Re: maximum ipv4 bgp prefix length of /24 ?

[Owen DeLong via NANOG <nanog () nanog org>]

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@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.