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Re: [Isis-wg] [rbridge] Why is MTU discovery important?



 Hi Don,
 
2- In both TRILL and IEEE, control packets can be lost because of additional encapsulation overhead. In TRILL, LSPs that exceed 1500 bytes will be lost with indeterministic effect on the network and in IEEE MVRP, MMRP, and other control packets that exceed 1500 bytes will be lost with undesirable effect on the network
Again worlds apart.  IEEE Provider Backbone Bridging was prototyped, deployed and standardized without any fanfare on this issue. IEEE 802.3as was a proactive increase in the IEEE minimum frames size to support a future where multiple encapsulation of the PBB variety could be envisioned and still support the 1500 limit.  There is no law that say you cannot break your network with certain configurations but if that network breaks it should do so gracefully.  
 
 You are missing the point in there - we are not talking about BEBs but BCBs. BCB bridges are supposed to be standard s-vlan aware bridges which can be limited to 1516 or 1522 bytes in frame-size handling  !! So, the problem that I describe above can easily happen.
 
Cheers,
Ali