien and Marakas, 2011, multiprocessor architecture has been commonly used as a solution to combat this disadvantage.[6] Notes 1. A point-to-point link (described above) is sometimes categorized as a special instance of the physical star topology – therefore, the simplest type of network that is based upon the physical star topology would consist of one node with a single point-to-point link to a second node, the choice of which node is the 'hub' and which node is the 'spoke' being arbitrary. [1] 2. After the special case of the point-to-point link, as in note (1) above, the next simplest type of network that is based upon the physical star topology would consist of one central node – the 'hub' – with two separate point-to-point links to two peripheral nodes – the 'spokes'. 3. Although most networks that are based upon the physical star topology are commonly implemented using a special device such as a hub or switch as the central node (i.e., the 'hub' of the star), it is also possible to implement a network that is based upon the physical star topology using a computer or even a simple common connection point as the 'hub' or central node.[citation needed]

4. Star networks may also be described as either broadcast multi-access or no broadcast multiaccess (NBMA), depending on whether the technology of the network either automatically propagates a signal at the hub to all spokes, or only addresses individual spokes with each communication. Extended star A type of network topology in which a network that is based upon the physical star topology has one or more repeaters between the central node (the 'hub' of the star) and the peripheral or 'spoke' nodes, the repeaters being used to extend the maximum transmission distance of the point-to-point links between the central node and the peripheral nodes beyond that which is supported by the transmitter power of the central node or beyond that which is supported by the standard upon which the physical layer of the physical star network is based. If the repeaters in a network that is based upon the physical extended star topology are replaced with hubs or switches, then a hybrid network topology is created that is referred to as a physical hierarchical star topology, although some texts make no distinction between the two topologies. Distributed Star A type of network topology that is composed of individual networks that are based upon the physical star topology connected in a linear fashion – i.e., 'daisy-chained' – with no central or top level connection point (e.g., two or more 'stacked' hubs, along with their associated star connected nodes or 'spokes'). Ring: Main article: Ring network

Ring network topology A network topology that is set up in a circular fashion in which data travels around the ring in one direction and each device on the right acts as a repeater to keep the signal strong as it travels. Each device incorporates a receiver for the incoming signal and a transmitter to send the data on to the next device in the ring. The network is dependent on the ability of the signal to travel around the ring.[4] Mesh Main article: Mesh networking The value of fully meshed networks is proportional to the exponent of the number of subscribers, assuming that communicating groups of any two endpoints, up to and including all the endpoints, is approximated by Reed's Law. Fully connected

Fully connected mesh topology The number of connections in a full mesh = n (n - 1) / 2. Note: The physical fully connected mesh topology is generally too costly and complex for practical networks, although the topology is used when there are only a small number of nodes to be interconnected (see combinatorial explosion). Partially connected

Partially connected mesh topology The type of network topology in which some of the nodes of the network are connected to more than one other node in the network with a point-to-point link â&#x20AC;&#x201C; this makes it possible to take advantage of some of the redundancy that is provided by a physical fully connected mesh topology without the expense and complexity required for a connection between every node in the network. Note: In most practical networks that are based upon the partially connected mesh topology, all of the data that is transmitted between nodes in the network takes the shortest path between nodes, [citation needed] except in the case of a failure or break in one of the links, in which case the data takes an alternative path to the destination. This requires that the nodes of the network possess some type of logical 'routing' algorithm to determine the correct path to use at any particular time. Tree:

Tree network topology The type of network topology in which a central 'root' node (the top level of the hierarchy) is connected to one or more other nodes that are one level lower in the hierarchy (i.e., the second level) with a point-to-point link between each of the second level nodes and the top level central 'root' node, while each of the second level nodes that are connected to the top level central 'root' node will also have one or more other nodes that are one level lower in the hierarchy (i.e., the third level) connected to it, also with a point-to-point link, the top level central 'root' node being the only node that has no other node above it in the hierarchy (The hierarchy of the tree is symmetrical.) Each node in the network having a specific fixed number, of nodes connected to it at the next lower level in the hierarchy, the number, being referred to as the 'branching factor' of the hierarchical tree. This tree has individual peripheral nodes. 1. A network that is based upon the physical hierarchical topology must have at least three levels in the hierarchy of the tree, since a network with a central 'root' node and only one hierarchical level below it would exhibit the physical topology of a star. 2. A network that is based upon the physical hierarchical topology and with a branching factor of 1 would be classified as a physical linear topology. 3. The branching factor, f, is independent of the total number of nodes in the network and, therefore, if the nodes in the network require ports for connection to other nodes the total number of ports per node may be kept low even though the total number of nodes is large â&#x20AC;&#x201C; this makes the effect of the cost of adding ports to each node totally dependent upon the branching factor and may therefore be kept as low as required without any effect upon the total number of nodes that are possible. 4. The total number of point-to-point links in a network that is based upon the physical hierarchical topology will be one less than the total number of nodes in the network. 5. If the nodes in a network that is based upon the physical hierarchical topology are required to perform any processing upon the data that is transmitted between nodes in the network, the nodes that are at higher levels in the hierarchy will be required to perform more processing operations

on behalf of other nodes than the nodes that are lower in the hierarchy. Such a type of network topology is very useful and highly recommended. Definition: Tree topology is a combination of Bus and Star topology. Hybrid: Hybrid networks use a combination of any two or more topologies in such a way that the resulting network does not exhibit one of the standard topologies (e.g., bus, star, ring, etc.). For example, a tree network connected to a tree network is still a tree network topology. A hybrid topology is always produced when two different basic network topologies are connected. Two common examples for Hybrid network are: starring network and star bus network •

A Starring network consists of two or more star topologies connected using a multistation access unit (MAU) as a centralized hub.

