Internet Engineering Task Force P. Resnick
Internet-Draft Qualcomm Technologies, Inc.
Intended status: Informational June 23, 2016
Expires: December 25, 2016

On Consensus and Humming in the IETF


The IETF has had a long tradition of doing its technical work through a consensus process, taking into account the different views among IETF participants and coming to (at least rough) consensus on technical matters. In particular, the IETF is supposed not to be run by a "majority rules" philosophy. This is why we engage in rituals like "humming" instead of voting. However, more and more of our actions are now indistinguishable from voting, and quite often we are letting the majority win the day. This document is a collection of thoughts on what rough consensus is, how we have gotten away from it, and the things we can do in order to really achieve rough consensus.

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Table of Contents

1. Introduction

Almost every IETF participant knows the aphorism from Dave Clark's 1992 plenary presentation [Clark] regarding how we make decisions in the IETF:

That is, we don't let a single individual make the decisions, nor do we let the majority dictate decisions, nor do we allow decisions to be made in a vacuum without practical experience. Instead, decisions are made by (more or less) consent of all participants, and the actual products of engineering trump theoretical designs. We don't require full consensus; that would allow a single intransigent person who simply keeps saying "No!" to stop the process cold. We only require rough consensus: If the chair of a working group determines that a technical issue brought forward by an objector has been truly considered by the working group, and the working group has made an informed decision that the objection has been answered or is not enough of a technical problem to move forward, the chair can declare that there is rough consensus to move forward, the objection notwithstanding. To reinforce that we do not vote, we have also adopted the tradition of "humming": When (for example) the chair of the working group wants to get a "sense of the room", instead of a show of hands, the chair asks for each side to hum for or against a question.

However, in recent years we have seen participants (including folks in IETF leadership) who do not understand some of the subtleties of consensus-based decision making. Participants ask, "Why are we bothering with this 'humming' thing? Wouldn't a show of hands be easier? That way we could really see how many people want one thing over another." Chairs are faced with factious working groups with polarized viewpoints and long-running unresolved issues that return again and again to the agenda. More and more frequently, people walk away from working groups, thinking that "consensus" has created a document with horrible compromises to satisfy everyone's pet peeve instead of doing "the right thing". None of these things are indicators of a rough consensus process being used, and are likely due to some basic misperceptions.

This document attempts to explain some features of rough consensus, explain what is not rough consensus, and suggest ways that we might achieve rough consensus and judge it in the IETF.

2. Lack of disagreement is more important than agreement

A working group comes to a technical question of whether to use format A or format B for a particular data structure. The chair notices that a number of experienced people think format A is a good choice. The chair asks on the mailing, "Is everyone OK with format A?" Inevitably, a number of people object to format A for one or another technical reason. The chair then says, "It sounds like we don't have consensus to use format A. Is everyone OK with format B?" This time even more people object to format B, on different technical grounds. The chair, not having agreement on either format A or format B, is left perplexed, thinking the working group has deadlocked.

The problem that the chair got into in the above case was to think that what they were searching for was agreement. "After all", thinks the chair, "consensus is a matter of getting everyone to agree, so asking whether everyone agrees is what the chair ought to do. And if lots of people disagree, there's no consensus." But determining consensus and coming to consensus are different things than having consensus. Consensus is not when everyone is happy and agrees that the chosen solution is the best one. Consensus is when everyone is satisfied enough with the chosen solution that they do not object to it. The distinction might be a bit subtle, but it's important. Engineering always involves a set of tradeoffs. It is almost certain that any time engineering choices need to be made, there will be options that appeal to some people that are not appealing to some others. The key is to separate those choices that are simply unappealing from those that are truly problematic. [Example:]PR: Insert catchy example here. So in the case of a working group decision, it is most important to ask not just for objections to a particular proposal, but for the nature of those objections. A chair who asks, "Is everyone OK with choice A?" is going to get objections. But a chair who asks, "Can anyone not live with choice A?" is more likely to only hear from folks who think that choice A is impossible to engineer given some constraints. Then the purported failings of the choice can be examined by the working group. The objector can convince the rest of the group that the objections are valid, or the working group might convince the objector that the concerns can be addressed, or that the choice is simply unappealing (i.e., something the objector can "live with") and not a show-stopper. In any event, closure is much more likely to be achieved quickly by asking for and trying to accomodate the objections rather than asking for agreement.

