Re: Size of CR in CRH

[Nick Hilliard <[e-mail]>]

Bob Hinden wrote on 19/05/2020 00:08:
> I also prefer a single size (and only one SR header definition).   If
> it’s 16-bits, that would allow 64K routers in one CRH domain assuming
> it needs to uniquely identify each router, if there is more than 64K
> routers, then it only needs to identify the routers that are serving
> as hops in the source route.
> 
> As you note 24 bits is better, but may not align as well.   Or then
> 32-bits.

Having multiple options for SID size increases complexity at several 
levels: hardware programming, CLI, network compatibility, 
troubleshooting, etc.  What happens if a network wants to change from 
using one type of SID to another because of whatever reason?  Does a 
node need to be configured with multiple IDs?  Can you mix and match? 
These sorts of things matter when you run networks.  You're increasing 
the complexity of some aspects by a factor of two.

Simplicity is a huge gain from an operational point of view.

32 bits has the advantage of being the same size as a node's bgp or ospf 
router-id.  This would be something ranging from helpful to important if 
the device has an option for manual programming.

The EH packet header lookup size of a device obviously impacts this.

Nick