Yu:

  A small clarification. There is no surety that your
  LS request goes through. Mean while, other router
  can still send an LS Update packet and can wait
  for Acknowledgement. This is just a crossover case,
  where LS Request didn't reach the destination but
  LS update reaches the destination. That is why, Alex
  may be suggesting to send LS Ack always.

--Venkata Naidu

-> Alex,
->
-> That is what the second bullet says. If the received LSA is
-> not less or more
-> recent than the one on the request list, the LSA can be
-> treated as the reply
-> to the request. Am I missing something?
->
-> Yu
->
-> > -----Original Message-----
-> > From: Alex Zinin [mailto:azininNEXSI.COM]
-> > Sent: Wednesday, October 24, 2001 5:22 PM
-> > To: OSPFDISCUSS.MICROSOFT.COM
-> > Subject: Re: Acknowledgement for Router LSA from DROther.
-> >
-> >
-> > Yu,
-> >
-> > You always receive the nbr's *most recent* copy
-> > of the LSA that you requested and you can't
-> > tell why it was sent.
-> >
-> > --
-> > Alex Zinin
-> >
-> > Wednesday, October 24, 2001, 1:31:15 PM, Ju, Yu wrote:
-> >
-> > > Alex,
-> >
-> > > On page 149 of rfc2328, part (b) says
-> >
-> > > "
-> > > (b) Else, if the adjacency is not yet full (neighbor state
-> > > is Exchange or Loading), examine the Link
-> > state request
-> > > list associated with this adjacency. If
-> there is an
-> > > instance of the new LSA on the list, it
-> > indicates that
-> > > the neighboring router has an instance of the LSA
-> > > already. Compare the new LSA to the
-> > neighbor's copy:
-> >
-> > > o If the new LSA is less recent, then
-> > examine the next
-> > > neighbor.
-> >
-> > > o If the two copies are the same
-> > instance, then delete
-> > > the LSA from the Link state request list, and
-> > > examine the next neighbor.[20]
-> >
-> > > o Else, the new LSA is more recent.
-> > Delete the LSA
-> > > from the Link state request list.
-> > > ....
-> > > "
-> >
-> > > The second bullet is the place that you can tell the LSA
-> > has been requested
-> > > and the ACK is not necessary here. Note [20] says "[20]This
-> > is how the Link
-> > > state request list is emptied, which eventually causes the
-> > neighbor state to
-> > > transition to Full. See Section 10.9 for more details.".
-> >
-> > > Thanks,
-> >
-> > > Yu
-> >
-õÿt; >
-> > >> -----Original Message-----
-> > >> From: Alex Zinin [mailto:azininNEXSI.COM]
-> > >> Sent: Wednesday, October 24, 2001 3:49 PM
-> > >> To: OSPFDISCUSS.MICROSOFT.COM
-> > >> Subject: Re: Acknowledgement for Router LSA from DROther.
-> > >>
-> > >>
-> > >> Feng, Yu
-> > >>
-> > >> Acks _are_ necessary.
-> > >>
-> > >> When you're in the middle of a DB exchange process,
-> > >> the adjacency already participates in flooding, so
-> > >> you never know why you've received an LSA---because
-> > >> you've requested it or because the other guy has
-> > >> sent it to you as part of the flooding procedure.
-> > >>
-> > >> As for the past discussions, http://discuss.microsoft.com
-> > >> is your friend.
-> > >>
-> > >> --
-> > >> Alex Zinin
-> > >>
-> > >>
-> > >> Wednesday, October 24, 2001, 10:36:43 AM, Xie, Feng wrote:
-> > >>
-> > >> > Hi, Alex:
-> > >>
-> > >> > I aggree with Yu. In RFC2328, there is no
-> > >> specification that ACKs
-> > >> > should be sent when receiving a new update in lsdb sync.
-> > In fact, on
-> > >> > RFC2328, p103, it says:
-> > >>
-> > >> > "Each LSA specified in the Link State Request packet
-> > >> should be
-> > >> > located in the router's database, and copied
-> > into Link State
-> > >> > Update packets for transmission to the neighbor.
-> > These LSAs
-> > >> > should NOT be placed on the Link state
-> > >> retransmission list for
-> > >> > the neighbor. "
-> > >>
-> > >> > My understanding is that if ACKs were needed, these
-> > >> lsas should be put
-> > >> > in the retransmission list. The reason why these LSAs are
-> > >> not put into the
-> > >> > retransmission list is because the receiver will send a
-> > >> request for the same
-> > >> > lsa if the previous LSA update is not received. In this
-> > >> case, the new LSA
-> > >> > request or no further request serves as an implicit ACK.
-> > >>
-> > >> > In summary, I think this may be an implementation
-> > >> issue: there is
-> > >> > nothing wrong to send ACKs in LSDB sync but ACKs may not be
-> > >> necessary. If
-> > >> > the above understanding is not correct, could you please
-> > >> give an example or
-> > >> > a reference to the related previous discussion? Thanks.
-> > >>
-> > >> > Feng Xie
-> > >>
-> > >> > -----Original Message-----
-> > >> > From: Ju, Yu [mailto:Yu.JuMARCONI.COM]
-> > >> > Sent: Wednesday, October 24, 2001 1:06 PM
-> > >> > To: OSPFDISCUSS.MICROSOFT.COM
-> > >> > Subject: Re: Acknowledgement for Router LSA from DROther.
-> > >>
-> > >>
-> > >> > Alex,
-> > >>
-> > >> > I think LSA ack applies to flooding procedure. During LSDB
