Web And Email Hosting, Jsp, Tomcat, J2Ee, Hibernate Programming Blog

The questions you need to answer when choosing a hub are how many ports you need and how fast you want your network to go. If you need to expand in the future, hubs can be connected together. Choice of speeds is 10 Mbps or 100 Mbps. The higher speed means more expensive cards and a more expensive hub, but significantly better performance. Some 10 Mbps hubs offer one or more coaxial connectors. Switches A switch lets you divide subnetworks that are getting too large into segments that are more manageable. A switch can reduce network traffic by directing messages intended for a specific computer directly to that computer. This is as opposed to a hub, which broadcasts all data to all nodes. One piece of equipment that I won t go into yet is a router. A router is used to direct information from the LAN to other LANs or the Internet. Cross-Reference Machines that carry out routing functions are described in Chapter 16. Choosing peer-to-peer vs. client/server models Although the Ethernet hub sees all computers on the network as equal, the computers on that hub can actually play different roles. The models used to describe the two general types of computing environments are client/server and peer-to-peer. Red Hat Linux is usually described as a server computer. However, Red Hat Linux can also function quite happily as a client machine or in a peer-to-peer network. Client/server model In a client/server model, one or more server computers manage most network services. The server acts as a focal point for administration and security of the network. It may also control printers, databases of information, backup media, and other resources that need to be made available to client computers on the network. The client is the person (or more correctly, the software program) that requests services from the network. A server computer can act as a server for some or all of these services: Print Server This maintains and manages one or more printers. File Server A central repository for documents and databases of information. Mail Server This gathers e-mail intended for clients on the network and makes it accessible to those clients. FTP Server This is used to make files available to users who log in to the server over the network. (Anonymous FTP is a way of making files available to strangers.) Web Server This makes Web pages (HTML) and related content available to users on the network. News Server This gathers messages from Usenet newsgroups, allowing users to read and respond to topics of interest.
Note: In case you are looking for affordable and reliable webhost to host and run your j2ee application check Vision web and email hosting services

10Base-T (10 Mbps speeds) or 100Base-TX (100 Mbps speeds). These cables plug into the computer s NIC on one end and the hub on the other. For bus topologies, coaxial cables are used. These cables are also referred to as thin Ethernet cables, or thin net. (There are also thick net cables, which are more expensive and more cumbersome to deal with. These are rarely used and are primarily for network backbones.) The connector on coaxial cables is a barrel connector (BNC). A T connector attaches to the BNC port on the NIC. In the middle of the daisy chain, each computer connects to two adjacent computers using the T connector. At the two ends of the chain, the computer connects to one adjacent computer, then uses a terminator at the other end of the T to end the chain. Figure 15-3 shows an example of a twisted pair cable with an RJ-45 connector used for star topologies. Figure 15-4 shows a coaxial (thin net) cable with a BNC connector and a T connector used for bus topologies. A terminator at the end of the T connector shows that this is the end of a chain. If it were in the middle of the chain, the other side of the T would be connected to the next computer in the chain. Figure 15-3: A star topology’s twisted pair cables have RJ-45 connectors (similar to telephone cable connectors). Figure 15-4: A bus topology has coaxial cables that must be terminated (as shown) or continued from the T. Hubs With the star topology, a hub is required to connect the computers. For the bus topology a hub can be used, but is not necessary. Sometimes hubs are also referred to as repeaters or concentrators because they receive signals from the nodes connected to them and send the signals on to other nodes. Intel and 3Com make popular, inexpensive hubs for small offices.
Note: If you are looking for cheap and reliable webhost to host and run your mysql application check Vision professional web hosting services

