More about Sequence Reset - Reset

, ,
1

Imported from previous forum

2

Hi All,

I have a question regarding Sequence Reset - Reset which was not answered in the prior discussion on this topic.

The scenario is as follows.

An out-of-sequence condition has occurred due to which one side has logged out and the connection has been dropped. Now the first message in any session is always a logon, hence a logon will be sent which might carry a sequence number that is less than the counter party’s expected sequence number, in which case a returning logon will not be sent and the counter party will end the session. In such a scenario, after the telecommunication link is re-established, can a Sequence Reset-Reset message be sent instead of a logon? If not, what needs to be done???

Thanks and Regards,
Manali

3

[ original email was from Ryan Pierce - rpierce@taltrade.com ]
I’m wondering how this scenario is possible.

You, to a limited extent, control the sequence number your counterparty expects. By sending messages and SeqReset’s you can increase what they expect.

Now it is possible that the other party will fail to receive messages that you send. Hence it is possible that the sequence number on your Logon will be greater than what they expect; in this case they respond with a Logon and a Resend Request.

However in no case should the Logon you send have a sequence number less than what they expect. The Logon you send must have a sequence number greater than the sequence number of any messages you sent, and >= the largest NewSeqNo in any SeqReset message you send. If this is not the case, you’ve done something seriously wrong. If your counterparty expect s sequence number > the highest MsgSeqNo you sent + 1, or the highest NewSeqNo field, then your counterparty has done something seriously wrong.