[j-nsp] Juniper route age reset behavior

[Niall Donaghy]

Hello Magnus,

I would also prefer the old behaviour was retained as default, and that a configuration knob was provided to enable the new behaviour.

My arguments to Juniper would be:

	- It should be a low-cost effort to make the code change so that TWO timers are kept, as the code already exists. Increased RAM utilisation ought to be slight.

	- It should be fairly trivial to include a configuration knob to select the behaviour you want; ideally the default is the old behaviour, but either way achieves the same goal.

	- BGP route age timer should reflect changes in the eBGP route advertisement, because:
		- Changes in your internal network which affect BGP route selection or next hop interface are a holistic function of your router's internal routing.
		- The BGP route's age is, intuitively, the age since the route was received from the eBGP speaker, ie: RIB-In, not inet.0 (or whichever table).

	- Why not give the best of both? Retain two route age timers and display both in the CLI. 

We haven't found this change in behaviour to adversely affect us in GEANT, but have the view that having both timers would be ideal.

Best regards,
Niall


Niall Donaghy
Senior Network Engineer
GÉANT
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-----Original Message-----
From: juniper-nsp [mailto:juniper-nsp-bounces at puck.nether.net] On Behalf Of Magnus Bergroth
Sent: 26 January 2018 11:45
To: juniper-nsp <juniper-nsp at puck.nether.net>
Subject: [j-nsp] Juniper route age reset behavior

Hi

We have seen a change in how junos handles age in command "show route".
In Junos 15.1R bgp routes age told you how long the route had been present in the routing table. If you have a dual homed customer bgp age timer showed how long time ago the customer advertised the route. Very practical to see how stable the customer connection has been.

In 15.F and new releases this has been changed so that any change to the route will reset the age time. If a route goes from inactive to active "route age" gets reset. If your igp changes so the outgoing interface changes the "route age" gets reset.

We been trying to get juniper to change back the behavior but Juniper engineering thinks it's now working as it should.

We haven't been able to find any RFC the describes route age. The only argument towards Juniper that we have is that they are changing default behavior.

Are there any one else that has seen this new "route age" behavior and have any open cases with Juniper, or have any good argument that we can throw at Juniper?


Kindly

Magnus Bergroth
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