tailieunhanh - Ethernet Networking- P5

Ethernet Networking- P5:One of the biggest problems when discussing networking is knowing where to start. The subject of computer networks is one of those areas for which you have to "know everything to do anything." Usually, the easiest way to ease into the topic is to begin with some basic networking terminology and then look at exactly what it means when we use the word Ethernet. | 108 Connecting to the Internet Leased Lines If you need high bandwidth that is dedicated to your use between your premises and your ISP you can consider leasing the use of a line from a telecommunications provider. A leased line is a specially conditioned digital line that can support data and voice traffic. Leased lines come in varous speeds and capacities some of which are summarized in Table 5-2. As you can see once you move beyond a fractional or full Tl you re looking at much more bandwidth than a small or home business is likely to need. The cost is also significant. Table 5-2 Leased Line Options Designation Speed Sample Cost Comments Fractional Tl 256 Kpbs to 768 Kbps Under 300 per month for example 260 per month for 512 Kbps Supports 5 to 30 users. Tl also known as DS1 Mbps 300 to 1200 per month A full Tl supports 20 to 50 data users up to 24 voice channels or a mixture of both voice and data. Fractional T3 10 Mbps to 40 Mpbs Depends on bandwidth May be cheaper than multiple Tls. T3 also called DS3 45 Mpbs - 2600 and up per month Supports more than 100 users or upt to 672 voice channels. OC3 155 Mbps - 5000 per month Used by large Internet backbone providers. OC12 620 Mpbs - 15 000 per month Used primarily for point-to-point WAN connections. OC48 Gbps 80 000a per month Used only by the largest Internet providers. OC192 Gbps Prices not publicly available Used only by the largest Internet providers. a. No this is not a typographic error Direct Connections 109 Note Specific costs for leased lines are very difficult to obtain because they depend on location line availability and the specific services ordered. The only prices you are likely to find published are T1 and fractional Tl the rest require specific quotes from service providers. Leased lines provide better privacy and security than cable access or DSL high reliability low error rates support for static IP addresses and of course high bandwidth. They are generally also available in places .