From: Sean C (Upp_and_Upp@hotmail.com)
Date: Wed Apr 13 2005 - 10:15:52 GMT-3
"If you pay for 2 pvc's, you get 2 pvc's."
That's all I was asking for - "do I need the same DLCIs on each circut?"
Thanks, Sean
----- Original Message -----
From: "ccie2be" <ccie2be@nyc.rr.com>
To: "'Sean C'" <Upp_and_Upp@hotmail.com>; "'Mark Lasarko'"
<mlasarko@co.ba.md.us>; <ccielab@groupstudy.com>
Sent: Tuesday, April 12, 2005 8:47 PM
Subject: RE: Realworld use of Multilink Frame Relay
> NO, Sean,
>
> The carrier doesn't know and doesn't care how you configure your routers.
>
> The carrier just gives you whatever pvc's you pay for - that's it.
>
> If you pay for 2 pvc's, you get 2 pvc's.
>
> Now, I've assumed that since you're using 2 separate physical interfaces,
> you've arranged with your carrier for each pvc to run over a separate
> physical circuit, otherwise there's no point in using multilink to
> aggregate
> the pvc into 1 logical circuit.
>
> So, what you'll have is one interface using one pvc and one dlci. And,
> then
> another interface using another pvc, and another dlci. The same will be
> true
> at the other end.
>
> Just remember multilink is just like etherchannel. If one phy link goes,
> all the traffic goes over the other link.
>
> HTH, Tim
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
> Sean
> C
> Sent: Tuesday, April 12, 2005 7:37 PM
> To: ccie2be; 'Mark Lasarko'; ccielab@groupstudy.com
> Subject: Re: Realworld use of Multilink Frame Relay
>
> Tim,
>
> You're looking at this from a different level. Sorry if anything is
> misleading. Just trying to understand how the carrier handles resiliency
> if
>
> one of the physical circuits are down - does the carrier provision all
> PVCs
> on each physical circuit (so in case circuit 1 goes down, circuit 2 can
> still transmit all PVCs) or does the carrier use a subinterface like Jaffe
> suggested.
>
> When you write: "If one of those pvc's isn't available, then the decision
> of
>
> which pvc to use is easy - it using the remaining pvc." Sure, I
> understand
> what my router will do, never questioned that. But how does the carrier
> handle the failure? The only way I see this is by the carrier
> provisioning
> the same DLCIs on each physical circuit.
>
> What would happen if I configured some subints with fake DLCIs on an
> interface where the carrier did not provision any PVCs? Answer-not much.
> The PVCs would show up as deleted on my router. I could create any number
> of fake DLCIs and apply them to my router, but if the carrier hasn't
> programmed the same DLCIs in their cloud, nothing is going to happen.
> So..., how does the carrier provision the multilink for DLCIs to utilize
> what Cisco calls "Resilience When Links Fail". The only way I can think
> of
> this is by the carrier provisioning all DLCIs on each circuit. Otherwise,
> how would the circuit 1 know to carry the DLCIs from circuit 2? Jaffe
> suggested the carrier uses a subinterface to map up - not sure how this
> would work.
>
> Nothing is configured yet - and the Frame will have static, point-to-point
> subints utilizing interface-dlci commands (haven't see too much
> implementation of inverse arp in the real world).
>
> Hope this makes sense,
> Sean
> ----- Original Message -----
> From: "ccie2be" <ccie2be@nyc.rr.com>
> To: "'Sean C'" <Upp_and_Upp@hotmail.com>; "'Mark Lasarko'"
> <mlasarko@co.ba.md.us>; <ccielab@groupstudy.com>
> Sent: Tuesday, April 12, 2005 7:10 PM
> Subject: RE: Realworld use of Multilink Frame Relay
>
>
>> Sorry, Sean,
>>
>> I have to disagree.
>>
>> How is your f/r int configured?
>>
>> Are u mapping or using inv arp?
>>
>> Either way, when rtr a has a packet to send to send to rtr b, it looks up
>> the next hop in the route table and sees it should use the multilink int
>> and
>> sends it to the multilink for forwarding.
>>
>> When the multilink interface gets the packet, it has to decide which pvc
>> to
>> use.
>>
>> If one of those pvc's isn't available, then the decision of which pvc to
>> use
>> is easy - it using the remaining pvc.
