CECS 5460 – Assignment 3 Stacey VanderHeiden Güney

 Hubs  Bridges  Switches  Router  Gateway  Firewall  Wireless AP

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A hub interconnects two or more workstations into a local area network. Hubs are used on small networks where data transmission is not very high.

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A bridge connects a local area network (LAN) to another local area network that uses the same protocol – forwards frames from one network to another. Having a single incoming and outgoing port and filters traffic on the LAN by looking at the MAC address, bridge is more complex than hub. Bridge looks at the destination of the packet before forwarding unlike a hub. It restricts transmission on other LAN segment if destination is not found.

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A switch is like a bridge, but it has multiple ports. Like a bridge, it observes traffic flow and learns. When a frame arrives at a switch, the switch examines the destination address and forwards the frame out the one necessary connection. They use this to build forwarding tables to determine the destination of data being sent by one computer to another on the network. Switches can perform error checking before forwarding data. Switches are considered layer-two devices, using MAC addresses to forward frames to their proper destination. Usually large networks use switches instead of hubs to connect computers within the same subnet.

Routers are more complex than switches. Routers are layer-three devices, using microprocessor-based circuitry to route packets between networks based on their IP address. Routers operate at the Network layer of the OSI model. They are slower than bridges and switches but make "smart" decisions on how to route packets received on one port to a network on another port. Routers are capable of segmenting the network. Routers are capable of segmenting a network into multiple collision domains as well as into multiple broadcast domains.

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Hub - A hub is the simplest of these devices. Any data packet coming from one port is sent to all other ports. It is then up to the receiving computer to decide if the packet is for it. Imagine packets going through a hub as messages going into a mailing list. The mail is sent out to everyone and it is up to the receiving party to decide if it is of interest. The biggest problem with hubs is their simplicity. Since every packet is sent out to every computer on the network, there is a lot of wasted transmission. This means that the network can easily become bogged down. Hubs are typically used on small networks where the amount of data going across the network is never very high. Bridge- A bridge goes one step up on a hub in that it looks at the destination of the packet before sending. If the destination address is not on the other side of the bridge it will not transmit the data. A bridge only has one incoming and one outgoing port. To build on the analogy above, the bridge is allowed to decide if the message should continue on. It reads the address and decides if there is a on the other side. If there isn't, the message will not be transmitted. Bridges are typically used to separate parts of a network that do not need to communicate regularly, but still need to be connected.

Switch- A switch steps up on a bridge in that it has multiple ports. When a packet comes through a switch it is read to determine which computer to send the data to. This leads to increased efficiency in that packets are not going to computers that do not require them. Now the analogy has multiple people able to send to multiple users. The switch can decide where to send the mail based on the address. Most large networks use switches rather than hubs to connect computers within the same subnet. Router - A router is similar in a switch in that it forwards packets based on address. But, instead of the MAC address that a switch uses, a router can use the IP address. This allows the network to go across different protocols. The most common home use for routers is to share a broadband internet connection. The router has a public IP address and that address is shared with the network. When data comes through the router it is forwarded to the correct computer. This comparison to gets a little off base. This would be similar to the router being able to receive a packet as and sending it to the user as a fax.

A bridge or router may be referred to as a "switch" because it uses information in the data packet to choose a path from one network segment to another. A bridge may be referred to as a "layer 2 switch" because it uses information from layer 2, the Data Link layer of the OSI model. A router may be referred to as a "layer 3 switch" because it uses information from layer 3, the Network layer of the OSI model. A network device that uses a higher layer of the OSI model may be referred to as a "layer 4 switch", and so on.

14 Network Layer Data Link Layer Physical Layer Application Layer Presentation Layer Session Layer Transport Layer Network Layer Data Link Layer Physical Layer Application Layer Presentation Layer Session Layer Transport Layer

15 Network Layer Data Link Layer Physical Layer Application Layer Presentation Layer Session Layer Transport Layer Network Layer Data Link Layer Physical Layer Application Layer Presentation Layer Session Layer Transport Layer Specifies electrical connection

16 Network Layer Data Link Layer Physical Layer Application Layer Presentation Layer Session Layer Transport Layer Network Layer Data Link Layer Physical Layer Application Layer Presentation Layer Session Layer Transport Layer Hub AmplificationRegeneration

17 Network Layer Data Link Layer Physical Layer Application Layer Presentation Layer Session Layer Transport Layer Network Layer Data Link Layer Physical Layer Application Layer Presentation Layer Session Layer Transport Layer Delineation of Data Error Detection Address Formatting

18 Network Layer Data Link Layer Physical Layer Application Layer Presentation Layer Session Layer Transport Layer Network Layer Data Link Layer Physical Layer Application Layer Presentation Layer Session Layer Transport Layer Bridge & Switch

19 Network Layer Data Link Layer Physical Layer Application Layer Presentation Layer Session Layer Transport Layer Network Layer Data Link Layer Physical Layer Application Layer Presentation Layer Session Layer Transport Layer End to end routing

20 Network Layer Data Link Layer Physical Layer Application Layer Presentation Layer Session Layer Transport Layer Network Layer Data Link Layer Physical Layer Application Layer Presentation Layer Session Layer Transport Layer Router

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The activities of a gateway are more complex than that of the router or switch as it communicates using more than one protocol. Both the computers of Internet users and the computers that serve pages to users are host nodes, while the nodes that connect the networks in between are gateways. 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.

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Protects a computer network from unauthorized access. Network firewalls may be hardware devices, software programs, or a combination of the two. Network firewalls guard an internal computer network (home, school, business intranet) against malicious access from the outside. Network firewalls may also be configured to limit access to the outside from internal users.

Network Firewalls and Broadband Routers Many home network router products include built-in firewall support. The administrative interface of these routers include configuration options for the firewall. Router firewalls can be turned off (disabled), or they can be set to filter certain types of network traffic through so- called firewall rules. Network Firewalls and Proxy Servers Another common form of network firewall is a proxy server. Proxy servers act as an intermediary between internal computers and external networks by receiving and selectively blocking data packets at the network boundary. These network firewalls also provide an extra measure of safety by hiding internal LAN addresses from the outside Internet. In a proxy server firewall environment, network requests from multiple clients appear to the outsider as all coming from the same proxy server address.

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Device that allows wireless devices to connect to a wired network using Wi- Fi, or related standards. The AP usually connects to a router (via a wired network) as a standalone device, but it can also be an integral component of the router itself. Cost $80 to $$$$ depending on range and standards Most operate with the IEEE specs –802.11a 54 Mbps –802.11b 11 Mbps –802.11g 54 Mbps –802.11n up to 600 Mbps

Network Firewalls and Broadband Routers Many home network router products include built-in firewall support. The administrative interface of these routers include configuration options for the firewall. Router firewalls can be turned off (disabled), or they can be set to filter certain types of network traffic through so- called firewall rules. Network Firewalls and Proxy Servers Another common form of network firewall is a proxy server. Proxy servers act as an intermediary between internal computers and external networks by receiving and selectively blocking data packets at the network boundary. These network firewalls also provide an extra measure of safety by hiding internal LAN addresses from the outside Internet. In a proxy server firewall environment, network requests from multiple clients appear to the outsider as all coming from the same proxy server address.