Re: Old TCP connections after IP address change

From: Clifford Kite (kite_at_see.signature.id)
Date: 06/10/05 

Date: Fri, 10 Jun 2005 12:36:48 -0500

Grant Coady <grant_lkml@dodo.com.au> wrote:
> On Fri, 10 Jun 2005 08:54:15 -0500, Clifford Kite <kite@see.signature.id>
> wrote:
>>
>> > You guys still missing the point, properly configured linux running
>> > modem in _bridge_ mode (PPPoE) will see the IP change and drop all
>> > current TCP connections... If you being wimpy and plugging into
>> > ADSL modem in 'windows' mode, you deserve what you get :o)
>>
>> How about expanding this so we can understand what you really mean.
>> As the OP pointed out in his follow-up there is Bridged/DHCP and PPPoE
>> ADSL, and you seem to lumped them together. Most ISPs are now using
>> PPPoE because it's to their advantage to do so; it offers little,
>> if any, benefit to the consumer. And I have no idea what "windows
>> mode" means - but then I don't do Windows.

> Windows mode: Plug PC into adsl modem and hope for the best

That I do understand, but not when "Windows mode" is implicitly
designated as a type of ADSL.

> PPPoE: as an end-user, I have little control over ISP, they use it.

Yes, you have to use what the ISP offers. I understand that.

> Your Bridged/DHCP seems a contradiction, if you running dhcp client
> to connect to modem, you running 'windows mode', see?

No, I don't see. Bridged ADSL (no PPPoE) requires DHCP to get your
dynamic IP address. PPPoE uses PPP IPCP to get your IP address.
In fact the reason PPPoE will never get beyond an "Informational"
RFC is that DHCP already existed and PPPoE isn't necessary at all.

> If you switch the modem into bridge mode, and run PPPoE in linux
> box you in full control of connection: 'non-windows mode'.

Huh?!?

>> Maybe you could point us toward what part(s) can be configured to
>> help with this?

> iptables: NAT: MASQUERADE vs SNAT, example:

> #######################################
> # NAT table
> # ``````````
> # Perform SNAT or MASQUERADE for localnet to world connections

> # Difference between SNAT and MASQUERADE?
> # SNAT is more efficient for static public IP address and established
> # connections will survive a reconnect. MASQUERADE is for dynamic IP
> # and established connections are dropped when ADSL goes down as a new
> # and probably different IP address is expected on next connection.

Well, it does say "established connections will survive a reconnect
with SNAT" but I don't see how that is possible unless a *static*
client IP address is being used. The writer likely had a static IP
address in mind for SNAT but that's mind-set; it can also be used with
dynamic IP addresses - I'm doing it right now over a regular landline
PPP connection, i.e., SNAT using dynamic IP addresses. But have a TCP
connection automatically reestablished itself upon acquiring a different
IP address should the PPP connection go down? I don't think so.

If someone _knows_ that a TCP connection can survive when a different
dynamic IP address replaces a dynamic IP address in the middle of a TCP
connection then please speak up and explain, in detail, how. I'm always
ready to learn. 

-- 
Clifford Kite                Email: "echo xvgr_yvahk-ccc@ri1.arg|rot13"
PPP-Q&A links, downloads:                      http://ckite.no-ip.net/
/* 97.3% of all statistics are made up. */

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