Hi Gerrit,

Am 01.09.2010 um 07:23 schrieb Gerrit Renker:

quoted text
> | > This patch consolidates initial-window code common to TCP and CCID-2:
> | >  * TCP uses RFC 3390 in a packet-oriented manner (tcp_input.c) and
> | >  * CCID-2 uses RFC 3390 in packet-oriented manner (RFC 4341).
> ...
> | > +static inline u32 rfc3390_bytes_to_packets(const u32 smss)
> | > +{
> | > +	return smss <= 1095 ? 4 : (smss > 1460 ? 2 : 3);
> | > +}
> | > +
> ...
> | 
> | What is spelled out in tcp_select_initial_window might also need to follow 
> | the same logic?
> | 
> Thank you for paying attention, can you please have a look at the subsequent
> patch. I went through this yesterday and found that in 4 different places 
> there are 4 different interpretations of what RFC 3390 means.
> 
> Having asked someone more familiar with IETF issues, it seems that the RFC 5681
> interpretation of RFC 3390 is now the 'official' one.
> 
> +------------+--------------------+--------------------+--------------------+--------------------+
> | Condition  |     RFC 2414       |        Linux       |       Linux        |     RFC 5681       |
> |            |     RFC 3390       |      tcp_input     |     tcp_output     |                    |
> +------------+--------------------+--------------------+--------------------+--------------------+
> | 2 segments | 2190 < MSS         | 1460 < MSS         | 4380 < MSS         | 2190 < MSS         |
> | 3 segments | 1095 < MSS <= 1460 | 1095 < MSS <= 1460 | 1460 < MSS <= 4380 | 1095 < MSS <= 2190 |

                              ^^^^^

Are you sure about this?

RFC3390 says (page 2):
 If (1095 bytes < MSS < 2190 bytes) then win <= 4380;

So, IMO it should be 1095 < MSS < 2190 for 3 segments, and 2190 <= MSS for 2 segments
in the "RFC 3390" column.

BTW: I think that we should not reference RFC2414, since RFC3390 obsoletes it.

Alex


quoted text
> | 4 segments |        MSS <= 1095 |        MSS <= 1095 |        MSS <= 1460 |        MSS <= 1095 |
> +------------+--------------------+--------------------+--------------------+--------------------+
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