AN ANALYTICAL STUDY OF INTERNET AND INTRANET CONNECTIONS AND CONFIGURATIONS IN ISP Mst. Najnin Sultana, Abu Jafar Md. Masud Karim Daffodil International University, Dhaka, Bangladesh E-mail: apesnajnin@yahoo.com Abstract: An Internet service provider (ISP) is a business or organization that provides to consumers access to the Internet and related services.. In addition to serving individuals, ISPs also serve large companies, providing a direct connection from the company's networks to the Internet. In this paper an elaborate description has been given about the ISP components and different connections related with Nationwide Internet and Data connectivity such as DSL (Digital Subscriber Line), Fiber optic, devices, technologies and bandwidth and implementation techniques. Optical fiber has been used as backbone of the entire network and the connections have been made to the end user levels using UTP (Unshielded Twisted Pair), STP (Shielded Twisted Pair) cables. All the connections such as broadband (dedicated and shared line) and dial-up Internet connection, intranet have been made by hardwire (using CISCO device and technology). In this publication it has been assessed that the users have good performing and smooth Internet and/ or Intranet connections by using all these standards. And they have enjoyed high quality services from the ISP. Keywords: ISP, LAN, WAN, CISCO router. 1. Introduction In the past, most ISPs were run by the phone companies. Now, ISPs can be started by just about any individual or group with sufficient money and expertise. In addition to Internet access via various technologies such as dial-up and DSL, they may provide a combination of services including Internet transit, domain name registration and hosting, web hosting, and collocation. ISPs employ a range of technologies to enable consumers to connect to their network. For "home users", the most popular options include dial-up, DSL (typically ADSL), Broadband wireless access, Cable modem, and ISDN (typically BRI). For customers who have more demanding requirements, such as medium-to-large businesses, or other ISPs, DSL (often SHDSL or ADSL), Ethernet, Metro Ethernet, Gigabit Ethernet, Frame Relay, ISDN (BRI or PRI), ATM, satellite Internet access and SONET are more likely. With the increasing popularity of downloading music and online video and the general demand for faster page loads, higher bandwidth connections are becoming more popular [1]. In a word Internet service provider is a company that provides access to the Internet, services to individuals and companies on to the web, owns or hires a permanent TCP/IP connection and uses servers permanently, it will offer web hosting (web pages stored on its web servers), access to news group, and access to FTTP server and electronic mail [2]. 2. ISP Hardware The following equipments are used to set up an ISP: VSAT Antenna, VSAT Modem, Router, Switch, Hub, Repeater, Bridge, Total Control, Telephone lines, Patch Panel etc [3]. 3. The ISP System The ISP system consists of different servers combined together, which run twenty-four hours continuously. The system is designed with all servers, which are connected to the VSAT through Router and Switches. These different servers are using different OS. There re back up servers for DNS, Mail and Proxy to provide support in case of any failure of the according server. The lists of the servers are as follows [3]: Table 1. Servers and Their OS Server No. of OS Machines DNS 1 1 SUN DNS 2 + Proxy 1 SUN Mail+ Backup Mail 2 SUN+LINUX DSL GATEWAY 2 LINUX Proxy 1 LINUX Web 1 LINUX Billing 1 Windows 2000 HRC 1 LINUX 185
Fig. 3 Network topology 3.4 Media As a media we can use co-axial cable, STP cable, UTP cable, Optical fiber etc. Fig. 1 ISP 3.1 Proxy Server It is a server that sits between a client application, such as a Web browser, and a real server. 4. Network Connection Establishment 4.1 Cabling LAN Ethernet is the most widely used LAN technology. Ethernet was first implemented by the Digital, Intel, and Xerox group (DIX). IEEE extended 802.3 to three new committees known as 802.3u for Fast Ethernet, 802.3z for Gigabit Ethernet over fiber, and 802.3ab for Gigabit Ethernet over UTP [6]. The cables and connector specifications used to support Ethernet implementations are derived from the EIA/TIA standards. EIA/TIA specifies an RJ-45 connector for UTP cable. The RJ-45 connector can be connected as a straight through cable or crossover cable. The category of UTP cable required is based on the type of Ethernet that is chosen. Fig. 2 Proxy Server 3.2 Web Server It is a computer that delivers (serves up) Web pages. Every Web server has an IP address and possibly a domain name [4]. 3.3 Network Topology Network topology defines the structure of the network. The physical topology defines the actual layout of the wire or media. The logical topology defines how the hosts access the media to send data [5]. The physical topologies that are commonly used are as follows: Fig. 4 Wire connection of RJ-45 4.1.1 Cabling Repeaters It can regenerate and retime network signals at the bit level to allow them to travel a longer distance on the media. Ethernet and IEEE 802.3 implement a rule, known as the 5-4-3 rule, for the number of repeaters and segments on shared access Ethernet backbones in a tree topology. The 5-4-3 rule divides the network into two types of physical segments: populated (user) segments, and unpopulated (link) 186