Figure 15-2: A bus topology chains computers together without using a hub. Ring topology This is a far less popular topology than star and bus topologies. In a ring topology, computers connect to a ring of wires on which tokens are taken and passed by computers that want to send information on the network. This type of topology typically uses IBM s token ring protocols. For our purposes, we focus on star and bus topologies. Common to both topologies is the protocol used to send data over those wires the Ethernet protocol. Star topology is the more common one among small office and home networks. There are several reasons why this is so. It s easy to add and remove computers without disrupting other computers on the network. The star cabling (twisted pair) is more flexible, less expensive, and generally easier to handle than bus cabling (coaxial). Also, many inexpensive NICs do not have the BNC connectors needed for the bus topology. Tip I have used bus topology (coaxial cables and BNC connectors) when I had some old 10 Mbps NICs hanging around and only a couple of computers to connect. If you are starting a new installation, I recommend star topology. The equipment is easier to deal with and more readily available. Also, coaxial cables offer no easy way to upgrade to 100 Mbps technology. Bus topology does have some advantages over star topology, however. Although the cabling is slightly more expensive, cost savings can occur because no hub is needed. The coaxial cables are also considered extremely reliable. Both topologies have different limitations on the number of machines that can be connected and the distances between machines. Star topology s limit is 1024 nodes on the network; bus topology s limit is 30 nodes. The total length of a bus network cannot be more than 185 meters. For a star topology, each computer must be no more than 100 meters from the farthest computer on the LAN. In other words, a 50-meter cable connecting each of two computers would reach the limit. LAN equipment The equipment that you need to connect your LAN can include some or all of the following: Network Interface Card (NIC) Typically, one of these cards goes into a slot in each computer. For Ethernet networks, the cards can transmit data at 10 Mbps or 100 Mbps. Gigabit (1000 Mbps) NICs are also now available, but are quite a bit more expensive. Tip If you are looking to upgrade your network in the near future, but still have a lot of computers around that run at 10 Mbps, you may want to consider buying new NICs that run at both 10 Mbps and 100 Mbps. When you switch over to 100 Mbps, you will have fewer cards to replace. Cables For star topologies, cables are referred to as twisted pair. Connectors at each end of the cable are RJ-45 plugs, similar to those used on telephone cables. Ethernet interfaces are either
Note: If you are looking for cheap and reliable webhost to host and run your mysql application check Vision mysql hosting services

computer for which the information is intended. The collision detection part is what helps the network detect and recover from data collisions. Cross-Reference Information on how to set up routers to communicate beyond your LAN is contained in Chapter 16. In addition to Ethernet, you need to configure TCP/IP. TCP/IP is the standard that defines the protocols and addressing scheme (unique names and numbers) that allow computers to interoperate around the entire world. TCP/IP is a transport protocol. This means that it provides end-to-end connection service between host computers. The actual underlying physical network can be carried out by a variety of network service providers, which can rely on Ethernet, telephone lines, direct connections, or other media to physically carry messages. Different ways of arranging and connecting your computers in a LAN are discussed in the next section. Choosing a network topology and equipment Even with a simple LAN, you need to make some decisions about network topology (how computers are connected). You also need to make some decisions about network equipment (network interface cards, wires, hubs, and so on). LAN topologies Most small office and home LANs connect computers together in one of the following topologies: Star topology In this arrangement, each computer contains a Network Interface Card (NIC) that connects with a cable to a central hub. The cabling is referred to as twisted pair cable, resembling the wires used to plug a telephone into the wall. Other equipment, such as printers and fax machines, can also be connected to the hub in a star topology. Figure 15-1 is an example of a star topology. Figure 15-1: In a star topology, machines on the network connect to a central hub. Bus topology Instead of using hubs, the bus topology connects computers in a chain from one to the next. The cabling usually used is referred to as coaxial, or Thin Ethernet cable. A T connector attaches to each computer s NIC, then to two adjacent computers in the chain. At the two ends of the chain, the T connectors are terminated. Figure 15-2 is an example of a bus topology.
Note: If you are looking for best quality webspace to host and run your tomcat application check Vision tomcat hosting services

