[Make-wifi-fast] Make - fast - wifi project plan review from 2014....
Bob McMahon
bob.mcmahon at broadcom.com
Sat Sep 19 03:33:12 EDT 2020
On the tools, iperf 2.0.14 is going through a lot of development. My hope
is to have the code done soon so it can be tested internally at Broadcom.
We're testing with WiFi , to 100G NICs and thousands of parallel threads.
I've been able to find time for this refactoring per COVID-19 stay at home
work.
What I think the industry should move to is measuring both throughput and
latency in a direct manner. 2.0.14 also supports full duplex traffic (as
well as --reverse) TCP server output shows the following (these are 10G
NICs)
[rjmcmahon at localhost iperf2-code]$ src/iperf -s -i 1
------------------------------------------------------------
Server listening on TCP port 5001
TCP window size: 128 KByte (default)
------------------------------------------------------------
[ 4] local 192.168.1.10%enp2s0 port 5001 connected with 192.168.1.80 port
47420 (trip-times) (MSS=1448) (peer 2.0.14-alpha)
[ ID] Interval Transfer Bandwidth Reads Dist(bin=16.0K)
Burst Latency avg/min/max/stdev (cnt/size) inP NetPwr
[ 4] 0.00-1.00 sec 1.09 GBytes 9.34 Gbits/sec 18733
2469:2552:2753:2456:2230:2272:1859:2142 2.988/ 0.971/ 3.668/ 0.370 ms
(8908/131072) 3.34 MByte 390759.84
[ 4] 1.00-2.00 sec 1.10 GBytes 9.42 Gbits/sec 19844
2690:2984:3211:2858:2255:2039:1893:1914 3.000/ 2.320/ 3.704/ 0.346 ms
(8979/131073) 3.37 MByte 392263.52
[ 4] 2.00-3.00 sec 1.10 GBytes 9.41 Gbits/sec 18897
2458:2668:2764:2412:2216:2300:2019:2060 3.003/ 2.310/ 3.665/ 0.347 ms
(8978/131070) 3.37 MByte 391878.92
[ 4] 3.00-4.00 sec 1.10 GBytes 9.42 Gbits/sec 18389
2339:2542:2443:2268:2211:2232:2144:2210 3.009/ 2.315/ 3.659/ 0.347 ms
(8979/131073) 3.38 MByte 391101.00
[ 4] 4.00-5.00 sec 1.10 GBytes 9.41 Gbits/sec 19468
2588:2889:3017:2623:2250:2221:1947:1933 2.971/ 2.259/ 3.671/ 0.364 ms
(8979/131069) 3.33 MByte 396075.85
[ 4] 5.00-6.00 sec 1.10 GBytes 9.41 Gbits/sec 18547
2357:2596:2582:2344:2170:2192:2104:2202 2.971/ 2.276/ 3.699/ 0.365 ms
(8978/131072) 3.34 MByte 396149.20
[ 4] 6.00-7.00 sec 1.10 GBytes 9.42 Gbits/sec 18479
2363:2598:2430:2332:2234:2184:2155:2183 2.976/ 2.279/ 3.667/ 0.363 ms
(8978/131084) 3.34 MByte 395486.89
[ 4] 7.00-8.00 sec 1.10 GBytes 9.42 Gbits/sec 18506
2387:2549:2519:2339:2229:2183:2060:2240 2.971/ 2.266/ 3.667/ 0.365 ms
(8979/131071) 3.33 MByte 396155.84
[ 4] 8.00-9.00 sec 1.10 GBytes 9.41 Gbits/sec 18732
2398:2640:2750:2352:2113:2286:2030:2163 2.973/ 2.271/ 3.691/ 0.364 ms
(8979/131059) 3.34 MByte 395780.90
[ 4] 9.00-10.00 sec 1.10 GBytes 9.41 Gbits/sec 19585
2659:2901:3073:2619:2285:2221:1854:1973 2.976/ 2.264/ 3.666/ 0.361 ms
(8978/131081) 3.34 MByte 395467.57
[ 4] 10.00-10.00 sec 3.17 MBytes 9.51 Gbits/sec 51 0:6:20:0:0:19:6:0
3.112/ 2.410/ 3.609/ 0.406 ms (26/127692) 2.92 MByte 381912.79
[ 4] 0.00-10.00 sec 11.0 GBytes 9.41 Gbits/sec 189231
24708:26925:27562:24603:22193:22149:20071:21020 2.983/ 0.971/ 3.704/
0.360 ms (89741/131072) 3.35 MByte 394144.05
Some bidir output looks like:
[rjmcmahon at localhost iperf2-code]$ src/iperf -c 192.168.1.10 --trip-times
--bidir
------------------------------------------------------------
Client connecting to 192.168.1.10, TCP port 5001 with pid 4322 (1 flows)
Write buffer size: 128 KByte
TCP window size: 85.0 KByte (default)
