[ax25-layer2] layer 2 hub and switch

[Christensen, Eric H]

I think it is safer to say that a hub equals a digi and a switch equals a
node.  But you have to be real loose with that interpretation but here is
why I say that.

In a hub traffic goes from one point to multipoint and is subject to
collisions.  When a collision occurs the transmitting station must
retransmit that information, not the hub (because the hub is dumb and didn't
listen to see if the packet was a full packet, etc).  Now a node, on the
other hand, actually listens to the packet and determines if it is a full
packet, etc, and will then repeat that packet up the line.  If there is a
collision up the line the node handles it and not the originating station.
You can, hence, get a more reliable network using nodes than digipeaters.

Now a node isn't exactly like a switch.  A switch creates multiple collision
zones so that each user can send data up and the switch will put everyone's
packet in order and forward them up without having a collision.  You can't
do that on one frequency, however.  So a node is more like a smarter hub.  

Did I confuse anyone with that description??? 


73s,
Eric KF4OTN
 
-----Original Message-----
From: ax25-layer2-bounces at lists.tapr.org
[mailto:ax25-layer2-bounces at lists.tapr.org] On Behalf Of Andre PE1RDW
Sent: Wednesday, September 21, 2005 6:53 AM
To: Discussion of Link Layer use of AX.25
Subject: [ax25-layer2] layer 2 hub and switch

In the layer 2 ethernet world we have seen hubs being replaced by switches
to improve throughput.
Would in the layer 2 ax25 world a straight trough digi be the same as a hub
and flexnet type digi be a switch?
After all flexnet digi and hub do the same, they route based on mac address,
the only difference is that flexnet digi won´t act unless it´s mac address
is in the digifield and flexnet does hop to hop acknowledgment.

73 de Andre PE1RDW

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