Chapter 15: Setting Up a Local Area Network In the home or in a small business, Red Hat Linux can help you connect to other Linux, Windows, and Macintosh computers so that you can share your computing equipment (files, printers, and devices). Add a connection to the Internet and routing among multiple LANs (described in Chapter 16), and Red Hat Linux can serve as a focal point for network computing in a larger enterprise. This chapter helps you set up your own local area network (LAN). The procedures described here provide a foundation for sharing the computing resources in your home or organization. In particular, the chapter describes how to use Ethernet cards, wiring, and protocols to connect computers. It then tells you specifically how to configure your Red Hat Linux computer so that it can communicate with other computers. Understanding Red Hat Linux and Local Area Networks Connecting the computers in your organization via a LAN can save you a lot of time and money. The amount of money you put into networking hardware, even in a small configuration (less than five or six users), can save you from buying multiple printers, backup media, and other hardware. Add a single, shared Internet connection and you no longer need multiple modems and Internet accounts. With a LAN, you don t have to run down the hall anymore with your file on a floppy disk to print it on your friend s printer. Information that had to wait for the mailroom to make the rounds can be sent in an instant to anyone (or everyone) on your LAN. With a LAN, you begin to open the greatest potential of Red Hat Linux its ability to act as a server on a network. Because Red Hat Linux is more robust and feature-rich than other computing systems (certainly for the price), adding it to your LAN can provide a focal point to workstations that could use Red Hat Linux as a file server, a mail server, a printer server, or a news server. (Those features are described later in this book.) Creating a LAN and configuring it to be useful consists of three steps: 1. Setting up the hardware This entails choosing a network topology, purchasing the equipment you need, and installing it (adding cards and connecting wires). 2. Setting up Ethernet Red Hat Linux must be able to recognize the Ethernet card in your computer, install a driver for it, and make it available for use by Linux. (For supported cards, this is done easily during Red Hat Linux installation.) Ethernet is the protocol that enables messages to get from one machine to another on your LAN. 3. Configuring TCP/IP To use most of the networking applications and tools that come with Red Hat Linux, you must have TCP/IP configured. TCP/IP lets you communicate not only with computers on your LAN, but to any computers that you can reach on your LAN, modem, or other network connection. This chapter focuses on Ethernet as the underlying network because it is by far the most popular LAN protocol. Protocols are rules for communications between computers. To expand beyond your LAN for example, to share an Internet connection from your LAN to the Internet there are several other protocols that you could use. Ethernet is a CSMA-CD type of network, which stands for Carrier Sense Multiple Access with Collision Detection. On this type of network, data is broadcast on the network for all to see, then picked up by the
Note: If you are looking for high quality webhost to host and run your jsp application check Vision florida web design services

Part IV: Red Hat Linux Network and Server Setup Chapter List Chapter 15: Setting Up a Local Area Network Chapter 16: Connecting to the Internet Chapter 17: Setting Up a Print Server Chapter 18: Setting Up a File Server Chapter 19: Setting Up a Mail Server Chapter 20: Setting Up an FTP Server Chapter 21: Setting Up a Web Server Chapter 22: Setting Up a News Server Chapter 23: Setting Up Boot Servers: DHCP and NIS Chapter 24: Setting Up a MySQL Database Server Chapter 25: Building a Wireless Linux LAN Chapter 26: Getting Red Hat Linux “up2date”
Note: In case you are looking for affordable and reliable webhost to host and run your j2ee application check Vision web design programs services

SSL: Secure Sockets Layer. A network protocol that uses public-key encryption. It is the primary protocol used for electronic commerce on the Web. Trojan horse: A malicious program that mimics the behavior of a legitimate system program, usually for the purpose of stealing passwords. virus: A self-replicating program that can spread itself from computer to computer, usually by attaching itself to other programs. worm: A program that copies itself from computer to computer over the network, consuming system resources as it goes. Summary With the rise of the Internet, security has become a critical issue for nearly all computer users. The Red Hat Linux operating system is a powerful tool that can help you get the most out of the Internet, but care must be taken to prevent break-ins by crackers. Proper use of password security in Red Hat Linux is critical, as is proper configuration of the various network services. Understanding system log files so that you can recognize a cracker attack is another important part of defending your system from crackers. In general, knowledge is your most important tool. Learn everything you can about how your Linux system works and where the vulnerabilities are. And remember, good security is not a one-time job; it is an ongoing process that requires constant vigilance. Take advantage of the many great security tools that are available on the Internet. Applications such as Crack, Tiger, and Tripwire can help you keep your system secure. Run them periodically to make sure your system stays secure. Logcheck and PortSentry are software packages produced by Psionic Software, Inc., to help protect your Red Hat Linux system from intrusions from the network. The Logcheck package scans your system logs for messages that may represent break-in attempts. PortSentry takes an active approach to protecting your system by monitoring ports and responding in a variety of ways to those who try to improperly access those ports. Subscribe to the CERT and CIAC mailing lists and install security-related patches as soon as they become available. It is better to spend a few minutes upgrading a system program than to spend many hours rebuilding an entire server.
Note: If you are looking for best quality webspace to host and run your tomcat application check Vision tomcat hosting services

