maximum ipv4 bgp prefix length of /24 ?

Sun Oct 1 03:04:29 UTC 2023

Not sure why you think FIB compression is a risk or will be a mess. It’s a pretty straightforward task. 

Owen

> On Sep 30, 2023, at 00:03, Mark Tinka <mark at tinka.africa> wrote:
> 
>  
> 
>> On 9/30/23 01:36, William Herrin wrote:
>> 
>> 
>>  If I were designing the product, I'd size the SRAM with that in mind.
>> I'd also keep two full copies of the FIB in the outer DRAM so that the
>> PPEs could locklessly access the active one while the standby one gets
>> updated with changes from the RIB. But I'd design the router to
>> gracefully fail if the FIB exceeded what the SRAM could hold.
>> 
>> When a TCAM fills, the shortest prefixes are ejected to the router's
>> main CPU. That fails pretty hard since the shortest prefixes tend to
>> be among the most commonly used. By comparison, an SRAM cache tends to
>> retain the most commonly used prefixes as an inherent part of how
>> caches work, regardless of prefix length. It can operate close to full
>> speed until the actively used routes no longer fit in the cache.
> 
> Well, not sure if you're aware, but starting Junos 21.2, Juniper are implementing FIB Compression on the PTX routers running Express 4 and Junos EVO.
> 
> We have some of these boxes in our network (PTX10001), and I have asked Juniper to provide a knob to allow us to turn it off, as it is currently going to ship as a default-on feature. I'd rather not be part of the potential mess that is going to come with the experimentation of that over the next decade.
> 
> Mark.