[B.A.T.M.A.N.] How is the metric calculated and interpreted?

[B.A.T.M.A.N.] How is the metric calculated and interpreted?

[Sutter Nino]

Hello there

I have some basic Issues which I was not able to solve with the Wiki.

How is the metric (?/255) calculated?

Concerning the output of  "batctl o" below, how can I interpret the following? 
-What is the meaning when the originator is the same as the next hop (Line 1)?
-Is that correct that the originator car 29 will send all packets to car20 directly without a node in-between (Line 2)?
-How can the potential nexthops be interpreted?

[B.A.T.M.A.N. adv 2015.1, MainIF/MAC: adhoc0/c4:93:00:02:d1:4f (bat0 BATMAN_IV)]
  Originator      last-seen (#/255)           Nexthop [outgoingIF]:   Potential nexthops ...
car23                     0.300s (255)                        car23 [ wlan0]: car35 ( 0) car24 ( 0) car31 (103) car21 (183) car36 ( 68) car20 (178) car23 (255) 
car29                     0.864s (175)                        car20 [ wlan0]: car23 ( 0) car36 ( 0) car31 ( 0) car35 ( 0) car21 ( 0) car24 ( 0) car20 (175) car29 ( 0)

Thank you for your answers

Regards 
Nino

Re: [B.A.T.M.A.N.] How is the metric calculated and interpreted?

[Sven Eckelmann]

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> How is the metric (?/255) calculated?

Puh, please read the section 3.1 of "Inter-Flow Network Coding for
Wireless Mesh Networks" to get the basic concept. Details about the
TQ calculations can be found in the source code [2].

> Concerning the output of  "batctl o" below, how can I interpret the following? 
> -What is the meaning when the originator is the same as the next hop (Line 1)?

The best next hop to the originator was detected to be the originator itself.
So this noed doesn't have to transmit packets to this originator via a
different direct neighbor.

> -Is that correct that the originator car 29 will send all packets to car20 directly without a node in-between (Line 2)?
[...]
> car29                     0.864s (175)                        car20 [ wlan0]: car23 ( 0) car36 ( 0) car31 ( 0) car35 ( 0) car21 ( 0) car24 ( 0) car20 (175) car29 ( 0)

No, this node only knows its own view of the network (next hop to
destinations). It knows nearly nothing about what car29 learned about
the network.

But this node knows that the "best way" to reach car29 from his position is to
send packets via its neighbor car20.

> -How can the potential nexthops be interpreted?

These are just ways to reach this originator + the calculated TQ when sending
over this originator/neighbor.


This was a little bit simplified but should give you a starting point.

Kind regarding,
	Sven


[1] https://downloads.open-mesh.org/batman/papers/batman-adv_network_coding.pdf
[2] https://git.open-mesh.org/batman-adv.git/blob/789b846af6a9471982b181687a1cba8dc996b269:/net/batman-adv/bat_iv_ogm.c#l1119

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