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OSPF minutia, and, technote publication venues

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vixie at isc

May 5, 2008, 9:07 AM

Post #1 of 19 (475 views)
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OSPF minutia, and, technote publication venues

scg[at]gibbard.org (Steve Gibbard) writes:

> > ... if each anycast cluster is really several servers, each using OSPF
> > ECMP, then you can lose a server and still have that cluster advertising
> > the route upstream, and only when you lose all servers in a cluster will
> > that route be withdrawn.
>
> This is getting into minutia, but using multipath BGP will also accomplish
> this without having to get the route from OSPF to BGP. This simplifies
> things a bit, and makes it safer to have the servers and routers under
> independent control.

i think the minutia is good, especially after a long weekend of layer 9
threads. my limited understanding of multipath bgp is that it's a global
config knob for routers, not a per peer knob, and that it has disasterous
consequences if the router is also carrying a full table and has many peers.
also, in OSPF, ECMP is not optional, even though most BSD-based software
routers don't implement it yet (since multipath routing is very new.) so,
we have been using OSPF for this, it just works out better. i dearly do
wish that something like a "service advertisement protocol" existed, that
did what OSPF ECMP did, without a router operator effectively giving every
customer the ability to inject other customer routes, or default routes.
in that sense, i agree with your "safer... independent control" assertion.

> But yes, Joe's ISC TechNote is an excellent document, and was a big help
> in figuring out how to set this up a few years ago.

and now for something completely different -- where in the interpipes could
a document like that have been published, vs. ISC's web site? the amount
of red tape and delay involved in Usenix or IETF or IEEE or ACM are vastly
more than most smart ops people are willing to put in. where is the light /
middle weight class, or is every organization or person who wants to publish
this kind of thing going to continue to have the exclusive and bad choice of
"blog it, or write an article for ;login:/ACM-Queue/Circle-ID, or write an
academic paper and wait ten months"? isn't this a job for... NANOG?
--
Paul Vixie

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babydr at baby-dragons

May 5, 2008, 10:01 AM

Post #2 of 19 (464 views)
Permalink

Re: OSPF minutia, and, technote publication venues [In reply to]

Hello All ,

On Mon, 5 May 2008, Paul Vixie wrote:
> scg[at]gibbard.org (Steve Gibbard) writes:
...snip...
>> But yes, Joe's ISC TechNote is an excellent document, and was a big help
>> in figuring out how to set this up a few years ago.
>
> and now for something completely different -- where in the interpipes could
> a document like that have been published, vs. ISC's web site? the amount
> of red tape and delay involved in Usenix or IETF or IEEE or ACM are vastly
> more than most smart ops people are willing to put in. where is the light /
> middle weight class, or is every organization or person who wants to publish
> this kind of thing going to continue to have the exclusive and bad choice of
> "blog it, or write an article for ;login:/ACM-Queue/Circle-ID, or write an
> academic paper and wait ten months"? isn't this a job for... NANOG?
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Hear , Hear ! I second the motion .
Sorry about the 1-2 line response , But I beleive it was needed .

Twyl , JimL
--
+------------------------------------------------------------------+
| James W. Laferriere | System Techniques | Give me VMS |
| Network&System Engineer | 2133 McCullam Ave | Give me Linux |
| babydr[at]baby-dragons.com | Fairbanks, AK. 99701 | only on AXP |
+------------------------------------------------------------------+

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dga at cs

May 5, 2008, 10:16 AM

Post #3 of 19 (463 views)
Permalink

Re: OSPF minutia, and, technote publication venues [In reply to]

On May 5, 2008, at 12:07 PM, Paul Vixie wrote:
>
>> But yes, Joe's ISC TechNote is an excellent document, and was a big
>> help
>> in figuring out how to set this up a few years ago.
>
> and now for something completely different -- where in the
> interpipes could
> a document like that have been published, vs. ISC's web site? the
> amount
> of red tape and delay involved in Usenix or IETF or IEEE or ACM are
> vastly
> more than most smart ops people are willing to put in. where is the
> light /
> middle weight class, or is every organization or person who wants to
> publish
> this kind of thing going to continue to have the exclusive and bad
> choice of
> "blog it, or write an article for ;login:/ACM-Queue/Circle-ID, or
> write an
> academic paper and wait ten months"? isn't this a job for... NANOG?

