Subject: [Dime] DWR & REOPEN Peer State

From: "J V, Kishore Kumar (Communication & Media Solutions)" <[email-masked]>
Date: Mon, 10 Oct 2011 09:14:42 +0000

Description of issue: 

When peer is REOPEN state, any non-DWA message (including DWR) are "thrown away". This may cause the peer who sent the DWR to failover and when this issue occurs, this peer can never be in OPEN state.

Submitter name: Kishore
Submitter email address: [email-masked]

Date first submitted: October/10/2011 
Document: AAATRANS

Comment type: T

Priority: S

Section: Appendix A - Detailed Watchdog Algorithm

Rationale/Explanation of issue: 
Peer-1 and Peer-2 have established diameter connection and they are in OPEN state. For some reason, Peer-2 loses connection to Peer-1. This causes Peer-2 to move Peer-1 to "DOWN" state.
When Peer-1 connects again to Peer-2, then Peer-2 moves the state of Peer-1 to "REOPEN" state. Then it sends a DWR immediately. If Tw period of Peer-2 happens to be larger than Tw period of Peer-1 ( Eg., Tw(Peer-2) > 3 * Tw(Peer-1)), then it is possible that a DWR might be received from Peer-1 before second/third DWR are sent from Peer-2. Since Peer-1 is in "REOPEN" state in Peer-2, the DWR would Be "thrown away". This causes Peer-1 to initiate failback. When Peer-1 establishes the connection again, the above set of events are repeated and hence the state can never change to [R/I]-OPEN.