------------------------------------------------------------
[ 3] local 192.168.1.80%enp2s0 port 47928 connected with 192.168.1.10 port
5001 (bidir) (trip-times) (MSS=1448) (ct=0.37 ms)
[ ID] Interval Transfer Bandwidth Write/Err Rtry
Cwnd/RTT NetPwr
[ 3] 0.00-10.00 sec 10.9 GBytes 9.35 Gbits/sec 89183/0 0
3021K/2079 us 562251.48
[ ID] Interval Transfer Bandwidth Reads Dist(bin=16.0K)
Burst Latency avg/min/max/stdev (cnt/size) inP NetPwr
[ 3] 0.00-10.00 sec 10.9 GBytes 9.39 Gbits/sec 174319
21097:23110:24661:21619:18723:17600:13153:34356 2.664/ 1.045/ 6.521/
0.235 ms (89550/131072) 2.98 MByte 440455.93
[ ID] Interval Transfer Bandwidth
[FD3] 0.00-10.00 sec 21.8 GBytes 18.7 Gbits/sec
Man page notes:
NOTES
Numeric options: Some numeric options support format characters per
'<value>c' (e.g. 10M) where the c format characters are k,m,g,K,M,G.
Lowercase format characters are 10^3 based and uppercase are 2^n based,
e.g. 1k = 1000, 1K = 1024, 1m =
1,000,000 and 1M = 1,048,576
Rate limiting: The -b option supports read and write rate limiting
at the application level. The -b option on the client also supports
variable offered loads through the <mean>,<standard deviation> format, e.g.
-b 100m,10m. The distribution used
is log normal. Similar for the isochronous option. The -b on the
server rate limits the reads. Socket based pacing is also supported using
the --fq-rate long option. This will work with the --reverse and --bidir
options as well.
Synchronized clocks: The --trip-times option indicates that the
client's and server's clocks are synchronized to a common reference.
Network Time Protocol (NTP) or Precision Time Protocol (PTP) are commonly
used for this. The reference clock(s)
error and the synchronization protocols will affect the accuracy of
any end to end latency measurements.
Binding is done at the logical level (ip address or layer 3) using
the -B option and at the device (or layer 2) level using the percent (%)
separator for both the client and tne server. On the client, the -B option
affects the bind(2) system call,
and will set the source ip address and the source port, e.g. iperf
-c <host> -B 192.168.100.2:6002. This controls the packet's source values
but not routing. These can be confusing in that a route or device lookup
may not be that of the device
with the configured source IP. So, for example, if the IP address
of eth0 is used for -B and the routing table for the destination IP address
resolves the output interface to be eth1, then the host will send the
packet out device eth1 while using
the source IP address of eth0 in the packet. To affect the physical
output interface (e.g. dual homed systems) either use -c <host>%<dev>
(requires root) which bypasses this host route table lookup, or configure
policy routing per each -B source
address and set the output interface appropriately in the policy
routes. On the server or receive, only packets destined to -B IP address
will be received. It's also useful for multicast. For example, iperf -s -B
224.0.0.1%eth0 will only accept ip
multicast packets with dest ip 224.0.0.1 that are received on the
eth0 interface, while iperf -s -B 224.0.0.1 will receive those packets on
any interface, Finally, the device specifier is required for v6 link-local,
e.g. -c [v6addr]%<dev> -V, to
select the output interface.