If you're asking seriously: arXiv.org is a pretty reasonable
candidate for less-formal but more-public publication of things like
Joe's TechNote.

It's taken off seriously in physics, but I don't know anyone who uses
it seriously for computer science stuff. Probably because our
conferences have much faster turnaround than most discipline's
journals do. But arXiv exists, it'll probably be around for a while,
and it provides a reasonable starting point for hosting and citing the
documents...

-Dave

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cgrundemann at gmail

May 5, 2008, 10:18 AM

Post #4 of 19 (464 views)
Permalink

Re: OSPF minutia, and, technote publication venues [In reply to]

On Mon, May 5, 2008 at 10:07 AM, Paul Vixie <vixie[at]isc.org> wrote:
> scg[at]gibbard.org (Steve Gibbard) writes:
>
> > > ... if each anycast cluster is really several servers, each using OSPF
> > > ECMP, then you can lose a server and still have that cluster advertising
> > > the route upstream, and only when you lose all servers in a cluster will
> > > that route be withdrawn.
> >
> > This is getting into minutia, but using multipath BGP will also accomplish
> > this without having to get the route from OSPF to BGP. This simplifies
> > things a bit, and makes it safer to have the servers and routers under
> > independent control.
>
> i think the minutia is good, especially after a long weekend of layer 9
> threads. my limited understanding of multipath bgp is that it's a global
> config knob for routers, not a per peer knob, and that it has disasterous
> consequences if the router is also carrying a full table and has many peers.

I am not sure what routers specifically are being discussed here, but
in JunOS you can enable multipath on a global, group or single
neighbor level, possibly eliminating your concern...

> also, in OSPF, ECMP is not optional, even though most BSD-based software
> routers don't implement it yet (since multipath routing is very new.) so,
> we have been using OSPF for this, it just works out better. i dearly do
> wish that something like a "service advertisement protocol" existed, that
> did what OSPF ECMP did, without a router operator effectively giving every
> customer the ability to inject other customer routes, or default routes.
> in that sense, i agree with your "safer... independent control" assertion.
>
> > But yes, Joe's ISC TechNote is an excellent document, and was a big help
> > in figuring out how to set this up a few years ago.
>
> and now for something completely different -- where in the interpipes could
> a document like that have been published, vs. ISC's web site? the amount
> of red tape and delay involved in Usenix or IETF or IEEE or ACM are vastly
> more than most smart ops people are willing to put in. where is the light /
> middle weight class, or is every organization or person who wants to publish
> this kind of thing going to continue to have the exclusive and bad choice of
> "blog it, or write an article for ;login:/ACM-Queue/Circle-ID, or write an
> academic paper and wait ten months"? isn't this a job for... NANOG?
> --
> Paul Vixie
>
> _______________________________________________
> NANOG mailing list
> NANOG[at]nanog.org
> http://mailman.nanog.org/mailman/listinfo/nanog
>

--
Chris Grundemann
www.linkedin.com/in/cgrundemann

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tme at multicasttech

May 5, 2008, 10:28 AM

Post #5 of 19 (463 views)
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Re: OSPF minutia, and, technote publication venues [In reply to]

On May 5, 2008, at 1:16 PM, David Andersen wrote:

> On May 5, 2008, at 12:07 PM, Paul Vixie wrote:
>>
>>> But yes, Joe's ISC TechNote is an excellent document, and was a big
>>> help
>>> in figuring out how to set this up a few years ago.
>>
>> and now for something completely different -- where in the
>> interpipes could
>> a document like that have been published, vs. ISC's web site? the
>> amount
>> of red tape and delay involved in Usenix or IETF or IEEE or ACM are
>> vastly
>> more than most smart ops people are willing to put in. where is the
>> light /
>> middle weight class, or is every organization or person who wants to
>> publish
>> this kind of thing going to continue to have the exclusive and bad
>> choice of
>> "blog it, or write an article for ;login:/ACM-Queue/Circle-ID, or
>> write an
>> academic paper and wait ten months"? isn't this a job for... NANOG?
>
> If you're asking seriously: arXiv.org is a pretty reasonable
> candidate for less-formal but more-public publication of things like
> Joe's TechNote.
>
> It's taken off seriously in physics, but I don't know anyone who uses
> it seriously for computer science stuff.