A Star Bus network consists of two or more star topologies connected using a bus trunk (the bus trunk serves as the network's backbone).

While grid and torus networks have found popularity in high-performance computing applications, some systems have used genetic algorithms to design custom networks that have the fewest possible hops in between different nodes. Some of the resulting layouts are nearly incomprehensible, although they function quite well. [Citation needed]

A Snowflake topology is really a "Star of Stars" network, so it exhibits characteristics of a hybrid network topology but is not composed of two different basic network topologies being connected. Definition: Hybrid topology is a combination of Bus, Star and ring topology. Daisy chain Except for star-based networks, the easiest way to add more computers into a network is by daisy-chaining, or connecting each computer in series to the next. If a message is intended for a computer partway down the line, each system bounces it along in sequence until it reaches the destination. A daisy-chained network can take two basic forms: linear and ring. •

A linear topology puts a two-way link between one computer and the next. However, this was expensive in the early days of computing, since each computer (except for the ones at each end) required two receivers and two transmitters.

By connecting the computers at each end, a ring topology can be formed. An advantage of the ring is that the number of transmitters and receivers can be cut in half, since a message will eventually loop all of the way around. When a node sends a message, the message is processed by each computer in the ring. If a computer is not the destination node, it will pass the message to the next node, until the message arrives at its destination. If the message is not accepted by any node on the network, it will travel around the entire ring and return to the sender. This potentially results in a doubling of travel time for data.

Centralization The star topology reduces the probability of a network failure by connecting all of the peripheral nodes (computers, etc.) to a central node. When the physical star topology is applied to a logical bus network such as Ethernet, this central node (traditionally a hub) rebroadcasts all transmissions received from any peripheral node to all peripheral nodes on the network, sometimes including the originating node. All peripheral nodes may thus communicate with all others by transmitting to, and receiving from, the central node only. The failure of a transmission line linking any peripheral node to the central node will result in the isolation of that peripheral node from all others, but the remaining peripheral nodes will be unaffected. However, the disadvantage is that the failure of the central node will cause the failure of all of the peripheral nodes also,

"10/100 Ethernet ports" or

â&#x20AC;˘

"N-port Ethernet switch" (where N is a number such as "4" or "5") or

â&#x20AC;˘

"wired LAN ports"

A mention of any of the above specs (and slight variations on these) indicate hybrid network capability. The majority of hybrid network routers allow connection of up to four (4) wired devices. These can be 4 computers or any combination of computers and other Ethernet devices. Connecting an Ethernet hub to one of the router's ports allow more than 4 wired devices to be joined to the LAN through the method of daisy chaining. Finally, note that wireless routers offering only one Ethernet port are generally incapable of hybrid networking. This one port will typically be reserved for use by the broadband modem and connection to the wide area network (WAN). Wired vs Wireless Networking: Computer networks for the home and small business can be built using either wired or wireless technology. Wired Ethernet has been the traditional choice in homes, but Wi-Fi wireless technologies are gaining ground fast. Both wired and wireless can claim advantages over the other; both represent viable options for home and other local area networks (LANs). Below we compare wired and wireless networking in five key areas: •

ease of installation

total cost

reliability

performance

security

About Wired LANs Wired LANs use Ethernet cables and network adapters. Although two computers can be directly wired to each other using an Ethernet crossover cable, wired LANs generally also require central devices like hubs, switches, or routers to accommodate more computers. For dial-up connections to the Internet, the computer hosting the modem must run Internet Connection Sharing or similar software to share the connection with all other computers on the LAN. Broadband routers allow easier sharing of cable modem or DSL Internet connections, plus they often include built-in firewall support. Installation Ethernet cables must be run from each computer to another computer or to the central device. It can be timeconsuming and difficult to run cables under the floor or through walls, especially when computers sit in different rooms. Some newer homes are pre-wired with CAT5 cable, greatly simplifying the cabling process and minimizing unsightly cable runs. The correct cabling configuration for a wired LAN varies depending on the mix of devices, the type of Internet connection, and whether internal or external modems are used. However, none of these options pose any more difficulty than, for example, wiring a home theater system. After hardware installation, the remaining steps in configuring either wired or wireless LANs do not differ much. Both rely on standard Internet Protocol and network operating system configuration options. Laptops and other portable devices often enjoy greater mobility in wireless home network installations (at least for as long as their batteries allow).

