I've a feeling that the fact that everyone shares at least the view that a /24 is minimum helps to contain the routing table. (even if there are still thousands of /24 announcements) If a significant number of providers starting accepting any prefix then the others would need to follow (else they'd get no transit traffic as it will always prefer the most specific). This really would lead to route explosion! I guess the counter argument is that you'd still get the same number of announcements at longer prefixes as there are only lots of /24s as its the current shortest (if you catch my drift here). But I doubt it is quite that straight forward and there would be a growth in announcements.. Steve On Sat, 27 Jul 2002, David Schwartz wrote:
I've never suggested accepting /25's thru /32's. I'm wondering if the people saying I should not de-aggregage my /20 actually practice what they preach and filter /24's and don't globally announce /24's from their customers.
-Ralph
What's wrong with announcing routes from your customers? Even /32s if you want. Only those people who choose to accept them will be affected by them and anyone who you have a BGP session with can insist you filter them out. Treating different situations as if they were the same is not practicing what you preach.
DS
On Sat, 27 Jul 2002 23:04:02 +0100 (BST), Stephen J. Wilcox wrote:
I've a feeling that the fact that everyone shares at least the view that a /24 is minimum helps to contain the routing table. (even if there are still thousands of /24 announcements)
If a significant number of providers starting accepting any prefix then the others would need to follow (else they'd get no transit traffic as it will always prefer the most specific). This really would lead to route explosion!
I guess the counter argument is that you'd still get the same number of announcements at longer prefixes as there are only lots of /24s as its the current shortest (if you catch my drift here). But I doubt it is quite that straight forward and there would be a growth in announcements..
Steve
My point is simply that only those who felt the /32s were worth carrying would carry them. And those who chose to announce them would have to factor the effects of selective carrying into their decisions. But nobody would be imposing any unwanted costs on anyone else. That's the difference. Nothing you can possibly do with a customer can impose unwanted costs on you or the customer. If you don't want the costs, don't do it. If the customer won't pay you the cost of doing it, don't do it. it's only in the relationship between ISPs and non-customers that there's a pollution and inequitable cost distribution issue. Practicing what you preach does not require treating fundamentally different situations as the same. DS
the large quantity of /24 announcements is, I suspect, from comapnies just large enough to want the benefits of multihoming. You know, 2 t1s on a small router, and stuff like that.. Bri On Sat, 27 Jul 2002, Stephen J. Wilcox wrote:
I've a feeling that the fact that everyone shares at least the view that a /24 is minimum helps to contain the routing table. (even if there are still thousands of /24 announcements)
If a significant number of providers starting accepting any prefix then the others would need to follow (else they'd get no transit traffic as it will always prefer the most specific). This really would lead to route explosion!
I guess the counter argument is that you'd still get the same number of announcements at longer prefixes as there are only lots of /24s as its the current shortest (if you catch my drift here). But I doubt it is quite that straight forward and there would be a growth in announcements..
Steve
On Sat, 27 Jul 2002, David Schwartz wrote:
I've never suggested accepting /25's thru /32's. I'm wondering if the people saying I should not de-aggregage my /20 actually practice what they preach and filter /24's and don't globally announce /24's from their customers.
-Ralph
What's wrong with announcing routes from your customers? Even /32s if you want. Only those people who choose to accept them will be affected by them and anyone who you have a BGP session with can insist you filter them out. Treating different situations as if they were the same is not practicing what you preach.
DS
On Mon, Jul 29, 2002 at 03:35:19PM -0700, Brian wrote:
the large quantity of /24 announcements is, I suspect, from comapnies just large enough to want the benefits of multihoming. You know, 2 t1s on a small router, and stuff like that..
