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 Post subject: [RFC] dynamips auto speed/duplex/link + physical layer stuff
PostPosted: Tue Apr 15, 2014 1:13 pm 

Joined: Wed May 22, 2013 7:48 am
Posts: 93
Location: Portugal
As the title states, this is a "Request For Comments" on how to handle auto speed/duplex/link and other physical layer stuff.
dynamips doesn't emulate the physical layer and currently uses hard-coded values for all physical layer stuff.


I have been slowly pondering about the duplex issue (topic8276.html) and the link up/down issue ( and I finally settled on a flexible approach that can handle these and more.

* hypervisor command to get the capabilities of a nio (gets other properties/optional capabilities too?)
* hypervisor command to set the link partner capabilities of a nio (sets default/startup behavior too?)
* use JSON for the data of the hypervisor commands?
* by default a network card would report that auto-negotiation failed, the defaults and IOS decide what is 'used' (new behavior)
* if the capabilities of the link partner are provided, it will report auto-negotiation as successful and choose the best match (new behavior)
* other optional behaviors can be used. (reported and set through the same hypervisor commands?)

Optional behaviors being considered:
* link down if no packet received after X time
* while link is (administratively) up, send an empty keepalive packet if nothing is sent after Y time
* send and intercept information in some protocol to do auto-negotiation, report link up/down and other physical layer stuff (SNMP with custom MIBs? LLDP? what encapsulation?)
* while auto-negotiation is enabled, report auto-negotiation as successful, intercept CDP packets and self-adjust? (what happens when connected to a hub/repeater with multiple routers?)

What use cases were considered:
* a dynamips device and a non-dynamips device connected
* two devices of the same dynamips instance connected
* two devices in separate dynamips instances connected
* the default duplex+speed of a non-dynamips device is known
* the default duplex+speed of a non-dynamips device is not known
* link types (ethernet and serial use different encapsulation)

How would GNS3/dynagen use it:
* create the two nio endpoints of a link (already being done)
* connect the two nio endpoints (already being done)
* get the capabilities of each nio and set it as the link parter capabilities in the other nio (also send custom defaults and enable/disable optional behaviors) (can be done whenever and how many times we want after the nio is created)

Dynamips maintainer and sporadic developer

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