Re: TTL modification while routing IP packets

From: Herb Martin (news_at_LearnQuick.com)
Date: 01/14/05 

Date: Thu, 13 Jan 2005 20:58:47 -0600

"Steve Riley [MSFT]" <steriley@microsoft.com> wrote in message
news:49929632412265830105790@news.microsoft.com...
> It's ok, Herb, this way we know you're human, like (most of) the rest of
> us :)
>
> Long time ago 30 was a de facto TTL used in a lot of devices. We set the
> default TTL in Windows NT 3.51 to 32. Starting with NT 4.0 we increased
the
> default TTL to 128, which is still where it is today.

That's what I remembered. It was 30, then one day I
blinked and it was 128.

> You can change the default, if you wish, with the "DefaultTTL : REG_DWORD"
> key in the "Tcpip\Parameters" branch. The range can be from 1 to 255. Of
> course, this applies only to packets that the computer generates. RRAS
follows
> its normal decrement-whatever-the-current-is-by-1 behavior when forwarding
> packets.

In order to have >128 be useful, it would imply he is trying to
reach a destination more than 128 routers away. What is that,
Alpha Centauri, or Andromeda? 

-- 
Herb Martin
"Steve Riley [MSFT]" <steriley@microsoft.com> wrote in message
news:49929632412265830105790@news.microsoft.com...
> It's ok, Herb, this way we know you're human, like (most of) the rest of
> us :)
>
> Long time ago 30 was a de facto TTL used in a lot of devices. We set the
> default TTL in Windows NT 3.51 to 32. Starting with NT 4.0 we increased
the
> default TTL to 128, which is still where it is today.
>
> You can change the default, if you wish, with the "DefaultTTL : REG_DWORD"
> key in the "Tcpip\Parameters" branch. The range can be from 1 to 255. Of
> course, this applies only to packets that the computer generates. RRAS
follows
> its normal decrement-whatever-the-current-is-by-1 behavior when forwarding
> packets.
>
> Steve Riley
> steriley@microsoft.com
>
>
>
> > "Steve Riley [MSFT]" <steriley@microsoft.com> wrote in message
> > news:49038632412067451211383@news.microsoft.com...
> >
> >> Don't confuse IP packet TTLs with DNS record TTLs, they're different.
> >> The OP is asking about Windows RRAS routing functionality for IP
> >> packet TTLs.
> >>
> > Excuse me.
> >
> > For some (strange) reason, I though the question
> > was about DNS.
> >> Jakub, there's no facility in Windows that will let you do this. RRAS
> >> does what any router should: it decremets the TTL by one when it
> >> forwards a
> >>
> > packet
> >
> >> across an interface. You can't change or alter this behavior. Why do
> >> you need this functionality?
> >>
> > Aren't the modern default VERY high anyway?
> >
> >> Steve Riley
> >> steriley@microsoft.com
> >>> "Jakub Lida" <shibbsd@o2.pl> wrote in message
> >>> news:cs638e$8tn$1@srv.cyf-kr.edu.pl...
> >>>> Hello,
> >>>>
> >>>> Is it possible to modify the TTL of packets that are being
> >>>> forwarded by a Windows 2000/2003 router? I mean re-setting TTL for
> >>>> them or ensuring that it is not lower/higher than a specified value
> >>>> (as it is possible for example in OpenBSD's pf filter with a "scrub
> >>>> all reassemble tcp min-ttl 2").
> >>>>
> >>> Anything is "possible" but the is no built in facility for that and
> >>> it seems rather silly since the OWNER (authoritative servers) for
> >>> the zone decides the correct TTL for his own records.
> >>>
> >>> Their are settings on MS DNS Server and Client DNS cache that sets a
> >>> MAXIMUM however (I believe).
> >>>
> >>> The clients default to 1 day max rather than the actual value of the
> >>> TTL (if it is greater.)
> >>>
> >>>> Thank you very much for your help!
> >>>>
> >>>> Kuba <shibbsd@o2.pl>
> >>>> Krakow, PL
>
>

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