[Cake] overhead for double nat VDSL2 connection

Mark Captur mark.captur at gmail.com
Sun Dec 17 05:45:27 EST 2017


My setup is as follows

vdsl2 modem doing pppoe itself and nat to 10.x.x.x -> lede master eth0.2
(wan static ip in modem's DMZ) eth0.1 (lan) doing nat to 192.168.1.x

Here is my current SQM config

config queue 'eth1'
        option debug_logging '0'
        option verbosity '5'
        option qdisc 'cake'
        option qdisc_advanced '1'
        option ingress_ecn 'ECN'
        option egress_ecn 'NOECN'
        option qdisc_really_really_advanced '1'
        option script 'layer_cake.qos'
        option interface 'eth0.2'
        option enabled '1'
        option eqdisc_opts 'nat rtt 50000 bridged-ptm dual-srchost
diffserv4'
        option upload '2400'
        option linklayer 'ethernet'
        option overhead '8'
        option squash_dscp '1'
        option squash_ingress '1'
        option iqdisc_opts 'nat rtt 50000 bridged-ptm dual-dsthost'
        option download '0'

config queue
        option debug_logging '0'
        option verbosity '5'
        option download '0'
        option qdisc 'cake'
        option script 'layer_cake.qos'
        option qdisc_advanced '1'
        option squash_dscp '0'
        option squash_ingress '0'
        option ingress_ecn 'ECN'
        option qdisc_really_really_advanced '1'
        option egress_ecn 'ECN'
        option interface 'eth0.1'
        option enabled '1'
        option eqdisc_opts 'nat rtt 50000 bridged-ptm dual-dsthost
diffserv4'
        option upload '30000'
        option linklayer 'ethernet'
        option overhead '8'


Is the overhead correct? should i use the bridged-ptm keyword (or should i
use pppoe-ptm). I tried using ATM_overhead_detector and get the following
output

869001 lines parsed...
Found 144921 ping packets in
/home/mark/src/ATM_overhead_detector/ping_sweep__20171217_075202.txt
Elapsed time is 972.739 seconds.
Minimum size of ping payload used: 16 bytes.
warning: division by zero
warning: called from
    ATM_overhead_detector at line 201 column 15
warning: legend: ignoring extra labels
Unknown or ambiguous terminal name 'wxt'
Unknown or ambiguous terminal name 'wxt'
Saved figure (5) to:
/home/mark/src/ATM_overhead_detector/ping_sweep__20171217_075202_data.png
lower bound estimate for one ATM cell RTT based of specified up and
downlink is 0.052419 ms.
estimate for one ATM cell RTT based on linear fit of the ping sweep data is
0.052419 ms.
Starting brute-force search for optimal stair fit, might take a while...
Unknown or ambiguous terminal name 'wxt'
Unknown or ambiguous terminal name 'wxt'
Best staircase fit cumulative difference is: 2.6952
Best linear fit cumulative difference is: 2.7314
Quantized ATM carrier LIKELY (cummulative residual: stair fit 2.6952 linear
fit 2.7314
remaining ATM cell length after ICMP header is 5 bytes.
ICMP RTT of a single ATM cell is 0.05871 ms.

Estimated overhead preceding the IP header: 48 bytes
Saved figure (6) to:
/home/mark/src/ATM_overhead_detector/ping_sweep__20171217_075202_results.png

According to http://ace-host.stuart.id.au/russell/files/tc/tc-atm/
48 bytes overhead indicate
Overhead of 0 bytes is not possible so assume 1 full packet (48 bytes)
overhead...
Connection: Bridged, LLC/SNAP+FCS RFC-1483/2684 + VLAN tag terminated at
modem
Protocol (bytes): Ethernet Header (14), VLAN tag (4), Ethernet PAD [8] (0),
Ethernet Checksum (4), ATM LLC (3), ATM SNAP (5), ATM pad (2), ATM AAL5 SAR
(8) : Total 36

Add the following to both the egress root qdisc:
A) Assuming the router connects over ethernet to the DSL-modem:
stab mtu 2048 tsize 128 overhead 48 linklayer atm

Add the following to both the ingress root qdisc:

A) Assuming the router connects over ethernet to the DSL-modem:
stab mtu 2048 tsize 128 overhead 48 linklayer atm