Reverse and bidirectional traffic: The --reverse (-R) and --bidir
options can be confusing when compared to the legacy options of -r and -d.
It's suggested to use --reverse if you want to test through a NAT firewall
(or -R on non-windows systems).
This applies role reversal of the test after opening the full duplex
socket. The latter two of -d and -r remain supported for legacy support and
compatibility reasons. These open new sockets in the opposite direction
vs treat the originating
socket as full duplex. Firewall piercing is typically required to
use -d and -r if a NAT gateway is in the path. That's part of the reason
it's highly encouraged to use the newer --reverse and --bidir and deprecate
the use of the -r and -d options.
Also, the --reverse -b <rate> setting behaves differently for TCP
and UDP. For TCP it will rate limit the read side, i.e. the iperf client
(role reversed to act as a server) reading from the full duplex socket.
This will in turn flow control the
reverse traffic per standard TCP congestion control. The --reverse
-b <rate> will be applied on transmit (i.e. the server role reversed to act
as a client) for UDP since there is no flow control with UDP. There is no
option to directly rate limit
the writes with TCP testing when using --reverse.
TCP Connect times: The TCP connect time (or three way handshake)
can be seen on the iperf client when the -e (--enhancedreports) option is
set. Look for the ct=<value> in the connected message, e.g.in '[ 3] local
192.168.1.4 port 48736 connected
with 192.168.1.1 port 5001 (ct=1.84 ms)' shows the 3WHS took 1.84
milliseconds.
Little's Law in queueing theory is a theorem that determines the
average number of items (L) in a stationary queuing system based on the
average waiting time (W) of an item within a system and the average number
of items arriving at the system per
unit of time (lambda). Mathematically, it's L = lambda * W. As used
here, the units are bytes. The arrival rate is taken from the writes.
Network power: The network power (NetPwr) metric is experimental.
It's a convenience function defined as throughput/delay. For TCP
transmits, the delay is the sampled RTT times. For TCP receives, the delay
is the write to read latency. For UDP
the delay is the end/end latency. Don't confuse this with the
physics definition of power (delta energy/delta time) but more of a measure
of a desirable property divided by an undesirable property. Also note, one
must use -i interval with TCP to
get this as that's what sets the RTT sampling rate. The metric is
scaled to assist with human readability.
Fast Sampling: Use ./configure --enable-fastsampling and then
compile from source to enable four digit (e.g. 1.0000) precision in
reports' timestamps. Useful for sub-millisecond sampling.
Bob
On Fri, Sep 18, 2020 at 9:05 AM Dave Taht <dave.taht at gmail.com> wrote:
> I recently had cause to go review the original make-wifi-fast project
> plan (
> https://docs.google.com/document/d/1Se36svYE1Uzpppe1HWnEyat_sAGghB3kE285LElJBW4/edit
> )
>
> (and related presentation:
> https://www.youtube.com/watch?v=Rb-UnHDw02o&t=25m30s had the fun bit)
>
> I'm glad that since that time ATF and mesh networking became
> realities, fq_codel and per station queuing gained support in various
> products, and AQL started to work on ath10k, but I'm pretty sure
> things in that document like rate and power aware scheduling
> (minstrel-bluse), excessive counter based hw retries, and other
> problems we identified back then are still problems, not to mention
> the recent ofdma work....
>
> I have been observing pretty bad behavior with a lot of 802.11ac
> access points around, (recently one that
> went 4Mbits over 40 feet through glass outdoors, but 600 indoors and
> 10 feet) but have nothing but guesses as to the causes. Infinite
> retries? Everything on 160 mhz wide channels?
>
> Has there been any good news or good tools lately?
>
> I pulled my ax200s out of the box and was going to see if there was
> any progress there.
>
> --
> "For a successful technology, reality must take precedence over public
> relations, for Mother Nature cannot be fooled" - Richard Feynman
>
> dave at taht.net <Dave Täht> CTO, TekLibre, LLC Tel: 1-831-435-0729
> _______________________________________________
> Make-wifi-fast mailing list
> Make-wifi-fast at lists.bufferbloat.net
> https://lists.bufferbloat.net/listinfo/make-wifi-fast
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