-> > >> sync, one will
-> > >> > keep sending the request until it receives the LSA update.
-> > >> When receiving
-> > >> > the request, the other end will just sent out the LSA
-> > update without
-> > >> > expecting the ack. This way, the two routers will have the
-> > >> same LSDB.
-> > >>
-> > >> > Thanks,
-> > >>
-> > >> > Yu
-> > >>
-> > >> >> -----Original Message-----
-> > >> >> From: Alex Zinin [mailto:azininNEXSI.COM]
-> > >> >> Sent: Wednesday, October 24, 2001 2:43 AM
-> > >> >> To: OSPFDISCUSS.MICROSOFT.COM
-> > >> >> Subject: Re: Acknowledgement for Router LSA from DROther.
-> > >> >>
-> > >> >>
-> > >> >> Folks,
-> > >> >>
-> > >> >> To answer the original question---the DR should not
-> > >> >> explicitly ack the LSA received from a non-DR router,
-> > >> >> as it will flood the LSA back to the interface to
-> > >> >> AllSPFRouters, so the router that sent the LSA will treat
-> > >> >> this update as an implied ack.
-> > >> >>
-> > >> >> As for Feng's point 2 below, the statement is not correct.
-> > >> >> You have to ack LSAs during the LSDB exchange
-> process according
-> > >> >> to normal rules, there's no special case for the
-> > Exchange process.
-> > >> >> This question has been explained lately on the list, pls see
-> > >> >> the archives.
-> > >> >>
-> > >> >> --
-> > >> >> Alex Zinin
-> > >> >>
-> > >> >> Monday, October 22, 2001, 3:01:41 PM, Xie, Feng wrote:
-> > >> >>
-> > >> >> > Hi, Gurpreet:
-> > >> >>
-> > >> >> > I think there could be two cases in which no explict
-> > >> >> acknowledgments
-> > >> >> > are needed:
-> > >> >> > 1. The case described by section 13, 7(a);
-> > >> >> > 2. In DB sync in which router A sends a request to
-> > >> >> router C. When
-> > >> >> > router C responds to this request with some link state
-> > >> >> update, router A may
-> > >> >> > send the next request or do nothing if there is no further
-> > >> >> request. Refer to
-> > >> >> > RFC2328, p105. My understanding is that in this case, the
-> > >> >> next request or no
-> > >> >> > request may serve as an implicit ack because if the update
-> > >> >> is not received
-> > >> >> > by router A, it will resend its request again.
-> > >> >>
-> > >> >> > Feng Xie
-> > >> >>
-> > >> >> > -----Original Message-----
-> > >> >> > From: Singh, Gurpreet
-> [mailto:Gurpreet.SinghSPIRENTCOM.COM]
-> > >> >> > Sent: Monday, October 22, 2001 5:48 PM
-> > >> >> > To: OSPFDISCUSS.MICROSOFT.COM
-> > >> >> > Subject: Re: Acknowledgement for Router LSA from DROther.
-> > >> >>
-> > >> >>
-> > >> >> > Hi Xie
-> > >> >>
-> > >> >> > However,
-> > >> >> > acknowledgments can also be accomplished implicitly
-> > >> >> by sending
-> > >> >> > Link State Update packets (see step 7a of
-> > Section 13)."
-> > >> >>
-> > >> >> > Does this mean that implied acknowledgement is done only in
-> > >> >> the case of 7a
-> > >> >> > of section 13 ?
-> > >> >> > Section 7a is valid only for LSAs for which the router has
-> > >> >> the same instance
-> > >> >> > in the database as the received LSA.
-> > >> >>
-> > >> >>
-> > >> >> > Gurpreet
-> > >> >>
-> > >> >> > -----Original Message-----
-> > >> >> > From: Xie, Feng [mailto:Feng.XieMARCONI.COM]
-> > >> >> > Sent: Monday, October 22, 2001 5:36 PM
-> > >> >> > To: OSPFDISCUSS.MICROSOFT.COM
-> > >> >> > Subject: Re: Acknowledgement for Router LSA from DROther.
-> > >> >>
-> > >> >>
-> > >> >> > Hi, Gurpreet:
-> > >> >>
-> > >> >> > According to RFC2328, p152,
-> > >> >>
-> > >> >> > "Each newly received LSA must be acknowledged. This
-> > >> is usually
-> > >> >> > done by sending Link State Acknowledgment
-> > >> packets. However,
-> > >> >> > acknowledgments can also be accomplished implicitly
-> > >> >> by sending
-> > >> >> > Link State Update packets (see step 7a of
-> > Section 13)."
-> > >> >>
-> > >> >> > Base on the above statement, my understanding is that A
-> > >> >> may not need to
-> > >> >> > send an explicit link acknowledgment for every router lsa
-> > >> >> it receives from C
-> > >> >> > if the router lsa is received during DB sync.
-> > >> >>
-> > >> >> > Feng Xie
-> > >> >>
-> > >> >>
-> > >> >> > -----Original Message-----
-> > >> >> > From: Singh, Gurpreet
[mailto:Gurpreet.SinghSPIRENTCOM.COM]
> >> >> > Sent: Monday, October 22, 2001 5:27 PM
> >> >> > To: OSPFDISCUSS.MICROSOFT.COM
> >> >> > Subject: Acknowledgement for Router LSA from DROther.
> >> >>
> >> >>
> >> >> > Hi
> >> >>
> >> >> > If there are three routers on the same sub-net A (DR) ,
> >> >> B (Backup DR)
> >> >> > and C (DR Other). Should A acknowledge a router LSA (which
> >> >> A does not have a
> >> >> > copy in the database) received from C ? i.e. should router
> >> >> LSA from a
> >> >> > DROther be acknowledged by the DR (Designated Router)
> >> >>
> >> >>
> >> >> > Thanks
> >> >>
> >> >> > Gurpreet
> >> >>
> >>
>

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