The Differences Between Hubs

The Differences Between Hubs, Switches and Routers Some technicians have a tendency to use the terms routers, hubs and switches interchangeably. One minute they're talking about a switch. Two minutes later they're discussing router settings. Throughout all of this, though, they're still looking at only the one box. Ever wonder what the difference is among these boxes? The functions of the three devices are all quite different from one another, even if at times they are all integrated into a single device. Which one do you use when? Let's take a look... Hub, Switches, and Routers: Getting Started with Definitions Hub A common connection point for devices in a network. Hubs are commonly used to connect segments of a LAN. A hub contains multiple ports. When a packet arrives at one port, it is copied to the other ports so that all segments of the LAN can see all packets. Switch In networks, a device that filters and forwards packets between LAN segments. Switches operate at the data link layer (layer 2) and sometimes the network layer (layer 3) of the OSI Reference Model and therefore support any packet protocol. LANs that use switches to join segments are called switched LANs or, in the case of Ethernet networks, switched Ethernet LANs. Router A device that forwards data packets along networks. A router is connected to at least two networks, commonly two LANs or WANs or a LAN and its ISP.s network. Routers are located at gateways, the places where two or more networks connect. Routers use headers and forwarding tables to determine the best path for forwarding the packets, and they use protocols such as ICMP to communicate with each other and configure the best route between any two hosts.

Key Terms To Understanding Storage Servers: LAN A computer network that spans a relatively small area. Most LANs are confined to a single building or group of buildings. WAN A computer network that spans a relatively large geographical area. Typically, a WAN consists of two or more local-area networks (LANs). network A group of two or more computer systems linked together. MAC address Short for Media Access Control address, a hardware address that uniquely identifies each node of a network. OSI Short for Open System Interconnection, an ISO standard for worldwide communications that defines a networking framework for implementing protocols in seven layers.

The Differences Between These Devices on the Network Today most routers have become something of a Swiss Army knife, combining the features and functionality of a router and switch/hub into a single unit. So conversations regarding these devices can be a bit misleading — especially to someone new to computer networking. The functions of a router, hub and a switch are all quite different from one another, even if at times they are all integrated into a single device. Let's start with the hub and the switch since these two devices have similar roles on the network. Each serves as a central connection for all of your network equipment and handles a data type known as frames. Frames carry your data. When a frame is received, it is

amplified and then transmitted on to the port of the destination PC. The big difference between these two devices is in the method in which frames are being delivered. In a hub, a frame is passed along or "broadcast" to every one of its ports. It doesn't matter that the frame is only destined for one port. The hub has no way of distinguishing which port a frame should be sent to. Passing it along to every port ensures that it will reach its intended destination. This places a lot of traffic on the network and can lead to poor network response times. Additionally, a 10/100Mbps hub must share its bandwidth with each and every one of its ports. So when only one PC is broadcasting, it will have access to the maximum available bandwidth. If, however, multiple PCs are broadcasting, then that bandwidth will need to be divided among all of those systems, which will degrade performance. A switch, however, keeps a record of the MAC addresses of all the devices connected to it. With this information, a switch can identify which system is sitting on which port. So when a frame is received, it knows exactly which port to send it to, without significantly increasing network response times. And, unlike a hub, a 10/100Mbps switch will allocate a full 10/100Mbps to each of its ports. So regardless of the number of PCs transmitting, users will always have access to the maximum amount of bandwidth. It's for these reasons why a switch is considered to be a much better choice then a hub. Routers are completely different devices. Where a hub or switch is concerned with transmitting frames, a router's job, as its name implies, is to route packets to other networks until that packet ultimately reaches its destination. One of the key features of a packet is that it not only contains data, but the destination address of where it's going. A router is typically connected to at least two networks, commonly two Local Area Networks (LANs) or Wide Area Networks (WAN) or a LAN and its ISP's network . for example, your PC or workgroup and EarthLink. Routers are located at gateways, the places where two or more networks connect. Using headers and forwarding tables, routers determine the best path for forwarding the packets. Router use protocols such as ICMP to communicate with each other and configure the best route between any two hosts. Today, a wide variety of services are integrated into most broadband routers. A router will typically include a 4 - 8 port Ethernet switch (or hub) and a Network Address Translator (NAT). In addition, they usually include a Dynamic Host Configuration Protocol (DHCP) server, Domain Name Service (DNS) proxy server and a hardware firewall to protect the LAN from malicious intrusion from the Internet. All routers have a WAN Port that connects to a DSL or cable modem for broadband Internet service and the integrated switch allows users to easily create a LAN. This allows all the PCs on the LAN to have access to the Internet and Windows file and printer sharing services. Some routers have a single WAN port and a single LAN port and are designed to connect an existing LAN hub or switch to a WAN. Ethernet switches and hubs can be connected to a router with multiple PC ports to expand a LAN. Depending on the capabilities (kinds of available ports) of the router and the switches or hubs, the connection between the router and switches/hubs may require either straight-thru or crossover (null-modem) cables. Some routers even have USB ports, and more commonly, wireless access points built into them.

