Re: [lwip-users] Interniche and lwIP

[Timmy Brolin]

> But the problems/disadvantages with Interniche:
>
> 6  They support scatter-gather DMA in hardware but their driver doesn't take
> advantage of it.
>   
Unless things have changed recently in Interniche land, this is also the
main reason why Interniche uses much more RAM than lwIP.
A full 1518 Byte buffer has to be allocated for every incoming packet,
unless you want to do one extra copy and reallocation operation in the
Ethernet driver.

Just this week I found bugs in Interniche IP fragmentation routines as
well as in the handling of IP options.
> The good parts:
> 2. The scatter-gather DMA is nice if utilized.
>   
Most processors with integrated 100Mbit MAC supports scatter-gather.
Not really a noteworthy feature unless it supports some more advanced
features such as automatic TCP/IP header length detection so that the
scatter transfer can separate the TCP/IP or UDP/IP header from the
payload, even when the headers may have varying lengths due to header
options and vlan tags.
If combined with a finely grained MMU, such a feature would allow true
zero copy without the hazzle of having to handle pbuf chains in the
application layer.

/Timmy Brolin