Cost Ethernet cables, hubs and switches are very inexpensive. Some connection sharing software packages, like ICS, are free; some cost a nominal fee. Broadband routers cost more, but these are optional components of a wired LAN, and their higher cost is offset by the benefit of easier installation and built-in security features. Reliability Ethernet cables, hubs and switches are extremely reliable, mainly because manufacturers have been continually improving Ethernet technology over several decades. Loose cables likely remain the single most common and annoying source of failure in a wired network. When installing a wired LAN or moving any of the components later, be sure to carefully check the cable connections. Broadband routers have also suffered from some reliability problems in the past. Unlike other Ethernet gear, these products are relatively new, multi-function devices. Broadband routers have matured over the past several years and their reliability has improved greatly. Performance Wired LANs offer superior performance. Traditional Ethernet connections offer only 10 Mbps bandwidth, but 100 Mbps Fast Ethernet technology costs little more and is readily available. Although 100 Mbps represents a theoretical maximum performance never really achieved in practice, Fast Ethernet should be sufficient for home file sharing, gaming, and high-speed Internet access for many years into the future. Wired LANs utilizing hubs can suffer performance slowdown if computers heavily utilize the network simultaneously. Use Ethernet switches instead of hubs to avoid this problem; a switch costs little more than a hub. Security For any wired LAN connected to the Internet, firewalls are the primary security consideration. Wired Ethernet hubs and switches do not support firewalls. However, firewall software products like ZoneAlarm can be installed on the computers themselves. Broadband routers offer equivalent firewall capability built into the device, configurable through its own software.

How to Build a Wireless Home Network:

The building blocks of a wireless LAN are network adapters, access points, wireless routers, add-on wireless antennas and signal boosters. Of these, only network adapters are truly required to build a wireless home network. However, many wireless LANs also utilize some of the other equipment, as explained below.

Best 802.11b wireless access points for home

Wireless Routers A wireless router is a wireless access point with several other useful functions added. Like wired broadband routers, wireless routers also support Internet connection sharing and include firewall technology for improved network security. Wireless routers closely resemble access points (see Page 1 sidebar for illustration). A key benefit of both wireless routers and access points is scalability. Their strong built-in transceivers are designed to spread a wireless signal throughout the home. A home WLAN with a router or access point can better reach corner rooms and backyards, for example, than one without. Likewise, home wireless networks with a router or access point support many more computers than those without one. As we'll explain in more detail later, if your wireless LAN design includes a router or access point, you must run all network adapters in so-called infrastructure mode; otherwise they must run in ad-hoc mode. Wireless routers are a good choice for those building their first home network. See the following article for good examples of wireless router products for home networks: â&#x20AC;˘

Best 802.11g wireless routers for home

Wireless Antennas Wireless network adapters, access points, and routers all utilize an antenna to assist in receiving signals on the WLAN. Some wireless antennas, like those on adapters, are internal to the unit. Other antennas, like those on many access points, are externally visible. The normal antennas shipped with wireless products provide sufficient reception in most cases, but you can also usually install an optional, add-on antenna to improve reception. You generally won't know whether you'll need this piece of equipment until after you finish your basic network setup.

Wireless Signal Boosters Some manufacturers of wireless access points and routers also sell a small piece of equipment called a signal booster. Installed together with a wireless access point or router, a signal booster serves to increase the strength of the base station transmitter. It's possible to use signal boosters and add-on antennas together, to improve both wireless network transmission and reception simultaneously. Both antennas and signal boosters can be a useful addition to some home networks after the basics are in place. They can bring out-of-range computers back into range of the WLAN, and they can also improve network performance in some cases. Next - WLAN Configurations Now that you have a good understanding of the pieces of a wireless LAN, we're ready to set them up according to your needs. Don't worry if you haven't settled on a configuration yet; we will cover all of them.

do you want to extend your wired home network with a WLAN, or are you building a completely new network?

how many wireless computers do you plan to network, and where in the home will be they be located?

what operating systems do/will you run on your networked computers?

do you need to share your Internet connection among the wireless computers? how else will you use this WLAN? file sharing? network gaming?

Installing a Wireless Router One wireless router supports one WLAN. Use a wireless router on your network if: •

you are building your first home network, or

you want to re-build your home network to be all-wireless, or

you want to keep your WLAN installation as simple as possible

Try to install your wireless router in a central location within the home. The way Wi-Fi networking works, computers closer to the router (generally in the same room or in "line of sight") realize better network speed than computers further away. Connect the wireless router to a power outlet and optionally to a source of Internet connectivity. All wireless routers support broadband modems, and some support phone line connections to dial-up Internet service. If you need dial-up support, be sure to purchase a router having an RS-232 serial port. Finally, because wireless routers contain a built-in access point, you're also free to connect a wired router, switch, or hub. (See diagram Page 2 sidebar.) Next, choose your network name. In Wi-Fi networking, the network name is often called the SSID. Your router and all computers on the WLAN must share the same SSID. Although your router shipped with a default

name set by the manufacturer, it's best to change it for security reasons. Consult product documentation to find the network name for your particular wireless router, and follow this general advice for setting your SSID. Last, follow the router documentation to enable WEP security, turn on firewall features, and set any other recommended parameters. Installing a Wireless Access Point One wireless access point supports one WLAN. Use a wireless access point on your home network if: •

you don't need the extra features a wireless router provides AND

you are extending an existing wired Ethernet home network, or

you have (or plan to have) four or more wireless computers scattered throughout the home

common sources of wireless interference are 2.4 GHz cordless phones, baby monitors, garage door openers, and some home automation devices. If you live in a home with brick or plaster walls, or one with metal framing, you're may encounter difficulty maintaining a strong WLAN signal. Wi-Fi is designed to support signal range up to 300 feet (about 100 m), but barriers reduce this range substantially. All 802.11 communications (802.11a most of all) are affected by obstructions; keep this in mind when installing your access point. •