Some of the more high-end or business class routers will also incorporate a serial port that can be connected to an external dial-up modem, which is useful as a backup in the event that the primary broadband connection goes down, as well as a built in LAN printer server and printer port. Besides the inherent protection features provided by the NAT, many routers will also have a built-in, configurable, hardware-based firewall. Firewall capabilities can range from the very basic to quite sophisticated devices. Among the capabilities found on leading routers are those that permit configuring TCP/UDP ports for games, chat services, and the like, on the LAN behind the firewall. So, in short, a hub glues together an Ethernet network segment, a switch can connect multiple Ethernet segments more efficiently and a router can do those functions plus route TCP/IP packets between multiple LANs and/or WANs; and much more of course. Routers are also the only one of these devices that will allow you to share a single IP address among multiple network clients.

All About Broadband/ICS Routers Last updated August 28, 2009 A router is a device that forwards data packets Key Terms To along networks. A router is connected to at Understanding Routers least two networks, commonly two LANs or WANs or a LAN and its ISP's network. Routers • router are located at gateways, the places where two • packet or more networks connect, and are the critical • network device that keeps data flowing between • gateway networks and keeps the networks connected to the Internet. • header • protocol When data is sent between locations on one • ICMP network or from one network to a second • cable modem network the data is always seen and directed • ICS to the correct location by the router. The router accomplishes this by using headers and forwarding tables to determine the best path Related Articles on for forwarding the data packets, and they also Webopedia: use protocols such as ICMP to communicate with each other and configure the best route • Common Router between any two hosts. Settings The Internet itself is a global network connecting millions of computers and smaller networks — so you can see how crucial the role of a router is to our way of communicating and computing.

Why Would I Need a Router? For most home users, they may want to set-up a LAN (local Area Network) or WLAN (wireless LAN) and connect all computers to the Internet

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Routers, Switches and Hubs: What's the Difference?

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Windows XP Internet Connection Sharing

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

Routers for Home & Small Business Not all routers are created equal since their job will differ slightly from network to network. Additionally, you may look at a piece of hardware and not even realize it is a router. What defines a router is not its shape, color, size or manufacturer, but its job function of routing data packets between computers. A cable modem which routes data between your PC and your ISP can be considered a router. In its most basic form, a router could simply be one of two computers running the Windows 98 (or higher) operating system connected together using ICS (Internet Connection Sharing). In this scenario, the computer that is connected to the Internet is acting as the router for the second computer to obtain its Internet connection. Going a step up from ICS, we have a category of hardware routers that are used to perform the same basic task as ICS, albeit with more features and functions. Often called broadband or Internet connection sharing routers, these routers allow you to share one Internet connection between multiple computers.

This image shows the flow of data to multiple computers sharing one high speed Internet connection. [Image Source]

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

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

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 knowledgebase. 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.

Are Routers Expensive? Below is a sample price comparison of routers and expected features as well as current pricing in U.S. dollars from online vendors found through PriceWatch in August 2009.

ROUTER

NetGear WGR614 Wireless Cable/DSL Router

PORTS

4

Manufacturer Description / Features 802.11g router offers wired and wireless connections. Up to 54 Mbps of wireless throughput. Four RJ-45 Ethernet ports allow for wired connections to the network. Includes a double firewall, WPA and 128-bit WEP encryption

PRICE

$25

Linksys WRT110RM Draft-N 802.11N Wireless Broadband Router Linksys EtherFast BEFSR81 Broadband Router

D Link Systems NetDefend VPN Firewall

4

Internet-sharing Router with 4port switch and Wireless Access Point. Much faster than Wireless-G when connected to Wireless-N, but also works great with Wireless-G and -B devices

$30

8

Simply connect the Linksys BEF-SR81 Wireless Router 8 Port 10/100 Switch to your DSL or Cable Modem and all the computers in your home or office can share the Internet all at the same time.

$80

8

D-Link answers the need for a Broadband VPN Router. The DIR-130 is a simple-to-deploy routing VPN and firewall solution designed specifically for the Small Office / Home Office

$90

Today you can purchase a basic sub $90 broadband router that will enable you to share your broadband Internet connection with multiple computers in your home or small office. Before buying a router, however, you need to take into consideration the type of Internet connect you have, and how many ports you will need for individual computers, and of course, make the choice between wired or wireless. It is always a good idea to purchase a router with extra ports in case you need to connect additional computers at a later date. You can also decide if your broadband router will be providing your PC security or if you're going to purchase a separate hardware firewall for protection. If you are thinking of purchasing a firewall in addition to a broadband router, you may want to check out our recent article on software and hardware firewalls.

