From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ray Van Dolson Date: Thu, 30 Jun 2005 05:14:24 +0000 Subject: PPP Encapsulated in GRE with IP Precedence headers Message-Id: <20050630051424.GA13477@digitalpath.net> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-ppp@vger.kernel.org Background: We are using Poptop + PPP/MPPE and are running some VoIP applications over this and want to "prioritize" the voice traffic. This is easily done in a non-tunnelled environment because the voice protocol we are using (RTP) sets the "Expedite Immediately" flag in the DSCP headers of the IP packet. Cisco routers and iptables/tc can be made to flag on this and do the "right" thing (ie: prioritize). However, when Poptop encapsulates the PPP frames into GRE, it does not put any sort of DSCP flags in the corresponding GRE IP packets. We are hoping to have Poptop/pptpclient modified to unpack the PPP frame it receives, examine the IP packet within and copy any DSCP flags into the GRE IP packet. Thus if the IP packet in question was RTP, the resulting GRE packet would have the High Precedence DSCP flag set. The question is, does PPP go haywire if packets start arriving out of order as a result of this? Would we end up being worse-off than if we didn't do this at all? I can see how a GRE-only tunnel would handle this just fine, but the added layer of PPP makes me think any sort of re-ordering of the GRE packets would break the PPP connection. Thoughts? Flames? -- Ray Van Dolson Linux/Unix Systems Administrator Digital Path, Inc.