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P-870HN-5xb Support Notes
How fast can the data go?
The speed of the VDSL is only one part of the equation. There are a combination of
factors starting with how fast your PC can handle IP traffic, then how fast your PC to
cable modem interface is, then how fast the cable modem system runs and how
much congestion there is on the cable network, then how big a pipe there is at the
head end to the rest of the Internet.
Different models of PCs and Macs are able to handle IP traffic at varying speeds. Very
few can handle it at 100 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 100 Mbps. In the real world, with cost conscious cable companies running the
systems, the speed will probably fall behind the speed that the ISP appointed at the
first place.
What is Multi-NAT?
NAT (Network Address Translation-NAT RFC 1631) is the translation of an Internet
Protocol address used within one network to a different IP address known within
another network. One network is designated the inside network and the other is the
outside. Typically, a company maps its local inside network addresses to one or more
global outside IP addresses and "unmaps" the global IP addresses on incoming
packets back into local IP addresses. The IP addresses for the NAT can be either fixed
or dynamically assigned by the ISP. In addition, you can designate servers, e.g., a web
server and a telnet server, on your local network and make them accessible to the
outside world. If you do not define any servers, NAT offers the additional benefit of
firewall protection. In such case, all incoming connections to your network will be
filtered out by the device, thus preventing intruders from probing your network.
The SUA feature that the device supports previously operates by mapping the
private IP addresses to a global IP address. It is only one subset of the NAT. The
device supports most of the features of the NAT based on RFC 1631, and we call this
feature as 'Multi-NAT'. For more information on IP address translation, please refer
to RFC 1631, The IP Network Address Translator (NAT).
All contents copyright (c) 2009 ZyXEL Communications Corporation.
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