Mainframes (often colloquially referred to as Big Iron[1]) are computers used mainly by large organizations for critical applications, typically bulk data processing such as census, industry and consumer statistics, enterprise resource planning, and financial transaction processing. The term probably had originated from the early mainframes, as they were housed in enormous, room-sized metal boxes or frames.[2] Later the term was used to distinguish high-end commercial machines from less powerful units. Today in practice, the term usually refers to computers compatible with the IBM System/360 line, first introduced in 1965. (IBM System z10 is the latest incarnation.) Otherwise, large systems that are not based on the System/360 but are used for similar tasks are usually referred to as servers or even supercomputers. However, "server", "supercomputer" and "mainframe" are not synonymous (see client-server). Some non-System/360-compatible systems derived from or compatible with older (pre-Web) server technology may also be considered mainframes. These include the Burroughs large systems, the UNIVAC 1100/2200 series systems, and the pre-

System/360 IBM 700/7000 series. Most large-scale computer system architectures were firmly established in the 1960s and most large computers were based on architecture established during that era up until the advent of Web servers in the 1990s. (Interestingly, the first Web server running anywhere outside Switzerland ran on an IBM mainframe at Stanford University as early as 1990. See History of the World Wide Web for details.) There were several minicomputer operating systems and architectures that arose in the 1970s and 1980s, but minicomputers are generally not considered mainframes. (UNIX arose as a minicomputer operating system; Unix has scaled up over the years to acquire some mainframe characteristics.) A network switch is a computer networking device that connects network segments. The term commonly refers to a Network bridge that processes and routes data at the Data link layer (layer 2) of the OSI model. Switches that additionally process data at the Network layer (layer 3 and above) are often referred to as Layer 3 switches or Multilayer switches. The term network switch does not generally encompass unintelligent or passive network devices such as hubs and repeaters. A mainframe (also known as "big iron") is a high-performance computer used for large-scale computing purposes that require greater availability and security than a smaller-scale machine can offer. Historically, mainframes have been associated with centralized rather than distributed computing, although that distinction is blurring as smaller computers become more powerful and mainframes become more multipurpose. Today, IBM emphasizes that their mainframes can be used to serve distributed users and smaller servers in a computing network. The mainframe is sometimes referred to as a "dinosaur" not only because of its size but because of reports, going back many years, that it's becoming extinct. In 1991 Stewart Alsop, the editor of InfoWorld, predicted that the last mainframe would be retired by 1996. However, in February 2008 IBM released a new mainframe, the z10. Steve Lohr wrote about the mainframe as "the classic survivor technology" in The New York Times ("Why old technologies are still kicking"): I.B.M. overhauled the insides of the mainframe, using low-cost microprocessors as the computing engine. The company invested and updated the mainframe software, so that banks, corporations and government agencies could still rely on the mainframe as the rock-solid reliable and secure computer for vital transactions and data, while allowing it to take on new chores like running Web-based programs. The original mainframes were housed in room-sized metal frames, which is probably where the name derives from. In the past, a typical mainframe might have occupied 2,000 - 10,000 square feet. Newer mainframes are about the same size as a large refrigerator. A very large and expensive computer capable of supporting hundreds, or even thousands, of users simultaneously. In the hierarchy that starts with a simple microprocessor (in watches, for example) at the bottom and moves to supercomputers at the top, mainframes are just below supercomputers. In some ways, mainframes are more powerful than supercomputers because they support more simultaneous programs. But supercomputers can execute a single program faster than a mainframe. The distinction between small mainframes and minicomputers is vague, depending really on how the manufacturer wants to market its machines.

A mainframe (also known as "big iron") is a high-performance computer used for large-scale computing purposes that require greater availability and security than a smaller-scale machine can offer. Historically, mainframes have been associated with centralized rather than distributed computing, although that distinction is blurring as smaller computers become more powerful and mainframes …

A network bridge connects multiple network segments at the data link layer (Layer 2) of the OSI model, and the term Layer 2 switch is very often used interchangeably with bridge. Bridges are similar to repeaters or network hubs, devices that connect network segments at thephysical layer; however, with bridging, traffic from one network is managed rather than simply rebroadcast to adjacent network segments. In Ethernet networks, the term "bridge" formally means a device that behaves according to the IEEE 802.1D standard —this is most often referred to as a network switch in marketing literature.[citation needed]

Bridges tend to be more complex than hubs or repeaters. Bridges can analyze incoming data packets to determine if the bridge is able to send the given packet to another segment of the network.

Since bridging takes place at the data link layer of the OSI model, a bridge processes the information from each frame of data it receives. In anEthernet frame, this provides the MAC address of the frame's source and destination. Bridges use two methods to resolve the network segment that a MAC address belongs to.