segments. 4.1.2 Cabling Hubs A hub generally has from 4 to 24 ports. Hubs are most commonly used in Ethernet 10BASE-T or 100BASE-T networks. The use of a hub changes the network from a linear bus with each device plugged directly into the wire to a star topology. communication for the host on the network. NICs control host access to the medium. 4.1.3 Cabling Bridges Switches and bridges operate at the data link layer of the OSI model. The function of the bridge is to make intelligent decisions about whether or not to pass signals on to the next segment of a network. Fig. 7 Peer to Peer and Client to Server connection Fig. 5 Bridge connection When a bridge receives a frame on the network, the destination MAC address is looked up in the bridge table to determine whether to filter, flood, or copy the frame onto another segment. 4.1.4 Cabling Switches A switch has many ports with many network segments connected to them. A switch chooses the port to which the destination device or workstation is connected [6]. 4.2 Cabling WAN 4.2.1 WAN Physical Layer The physical layer implementations vary based on the distance of the equipment from each service, the speed, and the type of service. Serial connections are used to support WAN services such as dedicated leased lines that run PPP or Frame Relay. ISDN offers dial-on-demand connections or dial backup services. An ISDN Basic Rate Interface (BRI) is composed of two 64 kbps bearer channels (B channels) for data, and one delta channel (D channel) at 16 kbps used for signaling and other linkmanagement tasks. PPP is typically used to carry data over the B channels [6]. Fig. 6 Switch connection 4.1.5 Host Connectivity The function of a NIC is to connect a host device to the network medium. A NIC is a printed circuit board that fits into the expansion slot on the motherboard or peripheral device of a computer. NICs are considered Layer 2 devices because each NIC carries a unique code called a MAC address. This address is used to control data Fig. 8 Network connection at the CSU/DSU For a Cisco router, physical connectivity at the customer site is provided by one of two types of serial connections. The first type is a 60-pin connector. The second is a more compact smart serial connector. The provider connector will vary depending on 187
the type of service equipment. If the connection is made directly to a service provider, or a device that provides signal clocking such as a channel/data service unit (CSU/DSU), the router will be data terminal equipment (DTE) and use a DTE serial cable. Fig. 9 Serial connection of Router 4.2.2 Router Configurations To initially configure the Cisco device, a management connection must be directly connected to the device which is called a console port. The console port allows monitoring and configuration of a Cisco hub, switch, or router. The cable used between a terminal and a console port is a rollover cable, with RJ-45 connectors. 4.2.2.1 Initial startup of Cisco routers A router initializes by loading the bootstrap, the operating system, and a configuration file. The goal of the startup routines for Cisco IOS software is to start the router operations. To enter commands and configure a Cisco router, a user must log into the router to access the user interface. For security purposes, a Cisco router has two levels of access to commands: Fig. 10 Router EXEC mode 4.2.2.2 Configure a Router Global configuration mode commands are used in a router to apply configuration statements that affect the system as a whole. The following command moves the router into global configuration mode and allows entry of commands from the terminal: Router#configure terminal Router(config)# Configuring a router name--a router should be given a unique name as one of the first configuration tasks. This task is accomplished in global configuration mode with the following command: Router(config)#hostname daffodil Tokyo(config)# Configuring router passwords--- Passwords restrict access to routers. Passwords should always be configured for virtual terminal (vty) lines and the console line. Passwords are also used to control access to privileged EXEC mode so that only authorized users may make changes to the configuration file. The following commands are used to set an optional but recommended password on the console line: Router(config)#line console 0 Router(config-line)#login Router(config-line)#password <password > Fig. 11 Configure password 4.2.2.3 Configuring a Serial Interface Each connected serial interface must have an IP address and subnet mask to route IP packets. Configure the IP address with the following commands: Router(config)#interface serial 0/0 Router(config-if)#ip address <ip address > <netmask > The commands that are used to set a clock rate and enable a serial interface are as follows: Router(config)#interface serial 0/0 Router(config-if)#clock rate 56000 Router(config-if)#no shutdown 188
