From: Ronnie Angello (ronnie.angello@gmail.com)
Date: Wed Dec 20 2006 - 18:19:09 ART
RFC 1812, page 84:
A router MUST generate a Time Exceeded message Code 0 (In Transit) when it
discards a packet due to an expired TTL field. A router MAY have a
per-interface option to disable origination of these messages on that
interface, but that option MUST default to allowing the messages to be
originated.
RFC 1812, page 85:
The Time-to-Live (TTL) field of the IP header is defined to be a timer
limiting the lifetime of a datagram. When a router *forwards* a packet, it
MUST reduce the TTL by at least one. If it holds a packet for more than one
second, it MAY decrement the TTL by one for each second.
On 12/20/06, Nawaz, Ajaz <Ajaz.Nawaz@bskyb.com> wrote:
>
> Tim
>
> So what occurs when it receives an update with TTL of two or three for
> example?
>
> Are you suggesting it decrements that once for it's own use?
>
> What happens when it forwards this update to an onwards hop?
>
> Ajaz
>
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
> Tim
> Sent: 20 December 2006 16:08
> To: Nawaz, Ajaz; 'Iamgoingtobeaccie Iamgoingtobeaccie';
> ccielab@groupstudy.com
> Subject: RE: TTL
>
> Ajar,
>
> I'm pretty sure the TTL is decremented on Ingress. When a router receives
> a
> packet with a TTL of 1, the TTL is decremented making the TTL 0 and
> causing
> the router to send icmp time-exceeded message back.
>
> Please correct me if I'm mistaken.
>
> Thanks, Tim
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
> Nawaz, Ajaz
> Sent: Wednesday, December 20, 2006 5:48 AM
> To: Iamgoingtobeaccie Iamgoingtobeaccie; ccielab@groupstudy.com
> Subject: RE: TTL
>
> Egress. You can prove it easily through testing.
>
> Hth
> Ajaz Nawaz
> CCIE#15721
>
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
> sabrina pittarel
> Sent: 20 December 2006 06:52
> To: Iamgoingtobeaccie Iamgoingtobeaccie; ccielab@groupstudy.com
> Subject: Re: TTL
>
> Hi,
> let's put it in this way...a router will never forward a packet that has
> been received with TTL equal to 0 or 1
>
> Sabrina
>
> ----- Original Message ----
> From: Iamgoingtobeaccie Iamgoingtobeaccie <
> heyiamgoingtobeaccie@yahoo.co.in>
> To: ccielab@groupstudy.com
> Sent: Tuesday, December 19, 2006 5:29:43 AM
> Subject: TTL
>
> GS,
> Can someone let me know where does the TTL get
> decremented? Is it on the ingress of the receiving router or on the egress
> of
> the sending router.
>
> When I configure EBGP between two routers with
> their loopback IP addresses and enable 'debug ip packet',I am not seeing
> any
> packet coming in.So I assume that the TTL is decremented on the egress
> interface of the sending router.Can someone confirm.
>
>
>
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