Range of Wi-Fi LANs

Wireless Routers / Access Point Interference from Outside In densely populated areas, it's not uncommon for wireless signals from one person's home network to penetrate a neighboring home and interfere with their WLAN. This happens when both households set conflicting communication channels. Fortunately, when configuring an 802.11b or 802.11g access point or router, you can (except in a few locales) change the channel number employed. In the United States, for example, you may choose any WLAN channel number between 1 and 11. If you encounter interference from neighbors, you should coordinate channel settings with them. Simply using different channel numbers won't always solve the problem. However, if both parties use a different one of the channel numbers 1, 6 or 11, that will guarantee elimination of cross-WLAN interference. •

Change the Wi-Fi Channel Number to Avoid Interference

MAC Address Filtering Newer wireless routers and access points support a handy security feature called MAC address filtering. I wholeheartedly recommend it. This feature allows you to register wireless adapters with your access point (or router), and force the unit to reject communications from any wireless device that isn't on your list. MAC address filtering combined with WEP encryption affords very good security protection. •

Tip - Enable MAC Address Filtering

Can't reach the Internet? Temporarily turn off your firewall to determine whether you have a firewall configuration problem, or some other issue.

Likewise, turn on and test your wireless adapters one by one, to determine if problems are isolated to a single computer or common to all.

Try ad hoc networking if infrastructure networking isn't functional, and perhaps you'll identify a problem with your access point or router.

To help you work methodically, as you build your network, write down on paper the key settings like network name, WEP passkey, MAC addresses, and channel numbers (then eat the evidence afterward!).

Don't worry about making mistakes; you can go back and alter any of your WLAN settings any time.

Finally, don't be surprised if your wireless LAN performance doesn't match the numbers quoted by the manufacturer. For example, although 802.11b equipment technically supports 11 Mbps bandwidth, that is a theoretical maximum never achieved in practice. A significant amount of Wi-Fi network bandwidth is consumed by overhead that you cannot control. Expect to see more than about one-half the maximum bandwidth (5.5 Mbps at most for 802.11b, about 20 Mbps at most for the others) on your home WLAN. Conclusion Armed with the information contained in this tutorial, you're now well on your way to building a working home WLAN. Welcome to the world of wireless networking! What Are Hybrid Networks?

A hybrid network combines the best features of two of more networks. In networking terminology, a hybrid network--also called a hybrid network topology--combines the best features of two or more different networks. According to "Information Technology Control and Audit," hybrid topologies are reliable and versatile. They provide a large number of connections and data transmission paths to users. Most real life networks are hybrid networks, according to "Selected Readings on Telecommunications and Networking." Hybrid Topology Definition By David Dunning, eHow Contributor , last updated June 16, 2011

Hybrid Topology Definition The term "topology" is used to describe the way in which computers are connected together on a computer network. Popular network topologies include bus, star and ring, but it is possible for two or more basic topologies to be combined on a single network, to form what is known as a hybrid topology. 1. Star-Bus Topology o

A star-bus topology, as the name suggests, involves several star topology networks linked by a common connection, known as a busbar or bus for short. If a single computer on the network fails, the remainder can continue running unhindered. But if the hub -- a component that allows data sharing by all devices connected to it -- at the center of any of the star networks fails, all of the computers on that star become inaccessible.

Star-Ring Topology o

In a star-ring topology, computers are wired to form a ring network and, once again, connected to a central component. A process known as "token passing" allows the network traffic between segments of a star-ring topology to be greater than that on a star-bus topology.

o

Adoption Many research and education networks around the world rely on hybrid topologies, according to the Open Grid Forum. Hybrid topologies provide computer applications with guaranteed, reliable and reproducible Benefits of Hybrid Topology:

Combining different physical topologies can result in different benefits. A computer's physical topology is the way in which the cables and actual devices are set up. For instance, you could have a central connection device into which all computers are plugged, forming a circle of computers in a star pattern. You might alternatively have a line of computers set up in a bus topology. When you create a hybrid of multiple physical topologies, however, you can reap numerous benefits. 1. Customization o

One of the major benefits of combining topologies is that it allows you to customize the way your network is set up. This is a huge advantage for lots of companies who need to have multiple networks working together to achieve a single purpose. Depending on the machinery available, the skill of the IT professionals and the needs of the company, making a custom network topology can actually make activities run more smoothly and improve efficiency in the technology department.

Multiple Benefits o

When you combine different network topologies into a hybrid topology, you end up combining the benefits of several different topologies. For instance, according to a lesson from Del Mar College's Networking Hardware course, a company could place accounting database employees on a ring type of physical topology to get faster throughput (access speed), and that network could be linked into a bus network used by secretarial staff members because a bus is much easier to wire physically. In this case, you've essentially gained two benefits by combining two different topologies.

o

Interconnectivity o

Though it should be obvious, integrating two different topologies gives you the ability to cut down on wasted network space. Rather than creating multiple, separate networks with separate topologies, you can instead create your own, hybrid topology that includes both networks. This gives you greater communication and speed, but it may require some creative customization to make the network function properly. Since creating a hybrid topology may be difficult, it's beneficial to have an IT professional on hand to troubleshoot your new topology just in case things don't work out as expected.