There are certain types of networking problems where arxiv gets decent
traffic; I get about 1 paper
per day on networking and cryptography.

At any rate, I would encourage people to use it and this seems like a
possible appropriate paper for it.

Regards
Marshall

> Probably because our
> conferences have much faster turnaround than most discipline's
> journals do. But arXiv exists, it'll probably be around for a while,
> and it provides a reasonable starting point for hosting and citing the
> documents...
>
> -Dave
>
>
> _______________________________________________
> NANOG mailing list
> NANOG[at]nanog.org
> http://mailman.nanog.org/mailman/listinfo/nanog

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smb at cs

May 5, 2008, 10:59 AM

Post #6 of 19 (461 views)
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Re: OSPF minutia, and, technote publication venues [In reply to]

On 05 May 2008 16:07:03 +0000
Paul Vixie <vixie[at]isc.org> wrote:

>
> > But yes, Joe's ISC TechNote is an excellent document, and was a big
> > help in figuring out how to set this up a few years ago.
>
> and now for something completely different -- where in the interpipes
> could a document like that have been published, vs. ISC's web site?
> the amount of red tape and delay involved in Usenix or IETF or IEEE
> or ACM are vastly more than most smart ops people are willing to put
> in. where is the light / middle weight class, or is every
> organization or person who wants to publish this kind of thing going
> to continue to have the exclusive and bad choice of "blog it, or
> write an article for ;login:/ACM-Queue/Circle-ID, or write an
> academic paper and wait ten months"? isn't this a job for... NANOG?

I did some checking on this topic a few years ago. The consensus among
the people I talked to was that NANOG itself seemed to generate too
little that was publishable in a formal way to warrant a specific
mechanism.

A web site like arxiv is good for some stuff. But -- should there be a
link from nanog.org to operational content? Should nanog.org have
its own archive? Should there be a peer review process? If not, what
should the criteria be for an "official" note of the paper?

--Steve Bellovin, http://www.cs.columbia.edu/~smb

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stu at spacehopper

May 5, 2008, 11:15 AM

Post #7 of 19 (462 views)
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Re: OSPF minutia, and, technote publication venues [In reply to]

On 2008-05-05, Paul Vixie <vixie[at]isc.org> wrote:
> also, in OSPF, ECMP is not optional, even though most BSD-based software
> routers don't implement it yet (since multipath routing is very new.)

Some readers might be interested to know the exception to "most" here;
the OpenBSD kernel has supported ECMP for the last couple of releases
(activated by setting a sysctl); in the most recent release ECMP support
was also added to ospfd.

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rdobbins at cisco

May 5, 2008, 11:19 AM

Post #8 of 19 (463 views)
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Re: OSPF minutia, and, technote publication venues [In reply to]

On May 6, 2008, at 12:59 AM, Steven M. Bellovin wrote:

> If not, what should the criteria be for an "official" note of the
> paper?

Perhaps it's an oversimplification, but can't those who wish to
publish such information simply deliver their papers at a NANOG
meeting (after acceptance by the Program Committee, which acts as a
gate), and then the NANOG folks post the documents along with any
slides and the VoDs of their presentations, in the usual fashion?

-----------------------------------------------------------------------
Roland Dobbins <rdobbins[at]cisco.com> // +66.83.266.6344 mobile

History is a great teacher, but it also lies with impunity.