This also brings up an important point about reaching consensus: Consensus does not really involve compromising. "Compromising" implies that there remains something wrong with the outcome, but that the objector has simply given up. That is not coming to consensus. To truly come to consensus does not involve making a compromise, but rather coming to the conclusion that either the objection is valid (and therefore making a change the address the objection), or concluding that the objection was not really a matter of importance, but merely a matter of taste. Of course, coming to full consensus does not always happen.

3. Rough consensus is when all issues are addressed, but not necessarily accommodated

The preceding discussion gives an example where the working group comes to consensus on a point: Either the objector is satisfied, or the working group is satisfied. But certainly that doesn't happen all of the time, and it's certainly not the problematic case. Engineering is always a set of tradeoffs. Often, a working group will encounter an objection where everyone understands the issue, acknowledges that it is a real shortcoming in the proposed solution, but the vast majority of the working group believe that accommodating the objection is not worth the tradeoff of fixing the problem. So, an objector might say, "The proposal to go with protocol X is much more complicated than going with protocol Y. Protocol Y is a much more elegant and clean solution, and protocol X is a hack." The working group might consider this input, and someone might respond, "But we have a great deal of code already written that is similar to protocol X. While I agree that protocol Y is more elegant, the risks to interoperability with an untested solution is not worth it compared to the advantages of going with the well-understood protocol X." If the chair finds, in their technical judgement, that the issue has truly been considered, and that the vast majority of the working group has come to the conclusion that the tradeoff is worth making, even in the face of continued objection from the person(s) who raised the issue, the chair can declare that the group has come to rough consensus.

Now, a conclusion of only rough consensus relies heavily on the good judgement of the consensus caller. The group must truly consider and weigh an issue before the objection can be dismissed as being "in the rough". The chair of the working group in one of these cases is going to have to decide that not only has the working group taken the objection seriously, but that it has fully examined the ramifications of not making a change to accommodate it, and that the outcome does constitute a failure to meet the technical requirements of the work. In order to do this, the chair will need to have a good idea of the purpose and architecture of the work being done and use their own technical judgement to make sure that the solution meets those requirements. What can't happen is that the chair bases their decision solely on hearing a large number of voices simply saying, "The objection isn't valid." That would simply be to take a vote. A valid justification needs to me made.

Any finding of rough consensus needs at some level to be a satisfactory explanation to the person(s) raising the issue of why their concern is not going to be dealt with. A good outcome is for the objector to be satisfied that, although their issue is not being accommodated in the final product, they understand and accept the outcome. Remember, if the objector feels that the issue is so essential that it must be attended to, they always have the option to file an appeal. A technical error is always a valid basis for an appeal, and a chair or AD has the freedom and the responsibility to say, "The group did not take this technical issue into proper account." Simply having a number of people agreeing to dismiss an objection is not enough.

4. Humming is the start of a conversation, not the end

We don't vote in the IETF. In some ways, we can't vote: Since the IETF is not a membership organization, it's nearly impossible to figure out who would get a vote for any given question. We don't know who the members of any given working group are at any one time, and we certainly don't know who all of the members of the IETF are. So voting is not practical. We've also decided that coming to consensus (albeit sometimes rough consensus) is an important thing to do. So instead of voting, we "hum".

However, more and more we see people who think that a hum is a sort of anonymous vote, with some chairs calling every question they have for the working group by asking for a hum and judging the result by the loudest hum, even saying things like, "There were lots of hums for choice 1 and very few hums for choice 2, so it sounds like we have rough consensus for choice 1." This really misses the point of humming and is almost certainly mis-assessing the consensus. Hums should not be used as votes.