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Transparent bridging — This method uses a forwarding database to send frames across network segments. The

forwarding database is initially empty and entries in the database are built as the bridge receives frames. If an address entry is not found in the forwarding database, the frame is rebroadcast to all ports of the bridge, forwarding the frame to all segments except the source address. By means of these broadcast frames, the destination network will respond and a route will be created. Along with recording the network segment to which a particular frame is to be sent, bridges may also record a bandwidth metric to avoid looping when multiple paths are available. Devices that have this transparent bridging functionality are also known as adaptive bridges. They are primarily found in Ethernet networks.

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Source route bridging — With source route bridging two frame types are used in order to find the route to the destination

network segment. Single-Route (SR) frames make up most of the network traffic and have set destinations, while All-Route (AR) frames are used to find routes. Bridges send AR frames by broadcasting on all network branches; each step of the followed route is registered by the bridge performing it. Each frame has a maximum hop count, which is determined to be greater than the diameter of the network graph, and is decremented by each bridge. Frames are dropped when this hop count reaches zero, to avoid indefinite looping of AR frames. The first AR frame which reaches its destination is considered to have followed the best route, and the route can be used for subsequent SR frames; the other AR frames are discarded. This method of locating a destination network can allow for indirect load balancing among multiple bridges connecting two networks. The more a bridge is loaded, the less likely it is to take part in the route finding process for a new destination as it will be slow to forward packets. A new AR packet will find a different route over a less busy path if one exists. This method is very different from transparent bridge usage, where redundant bridges will be inactivated; however, more overhead is introduced to find routes, and space is wasted to store them in frames. A switch with a faster backplane can be just as good for performance, if not for fault tolerance. They are primarily found in Token Ring networks.

Repeaters, Bridges, Routers, and Gateways Network Repeater A repeater connects two segments of your network cable. It retimes and regenerates

the signals to proper amplitudes and sends them to the other segments. When talking about, ethernet topology, you are probably talking about using a hub as a repeater. Repeaters require a small amount of time to regenerate the signal. This can cause a propagation delay which can affect network communication when there are several repeaters in a row. Many network architectures limit the number of repeaters that can be used in a row. Repeaters work only at the physical layer of the OSI network model.

Bridge A bridge reads the outermost section of data on the data packet, to tell where the message is going. It reduces the traffic on other network segments, since it does not send all packets. Bridges can be programmed to reject packets from particular networks. Bridging occurs at the data link layer of the OSI model, which means the bridge cannot read IP addresses, but only the outermost hardware address of the packet. In our case the bridge can read the ethernet data which gives the hardware address of the destination address, not the IP address. Bridges forward all broadcast messages. Only a special bridge called a translation bridge will allow two networks of different architectures to be connected. Bridges do not normally allow connection of networks with different architectures. The hardware address is also called the MAC (media access control) address. To determine the network segment a MAC address belongs to, bridges use one of: •

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Transparent Bridging - They build a table of addresses (bridging table) as they receive packets. If the address is not in the bridging table, the packet is forwarded to all segments other than the one it came from. This type of bridge is used on ethernet networks. Source route bridging - The source computer provides path information inside the packet. This is used on Token Ring networks.

Network Router A router is used to route data packets between two networks. It reads the information in each packet to tell where it is going. If it is destined for an immediate network it has access to, it will strip the outer packet, readdress the packet to the proper ethernet address, and transmit it on that network. If it is destined for another network and must be sent to another router, it will re-package the outer packet to be received by the next router and send it to the next router. The section on routing explains the theory behind this and how routing tables are used to help determine packet destinations. Routing occurs at the network layer of the OSI model. They can connect networks with different architectures such as Token Ring and Ethernet. Although they can transform information at the data link level, routers cannot transform information from one data format such as TCP/IP to another such as IPX/SPX. Routers do not send broadcast packets or corrupted packets. If the routing table does not indicate the proper address of a packet, the packet is discarded.

Brouter 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.

Gateway A gateway can translate information between different network data formats or network architectures. It can translate TCP/IP to AppleTalk so computers supporting TCP/IP can communicate with Apple brand computers. Most gateways operate at the application layer, but can operate at the network or session layer of the OSI model. Gateways will start at the lower level and strip information until it gets to the required level and repackage the information and work its way back toward the hardware layer of the OSI model. To confuse issues, when talking about a router that is used to interface to another network, the word gateway is often used. This does not mean the routing machine is a gateway as defined here, although it could be.

A network gateway is an internetworking system capable of joining together two networks that use different base protocols. A network gateway can be implemented completely in software, completely in hardware, or as a combination of both. Depending on the types of protocols they support, network gateways can operate at any level of the OSI model. Because a network gateway, by definition, appears at the edge of a network, related capabilities like firewalls tend to be integrated with it. On home networks, a broadband router typically serves as the network gateway although ordinary computers can also be configured to perform equivalent functions