Re: [Idr] Question about draft-haas-flowspec-capability-bits-02

[Jeffrey Haas <[e-mail]>]

Linda,

On Tue, Jun 22, 2021 at 02:15:24PM +0000, Linda Dunbar wrote:
> Based on the TYPE, the receiver can get the "length" field properly. Why it is a problem? 

Because for a new component type, you don't know where length is for that
type, nor how long.

> Type 1 and Type 2 have Length Field. For the Types using "Numeric Operator" or "Bitmask Operator", there is "Length" field as well. 
> 
> If I introduce a new type, Type 14, can I just use the format as Type 1 or Type 2? 

We can do anything we like as long as we have rules for it.  Right now,
flowspec doesn't have consistent rules among the types.  We have two styles.

If this were a normal TLV protocol, length wouldn't be arbitrarily
specified.  That's one of the motivations for flowspec v2.  And, similarly,
it's what PCEP decided to do when it leveraged flowspec encodings.

The capability bits proposal attempts the middle road: An implementation
must KNOW the rule for a component type.  This lets two implementations
disclose to each other what types they understand.

-- Jeff