Elapsed time is 1042.06 seconds.
Done...
ans = [](0x0)



Could my VDSL2 be using ATM? so i have the wrong overhead set?

here is my tc -s qdisc output

root at OpenWrt-Mi3G:~# tc -s qdisc
qdisc noqueue 0: dev lo root refcnt 2
 Sent 0 bytes 0 pkts (dropped 0, overlimits 0)
qdisc fq_codel 0: dev eth0 root refcnt 2 limit 10240p flows 1024 quantum
1514 target 5.0ms interval 100.0ms memory_limit 4Mb ecn
 Sent 3460986864 bytes 3651814 pkts (dropped 0, overlimits 0)
  maxpacket 17032 drop_overlimit 0 new_flow_count 29673 ecn_mark 0
  new_flows_len 0 old_flows_len 0
qdisc noqueue 0: dev br-lan root refcnt 2
 Sent 0 bytes 0 pkts (dropped 0, overlimits 0)
qdisc cake 8055: dev eth0.1 root refcnt 2 bandwidth 30Mbit diffserv4
dual-dsthost nat rtt 50.0ms ptm overhead 22 via-ethernet total_overhead 22
hard_header_len 14
 Sent 20012069 bytes 35472 pkt (dropped 10, overlimits 7587 requeues 0)
 backlog 0b 0p requeues 0
 memory used: 36684b of 4Mb
 capacity estimate: 30Mbit
                   Bulk  Best Effort        Video        Voice
  thresh       1875Kbit       30Mbit       15Mbit     7500Kbit
  target          9.7ms        2.5ms        2.5ms        2.5ms
  interval       57.2ms       50.0ms       50.0ms       50.0ms
  pk_delay          0us        5.6ms        855us         15us
  av_delay          0us        436us         28us         10us
  sp_delay          0us         27us          8us          6us
  pkts                0        33679          457         1346
  bytes               0     19869595        80517        69940
  way_inds            0          249            0            0
  way_miss            0         3099           19            7
  way_cols            0            0            0            0
  drops               0           10            0            0
  marks               0            0            0            0
  ack_drop            0            0            0            0
  sp_flows            0            1            1            0
  bk_flows            0            1            0            0
  un_flows            0            0            0            0
  max_len             0         7064         2982          350

qdisc cake 8053: dev eth0.2 root refcnt 2 bandwidth 2400Kbit diffserv4
dual-srchost nat rtt 50.0ms ptm overhead 22 via-ethernet total_overhead 22
hard_header_len 14
 Sent 23218772 bytes 35904 pkt (dropped 205, overlimits 27550 requeues 0)
 backlog 0b 0p requeues 0
 memory used: 94752b of 4Mb
 capacity estimate: 2400Kbit
                   Bulk  Best Effort        Video        Voice
  thresh        150Kbit     2400Kbit     1200Kbit      600Kbit
  target        121.1ms        7.6ms       15.1ms       30.3ms
  interval      242.2ms       55.1ms       62.6ms       77.8ms
  pk_delay          0us       29.5ms         19us        4.4ms
  av_delay          0us        3.8ms          1us        2.3ms
  sp_delay          0us         50us          1us          9us
  pkts                0        34979           31         1099
  bytes               0     23342354         2930       162457
  way_inds            0          177            0            0
  way_miss            0         2003           27           16
  way_cols            0            0            0            0
  drops               0          205            0            0
  marks               0            0            0            0
  ack_drop            0            0            0            0
  sp_flows            0            1            0            0
  bk_flows            0            1            0            0
  un_flows            0            0            0            0
  max_len             0         8342           98          598

qdisc noqueue 0: dev wlan1 root refcnt 2
 Sent 0 bytes 0 pkts (dropped 0, overlimits 0)
qdisc noqueue 0: dev wlan0 root refcnt 2
 Sent 0 bytes 0 pkts (dropped 0, overlimits 0)
qdisc fq_codel 0: dev tun0 root refcnt 2 limit 10240p flows 1024 quantum
1500 target 5.0ms interval 100.0ms memory_limit 4Mb ecn
 Sent 304 bytes 4 pkts (dropped 0, overlimits 0)
  maxpacket 0 drop_overlimit 0 new_flow_count 0 ecn_mark 0
  new_flows_len 0 old_flows_len 0


Thanks,
Mark
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