Wireline and Wireless Connectivity: Spacenet provides a range of wireline and wireless technologies to provide an optimal balance of price and performance for your network. We can provide one technology solution or can combine multiple options such as DSL and satellite to support all of your voice, video and data applications at all of your nationwide locations. Technology Description VSAT

Satellite networks send and receive data via high-frequency radio waves bounced off a satellite in orbit, providing a single continent-wide wireless last-mile solution. A Very Small Aperture Terminal (VSAT) is a device that is used to receive satellite transmissions and is capable of sending and receiving high-speed video, data and audio.

Pros/Cons •

Independent of terrestrial infrastructure

Up to 6 Mbps

Available virtually

anywhere – one provider for broad coverage

DSL is a family of technologies that provide digital data transmission over the wires of a local telephone network. DSL/Cable

A cable modem is a type of modem that provides access to a data signal sent over the cable television infrastructure. Cable modems are primarily used to deliver broadband Internet access in the form of cable internet, taking advantage of unused bandwidth on a cable television network.

Fixed Wireless services connect two fixed locations with a radio or other wireless link to enable data communications. Fixed The point-to-point signal transmissions occur through the air Wireless/ EV- over a terrestrial microwave platform. DO EV-DO is a 3G high-speed digital data service provided by cellular carriers worldwide that use the CDMA technology.

T-1/Leased Line

A leased line is a symmetric telecommunications line connecting two locations. It is sometimes known as a 'Private Circuit' or 'Data Line', and can be used for telephone, data or Internet services. T-1 lines are a popular type of leased line option that provides a dedicated phone connection configured to carry voice or data traffic.

Uses existing last mile infrastructures

Up to 6 Mbps (Cable) and 3 Mbps (DSL)

Increasing geographic availability – requires multiple providers for broad coverage

Common carrier technology

Up to 1.5 Mbps

Available in most metropolitan U.S. cities

Common carrier technology

Up to 1.5 Mbps

Available in most locations – requires multiple providers for broad coverage

requirements. We offer our family of pre-packaged Connexstar™ networking services in addition to an array of customized networking options, including Private Satellite Networks, Virtual Private Satellite Networks and Hybrid Satellite & Common Carrier Networks. Connexstar is Spacenet’s line of commercial grade pre-packaged VSAT services, optimized for the best performance for mission critical application environments. Connexstar services include some of the best SLAs in satellite communications, including the industry’s only “Minimum Assured Speed” guarantee, as well as 24 x 7 customer support and professional-grade installation and maintenance options. All Connexstar services are based on the industry leading Gilat SkyEdge family of satellite communication products and are available with the Cisco® VSAT Network Module. Connexstar Performance - Up to 5Mbps :

Spacenet’s highest-performance services, designed specifically for converged communication environments with voice, video and high-throughput data applications. Suitable for emergency response vehicles, oilfield exploration, mining facilities, corporate offices, or other fixed or transportable locations requiring multi-seat voice, data, or video communications capability. Connexstar Broadband & Connexstar Enhanced - Up to 2Mbps :

High-speed services optimized for commercial-grade broadband data usage with high reliability Designed for corporate offices, retail stores, restaurants, financial institutions, healthcare organizations, and other fixed or transportable locations requiring multi-seat high-quality broadband data. Similar in performance and capabilities to the CX Broadband Series, Connexstar Enhanced is designed specifically for use in ultra remote locations, including customers in Alaska, Hawaii, and parts of western Canada. Connexstar Transaction - Up to 2Mbps :

Hybrid network : A network topology is the way in which hardware devices and cables are connected. A hybrid topology (sometimes called a mesh or mixed topology) connects network components by combining the features of two or more other topologies (such as star, bus, ring and token-ring). The resulting hybrid topology exhibits features (and limitations) of its comprising network components. Examples of hybrid topologies include the star-wired ring and star-wired bus. 1. Reliable o

Hybrid topologies are reliable and have increased fault tolerance than other topologies. A hybrid topology can efficiently diagnose and isolate faults. A network fault (such as a faulty node or a break in a network cable) will not affect the performance of the rest of the network. A hybrid network quickly scans all nodes and hardware points to detect where a fault lies, isolates it, and carries out further diagnostic tests. The rest of the network remains fully functional while this fault isolation and diagnosis is carried out.

Flexible o

Hybrid topologies are flexible and are designed to suit a variety of network environments and needs. They are built after a careful assessment of the requirements of the network and available resources. Hybrid topologies combine various configurations to bring about the most optimal conditions to suit network traffic, processing loads and data latency. Hybrid networks can be expanded easily to add new systems and nodes. Each concentration point (or the point at which a network connection is made) is designed to hold extra lobes. Additional network hardware peripherals can be attached to these lobes in order to increase capacity.

o

Effective o

o

A hybrid topology is able to tap into the strengths of other topologies and ignore their weaknesses. This results in a complex network that is more efficient and effective than individual topologies. It combines the optimal features of its combined topologies. For instance, a star-wired ring topology combines the features of a star topology with those of a ring topology. This hybrid topology combines the fault tolerance capability of the star topology with the data reliability of the ring topology. A star-wired bus topology combines the features of a star topology with a linear bus topology. It combines the network extension features of the bus topology with the simplicity and fault tolerance of the star topology.

