ZyXEL Communications 320W User Manual

 

All contents copyright (c) 2005 ZyXEL Communications Corporation.   

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Ethernet (10baseT) is the most popular cable modem interface standard for the PC. This automatically 

limits the speed of the connection to under 10 Mbps even if the cable modem can receive at 30 Mbps. 

Most Local Area Networks use 10baseT Ethernet, and although they are 10 Mbps networks, it takes a 

LOT longer than one second to transmit 10 megabits (or 1.25 megabytes) of data from one terminal to 

another.  

Cable modems on the same node share bandwidth, which means that congestion is created when too 

many people are on simultaneously. One user downloading large graphic or video files can use a 

significant portion of shared bandwidth, slowing down access for other users in the same neighborhood.   

Most independent Internet Service Providers today connect to the Internet using a single 1.5 Mbps "T1" 

telephone line. All of their subscribers share that 1.5 Mbps pipeline. Cable head-ends connecting to the 

Internet backbone using a T1 limit their subscribers to an absolute maximum of 1.5 Mbps.    

To create the appearance of faster network access, service companies plan to store or "cache" frequently 

requested web sites and Usenet newsgroups on a server at their head-end. Storing data locally will remove 

some of the bottleneck at the backbone connection.    

How fast can they go? In a perfect world (or lab) they can receive data at speeds up to 30 Mbps. In the 

real world, with cost conscious cable companies running the systems, the speed will probably fall to about 

1.5 Mbps.   

Currently, there are various ways that ISPs control their users. That is, the WAN IP is provided only when 

the user is checked as an authorized user. The ISPs currently use two ways: 

1.  Check if the 'MAC address' is valid 

2.  Check if the 'Host Name' is valid, e.g., @home 

If you are not able to get the Internet IP from the ISP, check which authentication method your ISP uses 

and troubleshoot the problem as described below. 

Some ISPs only provide an IP address to the user with an authorized MAC address. This authorized MAC 

can be the PC's MAC which is used by the ISP for the authentication. So, if a new network card is used or