few big monolithic PEs vs many small PEs

i3D.net - Martijn Schmidt martijnschmidt at i3d.net
Wed Jun 19 22:04:05 UTC 2019


Hi Adam,

Depends on how big of a router you need for your "small PE".

Taking Juniper as an example, the MX204 is pretty unbeatable cost wise if you can make do with its 4*QSFP28 & 8*SFP+ interfaces. There's a very big gap between the MX204 and the first chassis based router in the MX lineup, even if you only try to replicate the port configuration at first.

Best regards,
Martijn

PS, take note of the MX204 port profiles, not every combination of interface speeds is possible: https://apps.juniper.net/home/port-checker/

On 19 June 2019 22:22:45 CEST, adamv0025 at netconsultings.com wrote:

Hi folks,

Recently I ran into a peculiar situation where we had to cap couple of PE
even though merely a half of the rather big chassis was populated with
cards, reason being that the central RE/RP was not able to cope with the
combined number of routes/vrfs/bgp sessions/etc..

So this made me think about the best strategy in building out SP-Edge
nowadays (yes I'm aware of the centralize/decentralize pendulum swinging
every couple of years).
The conclusion I came to was that *currently the best approach would be to
use several medium to small(fixed) PEs to replace a big monolithic chasses
based system.
So what I was thinking is,
Yes it will cost a bit more (router is more expensive than a LC)
Will end up with more prefixes in IGP, more BGP sessions etc.. -don't care.
But the benefits are less eggs in one basket, simplified and hence faster
testing in case of specialized PEs and obviously better RP CPU/MEM to port
ratio.
Am I missing anything please?

*currently,
Yes some old chassis systems or even multi-chassis systems used to support
additional RPs and offloading some of the processes (e.g. BGP onto those)
-problem is these are custom hacks and still a single OS which needs
rebooting LC/ASICs when being upgraded -so the problem of too many eggs in
one basket still exists (yes cisco NCS6k and recent ASR9k lightspeed LCs are
an exception)
And yes there is the "node-slicing" approach from Juniper where one can
offload CP onto multiple x86 servers and assign LCs to each server (virtual
node) - which would solve my chassis full problem -but honestly how many of
you are running such setup? Exactly. And that's why I'd be hesitant to
deploy this solution in production just yet. I don't know of any other
vendor solution like this one, but who knows maybe in 5 years this is going
to be the new standard. Anyways I need a solution/strategy for the next 3-5
years.


Would like to hear what are your thoughts on this conundrum.

adam

netconsultings.com
::carrier-class solutions for the telecommunications industry::



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