This is good... Personally, I wouldn't use the word "Wrapper" to = describe NAT. Wrapping has a different means than what is used for NAT. = Technically NAT doesn't wrap or encapsulate the packet. It simply = changes/translates the Source Address and Port for packet going out, and = the Destination Address and Port for traffic coming into the Network.=20 -----Original Message----- From: Jim Betz [mailto:jimbetz@xxxxxxxxxxx] Sent: Sunday, December 15, 2002 1:35 PM To: mswindowsxp@xxxxxxxxxxxxx Subject: [mswindowsxp] Re: Routers 1) A router can't protect you from a virus in an email. Routers have no knowledge of the content of the packets they route and no capability for even looking inside the packet. They work only with the IP addresses of the packets. A router acts as an 'IP sorting machine' and as a low-level form of firewall (depending on the router you can block certain IP addresses, enable or disable certain ports, etc.). Most routers also provide DHCP and Gateway services.=20 The firewall aspects of a router are not why you use a router. You use it to provide efficient routing of your IP packets - primarily to and from the internet. Most routers now use a technology called NAT (Network Address Translation) which allows the router to 'hide' the internal LAN addresses from the WWW. In addition, most routers you buy today - and especially the ones that are targetted to the home environment and are combined routers and switches - also have the capability to do your internet logon for you (the router 'dials' the ISP and provides the userid and password to the ISP). In order for the router to function as a gateway it also has to either forward=20 DNS requests to the ISP or provide dynamic DNS addresses to the clients on the LAN side. Primarily, it is NAT that provides the firewall services. With a NAT router it is a LOT more difficult for a computer out on the WWW=20 (aka WAN-side) to find and attack any of the computers on the LAN side=20 of the router. The port enabling aspects of a router also provide a=20 small amount of firewalling - but most of the standard ports have to be=20 enabled in order for the router to be used as a gateway to the WWW so=20 those ports aren't 'protected'. NAT - what exactly is it? The way NAT works is that it puts a "wrapper" around the contents of a packet. The contents of the wrapper are only known to the router. It works like this. Your LAN side computer user clicks on a link on a page on the web (think of this is the "base" part of the request that will be sent), this causes the browser to send a "request" to the WWW to provide the pages of the web that that link points at, the local computer sends it to the gateway (ie. the router), the NAT part of the router takes the request and wraps its WAN-side address along with information on which LAN-side computer is requesting the info around the request and 'forwards' it to the ISP (ie. the WWW), it goes thru lots of forwards and eventually the page info starts coming back, included in that info that comes back is the "FROM" IP address, the NAT part of the router sees that part, strips off its 'wrapper', and sends the 'base' part of the request to the requesting computer. NAT stands for "Network Address Translation" but if you think of it as a wrapping and unwrapping service it is easier to understand how it works. The WWW actually 'runs' on Routers and NAT. The majority of the devices that are passing the packets back and forth on the WWW are=20 ROUTERS running NAT. Some of them are so complicated and powerful=20 that they are more rightly called "special purpose computers".=20 A lot of them are just more sophisticated and faster routers that=20 aren't significantly different than what you use at home! So when a packet gets passed along from router to router keeps the stuff that your NAT device/program put on it and when it gets back to the NAT device that is 'stripped off'. A lot of the routers that are in the 'middle' of the chain of devices between you and the actual website do NOT use NAT. But you can be certain that the closest 'outside' router to you (ie. the one at your ISP) is using NAT technology ... with all ports enabled and with everything=20 'inside' the packets coming and going just getting passed along. wrapped into larger and larger return addresses =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D To Unsubscribe, set digest or vacation mode or view archives use the below link. http://thethin.net/winxplist.cfm ================================== To Unsubscribe, set digest or vacation mode or view archives use the below link. http://thethin.net/winxplist.cfm