>>
>> Although very simplified, I think that's the essence of it.
>>
>> Keep in mind, from a Layer point of view, it doesn't matter which pvc is
>> used since both go to the same next hop.
>>
>> HTH, Tim
>>
>> -----Original Message-----
>> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
>> Sean
>> C
>> Sent: Tuesday, April 12, 2005 6:19 PM
>> To: ccie2be; 'Mark Lasarko'; ccielab@groupstudy.com
>> Subject: Re: Realworld use of Multilink Frame Relay
>>
>> Hi Tim,
>>
>> I think you're answering my question just by the explaining your example.
>> When you write that "both PVCs are up", then it's answering my question
>> that
>>
>> each physical circuit has to carry all PVCs. IOW - the carrier has to
>> provision all DLCIs on each circuit. 1 circuit couldn't carry just some
>> of
>> the DLCIs and the other circuit carry the rest of the DLCIs. This would
>> go
>> against what Jalle suggested earlier, the carrier utilizes a layer 3
>> interface that carries the DLCIs, not any circuit.
>>
>> I think we're on the same page, thanks,
>> Sean
>> ----- Original Message -----
>> From: "ccie2be" <ccie2be@nyc.rr.com>
>> To: "'Sean C'" <Upp_and_Upp@hotmail.com>; "'Mark Lasarko'"
>> <mlasarko@co.ba.md.us>; <ccielab@groupstudy.com>
>> Sent: Tuesday, April 12, 2005 5:27 PM
>> Subject: RE: Realworld use of Multilink Frame Relay
>>
>>
>>> Sean,
>>>
>>> As I said, I don't think there's a dlci issue if one of the pvc's fails.
>>>
>>> This is because with multilink the Layer 3 interface is virtual - the ip
>>> address is on the multilink interface, not the f/r interface.
>>>
>>> Therefore, when the router has packets to send to the other side of the
>>> multilink, it does the layer 3 to layer 2 resolution and finds one of
>>> the
>>> pvc's and sends the packet. If both pvc's are up, I don't know how the
>>> router decides which pvc to use but if one of the pvc's goes down, then
>>> there's no choice and the router will use that one.
>>>
>>> Does this make sense?
>>>
>>> But, what's an interesting question and one I don't know the answer to
>>> is:
>>>
>>> When more than one link in the multilink bundle can be used, which link
>>> is
>>> used?
>>>
>>> Does the router load balance? If so, how?
>>>
>>> Food for thought.
>>>
>>> Tim
>>>
>>> -----Original Message-----
>>> From: Sean C [mailto:Upp_and_Upp@hotmail.com]
>>> Sent: Tuesday, April 12, 2005 5:10 PM
>>> To: Mark Lasarko; ccielab@groupstudy.com; ccie2be@nyc.rr.com
>>> Subject: Re: Realworld use of Multilink Frame Relay
>>>
>>> Thanks Mark. So it looks like the resiliency is really only if the
>>> DLCIs
>>> are provisioned on both T1s.
>>>
>>> I'll let you know how it looks when we install some next week.
>>> Sean
>>> ----- Original Message -----
>>> From: "Mark Lasarko" <mlasarko@co.ba.md.us>
>>> To: <ccielab@groupstudy.com>; <Upp_and_Upp@hotmail.com>;
>>> <ccie2be@nyc.rr.com>
>>> Sent: Tuesday, April 12, 2005 1:02 PM
>>> Subject: Re: Realworld use of Multilink Frame Relay
>>>
>>>
>>>> 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
>>>>>
>>>>>
>>>> _______________________________________________________________________
>>>>> Subscription information may be found at:
>>>>> http://www.groupstudy.com/list/CCIELab.html
>>>>
>>>> _______________________________________________________________________
>>>> Subscription information may be found at:
>>>> http://www.groupstudy.com/list/CCIELab.html
>>>>
>>>> _______________________________________________________________________
>>>> Subscription information may be found at:
>>>> http://www.groupstudy.com/list/CCIELab.html
>>
>> _______________________________________________________________________
>> Subscription information may be found at:
>> http://www.groupstudy.com/list/CCIELab.html
>
> _______________________________________________________________________
> Subscription information may be found at:
> http://www.groupstudy.com/list/CCIELab.html
This archive was generated by hypermail 2.1.4 : Tue May 03 2005 - 07:54:57 GMT-3