Integrated Network Appliance – Prysm Pro : Introducing Prysm Pro – a more advanced, simplified and cost-effective option for supporting business applications over secure networks Enterprises today are faced with new challenges and are trying to do more with less. They are demanding a high ROI from all of their business investments, including their network infrastructure. To help meet these needs, Spacenet’s Prysm Pro helps multi-site organizations meet custom application requirements, streamline corporate-wide network management processes, and provide centralized network security. It is designed to solve a wide range of comprehensive networking and application challenges.

A modular, scalable, off-the-shelf IP network appliance, Prysm Pro is a completely PCI Data Security Standard compliant device that provides integrated support for a wide range of corporate applications including data acceleration, retail applications/POS hardware interfaces and multimedia content delivery such as digital media. It has the flexibility to address all site-level networking and application requirements on a single device solution. In addition, Prysm Pro can support reliable and seamless network backup, minimizing the risks of network downtime and lost revenue. It supports advanced applications over wireline and wireless networks and provides a seamless solution for automatic network failover in the case of a primary network outage. The Prysm Pro is designed for deployment in Wide Area Network (WAN) and Local Area Network (LAN) environments. On the WAN side it interfaces to a VSAT, DSL, cable, or 3G wireless modem, or a combination of multiple WAN links to support high availability hybrid networks. On the LAN side it attaches via Ethernet and USB to any IP-based devices and via serial ports to legacy serial devices. Features Include: •

PCI Data Security Standard compliant network appliance

IPSEC/VPN tunnels with policy-based tunneling

Automatic hybrid switching between satellite, wireline and wireless technologies

Virtual Router Redundancy Protocol based routing between primary and secondary links

Integrated Wi-Fi hotspot services including authentication and activity logging

HTTP filtering (supporting “White List” and “Black List”)

Integrated ATA for VoIP functionality

POS serial hardware interface expansion

Network infrastructure: SURFnet’s hybrid network is one of the fastest and most innovative networks in the world. It offers both Internet via IP and fixed and dynamic lightpaths. The network is used daily by students, instructors, researchers, and network administrators at more than 160 institutions affiliated with SURFnet. Current services You can make optimum use of the SURFnet network via a number of services: •

eduroam

SURFdomeinen

SURFinternet

SURFinternetpinnen

Innovation projects The GigaPort3 innovation programme is intended to take the existing network infrastructure to a higher level, make possible the next generation of networks, and provide support for dynamic services by means of a hybrid network that is both flexible and scalable. We are therefore engaged in the following innovation projects: •

Enabling Dynamic Services (EDS)

Next Generation Ethernet (NGE)

Mobility/Fixed Wireless

Photonics

NetherLight and Global Connectivity

IP innovation

Campus Infrastructure

Cloud infrastructure

Datamanagement

Next to these GigaPort3-projects, SURFnet is doing research in order to find the best way to implement DNSSEC. Ntworking group for marketing hybrid professionals: A networking group for marketing hybrid professionals

"The marketing hybrid is an individual equally at home in the worlds of marketing and technology"

* * * Next London event: 14th June 2012 * * * * * * Next New York Event: TBC * * *

Marketing Hybrid Network was established to help marketers who work in digital, data or direct marketing, to keep in touch and meet like minded individuals. It has been established from the outset as a social network with no agenda around selling or recruiting, more a handy way to keep in touch and increase your own network of contacts. So if you spend your days trying to make sense of marketing information and would like to spend at least one night every few months or so, sharing your joys and

frustrations, then please feel free to pop along.

Next London event

Next New York event

Thursday 14th June 2012

River Terrace Cafe at Somerset House - a great location overlooking the Thames, fantastic for our summer event.

Olde Bank of England - On Fleet Street and as the name suggests an old bank. A superb building and therefore pub with a gallery area and private rooms.

Davys' wine bars - Always interesting locations and quirky in character. We've tried quite a few now and they've never let us down.

Details of the next New York networking event

The next Marketing Hybrid Network New York meet-up takes place Tuesday April 3, delivering the customary opportunity for New York based digital, data and direct marketing professionals to catch-up and make new connections in an informal environment. Weâ&#x20AC;&#x2122;re very excited and privileged to announce that our meet-up this time is

being supported by Thomson Reuters who are not only generously sponsoring the event but also hosting it too, with a complimentary bar on the 30th floor of their Times Square offices, overlooking Broadway. Please note you must pre-register for this event for security access to the buildiing.

We look forward to meeting up with you at the next Marketing Hybrid Networking evening on: April 3, '12 - A GREAT EVENING AND THANKS TO ALL WHO ATTENDED AND TO THOMSON REUTERS FOR HOSTING! Next event: TBC, 2012 from 6pm - 9pm

atTBC New York

IMPORTANT NOTICE: Please note: due to security requirements for entry to the Thomson Reuters building, registration to this event is mandatory and places are limited.

The Marketing Hybrid Network New York meet-up is made possible by our generous sponsors:

Thomson Reuters is the world's leading source of intelligent information for businesses and professionals. They combine industry expertise with innovative technology to deliver critical information to leading decision makers in the financial, legal, tax and accounting, healthcare, science and media markets, powered by the worldâ&#x20AC;&#x2122;s most trusted news organization. http://thomsonreuters.com/

See who's already said they're going to attend and indicate whether youâ&#x20AC;&#x2122;re coming along too! it's easy to do and only takes a few seconds - thank you. RSVP

IMPORTANT NOTICE: Please note: due to security requirements for entry to the Thomson Reuters building, registration to this event is mandatory and places are limited.

