Hello, Now I am confused because I have got two sets of contradicting answers. Some say that anyone can multihome, some say that you need to be of a certain minimum size to multihome. May I know what is the right answer? I agree that allowing anyone to multihome would increase the size of the routing table. So does this mean that someone has to be of a certain size to multihome? Harsha. On Tue, 10 Dec 2002, David Schwartz wrote:
On Tue, 10 Dec 2002 12:36:39 -0600 (CST), Forrest wrote:
Maybe I'm missing something, but what good would it do for someone to multihome if only their own providers accept their route, but nobody else does? I realize that their block should be still announced with their ISP's larger aggregate, but what good does this do if your ISP goes down and can't announce the large aggregate.
Smaller multihomers elect to multihome for a variety of reasons. Those reasons typically include latency reduction and toleration of POP failures, router failures, and line failures. They're not looking to stay online is Sprint or MCI disappears entirely.
If you multihomed to 2 providers in this manner and made a table of all your downtime and its causes, loss of the larger aggregate would the tiniest fraction of your downtime, which is already a tiny fraction of the time.
We don't put parachutes on commuter jets. The failures where these would be helpful are but the tineiest fraction of the failures that occur. And any significant failure at all of such a redundant system is rare.
If you're a smaller organization, perhaps you'll only have a /23 from your upstream provider. With the filtering that seems to be in place, it seems like the only way you can truly multihome with a /23 is if it happens to be in the old Class C space. Or is this wrong?
You're just biasing the question with the choice of words you use ... "truly" multihome.
What seems to be needed is perhaps a /8 set aside by the RIR specifically to allocate to small organizations that wish to multihome that people would accept /24 and shorter from.
Not only would this increase the size of the global routing table, but this would actually decrease reliability for most basement multihomers. Basement multihomers tend to flap their routes more often than their upstreams. By not being inside a larger aggregate, these flaps are likely to result in more significant pockets of unreachability than they would be otherwise.
DS
Hello, Now I am confused because I have got two sets of contradicting answers. Some say that anyone can multihome, some say that you need to be of a certain minimum size to multihome. May I know what is the right answer?
I agree that allowing anyone to multihome would increase the size of the routing table. So does this mean that someone has to be of a certain size to multihome?
Harsha.
anyone can multihome, with the cooperation of others. current practice seems to dictate that the standard operating procedures to protect the integrity of the routing system mandate that only prefixes of certain lengths are allowed at -SOME- isp boundaries. you seem to have the assumption that there is a single standard here. There is not. --bill
Hello, Thank you very much everyone for all your replies. When Class C space gets used up, wouldn't the filtering policies have to change to allow the same kind of multihoming from the Class A space. Currently, a /24 from Class C is enough to get past filters. However later, a /22 (or is it /20) from Class A would be required to get past filters. Since there are only three /8s left in Class C, I was curious whether filtering policies would change to accommodate this. If filtering policies won't change ARIN will have to change its multihoming PA policy to giving away a /22 instead of a /24. Though officially it is RIR policy not to worry about the routability of an a prefix I guess they do worry about it? Thanks, Harsha. On Tue, 10 Dec 2002 bmanning@vacation.karoshi.com wrote:
Hello, Now I am confused because I have got two sets of contradicting answers. Some say that anyone can multihome, some say that you need to be of a certain minimum size to multihome. May I know what is the right answer?
I agree that allowing anyone to multihome would increase the size of the routing table. So does this mean that someone has to be of a certain size to multihome?
Harsha.
anyone can multihome, with the cooperation of others. current practice seems to dictate that the standard operating procedures to protect the integrity of the routing system mandate that only prefixes of certain lengths are allowed at -SOME- isp boundaries.
you seem to have the assumption that there is a single standard here. There is not.
--bill
but there is no "class C space" anymore. there is no "class A space" either. its all CIDR space and some providers have retained some vestigal classfull concepts in the creation/maintaince of their routing filters. a /24 may or may not get you past my filters. any you'll have no way to know until/unless you try to get to my sites or we develop a peering relationship. wrt the evolution of filters. yes, they do evolve. and so does ARIN policy. you presume too much to second guess that ARIN policy will evolve in the way you outline.
Hello, Thank you very much everyone for all your replies. When Class C space gets used up, wouldn't the filtering policies have to change to allow the same kind of multihoming from the Class A space. Currently, a /24 from Class C is enough to get past filters. However later, a /22 (or is it /20) from Class A would be required to get past filters.
