Re: PQC and QOSPF

[Yao-Min Chen <[e-mail]>]

Ohta-san, 

I checked the PQC paper again and have a question 
about its use of RSVP Path messages.  The resource 
reservation info (equivalent of qospf RRAs) is 
piggybacked in the Path messages.  However, since 
these messages follow the direction of a flow, 
only downstream routers receive resource reservation
info of upstream routers but not the other way
around.  The problem with this is that upstream
and downstream routers see different network
status.  For example, if S-R1-R2-R3-D is the 
path taken by a flow, R1 tells R2  
resource reservation info on link (R1,R2), 
and R2 tells R3 the resource reservation 
info on links (R1,R2) and (R2,R3).
However, R2 and R3 do not communicate their
resource reservation info 
(on links (R2,R3) and (R3,D)) to R1.  

Using the terminilogy of the paper,
R1 can "correct" the "generic" link state
of link (R1,R2);  R2 can correct 
generic link states of (R1,R2) and 
(R2,R3); and R3 can correct 
the generic link states of (R1,R2), 
(R2,R3) and (R3,D).  So different
routers see inconsistent link states.  
(Let me know if I miss anything in this 
reasoning.) 

I guess a simple fix would be to also 
piggyback resource reservation on the 
RESV messages.  Or maybe it is not 
necessary because receiving successful 
RSVP Resv message by a router would 
imply the resource reservation info 
on downstream links?

Regards,
-- 
Yao-Min Chen, Fujitsu Labs of America, [e-mail]  
595 Lawrence Expressway, Sunnyvale, CA 94086-3922
Phone: [phone] Fax: [phone]