Media support provided by:

As always, the evening is supported by our friends at DMI Magazine and Global Marketing Alliance.

Direct Marketing International magazine is the only publication which has global reach among international direct and interactive marketing professionals.The next London event is kindly sponsored by DMi. To visit the DMi web site click here.

The Global Marketing Alliance (GMA) - is a business club, formed for international marketing associates to meet up, communicate and share news. Become a member online - click here.

Sign up to the Marketing Hybrid Network New York LinkedIn Group to connect with fellow digital, data and direct marketing professionals, participate in discussions and receive future announcements!

Thomson Reuters is the world's leading source of intelligent information for businesses and professionals. They combine industry expertise with innovative technology to deliver critical information to leading decision makers in the financial, legal, tax and accounting, healthcare, science and media markets, powered by the worldâ&#x20AC;&#x2122;s most trusted news organization. http://thomsonreuters.com/

Harte-Hanks are a global direct and interactive marketing services agency which has operations in 10 countries. We deliver effective multi-channel programs through leading edge solutions including those from Trillium Software, the Aberdeen Group, Information Arts, and Mason Zimbler. Our capabilities range from data quality and management through to Social Media. http://www.harte-hanks.com/

Metametrics is a new breed of analytics agency that blends brand marketing, planning, CRM and insight practice to help our clients simplify marketing investment decisions and improve ROI. Find out more about metametric.

more2 LLC specializes in helping mail order, catalog and multi-channel retailers profit through more intelligent targeting of their house file campaigns. Using all your data, from all your data sources, we build a single customer view database and apply complex and highly specialized modeling techniques to enable to you to select more profitable customers than before and to suppress greater numbers of unprofitable customers. Find out more at more2 LLC

PulsePoint is a digital media technology company committed to helping marketers and publishers gain greater audience transparency and deeper engagement across digital channels at an unprecedented scale. PulsePointâ&#x20AC;&#x2122;s holistic platform integrates analytic and ad-serving solutions that power predictable audience engagement across display, social, mobile, video and email.Find out more at PulsePoint.

Cyance - Clever b2b marketing: that's what you get from Cyance. As award-winning b2b experts, they offer a level of business marketing intelligence that's hard to beat. By combining know-how with the most advanced

marketing science, they provide a unique insight into the world of digital and data marketing and then show you how to exploit it to your fullest advantage. Find out more at Cyance

DQM Group - DQM Group is the most trusted independent provider of Data Governance services to the UK marketing industry. Formed in 1996, 80% of the countryâ&#x20AC;&#x2122;s leading data suppliers, and increasingly leading brands too, rely on DQM Group to minimise their data risks and maximise the value of their data assets. Find out more at DQM Group.

Adobe, featuring Omniture technology, is the leading provider of online business optimization, which it delivers through the Adobe Digital Marketing Suite. Online business optimization is a strategy used to leverage consumer insights, drive innovation, and optimize online marketing initiatives. Find out more about Adobe Omniture.

Storm Post - A new dimension in Digital Marketing. StormPost offers unparalleled audience insights so you can optimize messages across email, social and mobile inbox. Deliver, Discover, Drive revenue. Find out more about StormPost.

Lead Forensics - Lead Forensics is intelligent software which enables you to uncover new and lost sales opportunities from your website. Enabling you to view and export data on who is visiting your website, including contact details, pages viewed, as well as how many visits they made to your site and specific pages, Lead Forensics gives your sales team all the information they need to close the sale. Find out more about Lead Forensics.

Direct Marketing International magazine is the only publication which has global reach among international direct and interactive marketing professionals.The next London event is kindly sponsored by DMi. To visit the DMi web site click here.

GMA – the Global Marketing Alliance - a new business club, formed for international marketing associates to meet up, communicate and share news. Become a member online or receive your temporary membership card on the 9th!

Global-Z - With more than 20 years of experience working with global marketing data, we have the knowledge, expertise, superior technology, and industry-leading customer service to help you get there.. Find out more about Global-Z

Dun & Bradstreet - D&B (NYSE:DNB) is the world’s leading source of commercial information and insight on businesses, enabling companies to Decide with Confidence® for 167 years. D&B’s global commercial database contains more than 140 million business records.. Click here

Founded in 1967, Data Services is the industry leader in providing global data processing services for U.S., Canadian, and international direct mail & email files/databases with competitive pricing and exceptional customer service.. Click here

Centurion - CENTURION Lists & Information Services, Inc. is the industry standard for quality postal, email, telemarketing lists, and social media management for all your direct marketing needs.. Find out more about Centurion.

Virgin Insight - Virgin Insight deliver data driven marketing solutions working with the Virgin Group of companies including: Virgin Active, Virgin Holidays, Virgin Money, Virgin Trains, Virgin Atlantic, Virgin Media and Virgin Management .