-- John Robb

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smb at cs

May 5, 2008, 11:38 AM

Post #9 of 19 (464 views)
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Re: OSPF minutia, and, technote publication venues [In reply to]

On Tue, 6 May 2008 01:19:36 +0700
Roland Dobbins <rdobbins[at]cisco.com> wrote:

>
> On May 6, 2008, at 12:59 AM, Steven M. Bellovin wrote:
>
> > If not, what should the criteria be for an "official" note of the
> > paper?
>
>
> Perhaps it's an oversimplification, but can't those who wish to
> publish such information simply deliver their papers at a NANOG
> meeting (after acceptance by the Program Committee, which acts as a
> gate), and then the NANOG folks post the documents along with any
> slides and the VoDs of their presentations, in the usual fashion?
>
That's certainly one very good answer. Are there others?

--Steve Bellovin, http://www.cs.columbia.edu/~smb

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paul at vix

May 5, 2008, 12:43 PM

Post #10 of 19 (459 views)
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Re: OSPF minutia, and, technote publication venues [In reply to]

> ...
> A web site like arxiv is good for some stuff. But -- should there be a
> link from nanog.org to operational content? Should nanog.org have
> its own archive? Should there be a peer review process? If not, what
> should the criteria be for an "official" note of the paper?
>
> --Steve Bellovin, http://www.cs.columbia.edu/~smb

i wouldn't want to see a full academia-style peer review process, since that
problem is pretty well solved elsewhere, and we're not having that problem.

but a nanog-style peer review process, where the nanog-pc acts as the judge
of how a technote was received by the mailing list, might work. such that if
nanog-pc puts their stamp of approval on it, the connotation would be "more
than one set of eyes has been laid on this, and it's not totally worthless."

i say nanog-like because it's a new trail to blaze based on nanog's culture
which, while often hard to cope with, has some innovative, genuine strengths.

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vixie at isc

May 5, 2008, 12:52 PM

Post #11 of 19 (458 views)
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Re: OSPF minutia, and, technote publication venues [In reply to]

smb[at]cs.columbia.edu ("Steven M. Bellovin") writes:

> > > If not, what should the criteria be for an "official" note of the paper?
> >
> > Perhaps it's an oversimplification, but can't those who wish to publish
> > such information simply deliver their papers at a NANOG meeting (after
> > acceptance by the Program Committee, which acts as a gate), and then
> > the NANOG folks post the documents along with any slides and the VoDs
> > of their presentations, in the usual fashion?
>
> That's certainly one very good answer. Are there others?
>
> --Steve Bellovin, http://www.cs.columbia.edu/~smb

i think that's a good first tier, but there's still delay and congestion in
that path. delay, because nanog meetings only happen N times per year, so
an idea may have to wait months before it's widely circulated. congestion,
because nanog meetings are of fixed duration and there is, and has to be,
competition for the slots, to make the meeting interesting, keep quality high.

as a second tier, if a technote draft could be sent to nanog-pc at any time,
and the readable ones sent to nanog@ (at a maximum of one per week, so there
would still be some quality-control related congestion, and rate limiting),
and if the nanog-pc could then use mailing list feedback to judge whether the
technote deserved to be given a number and put on www.nanog.org somewhere, we
could be doing something really interesting with the expertise assembled here.
--
Paul Vixie

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nanog at daork

May 5, 2008, 5:50 PM

Post #12 of 19 (440 views)
Permalink

Re: OSPF minutia, and, technote publication venues [In reply to]

On 6/05/2008, at 4:07 AM, Paul Vixie wrote:

> i dearly do
> wish that something like a "service advertisement protocol" existed,
> that
> did what OSPF ECMP did, without a router operator effectively giving
> every
> customer the ability to inject other customer routes, or default
> routes.

This stuff about customers and things sounds too hard.

Steve, have you actually had to do anycast without having control of
the routing hop in front of your service providing hosts, or is this
getting unnecessarily complicated? I'd imagine that the ability to
install routing equipment would be a pre-requisite for any anycast
service deployment..

Perhaps what would make more sense here is Foundry (F5, etc.) building
an anycast feature - anycast prefixes are withdrawn when a cluster
relying on that anycast prefix goes below a threshold. These load
balancing switches already do all this service health check stuff and
have done for years, so why are we re-inventing the wheel?