Since there are only three /8s left in Class C, I was curious whether filtering policies would change to accommodate this.
If filtering policies won't change ARIN will have to change its multihoming PA policy to giving away a /22 instead of a /24. Though officially it is RIR policy not to worry about the routability of an a prefix I guess they do worry about it?
Thanks, Harsha.
On Tue, 10 Dec 2002 bmanning@vacation.karoshi.com wrote:
Hello, Now I am confused because I have got two sets of contradicting answers. Some say that anyone can multihome, some say that you need to be of a certain minimum size to multihome. May I know what is the right answer?
I agree that allowing anyone to multihome would increase the size of the routing table. So does this mean that someone has to be of a certain size to multihome?
Harsha.
anyone can multihome, with the cooperation of others. current practice seems to dictate that the standard operating procedures to protect the integrity of the routing system mandate that only prefixes of certain lengths are allowed at -SOME- isp boundaries.
you seem to have the assumption that there is a single standard here. There is not.
--bill
Hello, Yes, it is all classless now, but I saw Verio's policies and thought that it is the way ISPs filter. Also, the Jippi group filters at /21 except in the 192.0/7 space (where it is a /24). I didn't have enough knowledge to realize that classful was "vestigal". Thanks, Harsha. On Tue, 10 Dec 2002 bmanning@vacation.karoshi.com wrote:
but there is no "class C space" anymore. there is no "class A space" either. its all CIDR space and some providers have retained some vestigal classfull concepts in the creation/maintaince of their routing filters. a /24 may or may not get you past my filters. any you'll have no way to know until/unless you try to get to my sites or we develop a peering relationship.
wrt the evolution of filters. yes, they do evolve. and so does ARIN policy. you presume too much to second guess that ARIN policy will evolve in the way you outline.
Hello, Thank you very much everyone for all your replies. When Class C space gets used up, wouldn't the filtering policies have to change to allow the same kind of multihoming from the Class A space. Currently, a /24 from Class C is enough to get past filters. However later, a /22 (or is it /20) from Class A would be required to get past filters.
Since there are only three /8s left in Class C, I was curious whether filtering policies would change to accommodate this.
If filtering policies won't change ARIN will have to change its multihoming PA policy to giving away a /22 instead of a /24. Though officially it is RIR policy not to worry about the routability of an a prefix I guess they do worry about it?
Thanks, Harsha.
On Tue, 10 Dec 2002 bmanning@vacation.karoshi.com wrote:
Hello, Now I am confused because I have got two sets of contradicting answers. Some say that anyone can multihome, some say that you need to be of a certain minimum size to multihome. May I know what is the right answer?
I agree that allowing anyone to multihome would increase the size of the routing table. So does this mean that someone has to be of a certain size to multihome?
Harsha.
anyone can multihome, with the cooperation of others. current practice seems to dictate that the standard operating procedures to protect the integrity of the routing system mandate that only prefixes of certain lengths are allowed at -SOME- isp boundaries.
you seem to have the assumption that there is a single standard here. There is not.
--bill
Clue! - as you know doubt are now aware, VERIO and Jippi are -two- of the tens of thousands of ISPs that make up the catanet that is the Internet. The published filtering policies of these two providers is a useful tool for others to determine why VERIO and Jippi are contributing to "odd" routing. WRT learning more, you may wish to review the IETF's CIDRd WG archives from 1993-1997. You may also wish to review RFC 2050 and the various RIR policies on the evolution of that work.
Hello, Yes, it is all classless now, but I saw Verio's policies and thought that it is the way ISPs filter. Also, the Jippi group filters at /21 except in the 192.0/7 space (where it is a /24). I didn't have enough knowledge to realize that classful was "vestigal".
Thanks, Harsha.
On Tue, 10 Dec 2002 bmanning@vacation.karoshi.com wrote:
but there is no "class C space" anymore. there is no "class A space" either. its all CIDR space and some providers have retained some vestigal classfull concepts in the creation/maintaince of their routing filters. a /24 may or may not get you past my filters. any you'll have no way to know until/unless you try to get to my sites or we develop a peering relationship.
wrt the evolution of filters. yes, they do evolve. and so does ARIN policy. you presume too much to second guess that ARIN policy will evolve in the way you outline.
Hello, Thank you very much everyone for all your replies. When Class C space gets used up, wouldn't the filtering policies have to change to allow the same kind of multihoming from the Class A space. Currently, a /24 from Class C is enough to get past filters. However later, a /22 (or is it /20) from Class A would be required to get past filters.