Jobsworth is a boutique recruitment consultancy specialising is sourcing quality candidates in the marketing services sector, covering a range of jobs and skills including Client Services, Planning, Analytics & Insight, Database Management and Sales from Managing Director down to 2nd/3rd jobbers. More >

Mustard Digital are specialists in alert and notification solutions. Through online data driven marketing we help our clients understand their customers better, acquire more of them and improve their relationship with them. We do this by enabling them to target them with more relevant and timely messages. More >

Portrait software. Portrait Software enables organizations to engage with each of their customers as individuals, resulting in improved customer profitability, increased retention, reduced risk, and outstanding customer experiences. More >

Direct Recruitment - Marketing, Digital, Media. Like to build great relationships with candidates, listening to their needs and helping them to make the right moves for their career. We like to build great relationships with clients, taking the time to find out what they need and what kind of individuals will best suit their culture. More >

Bebo an online social experience that helps you discover what's going on with your world and helps the world discover what's going on with you. More >

DMI News The Global Gateway to Marketing News Powered by DMI Magazine. More >

Blue Sheep Blue Sheep was founded in 1983 and is now recognised as an innovative, industry-leading B2B Marketing Services provider. The business has an enviable client portfolio which lists many household names and has grown organically through the development of its trademark services and leading online and offline products and services. More >

Cyan Search is a boutique executive search company, focusing on marketing services and media sectors. More >

Kinexus are expert Internet Marketing Solution providers. We expertly harness the power of the Internet to make complete customer connections and help you forge lasting relationships. More >

Email IQ. Permission email marketing from email iQ - track open and click through activity in emails, landing pages, surveys, websites and e-commerce sites. More >

EHS 4D Discovery is the data business within the EHS 4D Group, one of the worldâ&#x20AC;&#x2122;s leading direct marketing, data and digital communications groups, part of Euro RSCG 4D Worldwide. More >

Alterian is a global provider of marketing and customer insight solutions which enable businesses to improve the effectiveness of marketing activity through sophisticated customer insight. More >

smartFOCUS through their Intelligent Marketing solutions thousands of marketers are more effectively and affordably transforming marketing performance to inspire customers. Our powerful, easy to use Multi-Channel Marketing Solutions empower marketers. More >

Celerity is a pioneer of specialist data management techniques that give you real-life customer insight. More >

Zalpha a global provider of marketing and customer insight solutions, which enable businesses to improve the effectiveness of marketing activity through sophisticated customer insight. They were part of the WWAV Rapp Collins group now known as UK RAPP. Not sure if Zalpha as a brand still exists. Do you? More >

Jobsworth is a boutique recruitment consultancy specialising is sourcing quality candidates in the marketing services sector. We have been trading for over 5 years and through a combination of hard work and great service have built up an extensive network of excellent candidates covering the full range of jobs and skills including Client Services, Planning, Analytics & Insight, Database Management and Sales from Managing Director down to 2nd/3rd jobbers.

Resources and links you may find useful: Pick the brains and interact with other likeminded individuals A number of marketing hybrids run their own blogs and web sites. Feel free to dip in to these or contribute. There are also discussion threads on the Marketing Hybrid Networking Group on Linked In.

Simon Daniels Marketing Insight Guy Simon Daniels Marketing Insight Guy is the alter ego of experienced marketing insight and operations professional Simon Daniels. In the Diary of a Marketing Insight Guy blog he shares thoughts, ideas and anecdotes on marketing

insight and operations which you will hopefully find useful or interesting, together with raising the profile of the marketing insight/operations function. Visit the Marketing Insight Guy blog Link to Simon on LinkedIn

Gary Palmer Chief Alchemist Gary Palmer A seasoned direct marketing professional with considerable management experience in both operations and strategy. Gary also runs Information Alchemy, a free website dedicated to providing practitioners with resources and advice on Database Marketing, Data Quality and Information Management. Visit the Information Alchemy website. Visit the alchemy web site Link

to

Gary

on

Inder Monga, Chin Guok, William E. Johnston, and Brian Tierney, Lawrence Berkeley National Laboratory/ESnet See “National Lab” and “User Facilities” tabs at http://www.sc.doe.gov/ INTRODUCTION Across a number of scientific disciplines, users are demanding more network capabilities, including higher network end-to-end throughput, guaranteed bandwidth, and quality of service, in order to collaborate and share large amounts of data around the globe. In many fields, scientific discovery is now directly related to the amount of data that can be shared, accessed, and processed collaboratively. Our understanding of the requirements of modern science for network services has emerged from detailed discussions with researchers. ABSTRACT ESnet, the Energy Sciences Network, has the mission of providing the network infrastructure to the U.S. Department of Energy’s Office of Science programs and facilities, which depend on large collaborations and large-scale data sharing, enabling them to accomplish their science. ESnet4 — a hybrid IP and dynamic circuit network designed in 2006 and completed in 2008 — has managed to effectively satisfy the networking needs of the science community, easily handling dramatic growth in traffic requirements: around 80 percent growth year over year and 300 percent growth with the Large Hadron Collider (LHC) coming online. In this article, we examine the benefits and limitations of the current hybrid architecture based on actual production experience; discuss open research problems; and Predict factors that will drive the evolution of Hybrid networks, including advances in network technology, new computer architectures, and the onset of large-scale distributed computing. about how their analysis and simulation systems actually work: where the data originates, how many systems are involved in the analysis, how the systems and collaborators are distributed, how much data flows among these systems, how complex the work flow is, what the time sensitivities are , and so forth. Such applications are typically dataintensive and high-performance, frequently moving terabytes a day for months at a time; high-duty cycle, operating most of the day for months at a time in order to meet requirements for data movement and analysis; and widely distributed, typically spread over continental or intercontinental distances. Considering the overall requirements, a set of generic but important goals were identified for any network and network services implementation [1]: Bandwidth: Adequate network capacity is required to ensure timely and highperformance