So, why do we hum? The first reason is pragmatic. Quite often, a chair is faced with a room full of people who seem to be diametrically opposed on some choice facing the group. In order to find a starting place for the conversation, it is often useful for the chair to ask for a hum to see if one of the choices already has a stronger base of support than the other. If choice "foo" has a significant amount more support than choice "bar", it is likely easier to start the discussion by saying, "OK, 'foo' seems to have quite a bit of support. Let's have the people that think 'foo' is a bad idea come up and tell us why it is problematic." At that point, the group can start going through the issues and see if any of them are showstoppers. It may turn out that one of the objections is instantly recognized by the entire group as a fatal flaw in "foo" and the group will then turn to a discussion of the merits (and demerits) of "bar" instead. All that the hum does is give the chair a starting point: There were likely to be less objections to "foo" than to "bar" at the beginning of the discussion, so starting with whatever got the most hums can shorten the discussion.

But couldn't the above could have been done with a show of hands instead of a hum? Sure, but there are more formal reasons for using a hum instead of a show of hands. Another reason we hum is because it actually gives the chair the opportunity to take the temperature of the room. A smaller bunch of loud hums for choice A and a larger number of non-committal hums for choice B might indicate that some people believe that there are serious problems with choice B, albeit the more popular by sheer number of people. The chair might decide that starting with choice A and getting objections to it is the easier path forward and more likely to result in consensus in the end. Remember, coming to consensus is a matter of eliminating disagreements, so the chair wants to choose the path that gets to the least objections fastest. A bunch of people who are not strongly committed to B might have no real technical objection to A, even though it is not their first preference. Taking the hum is to figure out how to start the conversation. Unless, to the chair's surprise, the hum is unanimous, the hum begins the discussion; it doesn't end it. Of course, a chair could get the temperature of the room by doing a show of hands, and knowing who specifically feels one way or another can help a good chair guide the subsequent conversation. However, a show of hands will often leave the impression that the number of people matters in some formal way. It takes a chair and a working group with a solid understanding of how consensus works to do a show of hands and not end up reinforcing the mistaken notion that a vote is taking place. A chair can always take the hum and then later ask for specific folks to identify themselves to elicit more discussion. The hum makes it perfectly clear that the chair is simply figuring out the direction of the conversation.

This also points to another misuse of the hum: If the chair is already convinced that the group has come to consensus, there is no reason to take a hum. In fact, taking the hum only serves to discourage those who might be in the minority from voicing their concerns to the group in the face of a large majority who want to move forward. The right thing for the chair to do if they already sense consensus is to say, "It sounds to me like we have consensus for choice A. Does anybody have any concerns or objections to going with A?" This allows folks to bring up issues to the group that the chair might have mistakenly missed without having them feel that the majority has "already spoken".

There are times where the result of a hum is a pretty even split. In practical terms, that means it doesn't matter where the chair starts the discussion. And in fact, we've had working groups where a coin-flip decided which proposal to start with. That doesn't mean that the coin-flip determined the outcome; if a fatal technical flaw was found in the chosen solution, it is still incumbent upon the group to address the issue raised. Rough consensus on the technical points, in the end, is always required. Any way to find a place to start, be it the hum or the coin-flip, is only getting to the beginning of the discussion, not the end.

5. One Hundred people for and five people against might not be rough consensus

Remember that consensus is found when all of the objections have been addressed. Because of this, using rough consensus avoids a major pitfall of a straight vote: If there is a minority of folks who have a valid technical objection, that objection must be dealt with before consensus can be declared. This also reveals one of the great strengths of using consensus over voting: It isn't possible to use "vote stuffing" (simply recruiting a large number of people to support a particular side, even people who have never participated in a working group or the IETF at all) to change the outcome of a consensus call. As long as the chair is looking for outstanding technical objections and not counting heads, vote stuffing shouldn't affect the outcome of the consensus call. So in a large working group with over 100 active participants and broad agreement to go forward with a particular protocol, if a few participants say, "This protocol is going to cause congestion on the network, and it has no mechanism to back off when congestion occurs; we object to going forward without such a mechanism in place", and the objection is met with silence on the mailing list, there is no consensus. Even if the working group chair makes a working group last call on the document, and 100 people actively reply and say, "This document is ready to go forward", if the open issue hasn't been addressed, there's still no consensus. It's the existence of the unaddressed open issue, not the number of people, which is determinative in judging consensus. As discussed earlier, you can have rough consensus with issues that have been purposely dismissed, but not ones that have been ignored.

