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[Q] Metric value unit #83

Closed yanosz closed 5 years ago

yanosz commented 5 years ago

Hei folks,

having fun with o11s (great project, btw.) I stumpled up on mpath dump - e.g.

DEST ADDR         NEXT HOP          IFACE       SN      METRIC  QLEN    EXPTIME         DTIM    DRET    FLAGS
a0:f3:c1:74:91:be a0:f3:c1:74:91:be wlan1       4       257     0       3290    100     0       0x15

Metric is supposed explained at "airtime". However, I wasn't able to find further information. What does 257 represent? Is it ett or wcett? Is it ms, time-units, etc.?

I checked https://github.com/o11s/open80211s/wiki/mpath but it didn't contain any details. The howto (https://github.com/o11s/open80211s/wiki/HOWTO) suggests to reach out to http://lists.open80211s.org/cgi-bin/mailman/listinfo/devel - but that site appears to be down.

What is metric showing exactly? Is this tracker the way to ask such a question?

bcopeland commented 5 years ago

On Wed, Sep 04, 2019 at 08:21:05AM -0700, yanosz wrote:

Hei folks,

having fun with o11s (great project, btw.) I stumpled up on mpath dump - e.g.

DEST ADDR         NEXT HOP          IFACE       SN      METRIC  QLEN    EXPTIME         DTIM    DRET    FLAGS
a0:f3:c1:74:91:be a0:f3:c1:74:91:be wlan1       4       257     0       3290    100     0       0x15

Metric is supposed explained at "airtime". However, I wasn't able to find further information. What does 257 represent? Is it ett or wcett? Is it ms, time-units, etc.?

Not sure how to expand those, but I can answer that it is:

1 + 8192 / expected_throughput_mbps

So, if I did the math right, 257 corresponds to 32 Mbps.

Expected throughput is somewhat driver dependent -- some include retransmissions, some do not and expect rate control to do so, so it is difficult to compare it across different kinds of hardware or across kernel versions.

-- Bob Copeland %% https://bobcopeland.com/

chunyeow commented 5 years ago

Can get the details from airtime_link_metric_get at net/mac80211/mesh_hwmp.c.

Or referring to IEEE P802.11-REVmc/D6.0, June 2016 section 14.9 cited as follow: Airtime reflects the amount of channel resources consumed by transmitting the frame over a particular link. This measure is approximate and designed for ease of implementation and interoperability.

Chun-Yeow

On Thu, Sep 5, 2019 at 12:06 AM Bob Copeland notifications@github.com wrote:

On Wed, Sep 04, 2019 at 08:21:05AM -0700, yanosz wrote:

Hei folks,

having fun with o11s (great project, btw.) I stumpled up on mpath dump - e.g.

DEST ADDR NEXT HOP IFACE SN METRIC QLEN EXPTIME DTIM DRET FLAGS
a0:f3:c1:74:91:be a0:f3:c1:74:91:be wlan1 4 257 0 3290 100 0 0x15

Metric is supposed explained at "airtime". However, I wasn't able to find further information. What does 257 represent? Is it ett or wcett? Is it ms, time-units, etc.?

Not sure how to expand those, but I can answer that it is:

1 + 8192 / expected_throughput_mbps

So, if I did the math right, 257 corresponds to 32 Mbps.

Expected throughput is somewhat driver dependent -- some include retransmissions, some do not and expect rate control to do so, so it is difficult to compare it across different kinds of hardware or across kernel versions.

-- Bob Copeland %% https://bobcopeland.com/

— You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub https://github.com/o11s/open80211s/issues/83?email_source=notifications&email_token=AAIF5QRC3LYUCGPRA32F5UTQH7MIHA5CNFSM4ITTIT4KYY3PNVWWK3TUL52HS4DFVREXG43VMVBW63LNMVXHJKTDN5WW2ZLOORPWSZGOD54DDVQ#issuecomment-527970774, or mute the thread https://github.com/notifications/unsubscribe-auth/AAIF5QWVGNJA63AEVYGCXGTQH7MIHANCNFSM4ITTIT4A .

yanosz commented 5 years ago

Thanks for your response - that's fast :).

I tried to update the wiki accordingly. I hope its fine, now