🚀 go-pugleaf

Okay folks, my 2p worth ...

News problems are down to resent packets. Sometimes you get 'em, 
sometimes you don't. Here's how to tell ...

Wait until news is connected and it shows the first article has been 
retrieved. Now type "so" (for socket). You get a list of stuff 
something like this ...

S#  Type    PCB      Remote socket         Owner
128 Loc St  119dba                         119992   cmdintrp
129 Loc St  119dce                         119992   cmdintrp
130 TCP     167eee                         13f9b8   SMTP listener
131 TCP     167fc6                         141a6c   Discard listener
132 TCP     166704                         16503c   Finger listener
133 TCP     1667b0                         16666c   TTYlink listener
134 TCP     166800                         168888   NNTP_client_main

You are interested in the NNTP_client_main socket. Look at the socket 
number (in this case 134) now type "so 134". You will have a load of 
spiel displayed like this ...

TCP 2ed89c binary eol seq: 0d 0a
Local: 0.0.0.0:87 Remote: 0.0.0.0:0 State: Listen
      Init seq    Unack     Next Resent CWind Thrsh  Wind  MSS Queue Total
Send:        0        0        0      0   536 65535     1  536     0     0
Recv:        0                 0      0-            32000          0     0
Timer stopped SRTT 3000 ms Mean dev 0 ms\
                                         \
                                          \
                                 [value of concern]

The Recv/Resent value is what you are looking at. In an ideal world 
this value should be zero.

Subsequent "so <S#>" (in this case "so 134") commands will show you 
the number of resent packets up to that point.

So, if you issue "so" on the first article, another halfway through 
and a final one very near the last article, you get a reasonable idea 
what is happening.

My experience
-------------

There are initial resent packets between the point NNTP connects and 
the time the first article arrives. If the number of resent packets is 
"small", you get no more resent packets during the rest of the 
newsfeed. If the resent packets is "medium" then you get some resent 
packets during the news feed but they gradually fade to nothing. If 
the resent packets is "large" then you get a lot of resent packets 
during the newsfeed - the proportion of which compared with the 
Recv/Total can be up to as much as 3 times the Total. This proportion 
appears to depend on how big "large" is. (Wow really technical).

I've had both positive and negative effects from messing with MSS and 
MRU.

Contrary to advice, making the receive window huge seems to have a 
positive effect.

There may also be a relationship between the delays in initial routing 
and resent packets but this is more a feeling than anything concrete 
which can be put into words. Other things could equally well be 
possible.

Now you all know as much as me on the subject. As for tweeking the 
parameters then get hold of Tuning.faq which will explain what most 
things you tweek are actually supposed to do.


__

Guy Harrison

guy@swampdog.demon.co.uk