Everyone and their mother says they "suspect" that, but noone ever proves it. Ever wonder why? Let's take it by the numbers: Total ASes present in the Internet Routing Table: 13448 Origin-only ASes present in the Internet Routing Table: 11641 Origin ASes announcing only one prefix: 5154 Transit ASes present in the Internet Routing Table: 1807 Even if every origin-only AS was a smalltime company with just enough IPs for a /24, it would take around 6-7 /24s each to account for the number of /24s announced. If someone has done an actual study of where these /24s (and probably /23s too) come from, please point it out. Until then, my money is on clueless redist connected/statics, large cable/dsl providers who announce a /24 per pop/city/whatever to their single transit provider, and general ignorance. Why attribute to functionality what can easily be explained by incomptence. :) -- Richard A Steenbergen <ras@e-gerbil.net> http://www.e-gerbil.net/ras PGP Key ID: 0x138EA177 (67 29 D7 BC E8 18 3E DA B2 46 B3 D8 14 36 FE B6)
On Mon, 29 Jul 2002, Richard A Steenbergen wrote:
If someone has done an actual study of where these /24s (and probably /23s too) come from, please point it out. Until then, my money is on clueless redist connected/statics, large cable/dsl providers who announce a /24 per pop/city/whatever to their single transit provider, and general ignorance.
To ease my own curiousity I kludged together a script to look at how much of /24 land is taken up by smalltimers announcing few prefixes, and larger networks announcing many. My last snapshot of the routing table is from the end of june, so may be (very slightly) outdated. Data from June 29, 2002 Total /24's: 61931 ASN's announcing /24's: 8645 Number of /24's announced by AS breakdown /24's ASN Count ======= ========= 1 3474 2 1662 3 740 4 533 5 377 6 236 7 203 8 164 9 113 10-14 421 15-19 184 20-29 199 30-39 101 40-49 57 50-59 41 60-69 29 70-79 21 80-89 12 90-99 11 100-149 20 150-199 17 200+ 29 Those "basement multihomers" announcing 1-5 /24's only account for ~20% of the total number of /24's out there. Multihomers with slightly larger basements (6-10 /24's) account for 10% of the total. That leaves the remaining 70% of /24's in the DFZ announced by people pushing out over 10 /24's from their AS. Interpret however you will (I tend to lean towards Richard's take on the situation.) - Paul
If someone has done an actual study of where these /24s (and probably /23s too) come from, please point it out. Until then, my money is on clueless redist connected/statics, large cable/dsl providers who announce a /24
Now the question is, of that 70% figure, how much of that is aggregateable? --Phil -----Original Message----- From: owner-nanog@merit.edu [mailto:owner-nanog@merit.edu] On Behalf Of Paul Schultz Sent: Monday, July 29, 2002 10:28 PM To: nanog@merit.edu Subject: Re: routing table size On Mon, 29 Jul 2002, Richard A Steenbergen wrote: per
pop/city/whatever to their single transit provider, and general ignorance.
To ease my own curiousity I kludged together a script to look at how much of /24 land is taken up by smalltimers announcing few prefixes, and larger networks announcing many. My last snapshot of the routing table is from the end of june, so may be (very slightly) outdated. Data from June 29, 2002 Total /24's: 61931 ASN's announcing /24's: 8645 Number of /24's announced by AS breakdown /24's ASN Count ======= ========= 1 3474 2 1662 3 740 4 533 5 377 6 236 7 203 8 164 9 113 10-14 421 15-19 184 20-29 199 30-39 101 40-49 57 50-59 41 60-69 29 70-79 21 80-89 12 90-99 11 100-149 20 150-199 17 200+ 29 Those "basement multihomers" announcing 1-5 /24's only account for ~20% of the total number of /24's out there. Multihomers with slightly larger basements (6-10 /24's) account for 10% of the total. That leaves the remaining 70% of /24's in the DFZ announced by people pushing out over 10 /24's from their AS. Interpret however you will (I tend to lean towards Richard's take on the situation.) - Paul
If someone has done an actual study of where these /24s (and probably /23s too) come from, please point it out. Until then, my money is on clueless redist connected/statics, large cable/dsl providers who announce a /24
The slow-start scenario is valid, but only to a certain extent. My company was a "slow-start" company, requesting and validating to Management, ARIN, ISPs, and the guy working at the Quickie Mart. And although we've managed to get to the point of a /19 at a time, we still have a couple legacy /24s. What is one to do? Now, one network, one contiguous AS, has 15 network advertisements ranging from /24 to /18 when it could be one /15 with another year or two to grow. But we can't just pop off /15s to everyone who's promises to use it up, and I'm certainly not going to persuade thousands of customers to migrate their IPs to a new block. But why I say it is only valid to a certain extent is that you only have to "validate" a certain percentage of your existing IPs, that affords larger companies to have more flexibility and thus get away from adding /24s rather quickly. Does someone have some perl script handy that can aggregate from a hashlist dumped from router bgp output using NET::NETMASK? (I'd do it myself, but ...well, I suk!) JNULL PGP: 0x54B1A25C "There are 10 types of people: those that understand binary, and those that do not. -----Original Message----- From: owner-nanog@merit.edu [mailto:owner-nanog@merit.edu] On Behalf Of Phil Rosenthal Sent: Monday, July 29, 2002 9:58 PM To: 'Paul Schultz'; nanog@merit.edu Subject: RE: routing table size Now the question is, of that 70% figure, how much of that is aggregateable? --Phil -----Original Message----- From: owner-nanog@merit.edu [mailto:owner-nanog@merit.edu] On Behalf Of Paul Schultz Sent: Monday, July 29, 2002 10:28 PM To: nanog@merit.edu Subject: Re: routing table size On Mon, 29 Jul 2002, Richard A Steenbergen wrote: per
pop/city/whatever to their single transit provider, and general ignorance.
