From: Mark Lasarko (mlasarko@co.ba.md.us)
Date: Tue Apr 12 2005 - 14:02:50 GMT-3
Greetings Sean,
I share Tim's understanding.
I also "confirmed" this from our service provider.
I have to leave that in quotes as they often leave me
reason to question their advice and guidance at times.
I am under the impression that if you lose a link you
just lose that portion of your aggregate bandwidth.
(So watch your QoS configs) And the down DLCI's don't
get moved to another bundle... They're simply unavailable.
The MFR Link Integrity Protocol messages handle the part
that adds and removes links as they come and go.
Have you read the forum doc on this?
http://www.mplsforum.org/frame/frfia.shtml
I do interpret Cisco's "Service Resilience When Links Fail"
statement as being more market-esque than literal though...
That said, I still get the blank stare response when I enquire
about this more often than not. Seems a lot of well-seasoned
engineers don't know too much if anything about this
And don't bother asking sales about this unless you like responses
like
"You want to do what???"... <silence>... "What was that again??"
As for me, I guess I better lab it up :)
I would be very interested to hear more from others on this.
I have been considering bundling links from multiple providers,
granted the transit deltas are similar, of course.
Best,
~M
>>> "Sean C" <Upp_and_Upp@hotmail.com> 4/12/2005 11:36:09 AM >>>
Hi Tim,
One of the mentioned reasons for Multilink Frame is (per CCO): Greater
Service Resilience When Links Fail - Greater service resilience is
provided
when multiple physical interfaces are provisioned as a single bundle.
When a
link fails, the bundle continues to support the Frame Relay service by
transmitting across the remaining bundle links.
So, if using Multilink FR, and using the scenario I mentioned below:
unless
both T1s are advertising all DLCIs, how will the carrier let a circuit
carry
non-native DLCIs. IOW, from my example below, if the 2nd T1 fails, how
does
the carrier allow the 1st T1 to handle DLCIs 4, 5, 6. Won't DLCIs 4, 5
and
6 need to be configured on the 1st T1. I can't just hope the carrier
knows
to allow DLCIs 4, 5 and 6 on the 1st T1. What happens now if I tried
to
configure DLCIs on a circuit where they are not provisioned - nothing.
So,
how does the carrier carry all DLCIs. Do both circuits need to carry
all 6
DLCIs? Or, from what Jaffe mentioned in a different email, the carrier
is
also responsible for creating a virtual interface on their equipment
and all
DLCIs ride on the Virtual interface, not on the physical circuits.
Hope this makes sense and appreciate your comments,
Sean
----- Original Message -----
From: "ccie2be" <ccie2be@nyc.rr.com>
To: "'Sean C'" <Upp_and_Upp@hotmail.com>; "'Group Study'"
<ccielab@groupstudy.com>
Sent: Tuesday, April 12, 2005 11:13 AM
Subject: RE: Realworld use of Multilink Frame Relay
> I'm not sure I completely understand your question, but if I do, it
seems
> to
> me that multilink is independent of how the f/r switches behave.
>
> The way I think of it, multilink is to serial interfaces what
etherchannel
> is to ethernet links - it's just a way to aggregate links. I don't
think
> or
> see any reason for the behavior of the f/r switches to do anything
> differently just because you decided to aggregate multiple links
running
> f/r
> encap.
>
> Of course, the routers on each side have to know what's going on so
they
> can
> re-assemble fragmented packets if any, but you're use of multilink
should
> be
> transparent to the carrier, I think.
>
> Maybe someone knows differently.
>
> Tim
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
Of
> Sean
> C
> Sent: Tuesday, April 12, 2005 9:01 AM
> To: Group Study
> Subject: OT: Realworld use of Multilink Frame Relay
>
> Hello,
>
> When implementing Multilink Frame Relay (FRF.16) - I'm trying to
> understand
> how the carrier advertises PVCs. My question is this: does the
carrier
> advertise all PVCs on each T1?
>
> IOW - if an original implementation of FR had 2 T1s with the 1st T1
> utilizing
> PVCs # 1, 2 & 3 and the 2nd T1 utilizing PVCs # 4, 5 & 6. If wishing
to
> utilize Multilink FR, does the carrier now need to advertise all PVCs
on
> both
> T1s? IOW - will the 1st T1 now carry PVCs # 1, 2, 3, 4, 5 & 6 and
the 2nd
> T1
> will carry the same PVCs #1, 2, 3, 4, 5, & 6? It's the only way I
can see
> this happening because I can't figure out if the 2nd T1 fails, how
the 1st
> T1
> will be able to support PVCs 4, 5 & 6.
>
> I appreciate any answer supplied. I hope my question is stated
simply
> enough.
> I had searched on CCO:
>
http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122newft/122
> t
> /122t8/ft_mfr.htm
> and Googled some but have not found the appropriate answer.
>
> Thanks in advance,
> Sean
>
>
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