From: Dmitry Volkov (dmitry.volkov@rogers.com)
Date: Fri Jan 02 2004 - 23:56:01 GMT-3
Yes, sorry typo, default - to use SPT (shortest path tree) not Shared Tree,
i.e. default is "0" kbps, i.e. immediately to join SPT
and infinity - never joint SPT
Dmitry
> -----Original Message-----
> From: Scott Morris [mailto:swm@emanon.com]
> Sent: Friday, January 02, 2004 9:50 PM
> To: dmitry.volkov@rogers.com; 'Yasser Aly'
> Cc: ccielab@groupstudy.com
> Subject: RE: Role of Rendezvouz point in multicast
>
>
> The default of the command is not to always use the shared tree.. The
> default is to have no effect on operation. If you use the 'infinity'
> parameter with the command, that's how you get to always use
> the shared
> tree!
>
> Scott
>
> -----Original Message-----
> From: Dmitry Volkov [mailto:dmitry.volkov@rogers.com]
> Sent: Friday, January 02, 2004 9:28 PM
> To: 'Scott Morris'; 'Yasser Aly'
> Cc: ccielab@groupstudy.com
> Subject: RE: Role of Rendezvouz point in multicast
>
> Just to add :
> command "ip pim spt-threshold" can trigger whether to switch so SPT:
> http://www.cisco.com/en/US/products/sw/iosswrel/ps1835/product
> s_command_summ
> ary_chapter09186a008007fd31.html#xtocid62
> default: "Causes all sources for the specified group to use the shared
> tree."
>
> Dmitry
>
> > -----Original Message-----
> > From: nobody@groupstudy.com
> [mailto:nobody@groupstudy.com]On Behalf Of
> > Scott Morris
> > Sent: Friday, January 02, 2004 9:07 PM
> > To: 'Yasser Aly'; ccielab@groupstudy.com
> > Subject: RE: Role of Rendezvouz point in multicast
> >
> >
> > The RP is the "know it all" of the multicast network. It prevents
> > every router from needing to maintain state for every
> single multicast
> > group that exists. In our lab networks, we generally could
> care less
> > about this, but in real life, this could get ugly!
> >
> > Yes, an edge multicast router may decide to not go with the
> RP. But
> > only AFTER it joins the shared tree and starts to get multicast
> > traffic. Only then does it learn where the source actually is, and
> > can examine its routing table to determine whether it
> really is on the
> > shortest path tree (SPT) or not. If not, then it will
> create a source
> > distribution tree directly to the source.
> >
> > So while yes it's true, it's not always the case. Just depends on
> > where source and receivers are located compared to the RP.
> >
> > So specifically to your questions:
> >
> > 1. Only for the *,G tree and MAYBE for the S,G tree.
> > 2. Only after seeing multicast traffic and IF it
> determines that the
> > source is closer to itself than the RP is.
> >
> > HTH,
> >
> >
> > Scott Morris, CCIE4 (R&S/ISP-Dial/Security/Service Provider) #4713,
> > CISSP, JNCIS, et al.
> > IPExpert CCIE Program Manager
> > IPExpert Sr. Technical Instructor
> > swm@emanon.com/smorris@ipexpert.net
> > http://www.ipexpert.net
> >
> >
> > -----Original Message-----
> > From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]
> On Behalf
> > Of Yasser Aly
> > Sent: Monday, December 29, 2003 6:39 PM
> > To: ccielab@groupstudy.com
> > Subject: Role of Rendezvouz point in multicast
> >
> > Dear All,
> >
> > I am confused about the role of RP in multicast sparse-mode. I
> > thought that a shared distribution tree will be created
> where sources
> > register themselves with the RP and receivers send request to RP.
> >
> > However after reading the following lines from a PDF speaking about
> > configuring RP, I got confused.
> > Kindly have a look at the lines below and let me hear your feedback.
> >
> > My questions mainly are:
> > 1) Will multicast traffic pass by the PR all the time on
> its way from
> > source to receiver or not ?
> >
> > 2) Is it true that after the first hop router of the
> receiver learns
> > about the source, it will send a join message directly to
> the source,
> > creating a source-based distribution tree ??
> >
> > Your thoughts are highly appreciated
> >
> > ---------
> >
> > An RP acts as the meeting place for sources and receivers
> of multicast
> > data.
> >
> > In a PIM-SM network,
> > sources must send their traffic to the RP. This traffic is then
> > forwarded to receivers down a shared distribution tree. By default,
> > when the first hop router of the receiver learns about the
> source, it
> > will send a join message directly to the source, creating a
> > source-based distribution tree from the source to the
> receiver. This
> > source tree does not include the RP unless the RP is located within
> > the shortest path between the source and receiver.
> > In most cases, the placement of the RP in the network is
> not a complex
> > decision. By default, the RP is needed only to start new
> sessions with
> > sources and receivers. Consequently, the RP experiences little
> > overhead from traffic flow or processing. In PIM-SM version
> 2, the RP
> > requires less processing than in PIM-SM version 1 because
> sources must
> > only periodically register with the RP to create state.
> > -----------------------
> >
> > Regards,
> > Yasser
> >
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