Since there are only three /8s left in Class C, I was curious whether filtering policies would change to accommodate this.
If filtering policies won't change ARIN will have to change its multihoming PA policy to giving away a /22 instead of a /24. Though officially it is RIR policy not to worry about the routability of an a prefix I guess they do worry about it?
Thanks, Harsha.
On Tue, 10 Dec 2002 bmanning@vacation.karoshi.com wrote:
Hello, Now I am confused because I have got two sets of contradicting answers. Some say that anyone can multihome, some say that you need to be of a certain minimum size to multihome. May I know what is the right answer?
I agree that allowing anyone to multihome would increase the size of the routing table. So does this mean that someone has to be of a certain size to multihome?
Harsha.
anyone can multihome, with the cooperation of others. current practice seems to dictate that the standard operating procedures to protect the integrity of the routing system mandate that only prefixes of certain lengths are allowed at -SOME- isp boundaries.
you seem to have the assumption that there is a single standard here. There is not.
--bill
Hello, But how do you know how many of the rest filter where? Harsha. On Tue, 10 Dec 2002 bmanning@vacation.karoshi.com wrote:
Clue! - as you know doubt are now aware, VERIO and Jippi are -two- of the tens of thousands of ISPs that make up the catanet that is the Internet. The published filtering policies of these two providers is a useful tool for others to determine why VERIO and Jippi are contributing to "odd" routing.
quit trolling! you dont.. ask them, view their website, view their looking glass, phone their noc... the internet is a large group of networks under independent administrations, they can do as they please and frequently do! Steve On Tue, 10 Dec 2002, Harsha Narayan wrote:
Hello, But how do you know how many of the rest filter where?
Harsha.
On Tue, 10 Dec 2002 bmanning@vacation.karoshi.com wrote:
Clue! - as you know doubt are now aware, VERIO and Jippi are -two- of the tens of thousands of ISPs that make up the catanet that is the Internet. The published filtering policies of these two providers is a useful tool for others to determine why VERIO and Jippi are contributing to "odd" routing.
Nope. Don't care either. thats their business. When/If we need to develop a business relationship with any of them, then we get to discuss our filtering policies as aligned with theirs. why do you care?
Hello, But how do you know how many of the rest filter where?
Harsha.
On Tue, 10 Dec 2002 bmanning@vacation.karoshi.com wrote:
Clue! - as you know doubt are now aware, VERIO and Jippi are -two- of the tens of thousands of ISPs that make up the catanet that is the Internet. The published filtering policies of these two providers is a useful tool for others to determine why VERIO and Jippi are contributing to "odd" routing.
On Tue, 10 Dec 2002 11:32:03 -0800 (PST), Harsha Narayan wrote:
Now I am confused because I have got two sets of contradicting answers.
Because there are two questions, one about provider independent space and one about space allocated by an ISP to its customer.
Some say that anyone can multihome, some say that you need to be of a certain minimum size to multihome. May I know what is the right answer?
Anyone can multihome. There is no size requirement (except perhaps of your budget).
I agree that allowing anyone to multihome would increase the size of the routing table. So does this mean that someone has to be of a certain size to multihome?
No, because multihoming does not require that anyone but your direct providers see your route. Since you pay them, you aren't imposing any costs on anyone else. The people you don't pay can choose to accept your small route or not. Either way, you can reach them and they can reach you. Their route to you may not be optimum, but that's their choice. If you want them to hear your route, you can pay them to do so. It will work either way. To repeat: 1) Small multihomers should get IP address space from their most reliable provider. This is the one they trust the most and intend to remain with the longest. 2) Small multihomers must get the ISP that assigns them address space to allocate them at least a /24 (with multihoming as the justification if needed). The ISP must agree to allow them to advertise their allocation through other providers and must agree to hear and announce the block from the customer *and* *other* *ISPs*. 3) The ISP that assigns you IPs must prefer the more specific route from their peers if they don't hear it directly from the multihomer. 4) Small multhomers must get their other provider(s) to agree to hear their announcement and readvertise it. 5) Multihoming should be done only by those reasonably competent and experienced. You probably can't get enough help from a mailing list and may wind up signing contracts or purchasing equipment that harms you. DS
participants (4)
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bmanning＠vacation.karoshi.com -
David Schwartz -
Harsha Narayan -
Stephen J. Wilcox