Subject: RE: Size matters was Re: notification charter proposal

From: "Hector Trevino \(htrevino\)" <[email-masked]>
Date: Wed, 23 Nov 2005 10:08:10 -0800

I agree that this is part of the protocol definition but I see it as
outside the scope of the charter definition. I'd assume none of this
will be included in the charter.

I don't think the spec should set a hard limit on the max message size.
I agree w/Juergen about not limiting the protocol but rather allowing
implementations to advertise their max message sizes (if one is set). It
may be better to say something like app layer message segmentation is
not allowed. But recommendations/guidelines for max message sizes should
be provided in the spec. 

Hector

-----Original Message-----
From: [email-masked] [mailto:[email-masked]] On
Behalf Of Andy Bierman
Sent: Tuesday, November 22, 2005 4:01 PM
To: Tom Petch
Cc: [email-masked]
Subject: Re: Size matters was Re: notification charter proposal

Tom Petch wrote:

><inline>
>Tom Petch
>----- Original Message -----
>From: "Andy Bierman" <[email-masked]>
>To: <[email-masked]>
>Cc: "Tom Petch" <[email-masked]>; <[email-masked]>
>Sent: Tuesday, November 22, 2005 4:41 PM
>Subject: Re: notification charter proposal <snip>> >
>  
>
>>That would be fine with me.
>>I brought up the issue because the problem is obviously worse for 
>>notifications than RPCs, because the lack of an application layer ACK 
>>(which <rpc-reply> effectively is).
>>
>>The reason for setting a minimum is to allow NMS developers to code to

>>some reasonable minimum.  The market will help keep things somewhat 
>>reasonable, but we could see a range from 1500 to 64K as the minimum.

>>Is that OK?
>>
>>Andy
>>
>>    
>>
>
>I raised size because there are references appearing on the list 
>calling for something syslog-like and size has been an issue with 
>syslog that has not been satisfactorily resolved.  syslog unearthed two

>contrasting viewpoints, one that messages should not exceed 2k or even 
>1k, the other that 64k should be supported (for at least one
application).
>
>Netconf is more virgin territory than syslog is but I do believe is 
>setting a Maximum size, at least to start with; but I do not see this 
>as anything to do with the charter:-).
>  
>

This is part of protocol syntax and semantics.

IMO, the best approach is to have the NC peer advertise its
max-message-size.  The number should be an PositiveInteger, so that
would set a theoretical max-message-size of 4G-1 bytes.

A separate issue is whether there is a minimum an NC peer can set this
parameter to, somewhat higher than zero.  I don't see any consensus yet
on how much higher to set the minimum.

Another  important issue:  Can an NC peer (optionally?) send its
max-message-size in the <hello> exchange?  This doesn't mean the other
NC peer has to do anything with the value, it just provides a good guess
at the number instead of trying
various message sizes to see what breaks.   Advertising a
max-message-size doesn't mean you won't get messages greater than that
size. 

>Tom Petch

Andy

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---

From: Balazs Lengyel <[email-masked]>
Date: Fri, 25 Nov 2005 09:22:26 +0100

Please dont set a max message size generally for netconf !!!

For me one attractive usage of netconf would be to retrieve the complete configuration of 
a node. If we set a mandatory max-size for all netconf messages (as opposed to setting it 
  for notifications only) this usage would become impossible. For big nodes it is anyone's 
guess what the size of a full configuration can be. We have nodes that contain the data of 
10 million subscribers.

Balazs Lengyel                       Ericsson Hungary Ltd.

---

From: Andy Bierman <[email-masked]>
Date: Fri, 25 Nov 2005 09:25:50 -0800

> Please dont set a max message size generally for netconf !!!

We are discussing the notion of setting a minimum value
that conforming implementations can use.  We aren't setting
any maximum value, although I suggested 4 billion bytes
so my code can store your max-message-size in a 4 byte
number instead of an 8-byte (long long) number.

If anybody out there is planning an implementation with
a message size bigger than 4 billion bytes, please let me know :-)

>
> For me one attractive usage of netconf would be to retrieve the 
> complete configuration of a node. If we set a mandatory max-size for 
> all netconf messages (as opposed to setting it  for notifications 
> only) this usage would become impossible. For big nodes it is anyone's 
> guess what the size of a full configuration can be. We have nodes that 
> contain the data of 10 million subscribers.

You don't HAVE to design an application to get 10 million config
entries at once, but if even this will fit in a 4 billion byte message.

Andy

>>>> notifications than RPCs, because the lack of an application layer 
>>>> ACK (which <rpc-reply> effectively is).
>>>>
>>> contrasting viewpoints, one that messages should not exceed 2k or 
>>> even 1k, the other that 64k should be supported (for at least one
>>
>>
>> application).
>>
>>> setting a Maximum size, at least to start with; but I do not see 
>>> this as anything to do with the charter:-).
>>>
>>>
>>
>>

---

From: Phil Shafer <[email-masked]>
Date: Sun, 27 Nov 2005 01:23:08 -0500

Andy Bierman writes:
>that conforming implementations can use.

Setting a minimum maximum effectively sets the maximum an implementation
can count on the other side implementing, which quickly turns into
a hard restriction.

Instead we should have any message size restrictions be passed in
to the server at subscription time.  If the client gives a number
larger than the server can send, it's ignored.  If the number is
smaller, then the server must truncate.  If the number is not
provided, the server is freed from worrying about the client's
message size considerations.

>a message size bigger than 4 billion bytes, please let me know :-)

You are _so_ 32-bit, man ;^)

Thanks,
 Phil

---

From: Andy Bierman <[email-masked]>
Date: Sun, 27 Nov 2005 07:07:35 -0800

>can count on the other side implementing, which quickly turns into

This is possible, but IMO NMS developers from a company
will pressure the agent developers in that company to provide them
with a reasonable max-size.

You set the bar at 64K, and it's not such a bad restriction.
I don't think we should try to set a limit, especially if it is
a really low number like 1500.  I stated in the previous mail
that there isn't consensus to set a limit, so I think this topic can be 
closed now.

>message size considerations.

Well put.

>You are _so_ 32-bit, man ;^)

Hey! I switched over from ASM to C in '86, but I still hate to
waste memory or CPU cycles.  ;-)

Andy