[j-nsp] SRGB Allocation

[Andrew Alston]

(Apologies if this appears twice, seems my subscription wasn't right the first time!)

Hi Antti,

Sorry for starting a new thread - I wasn't actually subscribed and your email querying about SRGB allocation was brought to my attention by one of your friendly Juniper Ambassadors, so hopped on to give you my thoughts.

So - With regards to the SRGB Label Range - there are a number of things you need to ask yourself before you go down this road

Firstly - is this a multi-vendor network or a single vendor-network.  This is very important - because there is at least one vendor out there who does not support an SRGB range that ends in > 256k - and if you get it wrong you end up with issues trying to fix it.

Secondly - my advice is to make your SRGB range as wide as possible to avoid problems down the line.  We use a 64k label range which we then break up into fixed blocks per geographic location across the 15 odd countries we operate in.
We are currently using 195000 going up - which leaves us still compatible with the Huawei gear.

This however carries another caveat - if you look at devices like the Cisco ASR920 they only support a much more limited SRGB range - last I checked and unless its changed, its limited to something like 16k labels, so you gotta consider that as well.

Rolling this out - we set the label range on each router - and then did rolling reboots to bring it inline - theoretically the routers can move stuff around to free up the labels - practically speaking that doesn’t work 2 well, so a restart was the best option we had.

Hope this helps - please let me know if you need any other info or if I can be of assistance, we've been running SR-MPLS going all the way back to 17.x train, and so we've pretty much seen it all 😊

Thanks

Andrew Alston
Group Head Of IP Strategy - Liquid Telecommunications
Juniper Ambassador