6. Five people for and one hundred people against might still be rough consensus

This one is the real mind bender for most people, and certainly the most controversial. Say there is a very small working group, one with half a dozen truly active participants who are experts in the field; everybody else is just following along, but not contributing to the discussion. The active folks come up with a protocol document that they all agree is the right way forward, and people inside and outside the working group agree that the protocol is likely to get widespread adoption; it is a good solution to a real problem, even if the non-experts don't have the ability to fully judge the details.

However, one of the active members has an objection to a particular section: The protocol currently uses a well-known algorithm to address an issue, but the objector has a very elegant algorithm to address the issue, one which works especially well on their particular piece of hardware. There is some discussion, and all of the other contributors say, "Yes, that is elegant, but what we're using now is well-understood, widely-implemented, and it works perfectly acceptably, even on the objectors hardware. There is always some inherent risk to go with a new, albeit more elegant, algorithm. We should stick to the one we've got." The chair follows the conversation and says, "It sounds like the issue has been addressed and there's consensus to stick with the current solution." The objector is not satisfied, maybe even saying, "But this is silly. You've seen that my algorithm works. We should go with that." The chair makes the judgement that the consensus is rough, in that there is still an objector, but the issue has been addressed and the risk argument has won the day. The chair makes a working group last call.

Now the worst case scenario happens. The objector, still unhappy that their preferred solution was not chosen, recruits one hundred people, maybe a few who were silent participants in the working group already, but mostly people who are at the same company as the objector who never participated before. The objector gets them all to post a message to the list saying, "I believe we should go with the new elegant algorithm in section 5.6 instead of the current one. It is more elegant, and works better on our hardware." The chair sees these dozens of messages coming in and posts a query to each of them: "We discussed this on the list, and we seemed to have consensus that, given the inherent risk of a new algorithm, and the widespread deployment of this current one, it's better to stick with the current one. Do you have further information that indicates something different?" And in reply the chair gets utter silence. These posters to the list (say some of whom were from the company sales and marketing department) thought that they were simply voting and have no answer to give. At that point, it is within bounds for the chair to say, "We have objections, but the objections have been sufficiently answered, and the objectors seem uninterested in participating in the discussion. Albeit rough in the extreme, there is rough consensus to go with the current solution."

There is no doubt that this is the degenerate case and a clear indication of something pathological. But this is precisely what rough consensus is designed to guard against: vote stuffing. In the presence of an objection, the chair can use their technical judgement to decide that the objection has been answered by the group and that rough consensus overrides the objection. Now, the case described here is probably the hardest call for the chair to make (how many of us are willing to make the call that the vast majority of people in the room are simply stonewalling, not trying to come to consensus?), and if appealed it would be incredibly difficult for the appeals body to sort it out. Indeed, it is likely that if a working group got this dysfunctional, it would put the whole concept of coming to rough consensus at risk. But still, the correct outcome in this case is to look at the very weak signal against the huge background noise in order to find the rough consensus.

7. Security Considerations

"He who defends with love will be secure." -- Lao Tzu

8. Informative References

[Clark] Clark, D., "A Cloudy Crystal Ball - Visions of the Future", July 1992.


[IETF24] Davies, M., Clark, C. and D. Legare, "Proceedings of the Twenty-Fourth Internet Engineering Task Force", July 1992.
[Sheeran] Sheeran, M., "Beyond Majority Rule: Voteless Decisions in the Religious Society of Friends", December 1983.

Appendix A. Acknowledgements

This document is the result of conversations with many IETF participants, too many to name individually. I greatly appreciate all of the discussions and guidance. I do want to extend special thanks to Peter Saint-Andre, who sat me down and pushed me to start writing, and to Melinda Shore for pointing me to Beyond Majority Rule [Sheeran], which inspired some of the thinking in this document.

Author's Address

Pete Resnick Qualcomm Technologies, Inc. 5775 Morehouse Drive San Diego, CA 92121 US Phone: +1 858 6511 4478 EMail: