They are immune to electromagnetic interference, have very low signal attenuation up to 100 kilometers, and are very hard to tap. These characteristics have made fiber optics the preferred which of the following protocols can be used to centralize remote access authentication long-haul guided transmission media, particularly for overseas links. Many of the long-distance telephone networks in the United States and elsewhere now use fiber optics exclusively.
When you’re ready to purchase the equipment you need to build your Ethernet, you will soon see an wide variety of vendors, each one offering a range of products. Each section below will take a closer look at the technology choices available, and describe how they apply to the small business network environment. Currently, Microsoft Windows NT Server and Novell NetWare dominate this area.
Firewalls can be filtering gateways, application proxies with filtering gateways, or devices running specialized “firewall” software. In addition, NAT traversal does not automatically solve the problem with unsolicited incoming calls. To allow unsolicited incoming VoIP traffic, NAT has to be SIP aware. Similar to SIP-aware firewall, SIP-aware NAT may introduce new security vulnerabilities—allowing the remote attacker to penetrate NAT and attack the devices behind NAT. Network address translation is a critical technology, as the Internet becomes ever more widely used, with more devices becoming connected, and the availability of IP addresses is becoming a serious problem.
________ is a type of network interference for cable transmission media that can be caused by nearby television or radio signals. It allows more devices to be attached to a single central hub thus it decreases the distance that is traveled by the signal to come to the devices. Mesh topologies are reliable and stable, and the complex degree of interconnectivity between nodes makes the network resistant to failure.
With a network, a server can be set up to store data in such a way that it can be shared by any person in the organization. File servers are the network computers that specialize in providing shared data storage. Through the interface built into the file server’s network operating system, a network administrator can set up a variety of shared folders, and control access to them. A file server will generally also offer a private folder for each user.
These connectors look much like those for a telephone jack, except RJ-45s have eight connectors instead of four. Most varieties of Ethernet operate at 10 Mbps, and each of the nodes on a segment share this bandwidth. The stations on a segment share the overall available bandwidth and can cause collisions with one another in the process.
The home modem converts the digital output of the PC into analog format for transmission over the analog phone line. A modem in the ISP converts the analog signal back into digital form for input to the ISP router. In this case, the “access network” is simply a point-to-point dialup link into an edge router. (We will discuss twisted pair later in this section.) Today’s modem speeds allow dialup access at rates up to 56 Kbps.
We saw that dial-up modem technology enables access at rates of up to 56 Kbps over twisted pair. We also saw thatISDNis available in many communities, providing access rates of about 128 Kbps over twisted pair. We also saw that ADSL technology has enabled residential users to access the Web at rates in excess of 6 Mbps over twisted pair. A firewall is a network device for controlling network security and access rules.
Ethernet hubs and repeaters in LANs have been mostly obsoleted by modern switches. The NIC responds to traffic addressed to a network address for either the NIC or the computer as a whole. Free-space optical communication uses visible or invisible light for communications.