Fig. 12 Configure serial interface 4.2.2.4 Configuring An Ethernet Interface Each Ethernet interface must have an IP address and subnet mask to route IP packets. By default, interfaces are turned off, or disabled. To turn on or enable an interface, the command no shutdown is entered. If an interface needs to be disabled for maintenance or troubleshooting, use the shutdown command to turn off the interface [6]. Fig. 13 Configure Ethernet interface 5. Performance Analysis Now we summarize all the advantages and efficiency point by point. An Ethernet speed of 10 Mbps can be used at the user level to provide good performance. Clients or servers that require more bandwidth can use 100-Mbps Ethernet. Fast Ethernet is used as the link between user and network devices. It can support the combination of all traffic from each Ethernet segment. Also it can be used to connect enterprise servers. This will enhance client-server performance across the campus network and help prevent bottlenecks. The Ethernet protocol requires that a signal sent out over the LAN reach every part of the network within a specified length of time. The 5-4-3 rule ensures this. Each repeater that a signal goes through adds a small amount of time to the process, so the rule is designed to minimize transmission times of the signals. Among the three types of hubs intelligent hubs are sometimes called smart hubs. They function like active hubs with microprocessor chips and diagnostic capabilities. Intelligent hubs are more expensive than active hubs. They are also more useful in troubleshooting situations. If placed strategically, a bridge can greatly improve network performance by flooding, filtering or copying the data. Ethernet switches are popular connectivity solutions because they improve network speed, bandwidth, and performance. It allows many users to communicate at the same time through the use of virtual circuits and dedicated network segments in a virtually collisionfree environment. For long distance communication, WANs use serial transmission. This is a process by which bits of data are sent over a single channel. This process provides reliable long distance communication and the use of a specific electromagnetic or optical frequency range. Routers are responsible for routing data packets from source to destination within the LAN, and for providing connectivity to the WAN. Within a LAN environment the router contains broadcasts, provides local address resolution services, such as ARP and RARP, and may segment the network using a subnetwork structure. In order to provide these services the router must be connected to the LAN and WAN. The CISCO structure requires entry into different modes to accomplish particular tasks. For example, to configure a router interface, the user must enter interface configuration mode. All configurations that are entered in interface configuration mode apply only to that interface. Each configuration mode is indicated with a distinctive prompt and allows only commands that are appropriate for that mode. So network security is fully maintained by these configurations. As a security feature the Cisco IOS software separates the EXEC sessions into two access levels-- user EXEC mode and privileged EXEC mode. The user EXEC mode allows only a limited number of basic monitoring commands. This is often 189
referred to as a view only mode. The user EXEC level does not allow any commands that might change the configuration of the router. The privileged EXEC mode provides access to all router commands. This mode can be configured as to require a password. For added protection, it can also be configured as to require a user ID. This allows only authorized users to access the router. Configuration and management commands require that the network administrator be at the privileged EXEC level. Global configuration mode and all other more specific configuration modes can only be reached from the privileged EXEC mode. A password must be set on one or more of the vty lines for users to gain remote access to a router through Telnet. Most Cisco routers support five vty lines numbered 0 through 4. Other hardware platforms support different numbers of vty connections. The same password is generally used for all vty lines. Sometimes it is undesirable for passwords to be shown in clear text in the output from the show running-config or show startup-config commands. The service password-encryption command applies a weak encryption to all unencrypted passwords. 6. Conclusion Using CISCO equipments and technologies we can get a more secured network set up. So, the clients have a smooth and efficient Internet and Intranet access. 8. References [1] http://en.wikipedia.org/wiki/internet_service_ provider [2] http://en.wikipedia.org/wiki/history_of_the_ Internet [3] Tanenbaum S. Andrew, Computer Network, 4 th edition, Prentice Hall of India, 2003. [4] Maisha Technologies Ltd. H # 13, R # 3,Block B, Rampura, Dhaka [5] Cisco CCNA Cource Material (Student Version 3.1) [6] www.cisco.netacat.net 190