To ease my own curiousity I kludged together a script to look at how much of /24 land is taken up by smalltimers announcing few prefixes, and larger networks announcing many. My last snapshot of the routing table is from the end of june, so may be (very slightly) outdated. Data from June 29, 2002 Total /24's: 61931 ASN's announcing /24's: 8645 Number of /24's announced by AS breakdown /24's ASN Count ======= ========= 1 3474 2 1662 3 740 4 533 5 377 6 236 7 203 8 164 9 113 10-14 421 15-19 184 20-29 199 30-39 101 40-49 57 50-59 41 60-69 29 70-79 21 80-89 12 90-99 11 100-149 20 150-199 17 200+ 29 Those "basement multihomers" announcing 1-5 /24's only account for ~20% of the total number of /24's out there. Multihomers with slightly larger basements (6-10 /24's) account for 10% of the total. That leaves the remaining 70% of /24's in the DFZ announced by people pushing out over 10 /24's from their AS. Interpret however you will (I tend to lean towards Richard's take on the situation.) - Paul
Until then, my money is on clueless redist connected/statics, large cable/dsl providers who announce a /24 per pop/city/whatever to their single transit provider, and general ignorance.
Why attribute to functionality what can easily be explained by incomptence. :)
-- Richard A Steenbergen <ras@e-gerbil.net>
You forgot one of my favorite frustrations - slow start. Try this: a) start an ISP and tell your upstream you want a /21. They will tell you that you can only have a /24. b) Tell them that you understand they can't give you a /21 based on ARIN guidelines but you would like them to reserve it for you. Listen to them laugh. c) Keep requesting more space as you need it while you grow. Tell them you want contiguous space. Listen to them laugh. Your choice is take a new discontinuous block or renumber the whole network. This would be why we announce 2 /22's and 2 /23's even though given contiguous space we could make a single announcement. Add in the $2500 cost of obtaining a ARIN allocation versus what are 'free' addresses from our upstreams and we will probably continue as-is for a while. Why does ARIN need $2500 for an entry in a database anyway? End result is we would like to make a single announcement. By being truthful in requesting address space based on the guidelines we end up with address space that is fragmented - so we make the extra announcements. I have not seen a statistic for non-transit AS's announcing multiple discontinuous prefixes - I suspect that there are a lot of them for the same reason we do it. Obviously you can't keep leaving big 'reserved' holes in your allocations to downstreams for potential growth. You can't expect a network to renumber everytime they need more space. I don't have a good answer to this problem nor do I expect one - it's just another reason why we have additional growth in the routing tables. Mark Radabaugh Amplex (419) 833-3635
"Mark Radabaugh" <mark@amplex.net> wrote:
Obviously you can't keep leaving big 'reserved' holes in your allocations to downstreams for potential growth.
I've seen RIPE allocate /20s under the proviso that the customer use the first /23 now and apply to use the rest of the space as they grow. -- Tim
participants (9)
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jnull -
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Phil Rosenthal -
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