[pim] 答复: DR priority adjustment automatically according to the status of the tracked interfaces

[Xu Xiaohu <xuxh at huawei.com>]

>   PIM is designed as a protocol independent multicast. The 
> route to source/RP PIM depend on is up to IGP, not it self. 

Yes, PIM is Protocol Independent Multicast. However, it is not a ROUTE
indepedent multicast protocol.

> Just like the topology you give, the LAN is a backup transit 
> network to DR's up link. Why IGP doesn't converge through LAN 
> to reach RP or Source, 

I gather you are not much falimiar with the real network configuration. Why
don't you ask why we need VRRP or HSRP?

Xiaohu

> -----Original Message-----
> From: Xu Xiaohu [mailto:xuxh at huawei.com]
> Sent: Wednesday, August 05, 2009 11:39 AM
> To: 'Su Haiyang'; pim at ietf.org
> Subject: 答复: [pim] DR priority adjustment automatically 
> according to the status of the tracked interfaces
> 
> 
> >   I don't think that it is necessary for a DR to track it's 
> > upstream link to a source or RP, since IGP would care it for 
> > PIM. When a router's link to a source or RP is down, IGP 
> > would converge to another link to reach the source or RP. If 
> > there is no other link to source or RP, IGP may be fail to 
> > find a new route. 
> 
> If all uplinks are down, what do you want the DR to do next?
> 
> > But isn't that be a poor topology?
> 
> Poor topology?  Two routers, each with a uplink to the 
> Internet, are used on
> a LAN for redundancy. Not enough? 
> 
> Or do you even believe the tracking mechanism used in VRRP or HSRP is
> useless?
> 
> Xiaohu
> 
> > -----Original Message-----
> > From: pim-bounces at ietf.org [mailto:pim-bounces at ietf.org] On 
> > Behalf Of Xu Xiaohu
> > Sent: Wednesday, August 05, 2009 11:00 AM
> > To: pim at ietf.org
> > Subject: [pim] DR priority adjustment automatically according 
> > to the status of the tracked interfaces
> > 
> > Hi all,
> > 
> > In the following PIM-SM (or SSM) scenario, R!, R2 and Client 
> > are located with the same LAN. R1 is elected as the DR for 
> > that LAN. Now R1's uplink to the PIM-SM Network  is down, as 
> > long as R1 still acts as the DR, the multicast stream will be 
> > broken soon or later. 
> > 
> >              |
> >              |   +-----+    +------------------+
> >              +---+ R1  +----+                  |
> >              |   +-----+    |                  |
> >  +-------+   |              |                  |  +-------+
> >  |Client +---+              | PIM-SM Network   +--+Source |
> >  +-------+   |              |                  |  +-------+
> >              |   +-----+    |                  |
> >              +---+ R2  +----+                  |
> >              |   +-----+    +------------------+
> >              |
> > 
> > I wonder whether it is suitable for the DR (e.g., R1 in the 
> > above figure) to track the upstream link, and once the 
> > tracked link is down, its DR priority is reduced 
> > automatically so as to cease the DR role. Of couse, this 
> > mechanism is also suitable for the scenario where the 
> > Multicast Souce is connected to more than one PIM routers via LAN.
> > 
> > Any comment? Or whether some vendor has already implement 
> > this feature?
> > 
> > Xiaohu
> > 
> > 
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> > 
>