PPP Packet Prioritization.

PPP Packet Prioritization.

Post by Drew Einhor » Thu, 10 Aug 1995 04:00:00



I'd like to configure the Linux ppp similarly to the cisco box at the other
end of the link.  

Right now telnet, login, and ntp packets are in the cisco's "high" priority
queue.

Someone suggested that I also have short (length < 200) packets in the "high"
priority queue.  This sounds like it makes sense.  But the limit sounds a kind
of arbitrary.  Would a different number make sense.

I dropped the WWW (http) packets into the "medium" priority queue.

By default everything else is in the "normal" priority queue.  I'm assuming
"normal" is between "medium" and "low".  Haven't done any serious testing to
verify my assumptions yet.

I'm planning on moving ftp to the "low" priority queue.  

/etc/services mentions a lot of port numbers that I am familiar with and quite
a few that I am not.  Am I missing some important service that should be
included in the "high" or "medium" priority queues?

In some cases it is difficult to decide which priority queue to put nntp in.
Sometimes nntp is used to connect to a news reader and the medium priority
queue would be most appropriate.  Other times is used for bulk transmissions
between servers where the low priority queue would be more appropriate.

 
 
 

PPP Packet Prioritization.

Post by Terry Dawso » Tue, 15 Aug 1995 04:00:00



> I'd like to configure the Linux ppp similarly to the cisco box at the other
> end of the link.  

> Right now telnet, login, and ntp packets are in the cisco's "high" priority
> queue.

..

Quote:> /etc/services mentions a lot of port numbers that I am familiar with and quite
> a few that I am not.  Am I missing some important service that should be
> included in the "high" or "medium" priority queues?

I'd consider putting named (53) into a high or medium priority
queue as well. This will ensure that you nameserver lookups don't
suffer too much at the hands of a file transfer.

If you use services like irc, talk or MUD/MOO then you might also
consider putting those in your high priority queue.

Are you actually doing this one your linux machine ? If so, how ?

There was a question here recently from someone complaining that
file transfers were taking control of the link, I am not aware of
any mechanism for prioritising traffic with Linux ppp.

Terry

 
 
 

PPP Packet Prioritization.

Post by Dennis M Mo » Wed, 16 Aug 1995 04:00:00



: >
: > I'd like to configure the Linux ppp similarly to the cisco box at the other
: > end of the link.  
: >
: > Right now telnet, login, and ntp packets are in the cisco's "high" priority
: > queue.
: ...
: Are you actually doing this one your linux machine ? If so, how ?
:
: There was a question here recently from someone complaining that
: file transfers were taking control of the link, I am not aware of
: any mechanism for prioritising traffic with Linux ppp.

To my understanding, the prioritization occurs in the TCP/IP part of
the kernel, not in the ppp module. One of the socket options to
setsockopt() is SO_PRIORITY, which can be set to interactive, normal,
or background.

Unfortunately this only affects *outgoing* packets, i.e.  ones
generated by your own local apps. Incoming packets (like from FTP or
WWW servers) are not affected by this at all. In most cases the
offending FTP/WWW traffic is coming from the remote server because you
are downloading stuff.

The local kernel priority options are only helpful if the congestion
results from outgoing traffic, i.e. large uploads or remote users
downloading stuff from your machine.

If you have have access to the ppp server at the other end of the
link (like the original poster), you can set the priorities as you
desire. This *should* have the desired effect since the remote server
can move the high-priority packets up in its transmit queue.

Cheers,
Dennis

P.S. The setsockopt() man page doesn't mention SO_PRIORITY but you
can find it in /usr/include/linux/socket.h.

---------------------------------------------------------------------------
Dennis Moul                               Department of Information Science

WWW URL: "http://www.pitt.edu/~dmoul/"             University of Pittsburgh
412-521-4795 (h)            412-271-5040 (w)             412-271-7077 (fax)

 
 
 

1. IP packets over PPP hang, but LCP packets continue.

Hello everyone,

I'm having trouble establishing a reliable PPP link with Linux and pppd
2.1. The setup goes ok, and ifconfig, ping, ftp etc. all work, but the
connection stops after several minutes (or packets) for incoming data. I can
see data going out (using the debug log and the modem sd light) but no (IP)
packets coming in.

The problem occurs with two different Internet providers, one running
ppp-2.1, the other I'm not sure about. The strange thing is, LCP echo
requests (from one provider) still come through and are correctly
acknowledged by my pppd process, so it can't be a flow control problem.

A sure way to trigger the problem is starting ping, which doesn't receive
any packets after 70 or so outgoing icmp requests. After that, other pings,
telnets etc. don't work. An important detail might be that on or two
packets before ping stops, it sometimes misses a reply. E.g, it gets
replies to sequence numbers 68, 69, 71, but not 70.

I've tried various asyncmaps and escape sequences, to no avail.  Programs
like seyon, zmodem all work correctly, with no serial problems. My .ppprc
file is as follows:

-----------------------------------------------------------------------------
# This is a chat script.
connect /home/pieter/scripts/wirehub-connect

# kdebug 6
debug

# Use this port
/dev/cua3

# at this speed
38400

# Let the peer determine our ip address or specify it on the command line.
noipdefault

# Add this as the default route for all packets.
defaultroute

# Use hardware flow  control
crtscts

# use/don't use modem control lines
modem

# always let the peer tell you your ip address.
ipcp-accept-local

#
# Escape everything
asyncmap ffffffff
escape ff
-----------------------------------------------------------------------------

Hardware:

486DX33, Vesa bus, 8Mb.
16550A UART
Trust AE1414 external modem (Rockwell chipset).

Software info:

Kernel version is 1.1.91
pppd is 2.1.2b

Please let me know if I should supply more detailed debug logs or
configuration settings,

Many thanks, if anybody knows a solution to this problem,

Pieter

--
Pieter van Prooijen -- AND Software BV, Rotterdam.

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