1. A network without routers is a very simple concept. When information is sent across a network line, all devices connected to that line read the data. If it is not intended on being received by a device, it is not fully read. Only the device intended on receiving the data fully reads and interprets the packet. Although simple, this is a bad technique on a large scale as large delays can occur while the line is busy transmitting to one device. Routing is achieved by analyzing the packets of data being sent across a network by a router. Instead of sending the message to all computers in the entire LAN, it is decided by this higher level device. This allows parallel communication to occur within the LAN without being effected by the higher level. To do this, the router needs to have a Dynamic Host Configuration Protocol (DHCP) ability. DHCP assigns each device in the lower level LAN a specific IP address where it can be reached. This assignment is periodically checked by sending Address Resolution Protocol (ARP) packets. These packets make sure that the device given a certain IP is still available and at the location intended. Firewalls are an added bonus that are built within many routers. These act as a barrier between the higher and lower levels of the network by blocking ports that are not often used. By closing ports and only allowing access when necessary, many attempts to access a network unauthorized results in a dead end. An example of a commonly open port is 80, where HTTP internet traffic resides. ISU Science Center : Phase 2 : May 09-07 A router is a networking device whose software and hardware are usually tailored to the tasks of routing and forwarding information. Primarily used in Ethernet applications, a router connects a Local Area Network (LAN) to a higher level of a network. This is seen in many modern homes where the local home network is connected to the internet through an Internet Service Provider (ISP). The router takes data packets from the ISP and distributes them correspondingly to the computers that are interested in receiving the packets. Recent residential routers are now packaged with firewalls designed to prevent unauthorized access to parts of a LAN. Routers In General What Does A Router Do? Project Team Dan Miller, CprE danmills@iastate.edu Russell Schmidt, CprE RFSchmid@iastate.edu Faculty Advisor Client Dr. Douglas W Jacobson dougj@iastate.edu Vicky Thorland-Oster vlthorl@iastate.edu Steven Sawyer, EE scuba4@iastate.edu Kiran Eshcol, EE eshcol@iastate.edu Tim Hubert, EE thubert@iastate.edu Website http://seniord.ece.iastate.edu/may0907 Router In This Project In the ISU Science Center, the router is performing a typical role. The router uses DHCP to assign IP Addresses to each of the computers. As data is sent from each of the three interactive stations, the router forwards the information to the display computer. The higher level WAN or Uplink port of the router is connected to the Iowa State network for updates and maintenance. Devices: Address Assigned By DHCP w/ Static Routes Display Computer Station 192.168.254.100 Alternative Energy Station 192.168.254.101 Speedometer Station 192.168.254.102 Frequency Analyzer Station 192.168.254.103 What Is The Router Doing Here? How Does It Do It? IP Packet Header This is the area where the router looks to determine an action. Although this is only part of a typical IP Packet, it contains all the data necessary to determine where the packet is to be sent. The remaining portion of a typical packet would include the data that is being sent. This shows just how much background work occurs in networking.