Description: A program that monitors log files and reacts to unusual system activity, usually by alerting the system administrator. SecurityFocus Homepage: http://www.securityfocus.com/ Description: This Web site was set up to encourage discussion of computer security topics. It contains a database of security resources and information. SecurityFocus maintains the Bugtraq mailing list, which is a popular mailing list for discussing security topics. To subscribe to Bugtraq, send an e-mail message to LISTSERV@SECURITYFOCUS.COM, containing the message: SUBSCRIBE BUGTRAQ Lastname, Firstname. Security-related terminology Here are a few terms that are related to computer security. You may want to refer to these terms if you are posting questions to newsgroups about security. backdoor: A hole placed in your security by a cracker. It allows the cracker to bypass normal security and gain easy access to your system. buffer overflow: A security exploit that takes advantage of a specific type of software bug. A cracker sends excessive data to a faulty system program, causing the program to overwrite part of its running program code with code the cracker supplies. cracker: An individual with malicious intent who breaks into computer systems or breaks copy protection on software products. DES: Data Encryption Standard. A common form of private-key encryption. Other, stronger forms of encryption are replacing it. exploit: The method by which a cracker gains access to your system. hacker: Someone who works with or programs computers in a creative way for the pure enjoyment of it. NSA: The National Security Agency. The U.S. government agency that handles encryption and communications-related intelligence work. PAM: Pluggable Authentication Module. The software component on a Linux system that provides password authentication for user logins and other services.
Note: In case you are looking for affordable and reliable webhost to host and run your j2ee application check Vision web and email hosting services

comp.security.unix Covers UNIX security, including items that relate to Red Hat Linux system security. Other miscellaneous tools and resources The following are some useful tools that relate to computer security. Using the Web addresses provided for each, you can usually download the software. FWTK Homepage: www.fwtk.org/ Description: The FireWall Tool Kit. A useful collection of programs and libraries for building your own firewall. Kerberos Homepage: http://web.mit.edu/kerberos/www/ Description: An authentication system for network applications. It uses Private Key Cryptography. Merlin Homepage: www.ciac.org/ciac/ToolsUnixSysMon.html#Merlin Description: A single, graphical, front-end for a variety of security tools, including SPI-Net, Tiger, COPS, Crack, and Tripwire. SATAN Homepage: www.fish.com/~zen/satan Description: A security-auditing tool that tests your security by mimicking the behavior of an actual cracker. It tries a broad range of exploits to try and get into your system. Swatch Homepage: ftp://coast.cs.purdue.edu/pub/tools/unix/logutils/swatch/
Note: If you are looking for cheap and reliable webhost to host and run your mysql application check Vision professional web hosting services

Description A more in-depth discussion of the exploit and the service it attacks. Impact What sort of damage can occur. For example, By exploiting this bug, anyone with anonymous FTP access to your system can obtain root access. Solution What you can do to fix the problem, such as instructions for downloading and installing software patches, or the appropriate flags to change in configuration files. CERT also maintains an online library of security-related instructional materials and software tools. I strongly recommend that you visit CERT s Web site at http://www.cert.org/. CIAC Another good source for computer security information is the CIAC Web site at http://www.ciac.org/. CIAC stands for Computer Incident Advisory Capability and is affiliated with the Department of Energy. Like CERT, it posts advisories and other types of helpful security information. AntiOnline If you are really serious about defending your system from cracker attacks, you need to know the tools and resources that crackers have at their disposal. The AntiOnline Web site at http://www.antionline.com/ is very useful in that respect. AntiOnline has reports on actual computer break-ins and other cracker-related news. AntiOnline even keeps an archive of the actual tools that cracker use (though you will need to sign up as a registered AntiOnline member to access the archive). You may be surprised and frightened at the number of tools crackers have access to. Caution Remember, breaking into a computer you do not own is ILLEGAL! Don’t do it. The last I heard, they don’t let you take your Red Hat Linux box with you when they send you to prison. Breaking into your own computers, however, can be a great way to test your security, and that is where AntiOnline can be very useful. Make no mistake; the crackers already have these tools. By giving us a peek into the cracker’s tool bag, AntiOnline is helping to level the playing field. Newsgroups There are newsgroups that contain a wealth of knowledge about computer security. You may want to consider reading these newsgroups: comp.security.announce Contains announcements from CERT about security. This group is moderated. comp.security.misc Covers general security issues of computers and networks. comp.security.pgp.announce Covers the new PGP versions and utilities. comp.security.ssh Contains information about the SSH package, secure remote login, and tunneling tools.
Note: If you are looking for best quality webspace to host and run your tomcat application check Vision tomcat hosting services