Micro-allocation needed?
Hi everyone, We're going to anycast a /24 for some DNS servers (and possibly another UDP based service)[1]. I see that ARIN are listing on https://www.arin.net/knowledge/ip_blocks.html the smallest allocations from each prefix. Will we have trouble getting a /24 announced if we take it from a regular /20? Or in other words: Do we need to get a block from ARIN from one of the prefixes that they specify they allocate out in /24 chunks? - ask [1] For the NTP Pool system - http://www.pool.ntp.org/ - your network probably sent some of the 50-100,000 requests the pool members got this second. And this. And this. ... :-)
On Mon, 2010-06-21 at 23:32 +0200, Ask Bjørn Hansen wrote:
Hi everyone,
We're going to anycast a /24 for some DNS servers (and possibly another UDP based service)[1].
I see that ARIN are listing on https://www.arin.net/knowledge/ip_blocks.html the smallest allocations from each prefix. Will we have trouble getting a /24 announced if we take it from a regular /20?
No, you can split up allocations as you want, provided you can prove you own them. Some providers however, won't announce anything smaller than a /24. William
On Jun 21, 2010, at 23:34, William Pitcock wrote:
On Mon, 2010-06-21 at 23:32 +0200, Ask Bjørn Hansen wrote:
Hi everyone,
We're going to anycast a /24 for some DNS servers (and possibly another UDP based service)[1].
I see that ARIN are listing on https://www.arin.net/knowledge/ip_blocks.html the smallest allocations from each prefix. Will we have trouble getting a /24 announced if we take it from a regular /20?
No, you can split up allocations as you want, provided you can prove you own them.
Some providers however, won't announce anything smaller than a /24.
I guess to rephrase my question: Are there (a significant number of) providers that will filter a /24 announcement from an ARIN prefix not in the list of prefixes where they allocate /24 blocks. (I take it from what you wrote that the answer is "No"). - ask
On Mon, 2010-06-21 at 23:42 +0200, Ask Bjørn Hansen wrote:
On Jun 21, 2010, at 23:34, William Pitcock wrote:
On Mon, 2010-06-21 at 23:32 +0200, Ask Bjørn Hansen wrote:
Hi everyone,
We're going to anycast a /24 for some DNS servers (and possibly another UDP based service)[1].
I see that ARIN are listing on https://www.arin.net/knowledge/ip_blocks.html the smallest allocations from each prefix. Will we have trouble getting a /24 announced if we take it from a regular /20?
No, you can split up allocations as you want, provided you can prove you own them.
Some providers however, won't announce anything smaller than a /24.
I guess to rephrase my question:
Are there (a significant number of) providers that will filter a /24 announcement from an ARIN prefix not in the list of prefixes where they allocate /24 blocks.
I have yet to encounter any. They are "your IPs" as far as they are concerned, so they'll typically announce whatever you ask as long as they are "your IPs". William
On 2010-06-21, at 17:42, Ask Bjørn Hansen wrote:
Are there (a significant number of) providers that will filter a /24 announcement from an ARIN prefix not in the list of prefixes where they allocate /24 blocks.
Not in my experience, but I don't know how useful that is to know because I don't know how to characterise my experience in any meaningful way :-)
(I take it from what you wrote that the answer is "No").
I'm interested in the idea of anycasting one of the pool.ntp.org herd-members. Every time I've suggested such a thing I've been told (paraphrasing) that a good (server, client) NTP session exhibits reasonable RTT stability, this constitutes, in effect, a long-lived transaction, and hence anycast is not a good answer unless you have confidence that the potential for oscillations is low, or that the frequency of the oscillations is very low (i.e. in a private network this might be a good answer, but across the public Internet it's a poor answer). Has the thinking changed, or did I just misunderstand? Joe
On Jun 21, 2010, at 23:55, Joe Abley wrote: Everyone: Thanks for the replies regarding the /24 announcement from a "/20 allocated block". Yes, obviously the /20 announcement will handle the traffic, too. I'm a regular reader on NANOG and consistently impressed by the expertise on display and the speed with which it's generously handed out. :-)
I'm interested in the idea of anycasting one of the pool.ntp.org herd-members. Every time I've suggested such a thing I've been told (paraphrasing) that a good (server, client) NTP session exhibits reasonable RTT stability, this constitutes, in effect, a long-lived transaction, and hence anycast is not a good answer unless you have confidence that the potential for oscillations is low, or that the frequency of the oscillations is very low (i.e. in a private network this might be a good answer, but across the public Internet it's a poor answer).
Has the thinking changed, or did I just misunderstand?
I think the thinking on NTP [ see below ] is the same; but indeed when I wrote "possibly other UDP based services" experimenting with that was my idea, too. I believe some of the CDNs are anycast based (Cachefly?) and they did some extensive tests with very long http transactions. (And I guess do a big test daily in running the service...). However -- Much of the pool.ntp.org traffic is from SNTP clients where the NTP considerations don't apply. (In summary: SNTP = dumb client that just asks for the time now; NTP = clever server that keeps track of the time. The protocol is the same, but the usage quite different). - ask
From: Joe Abley <jabley@hopcount.ca> Date: Mon, 21 Jun 2010 17:55:40 -0400
I'm interested in the idea of anycasting one of the pool.ntp.org herd-members. Every time I've suggested such a thing I've been told (paraphrasing) that a good (server, client) NTP session exhibits reasonable RTT stability, this constitutes, in effect, a long-lived transaction, and hence anycast is not a good answer unless you have confidence that the potential for oscillations is low, or that the frequency of the oscillations is very low (i.e. in a private network this might be a good answer, but across the public Internet it's a poor answer).
