[j-nsp] Junos BNG PPPoE inside a VPLS

[Caillin Bathern]

ET> It's not that bad comparing to IPoE model. At least you got PPP
keepalives, so it won't take a long time for a CPE to re-establish
internet connectivity through terminating existing session and creating a
new one. As I recall, In IPoE scenario CPE will keep existing session up
for 75% of dhcp lease time configured which could take some time unless
your CPE supports ARP ping. Anybody knows if Juniper MX/E support this
feature? 

CB> DHCP leases can be quite short still, 5 min or less if your router/DHCP server can support it.  Some BNGs can also split-lease DHCP (not sure if Juniper can do this, anybody?) where the BNG maintains a short lease with the client but only relays a long lease (1 day etc) to the main DHCP server reducing the resource requirements of the servers.

ET> Nice feature. As far as I understand you can't achieve load sharing
using it, right? You've got single master for existing VRRP group and
master handles 
PADO replies, so when backup BNG takes over it would consider *every*
session unknown. Is my understanding correct?

CB>  Yes when the backup BNG takes over it does consider every session unknown and sends a PADT to kill the session immediately on the CPE so it is quite fast to failover.  You can also achieve load balancing by running multiple VRRP groups on each interface and tying some subinterfaces/vlan/vlan-ranges to each group.

ET> Since we're using the juniper mail list it's worth mentioning the
Virtual-chassis feature of JUNOS which is kinda nice I believe (didn't use
it though). 

CB>  I agree with you that Juniper VC on the MX is a fantastic feature and the stateful session failover is great but I would still like to see a last-line-of-defence in case a software bug or ISSU failure brings down the entire VC in one hit. 
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