CHAPTER 3 PLANNING INTERNET CONNECTIVITY

D ETERMINING INTERNET CONNECTIVITY REQUIREMENTS Factors to be considered in internet access strategy: Sufficient internet bandwidth to support the need Possibility of users abuses internet access Dangers of having your private network connected to internet How much bandwidth? To know how much bandwidth the users will need, we have to find out the type of WAN connection the network will need, the ISP account type required & how highly the monthly fees will be. You may need to know how many users will need access at one time, what application they will use & activities they will perform & when.

D ETERMINING INTERNET CONNECTIVITY REQUIREMENTS How many users? Need to know how many users are working at one time & how much of time they spend accessing the internet. What applications users need? Certain type of applications need certain amount of bandwidth. You must estimate the internet use patterns of network users & provide them with sufficient bandwidth. Allocate some bandwidth for the company’s server

D ETERMINING INTERNET CONNECTIVITY REQUIREMENTS When internet bandwidth is needed? Provide sufficient support during the peak time Where are the users located? Knowing the locations of computers to determine where you should place the routers & other equipments. Help in assigning IP addresses

C HOOSING AN INTERNET CONNECTION TYPE Dial up modem connections ISDN CATV & DSL Leased Lines Frame Relay Group Assignment 1 20%

C HOOSING A ROUTER TYPE Stand-alone internet routers are hardware devices that connect to your network & to the WAN providing access to the internet. All in one ( NAT, DHCP, basic routing) High-end modular routers enables you to add modules supporting many different types of WAN & LAN connections

C HOOSING AN ISP Multiple WAN support ISP’s oriented towards residential users might only support dial-up modem connections, but business oriented ISP’s can support a variety of WAN connection types such as ISDN, DSL, leased lines & provide internet access at a wide range of bandwidth levels IP Addresses Every access need at least one IP address. If you plan to use unregistered IP address, you still need one registered address to connect your NAT router or proxy server to the internet.

C HOOSING AN ISP DNS servers Internet clients need the DNS service to resolve the names of sites & users into IP addresses. services Stand-alone computer, the service an ISP provides include one account Ex: / Web Hosting Running a web server requires you to have registered IP with the ISP. If you rely on your ISP to host your web server, then you may need to pay the hosting fees but don’t have to worry about security

D ETERMINING INTERNET SECURITY REQUIREMENTS Using unregistered IP addresses is a simpler method to secure client computers rather than using firewalls. Determining the security requirements help you to identify the additional hardware & software you may need to install. Ways to secure the client on unregistered IP address; Limiting Applications Limiting users Regulating internet access (restriction on sites)

U SING NAT Is a primary method enabling computers with unregistered IP addresses to access the internet 3 basic types of NAT Static NAT – translates a number of unregistered IP addresses to an equal number of registered addresses so that each client always uses the same registered address. (NOT secure) Dynamic NAT – used in conditions where you have fewer registered IP addresses compared to unregistered computers. The IP addresses assigned changes regularly (More secure than static NAT) Masquerading – translates all the unregistered IP addresses on your network using a single registered IP address. IP address last for each single connection. (Secure)

U SING PROXY SERVER A proxy server is an intermediary between client & the internet just like a NAT router except that it function on the application layer. Unregistered clients sends their internet access request to the proxy server, which generates its own identical requests & sends them to the server on the internet. When a proxy server receives a response, it relays the information back to the client on unregistered network. Also capable of caching information downloaded from internet so accessing frequently visited site is fast.

S ELECTING AN INTERNET ACCESS METHOD When using unregistered IP addresses, deciding whether to use NAT router or proxy server to provide internet access, should be based on the amount of security needed!

T ROUBLESHOOTING INTERNET CONNECTIVITY Determining the scope of the problem Diagnosing client configuration problem Diagnosing NAT & proxy server problem Diagnosing internet connection problem

D ETERMINING THE SCOPE OF THE PROBLEM First, determine how wide spread the problem is. Begin with help desk technician to try to reproduce the fault on other computer using the same steps user took before experiencing the problem. If the problem cant be reproduced, then the problem is in the computer itself. If the problem can be reproduced then the problem is the computer’s connection to the network. Next, determine whether the problem is limited to internet connectivity. Try to access resource from the local network from the computer with the problem, & repeat with other LANs. If user’s computer cant contact the local network / Internet, then problem is related to internal network infrastructure.

D IAGNOSING CLIENT CONFIGURATION PROBLEM If computer cant connect to local network / Internet, then you should check the basic TCP/IP configuration parameters such as IP address & subnet mask. Default Gateway Problems Every computer must have access to a default gateway on the local network. If problematic computer can access local network but cant access Internet, the default gateway address in the TCP/IP configuration is pointing to a functional router but the router might not be configured to forward the internet traffic properly ! Check the routing table on the default gateway router.

D IAGNOSING CLIENT CONFIGURATION PROBLEM Name resolution problem Common cause of connectivity problem is the client computer’s failure to resolve DNS names into IP addresses. When a name resolution fails, client computer cant access the internet resources using names. Try by using IP address to see whether this is the cause & if you can access then ; The client computer is configured with incorrect DNS server address / the DNA server specified in the computer’s TCP/IP configuration is not functioning properly.

D IAGNOSING NAT & PROXY SERVER PROBLEMS If the connection problem is reproducible on other computers, then it can be due to NAT / proxy server. Both NAT router & proxy server must have an interface the connects to the internet using a registered IP address. Therefore, these devices can suffer from any of the same TCP/IP configuration problem as a client computer. Check the IP address, subnet mask, default gateway & DNS server addresses. Proxy servers may block access due to authentication issue, policy prohibits access.

D IAGNOSING INTERNET CONNECTION PROBLEM If individual computer is not at fault, NAT router or proxy server is functioning properly then the problem might lie with internet access router. Routing table might be having a problem. Your ISP’s also might be having problem