Mac OS X is Apple’s current operating system for Macintosh computers. It is a UNIX-like system, which in contrary to its early predecessors is able to communicate with other systems such as Netware, UNIX, Linux, and Windows servers, through TCP/IP. Macintosh computers are particularly popular in the graphical and publishing industry, but also in other industries you are more than likely to find a couple of Macs attached to the network. Read the rest of this entry »
Malware is a piece of software that can damage or alter data and programs on a system without permission and notice of the user. The goal of malware varies from gaining unauthorized access to simply disabling a system. Malware is typically delivered through email, but also IRC channels and websites are common sources of malicious code.
The most common type of malicious code is a virus. It can infect systems by attaching itself to files and programs. Just like its biological counterpart, it ne eds a host to infect and survive. A virus is usually a program that needs to be executed by a user before it can do any Read the rest of this entry »
Although wireless networking has been around a lot longer than many people assume, it is only since the past 5 years that the cost of wireless networking equipment has dropped dramatically and therefore became widely available to large enterprises, small companies and even home users. Nowadays, you can hardly walk through a populated area without absorbing someone’s wireless signal. Airports and hotels offer wireless Internet access to travelers, companies offer wireless access to mobile users within the organization, and wireless Internet access on cell phones is almost becoming a standard feature. Despite the negative reputation of wireless networking in regards to security, it is still increasing in popularity. Read the rest of this entry »
Authentication refers to verifying the identity of a user or computer. When a user logs on to the network, whether on a LAN or thru a remote access connection, she will need to provide a username and password, a smartcard, certificate, or other means of proving that she is who she claims she is. Several authentication protocols are developed to allow a secure exchange of authentication information over network connections and are described in the following paragraphs.
INTERNET CONNECTIONS
Before we discuss the services and devices that are used to connect LANs and WANs to the Internet, we will first have a look at why we need such services. As you know, corporate LANs and WANs use private address ranges, and the Internet uses public address ranges. This means that every IP address on the Internet is unique, but the addresses used in corporate networks are repeatedly used. For example, the private class A network 10.0.0.0 can be used at both company A and company B, while both their networks need to be connected to the Internet.
In this context, there are two main types of connections: routed and translated. In a routed network, every IP address must be unique. If in the above example, both company A and B would have a routed connection to the Internet, their internal addresses would be Read the rest of this entry »
Almost every company offers some type of remote access to accommodate employees working from home, business partners, or external technical support. Remote access became very popular partly due to the Remote Access Service (RAS) on Microsoft’s Windows NT. It allows remote clients to dial-in and connect and logon to network as if they were sitting in the office and locally connected. Nowadays the acronym RAS is used to define many types of remote dial-in solutions.
PPP is today’s most widely used RAS protocol and is supported by virtually every network system because it is part of the TCP/IP suite. In addition to point-to-point dial-up connections over POTS and ISDN, PPP is also used for router-to-router connections in WANs. PPP operates at the Data Link layer of the OSI model and consists of two types of control protocols: Read the rest of this entry »
Circuit switching and packet switching are both communication methods for large networks. The most common example of a circuit switching network is the telephone system: the sender and the receiver establish a dedicated physical path for the entire duration of the call. All of the transmitted information follows the same route and the circuit is available only to the nodes that established it. PSTN (Public Switched Telephone Network), covered in the Internet Connections TechNotes, and ISDN, covered below, both use the circuit switching technology. Read the rest of this entry »