FTP performance with pppd

FTP performance with pppd

Post by Cam Johnso » Sun, 04 Aug 1996 04:00:00



I'm experiencing poor ftp transfer rates when using pppd.  Approx 600
byes per sec
via pppd and 2800 bytes per sec when using ijppp.  This is true for both
2.1.5R and current.  Has anyone else seen this as my search of the
archives
has yielded nothing.

Thanks
--
Cam Johnson
SS NetCon, 5610 Guhn Rd., Houston, TX 77040 713-895-0500 or
SS Netcon, 3010 Possum Trot, Brenham, TX 77833 409-277-9507
FAX 713-690-2722

 
 
 

FTP performance with pppd

Post by Ken Bigelo » Sun, 04 Aug 1996 04:00:00



> I'm experiencing poor ftp transfer rates when using pppd.  Approx 600
> byes per sec
> via pppd and 2800 bytes per sec when using ijppp.  This is true for both
> 2.1.5R and current.  Has anyone else seen this as my search of the
> archives
> has yielded nothing.

> Thanks

Too many possibilities to be sure without further data, but...

Try adjusting your mtu size. As long as I'm on a dialup line, I set mtu
to 576. When/if I go to ISDN I'll up that.
--

Ken

Are you interested in   |
byte-sized education    |   http://www.play-hookey.com
over the Internet?      |

 
 
 

FTP performance with pppd

Post by S Marqua » Mon, 05 Aug 1996 04:00:00




>> I'm experiencing poor ftp transfer rates when using pppd.  Approx 600
>> byes per sec
>> via pppd and 2800 bytes per sec when using ijppp.  This is true for both
>> 2.1.5R and current.  Has anyone else seen this as my search of the
>> archives
>> has yielded nothing.

>> Thanks
>Too many possibilities to be sure without further data, but...
>Try adjusting your mtu size. As long as I'm on a dialup line, I set mtu
>to 576. When/if I go to ISDN I'll up that.

I have got throughput of about 2700bps using pppd, vs 3100bps using ijppp
(with 28.8 modems). Adjusting the mtu/mru values hasn't helped.
I'd also like to know what the difference is.

Stephen Marquard


 
 
 

FTP performance with pppd

Post by Cam Johnso » Mon, 05 Aug 1996 04:00:00





> >> I'm experiencing poor ftp transfer rates when using pppd.  Approx 600
> >> byes per sec
> >> via pppd and 2800 bytes per sec when using ijppp.  This is true for both
> >> 2.1.5R and current.  Has anyone else seen this as my search of the
> >> archives
> >> has yielded nothing.

> >> Thanks

> >Too many possibilities to be sure without further data, but...

> >Try adjusting your mtu size. As long as I'm on a dialup line, I set mtu
> >to 576. When/if I go to ISDN I'll up that.

> I have got throughput of about 2700bps using pppd, vs 3100bps using ijppp
> (with 28.8 modems). Adjusting the mtu/mru values hasn't helped.
> I'd also like to know what the difference is.

> Stephen Marquard



Lokks as though I have at least partially solved my performance problem
by
turning off vj compression i.e. in the /etc/ppp/options adding -vj.
Performace is still not up to that of ijppp, and I know that there have
been some bugs in the pppd vj implementation in the past.
--
Cam Johnson
SS NetCon, 5610 Guhn Rd., Houston, TX 77040 713-895-0500 or
SS Netcon, 3010 Possum Trot, Brenham, TX 77833 409-277-9507
FAX 713-690-2722

 
 
 

FTP performance with pppd

Post by Brian Some » Tue, 06 Aug 1996 04:00:00


: I have got throughput of about 2700bps using pppd, vs 3100bps using ijppp
: (with 28.8 modems). Adjusting the mtu/mru values hasn't helped.
: I'd also like to know what the difference is.

If you send 1500 byte packets, they may get fragmented further down the
"virtual" line.  If they do, and only one packet gets through, your
side will need to re-send both - worse than having a lower packet size.

Conversley, you've got more overhead......

Personally, I don't know what my MTU is - it doesn't matter that much
when you just exchange low volumes of news & mail, and play a mud.

--

Don't _EVER_ lose your sense of humour....

 
 
 

FTP performance with pppd

Post by Ken Bigelo » Thu, 08 Aug 1996 04:00:00



> >Try adjusting your mtu size. As long as I'm on a dialup line, I set mtu
> >to 576. When/if I go to ISDN I'll up that.

> I have got throughput of about 2700bps using pppd, vs 3100bps using ijppp
> (with 28.8 modems). Adjusting the mtu/mru values hasn't helped.
> I'd also like to know what the difference is.

mtu/mru = maximum transmit/receive unit. This is basically the block
size for your TCP/IP packets. If you don't specify something smaller,
default is typically 1500 bytes per block. On a dialup link, large
blocks can cause slowdowns and increased re-transmits if the line is
noisy or collisions or other problems occur. A smaller block size
reduces the likelihood of error, and also the size of the re-transmitted
block.

Of course, under 'ideal' conditions, a larger block size would be more
efficient. Are your conditions guaranteed to be 'ideal?' Mine sure
aren't!
--
Ken

Are you interested in   |
byte-sized education    |    http://www.play-hookey.com
over the Internet?      |

 
 
 

FTP performance with pppd

Post by Tim Ivers » Fri, 09 Aug 1996 04:00:00




|> I have got throughput of about 2700bps using pppd, vs 3100bps using ijppp
|> (with 28.8 modems). Adjusting the mtu/mru values hasn't helped.
|> I'd also like to know what the difference is.
|
|mtu/mru = maximum transmit/receive unit. This is basically the block
|size for your TCP/IP packets. If you don't specify something smaller,
|default is typically 1500 bytes per block. On a dialup link, large
|blocks can cause slowdowns and increased re-transmits if the line is
|noisy or collisions or other problems occur. A smaller block size
|reduces the likelihood of error, and also the size of the re-transmitted

A minor note -- you can't get collisions on a dialup line (full duplex and
point to point) and modem error correction should guarantee a clean line.

In general, a larger MTU will increase throughput on transfer protocols and
increase latency on interactive protocols (vice-versa for smaller MTU).  If
you only use a single network protocol at a time, use 1500.  If you telnet
with ftp in the background, you'll probably want to use something much
smaller (576 is a favorite for many people).

- Tim Iverson

 
 
 

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