[spring] SR-MPLS address space aggregation

[Vasilenko Eduard <[e-mail]>]

Hi all,
SRv6 has an advantage in address space aggregation. What if to add the same functionality to SR-MPLS? Something like:

SR-MPLS SID MAY be constructed hierarchically from the IPv4 or IPv6 loopback node addresses.
The smallest byte of the MPLS label SHOULD be left for functions reserved by IANA: Special-Purpose Multiprotocol Label Switching (MPLS) Label Values (iana.org)<https://www.iana.org/assignments/mpls-label-values/mpls-label-values.xhtml>.
Any number of bits between X and Y from the IP address MAY be copied to the Node SID bits from 32-8-(X-Y) to 8.
Alternatively, Node SIDs MAY be hierarchically assigned manually or with the help of a management system, the last byte should be still reserved for other MPLS functions.
It makes sense to do it only for global SIDs, local SIDs may continue to be random/consecutive/whatever. The global and local SIDs separation may be signaled by bit 7 of the SID.

24 bits (16,777,216) would be probably enough for any infrastructure domain.
SRv6 is often pushed with 16-bit compressed labels. 24 bits is a bigger scale - it has a higher probability of being enough.

Then Metro could signal only aggregated SID to the Backbone and vice versa.

Of course, the longest match MPLS forwarding should be enabled in this case, i.e. IPv4 machinery should be reused for MPLS labels.
Hence, it is a major MPLS upgrade, comparable to the MNA initiative.

Best Regards
Eduard Vasilenko
Senior Architect
Network Algorithm Laboratory
Tel: [phone]