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Re: [lwip-users] Why so many pbufs required?

From: JM
Subject: Re: [lwip-users] Why so many pbufs required?
Date: Thu, 13 Aug 2009 08:40:46 -0700 (PDT)

Ahh, never thought of the "unexpected" packets.  I learn a little more each day. 

--- On Thu, 8/13/09, Kieran Mansley <address@hidden> wrote:

From: Kieran Mansley <address@hidden>
Subject: Re: [lwip-users] Why so many pbufs required?
To: "Mailing list for lwIP users" <address@hidden>
Date: Thursday, August 13, 2009, 9:22 AM

On Thu, 2009-08-13 at 04:09 -0700, JM wrote:

You're assuming that the stack will only receive packets for your
application.  In most networks this is not true - there will be a fair
number of broadcasts, and other stuff that your application will never
see.  These will still be passed to the stack, and each will use (at
least) one PBUF_POOL pbuf.  There may be other things, such as TCP ACKs
for any data you send, that also come in as separate packets and each
use PBUF_POOL pbufs.

Chris's point about using more-but-smaller pbufs in the pool is a good
one.  It will mean you might get away with less memory and fewer dropped
packets, at the cost of a little extra overhead for the chaining.


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