--
Nathan Ward

ps. I'm amused that your message that started with "i think the
minutia is good, especially after a long weekend of layer 9 threads."
ended with a paragraph of L9 :-)

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rdobbins at cisco

May 5, 2008, 6:06 PM

Post #13 of 19 (441 views)
Permalink

Re: OSPF minutia, and, technote publication venues [In reply to]

On May 6, 2008, at 2:52 AM, Paul Vixie wrote:

> delay, because nanog meetings only happen N times per year, so
> an idea may have to wait months before it's widely circulated.
> congestion,
> because nanog meetings are of fixed duration and there is, and has
> to be,
> competition for the slots, to make the meeting interesting, keep
> quality high.

From one standpoint, these aren't necessarily unalloyed negatives, as
they act as a filter to keep the noise-level down, somewhat.

Are we convinced that there's a glut of useful technical/operational
information which folks have both the time and inclination to write
up, but which they don't due to the perceived lack of an appropriate
review/publication mechanism utilized by their intended audience?

-----------------------------------------------------------------------
Roland Dobbins <rdobbins[at]cisco.com> // +66.83.266.6344 mobile

History is a great teacher, but it also lies with impunity.

-- John Robb

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jabley at ca

May 5, 2008, 6:21 PM

Post #14 of 19 (440 views)
Permalink

Re: OSPF minutia, and, technote publication venues [In reply to]

On 5 May 2008, at 20:50, Nathan Ward wrote:

> Perhaps what would make more sense here is Foundry (F5, etc.) building
> an anycast feature - anycast prefixes are withdrawn when a cluster
> relying on that anycast prefix goes below a threshold.

I'm not sure exactly what feature is required, here. f5s of my
acquaintance are already very capable of making OSPF LSAs based on
virtual servers' pools being non-empty. Do it on more than one f5 in
the same area, and you're anycasting service availability with the
current feature set.

The general reason why people prefer to find alternative solutions
rather than use dedicated load-balancers are that the dedicated load-
balancers are hellishly more expensive than the $5 gigabit switch you
probably already have in your garage.

Joe

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nanog at daork

May 5, 2008, 6:24 PM

Post #15 of 19 (437 views)
Permalink

Re: OSPF minutia, and, technote publication venues [In reply to]

On 6/05/2008, at 1:19 PM, Steven M. Bellovin wrote:

> "Steve"? I assume you meant "Paul"....

No, Steve Gibbard referred to not having control of routers, Paul
referred to customers.

--
Nathan Ward

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smb at cs

May 5, 2008, 6:36 PM

Post #16 of 19 (439 views)
Permalink

Re: OSPF minutia, and, technote publication venues [In reply to]

On Tue, 6 May 2008 13:24:35 +1200
Nathan Ward <nanog[at]daork.net> wrote:

> On 6/05/2008, at 1:19 PM, Steven M. Bellovin wrote:
>
> > "Steve"? I assume you meant "Paul"....
>
> No, Steve Gibbard referred to not having control of routers, Paul
> referred to customers.
>
Ah. As has often been noted, "Steve is a multicast address".

--Steve Bellovin, http://www.cs.columbia.edu/~smb

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nanog at daork

May 5, 2008, 6:49 PM

Post #17 of 19 (439 views)
Permalink

Re: OSPF minutia, and, technote publication venues [In reply to]

On 6/05/2008, at 1:21 PM, Joe Abley wrote:

> On 5 May 2008, at 20:50, Nathan Ward wrote:
>
>> Perhaps what would make more sense here is Foundry (F5, etc.)
>> building
>> an anycast feature - anycast prefixes are withdrawn when a cluster
>> relying on that anycast prefix goes below a threshold.
>
> I'm not sure exactly what feature is required, here. f5s of my
> acquaintance are already very capable of making OSPF LSAs based on
> virtual servers' pools being non-empty. Do it on more than one f5 in
> the same area, and you're anycasting service availability with the
> current feature set.

