Subject: [Forces-protocol] topic 2:: HA

From: "Khosravi, Hormuzd M" <[email-masked]>
Date: Sun, 25 Apr 2004 22:44:37 -0700

Hi All

Here is my attempt to start some discussion on topic 2, we just have 1
week to complete All discussions so we need to move fast!

Based on our discussions on TML and PL as well as the 3 schemes proposed
by Jamal, here is my suggestion for HA scheme...

At any time there is one Primary CE controlling the FE and there can be
multiple secondary Ces. The FE PL is aware of the primary and secondary
Ces. Only the primary CE is sending Control messages to the Fes. The FE
may choose to send its events, redirection packets to all the Ces or
only Primary CE (we need to decide one or keep this configurable ?). A
CE-to-CE synchronization may be needed, however that is out of our
current scope for ForCES PL. The association between the FE and primary
CE may change based on the Connection State (triggered by TML) or an
explicit message (such as Move, described by Jamal) from the primary CE.

This scheme is similar to Scheme 2 proposed by Jamal with a few more
details. Hope we can agree on this and move to the other topics. We can
discuss more details around the Protocol Messages related to this scheme
during topic:4. 

Let me know what you guys think ?

Regards
Hormuzd

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From: "Weiming Wang" <[email-masked]>
Date: Mon, 26 Apr 2004 23:16:23 +0800

Hi Hormuzd, Jamal, Ram, et al.,

----- Original Message -----
From: "Khosravi, Hormuzd M" <[email-masked]>
Hi All

[Weiming] Based on the fact that ForCES requirements and framework have
explicitly defined CE-CE and FE-FE being out of scope of ForCES architecture
(not only out of the ForCES protocol), and CE-CE syncronization should surely be
supplied (by any means) by custumers when multi CEs are used, I suggest we limit
FE to only be responsible for one CE at a time so as to simplify the case.
Partial information like events, redirection packets in this case actually is of
little use for the redundant CEs.

CE-to-CE synchronization may be needed, however that is out of our
current scope for ForCES PL.
[Weiming] As I said above, this is even out of the scope of ForCES architecture,
according to RFC3654.

The association between the FE and primary
CE may change based on the Connection State (triggered by TML) or an
explicit message (such as Move, described by Jamal) from the primary CE.

[Weiming] Regarding this, I strongly ask to let us answer the questions first
"Is the TML only allowed to be statically configured, or can be configured
dynamically by CEM/FEM?" If it is a static one, we then definitely need PL to
have TML configuration ability (as I have posted for several times, and also Ram
proposed), or else, if TML can be dynamically configured by CEM/FEM all the time
during the protocol runtime, we then do not need to have the PL to do this.
This rule also applies to CE change or failover, connection link failure, etc.
From the TML-PL interface discussion and the HA discussion, I have a strong
feeling that some TML configuration from PL layer based on, as Ram said,
sessions are  also in great demand as well as per message based implicit
signaling.  Hormuzd &Jamal, I hope you can give some comments on this.
[/Weiming]

Best regards,
Weiming

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From: Jamal Hadi Salim <[email-masked]>
Date: 26 Apr 2004 16:52:41 -0400

Hi Hormuzd et al,

I apologize for starting with this specific email. I am doing so because
this one seems to be capturing good details. 

Now onto the email

> discuss more details around the Protocol Messages related to this scheme

There is a difference in that in my text i said the responsibility is
that of the TML - not the PL. The only role the PL may play is in the
move operation. That role could also be played by the FEM/CEM interface
making the decision making out of the control of the PL.

So i think actually your email adds some clarity to what i had said
earlier since you are thinking from a PL level and i was fromn the TML
level ;->
I see both as valuable and of different responsibilities:

1) TML level - Transport level:

a) The TML controls logical connection availability and failover. 
b) The TML also controls peer HA managements.

At this level in my opinion control of all lower layers
example transport level (such as IP addresses, MAC addresses etc)
and associated links going down are the role of the TML or whatever the
TML depends on.

2) PL Level:
If  you are talking about control of say CEids as the meaning of "FE
being aware of the primary and secondary Ces", then i think it would be
sensible. When i read the text it almost sounded like the PL layer knew
about details of things like physical links going up/down.
 
To put the two together, for example if a path to a master CE is down,
I would think the TML would take care of failing over to a backup path.
Should the CE be totaly unreachable i think only then would the PL
be informed and it may decide to move to a new CE.
Does this make sense?

cheers,
jamal