Hello,

I have been selected as the Routing Directorate reviewer for this draft. The Routing Directorate seeks to review all routing or routing-related drafts as they pass through IETF last call and IESG review, and sometimes on special request. The purpose of the review is to provide assistance to the Routing ADs. For more information about the Routing Directorate, please see ​http://trac.tools.ietf.org/area/rtg/trac/wiki/RtgDir

Although these comments are primarily for the use of the Routing ADs, it would be helpful if you could consider them along with any other IETF Last Call comments that you receive, and strive to resolve them through discussion or by updating the draft.

Document: draft-ietf-pim-drlb-13.txt
Reviewer: Ben Niven-Jenkins
Review Date: 5th November 2019
IETF LC End Date: 7th November 2019
Intended Status: Standards Track

Summary: I have some minor concerns about this document that I think should be resolved before publication.

Comments: The document is well written and easy to understand. 

Major Issues: No major issues found.

Minor Issues:

1) Section 4.1 says:

“To become a GDR Candidate, a router must have the same DR priority and run the same GDR election Hash Algorithm as the DR on the LAN.”

and

“Furthermore, assume router R1 wins the PIM DR election, R1 and R2 run the same Hash Algorithm for GDR election, while R3 runs a different one.”

I think it would be clearer if you said “support”/“supports” (or maybe “advertise”/“advertises”) rather than “run”/“runs”. As I think what you are trying to say is if a router has the same DR priority as the DR it is only a GDR candidate if it also supports the same hash algorithm as advertised by the DR.


2) In section 5.3.1 the PIM DR Load Balancing Capability (DRLB-Cap) Hello Option only contains a single value for Hash Algorithm. How is transition between different hash algorithm expected to be achieved?

Does a router that supports multiple hash algorithms include multiple DRLB-Cap Hello Options each containing a different hash algorithm and the DR selects the hash algorithm it prefers (or is configured to use)?

If so, then it might be worth explicitly mentioning that in the document.


3) Section 5.3 says “The DRLB-List Hello Option consists of three Hash Masks as defined above and also a sorted list of GDR Candidate addresses on the LAN.”

Section 5.3.2 says “All addresses MUST be in the same address family as the PIM Hello IP header.  It is RECOMMENDED that the addresses are sorted in descending order.”

Section 5.3 implies (without explicitly stating it) that GDR Candidate addresses MUST be sorted, but section 5.3.2 states that sorting is only RECOMMENDED.

Maybe remove any possibility of ambiguity by rewording Section 5.3 to something like “The DRLB-List Hello Option consists of three Hash Masks as defined above and also a list of GDR Candidate addresses on the LAN. It is RECOMMENDED that the GDR Candidate addresses are sorted in descending order.”


Nits:

Section 3 says “The extension specified in this document applies to PIM-SM when they act as last hop routers (there are directly connected receivers).”

Do you mean “applies to PIM-SM DRs”? Otherwise who is the “they” referring to in that sentence?

Section 3 says “This is because the source tree is built using the IP address of the sender, not the IP address of the PIM DR that sends the registers towards the RP.”

Do you mean “registration” instead of “registers”?