Can they do it with BGP for Internet anycast?

> The general reason why people prefer to find alternative solutions
> rather than use dedicated load-balancers are that the dedicated load-
> balancers are hellishly more expensive than the $5 gigabit switch
> you probably already have in your garage.

The dedicated load balancers also talk BGP (well, ones I've played
with), so that does away with the need for a BGP speaking router.

--
Nathan Ward

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jabley at ca

May 5, 2008, 7:03 PM

Post #18 of 19 (440 views)
Permalink

Re: OSPF minutia, and, technote publication venues [In reply to]

On 5 May 2008, at 21:49, Nathan Ward wrote:

> On 6/05/2008, at 1:21 PM, Joe Abley wrote:
>
>> On 5 May 2008, at 20:50, Nathan Ward wrote:
>>
>>> Perhaps what would make more sense here is Foundry (F5, etc.)
>>> building
>>> an anycast feature - anycast prefixes are withdrawn when a cluster
>>> relying on that anycast prefix goes below a threshold.
>>
>> I'm not sure exactly what feature is required, here. f5s of my
>> acquaintance are already very capable of making OSPF LSAs based on
>> virtual servers' pools being non-empty. Do it on more than one f5 in
>> the same area, and you're anycasting service availability with the
>> current feature set.
>
> Can they do it with BGP for Internet anycast?

They run ZebOS for routing stuff, so I would say so, although I
haven't tried. In our application the covering supernets are
synthesised as aggregates based on the presence of the OSPF /32.

>> The general reason why people prefer to find alternative solutions
>> rather than use dedicated load-balancers are that the dedicated load-
>> balancers are hellishly more expensive than the $5 gigabit switch
>> you probably already have in your garage.
>
> The dedicated load balancers also talk BGP (well, ones I've played
> with), so that does away with the need for a BGP speaking router.

There is a certain keenness to keep the peering edge free of multi-
function boxes in some sandboxes I have played in.

I can't say I would be tremendously enthusiastic about the idea of
using an (say) f5 BigIP 6800 as a peering router (not that I've tried
and failed, or anything; for all I know it would work just fine). But
perhaps some of that religion has just rubbed off on me.

Joe

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scg at gibbard

May 6, 2008, 3:09 AM

Post #19 of 19 (421 views)
Permalink

Re: OSPF minutia, and, technote publication venues [In reply to]

On Tue, 6 May 2008, Nathan Ward wrote:

> This stuff about customers and things sounds too hard.
>
> Steve, have you actually had to do anycast without having control of
> the routing hop in front of your service providing hosts, or is this
> getting unnecessarily complicated? I'd imagine that the ability to
> install routing equipment would be a pre-requisite for any anycast
> service deployment..

Yes I have. Or rather, I've done the network infrastructure for anycast
services without having administrative control of the anycasted servers.
PCH's anycast platform hosts some blade servers for some other DNS
infrastructure operators (in addition to the name servers PCH operates
itself). Those operators operate their own servers. PCH operates the
routing infrastructure. There is filtering in place to limit the routing
announcements from the servers.

But also, most of the larger organizations I've worked for have had
separate systems and network engineering groups. In general, the network
groups haven't wanted to let the systems engineers configure the routers,
and the systems groups haven't wanted to let network engineers configure
the servers (with good reason). Filtering of routing announcements from
anycast servers would be useful in that environment too.

To address Paul's point about multipath BGP, I never saw Cisco's
implementation of it causing a problem even with full routing tables. I
haven't used any other implementations.

In the Cisco version (and at least for EBGP; I haven't looked at this with
IBGP), it only applies to otherwise identical AS paths. Multiple
directly-connected DNS servers sourcing the same announcement with the
same AS path and other BGP attributes get load balanced between. Paths
learned from different peers had different AS paths and do not get
balanced between. I suppose there probably is load balancing in cases
where there are multiple sessions with the same peer at the same exchange.
That's a relatively rare case in this implementation, and using hash based
rather than per-packet load balancing makes it not really matter.

-Steve

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