Has the thinking changed, or did I just misunderstand?
Joe, This would be better asked on the NTP list, but I'd say it depends on the accuracy you want to achieve. For the NTP pool, the idea is to try for good accuracy and very good long-term stability are the goals. That does not work well of the actual source of the data changes very often. Aside from losing the advantages of long-term PLL filtering of the time, you also will see substantial changes in delay (i.e. RTT) and, almost certainly, jitter. Unless you are confident that the source of the anycast at any point in the network will remain stable over a very long term, it really does not sound like a good solution to me. Then again, with GPS time source available for <75 USD, anyone who is really trying for really good time should just buy one and run a local stratum 1 server. -- R. Kevin Oberman, Network Engineer Energy Sciences Network (ESnet) Ernest O. Lawrence Berkeley National Laboratory (Berkeley Lab) E-mail: oberman@es.net Phone: +1 510 486-8634 Key fingerprint:059B 2DDF 031C 9BA3 14A4 EADA 927D EBB3 987B 3751
Are you considering doing SNTP or regular NTP? If regular NTP... I once read some excellent advice on AnyCast: "It often doesn't make sense to go through the extra complexity in deploying a service with AnyCast addressing if it doesn't justify the benefit." In this sense, I really don't understand what you will gain. -----Original Message----- From: "Kevin Oberman" <oberman@es.net> Date: Mon, 21 Jun 2010 15:13:28 To: Joe Abley<jabley@hopcount.ca> Cc: <nanog@nanog.org> Subject: Re: Micro-allocation needed?
From: Joe Abley <jabley@hopcount.ca> Date: Mon, 21 Jun 2010 17:55:40 -0400
I'm interested in the idea of anycasting one of the pool.ntp.org herd-members. Every time I've suggested such a thing I've been told (paraphrasing) that a good (server, client) NTP session exhibits reasonable RTT stability, this constitutes, in effect, a long-lived transaction, and hence anycast is not a good answer unless you have confidence that the potential for oscillations is low, or that the frequency of the oscillations is very low (i.e. in a private network this might be a good answer, but across the public Internet it's a poor answer).
Has the thinking changed, or did I just misunderstand?
Joe, This would be better asked on the NTP list, but I'd say it depends on the accuracy you want to achieve. For the NTP pool, the idea is to try for good accuracy and very good long-term stability are the goals. That does not work well of the actual source of the data changes very often. Aside from losing the advantages of long-term PLL filtering of the time, you also will see substantial changes in delay (i.e. RTT) and, almost certainly, jitter. Unless you are confident that the source of the anycast at any point in the network will remain stable over a very long term, it really does not sound like a good solution to me. Then again, with GPS time source available for <75 USD, anyone who is really trying for really good time should just buy one and run a local stratum 1 server. -- R. Kevin Oberman, Network Engineer Energy Sciences Network (ESnet) Ernest O. Lawrence Berkeley National Laboratory (Berkeley Lab) E-mail: oberman@es.net Phone: +1 510 486-8634 Key fingerprint:059B 2DDF 031C 9BA3 14A4 EADA 927D EBB3 987B 3751
AT&T announces ours. It just took a little bit of prodding to get the sales people to ask the appropriate technical people. We have a very old ARIN-allocated /24 but we have only one upstream, so we have no AS number of our own. On Jun 21, 2010, at 4:42 PM, Ask Bjørn Hansen wrote:
On Jun 21, 2010, at 23:34, William Pitcock wrote:
On Mon, 2010-06-21 at 23:32 +0200, Ask Bjørn Hansen wrote:
Hi everyone,
We're going to anycast a /24 for some DNS servers (and possibly another UDP based service)[1].
I see that ARIN are listing on https://www.arin.net/knowledge/ip_blocks.html the smallest allocations from each prefix. Will we have trouble getting a /24 announced if we take it from a regular /20?
No, you can split up allocations as you want, provided you can prove you own them.
Some providers however, won't announce anything smaller than a /24.
I guess to rephrase my question:
Are there (a significant number of) providers that will filter a /24 announcement from an ARIN prefix not in the list of prefixes where they allocate /24 blocks.
(I take it from what you wrote that the answer is "No").
- ask
* Ask Bjørn Hansen:
Are there (a significant number of) providers that will filter a /24 announcement from an ARIN prefix not in the list of prefixes where they allocate /24 blocks.
I've seen such filters applied to RIPE's /8s which actually led to reachability problems because the shorter covering prefix was not announced. (Arguably, that's two failures.) -- Florian Weimer <fweimer@bfk.de> BFK edv-consulting GmbH http://www.bfk.de/ Kriegsstraße 100 tel: +49-721-96201-1 D-76133 Karlsruhe fax: +49-721-96201-99
participants (7)
-
Ask Bjørn Hansen -
Daniel Seagraves -
Florian Weimer -
Joe Abley -
Kevin Oberman -
khatfield＠socllc.net -
William Pitcock