Subject: From: Date:

RE: [ECS] Web access Martin Terry Thu, 29 Jun 2000 14:29:48 -0700

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I'm not Dario, but since this is my profession I'll take a stab at a brief
explaination. :)

First off, depending on how NAT is setup, you may not be able to connect at
all. On the routers we manage, NAT can be inbound (meaning someone is asking
to connect inward, for example a web server), outbound (meaning I'm
initiating a connection outward, for example a web browser), or
bi-directional (meaning both of the above are true).

The advantages of outbound connections is that you can map multiple outbound
connections to a single address, in our company as an example all 800
employees can be surfing the web and from the Internet's perspective they
all appear to be coming from a single address. You couldn't tell them from
800 web windows on a single machine.

The disadvantage is that you can't initiate an inbound connection - for
example an employee cannot host a web site on his personal computer and
allow people on the internet to connect - the router simple rejects these
requests.

So if your ISP doesn't allow you to host a web server, and has setup
outbound NAT only, you are out of luck.

If you have a bi-directional NAT mapping, basically it is simple a 1 to 1
address translation. Anything that "appears" to come from one address is
changed to another.

How can you tell where to connect to ECS?

This is a tough question, because the event and batch files I've seen with
ECS rely on the workstation finding out it's own address and then mailing
that address to the user. For NAT (Network Address Translation) this won't
work, because the IP address of the workstation isn't the same as what it
appears to be to the end user, on the other side of the router. It's not
taking the conversion into account (it can't). Here's an example:

Workstation ( IP 192.168.1.1 ) Internal network address often used with NAT.
with web server (ECS for example)
       |
       |
       | Network 192.168.1.x
       |
       |
Router (IP 192.168.1.2) with NAT entry for workstation 192.168.1.3 <->
207.46.131.30
       |   (IP 207.46.131.1)
       |
       | Network 207.46.131.x
       |
       |
 Internet "cloud"
       |
       |
       |
End user with browser (IP 192.18.97.195)

to contact ECS the browser would have to enter http://207.46.131.30:3000 in
order to make the connection. This request eventually translates to a
request to the router, which is masquerading as 207.46.131.30, and usually a
bunch of other addresses. The router has a table that says "if you get a
request for 207.46.131.30, change it to 192.168.1.1". It then passes the
data on, and it appears to come from the address 192.168.1.3.

NAT can be a real problem (read not work) when the machines communicating
pass their IP addresses in the data stream. NAT cannot see this and modify
it appropriately, therefore several protocols will not work via NAT.




-----Original Message-----
From: Don [mailto:donstephens@101freeway.net]
Sent: Thursday, June 29, 2000 9:19 AM
To: ecs-list@netbloc.com
Subject: Re: [ECS] Web access


Hi Dario:

Since you seem to know something about how this works, I'll ask you. I have
a router on my local lan that uses NAT for addressing, and I have a dynamic
address at my ISP, although I have a DSL line and it has never changed. I'm
want to access ECS from a remote computer. How do I come up with an URL for
ECS?

Thanks:
Don
----- Original Message -----
From: "Dario" <adpm.to@inwind.it>
To: <ecs-list@netbloc.com>
Sent: Thursday, June 29, 2000 7:31 AM
Subject: Re: [ECS] Web access


> Mark Gilmore ha scritto:
> >
> > Note that if another port # would be more conventional, I
> > could easily change the default to something other than
> 3000.
>
> As there's not yet a standard for home automation access via
> WEB, I
> guess everything is OK (IMHO)
> Actually, if ECS is working wuite like a WEB-server, then you
> could use
> port 80, the standard for HTTP (so nobody would have trouble).
> Of
> course, provided you're not using other webservers on ECS
> machine.
> I've set up port 80 on my system, and I can get to it via any
> computer.
>
> Dario
>

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