Hi,
Please find some review comments for draft - PCEP Extensions for Stateful
PCE draft-ietf-pce-stateful-pce-02
1. In section 5.4 State synchronization
A PCE SHOULD NOT send PCUpd messages to a PCC before State
Synchronization is complete. A PCC SHOULD NOT send PCReq messages to
a PCE before State Synchronization is complete. This is to allow the
PCE to get the best possible view of the network before it starts
computing new paths.
+-+-+ +-+-+
|PCC| |PCE|
+-+-+ +-+-+
| |
|-----PCRpt, SYNC=1----->| (Sync start)
| |
|-----PCRpt, SYNC=1----->|
| . |
| . |
| . |
|-----PCRpt, SYNC=1----->| (Sync done)è PCE doesnt
exactly know that sync is complete at this moment
| . |
| . |
| . |
| |
|-----PCRpt, SYNC=0----->| (Regular
| | LSP State Report)
Figure 3: Successful state synchronization
In the above case, how would PCE know that synchronization is complete if
there are no more PCRpt or PCReq received from PCC ?
For example, if some LSPs were delegated to PCE in previous session. After
session restart, PCE would not be able to send PCUpd messages to PCC until
it receives first PCRpt message with SYNC=0. And PCC wouldnt send PCRpt
until there is a change in LSP state.
Suggestion:
1. we should have a mechanism for PCE to know that sync is completed
at the end of last LSP state report. May be, we can send last report with
SYNC=0.
2. Rather than just allowing synchronization of LSP-DB immediately
after initialization completion, we can also have a mechanism to trigger LSP
sync when ever PCE wishes to get snapshot of LSP with PCC. This may be
useful when PCE goes down and comes UP without disturbing TCP session or
keepalive.
2. In section 5.4.1 state synchronization avoidance, suggest to change
highlighted text below to LSP state report from PCC
If a PCC's LSP State Database survived the restart, the PCC will
include
the LSP-DB-VERSION TLV in its OPEN object and the TLV will contain
the last LSP State Database version sent on an LSP State Update from
the PCC in the previous PCEP session.
3. In section 5.6.1. Passive Stateful PCE Path Computation Request/Response
Upon receiving a negative reply from a PCE, a PCC may decide to
resend a modified request or take any other appropriate action. For
each requested LSP, it also sends an LSP State Report carried on a
PCRpt message to the PCE, indicating that the LSP's status is 'Down'.
According to the text, PCC sends PCRpt message to the PCE, indicating that
the LSP's status is 'Pending' only in case of positive path computation
reply. In that case, we dont have to send PCRpt message to the PCE,
indicating that the LSP's status is 'Down' in case of negative path
computation reply.
Regards,
Venu
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