Kitz ADSL Broadband Information
adsl spacer  
Support this site
Home Broadband ISPs Tech Routers Wiki Forum
 
     
   Compare ISP   Rate your ISP
   Glossary   Glossary
 
Please login or register.

Login with username, password and session length
Advanced search  

News:

Pages: 1 ... 3 4 [5]

Author Topic: Is it possible to force on interleaving (upstream) on a VDSL modem in the UK?  (Read 6955 times)

Weaver

  • Senior Kitizen
  • ******
  • Posts: 11459
  • Retd s/w dev; A&A; 4x7km ADSL2 lines; Firebrick

An example of a flow is a TCP connection. A flow is a set of related packets that form part of a conversation. UDP based application layer protocols can be examples of flows where many packets share the same source and destination addresses. In IPv6 there is a header field that is supposed to identify particular flows. However when the standard was released, the suggested correct usage of the flow field was very poorly defined so it has never been used much. There has been some guidance since then. One suggestion is to take source and destination address and ports, if TCP, and the IP protocol number, then take that 5-tuple and hash it all down to n bits, and the result would be your flow id. In the case of the IPv6 flow header iirc n is 20 bits, and if the result is zero then we make it 1, as zero means ‘unused’. Supposedly routers could possibly use this flow id to help with the routing process.

However routers and firewalls might have a firewall id that is any number of bits wide; it could be an index into a table, or an address. Just comparing two calculated or explicitly declared flow ids to see if two packets belong to the same flow (conversation) would be quicker than comparing all the address and port fields (if TCP), and if it’s the same flow then the latest packet would suffer the same fate as the previous one, being blocked or let through, or NATed.

It’s been a long time since I thought about this so I hope that my memory has not failed me.
« Last Edit: May 23, 2022, 01:14:08 PM by Weaver »
Logged

Alex Atkin UK

  • Addicted Kitizen
  • *****
  • Posts: 5261
    • Thinkbroadband Quality Monitors

So a flow would be similar to a NAT state?
Logged
Broadband: Zen Full Fibre 900 + Three 5G Routers: pfSense (Intel N100) + Huawei CPE Pro 2 H122-373 WiFi: Zyxel NWA210AX
Switches: Netgear MS510TXUP, Netgear MS510TXPP, Netgear GS110EMX My Broadband History & Ping Monitors

Weaver

  • Senior Kitizen
  • ******
  • Posts: 11459
  • Retd s/w dev; A&A; 4x7km ADSL2 lines; Firebrick

No. If you’re a NAT translator you might associate the two concepts though. Flows are more general and don’t presume the existence of any NAT. A firewall using flows and hashing might just find this a faster way of doing lookup for the rule it needs to use. I haven’t heard th4 term used in conjunction with NAT; that was just my own deduction.
Logged

Alex Atkin UK

  • Addicted Kitizen
  • *****
  • Posts: 5261
    • Thinkbroadband Quality Monitors

That's pretty much what I meant, that they are similar and might tie into each other on a router in some way as they're both working on the packet filtering layer.
Logged
Broadband: Zen Full Fibre 900 + Three 5G Routers: pfSense (Intel N100) + Huawei CPE Pro 2 H122-373 WiFi: Zyxel NWA210AX
Switches: Netgear MS510TXUP, Netgear MS510TXPP, Netgear GS110EMX My Broadband History & Ping Monitors

cbdeakin

  • Reg Member
  • ***
  • Posts: 101

I've had to keep retuning my SQM settings, as the VDSL2 line packet loss /line stability seems to fluctuate over days/ weeks. The 'Link Layer Adaption' option has made this process generally quicker.

I'm wondering how much of this is to do with the line being aluminium, and how much of it is just problems with VDSL2 related noise (including crosstalk) in general... I've found that resetting the VDSL2 modem could sometimes increase the amount of packet loss reported, then the settings needed adjusting once more. I suppose it's possible that the line has just gotten worse over time.
« Last Edit: May 21, 2022, 10:42:04 PM by cbdeakin »
Logged
Aluminium line. ECI cabinet. Fun times.

Chrysalis

  • Content Team
  • Addicted Kitizen
  • *
  • Posts: 7382
  • VM Gig1 - AAISP L2TP

If you got packet loss due to the broadband tech such as errors on a DSL line, traffic shaping wont do anything for the packet loss.

If you got packet loss due to local congestion, basically high utilisation on your line, thats when it "may" help.

VDSL in this country is a "up to" service, so potentially rebooting the modem could make symptoms worse if it syncs at a lower speed meaning easier to hit congestion conditions.  But in most cases unless the conditions of the line have changed significantly or its DLM slowing things down, then fluctuations between resync's should be minimal.
Logged

cbdeakin

  • Reg Member
  • ***
  • Posts: 101

It looks like Openreach have done something to my line, or maybe the local BT exchange (maybe in the last week?), because I don't seem to need SQM anymore to reduce the packet loss on my line (with the 'flows' command). I disabled it completely and the line reported 0% packet loss on Mlab's test and very small amounts of loss when streaming in Stadia (these seem to correspond with bursts of streaming traffic from other devices).

I'm currently limiting download speed via a smart switch to 40mbps to keep the latency relatively low when the line is under heavy use, and it's working well  :)
« Last Edit: June 04, 2022, 03:15:43 AM by cbdeakin »
Logged
Aluminium line. ECI cabinet. Fun times.

cbdeakin

  • Reg Member
  • ***
  • Posts: 101

I'm not sure if this will help anyone else, but configuring the SQM latency like this has solved my packet loss problems on a FTTC aluminium line:



The 'latency target' options seem to do much the same thing as the two options below them, but they are much easier to configure and optimise. Curiously, the latency Stadia / other game streaming services doesn't seem to be affected with the above settings (latency reported in Stadia was between 10 - 35ms, depending on bandwidth usage). I've tested it for a couple of months now with these settings.

The problem with many routers, is that they don't have an SQM option, nor configurable options like what you get on a router with OpenWRT installed on it. I had to use the 'simplest_tbf.qos' Queue setup script for these configurable options to work properly, combined with a small bandwidth limit on the downstream and upstream.

The impression I get is that many routers by default automatically drop a certain percentage of WAN packets over a certain latency, perhaps 40-50ms.
« Last Edit: July 26, 2022, 02:14:57 AM by cbdeakin »
Logged
Aluminium line. ECI cabinet. Fun times.
Pages: 1 ... 3 4 [5]