Re: [p2pi] ALTO Information Export Service
Reinaldo Penno <rpenno@juniper.net> Tue, 28 October 2008 23:49 UTC
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Date: Tue, 28 Oct 2008 16:48:38 -0700
From: Reinaldo Penno <rpenno@juniper.net>
To: "Woundy, Richard" <Richard_Woundy@cable.comcast.com>, John Leslie <john@jlc.net>, Stanislav Shalunov <shalunov@shlang.com>
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Thread-Topic: [p2pi] ALTO Information Export Service
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Subject: Re: [p2pi] ALTO Information Export Service
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I agree with you Rich. Getting an accurate mapping of IP to 'owner' ASs is not an easy task. Some people spent a lot of time on this. I did not know this presentation. Here is a another very good reference: Towards an Accurate AS-Level Traceroute Tool Zhuoqing Morley Mao Jennifer Rexford Jia Wang Randy H. Katz UC Berkeley AT&T LabsResearch AT&T LabsResearch UC Berkeley zmao@cs.berkeley.edu jrex@research.att.com jiawang@research.att.com randy@cs.berkeley.edu In this paper they discuss in detail all the roadblocks to have a traceroute tool that maps IP to ASs. Thanks, Reinaldo On 10/28/08 4:00 PM, "Woundy, Richard" <Richard_Woundy@cable.comcast.com> wrote: >> The routing view which actually matters is the view of the ISP router > which dispatches the particular packet at a peering point. Thus, IMHO, > the ISP should usually be the provider of the mapping of IPs to ASNs. > > Before this email, my opinion was that if an ISP wanted to include > ASN(s) in the policy to be returned by the ALTO service, then the ISP > should also supply the IP prefix to ASN mappings, so that the combined > ALTO service guidance came from a consistent information source (the > ISP). But I didn't have a strong opinion against using a looking glass > server instead for the IP-to-ASN mappings. > > If I understood John correctly, the looking glass server's view of > IP-to-ASN mappings may depend on the server's location in the Internet > topology, and that view may not be equivalent to the view of the ISP > providing the ALTO service. > > Here is one example: Within one ISP's backbone, there may be a set of > specific IPv4 prefixes coming from many origin AS's. Within another > ISP's backbone, these specific prefixes may have been replaced (and > subsumed) by a single aggregate prefix with a different origin AS (e.g. > the first backbone). Therefore, the looking glass servers for the first > and second backbones would differ on the correct origin AS with respect > to this aggregated prefix. > > Here is a relevant RIPE presentation (from 2003) in which they faced > similar problems with reporting ASNs in traceroutes: > http://www.ripe.net/ripe/meetings/ripe-46/presentations/ripe46-tt-as-tra > ceroutes.pdf. In the scenario of the RIPE presentation, the route > information in the Internet Routing Registries and in the global BGP > routes were often at odds with one another; slides 8, 10, and 11 > describe some interesting cases that relate to this discussion about > looking glasses. > > John, in short, I think you make a very good point. > > -- Rich > > -----Original Message----- > From: p2pi-bounces@ietf.org [mailto:p2pi-bounces@ietf.org] On Behalf Of > John Leslie > Sent: Tuesday, October 28, 2008 1:23 PM > To: Stanislav Shalunov > Cc: p2pi@ietf.org > Subject: Re: [p2pi] ALTO Information Export Service > > Stanislav Shalunov <shalunov@shlang.com> wrote: >> >> We put together a first iteration of a very simple ALTO solution >> draft. We hope this will be useful as an example point in the >> solutions space and thus allow to refine the requirements document and > >> the problem statement. >> >> > http://www.ietf.org/internet-drafts/draft-shalunov-alto-infoexport-00.tx > t > ] ... > ] 7. Mapping IPs to ASNs > > I expect ISPs will sometimes mean different things by "preferring" > ASNs. (This is a pretty generic problem with ASNs in ALTO.) > > ISPs generally peer with a limited number of ASNs, and reach IPs > "owned" by other ASNs through routes from the ASNs they directly peer > with. > > What actually causes an ISP to "prefer" a set of IPs is knowing that > they will use a route to them through a particular AS they peer with. > This is _not_ the same as which AS "owns" the IP in question. (Nor is > "owned by an AS" necessarily a meaningful statement for a CIDR block.) > > BGP looking-glass views show which ASNs "originate" routes to a > CIDR block. It is not particularly unusual to find more than one AS > "originating" such a route. Thus, looking-glass results cannot assure > that the route a packet will actually follow to reach an IP address > _ever_ passes through a particular AS. > > Looking-glass views _will_ generally show "holes" punched in CIDR > blocks "owned" by one AS for the purpose of balancing traffic to a > multihomed customer of that AS (even though it may be that _none_ of > the traffic will actually pass through the "owner" AS). But looking- > glass views tend to contain routes that are never seen by routers > not "near the backbone". > > The routing view which actually matters is the view of the ISP > router which dispatches the particular packet at a peering point. > Thus, IMHO, the ISP should usually be the provider of the mapping of > IPs to ASNs. > > (This mapping may change several times per second when routes > "flap", but that's a balancing act the ISP is best able to attempt.) > > In any case, if ALTO provides ASN "preferences" at all we should > provide a mechanism for the ISP to perform mapping of IP to ASN. > (IMHO, at least...) > > -- > John Leslie <john@jlc.net> > _______________________________________________ > p2pi mailing list > p2pi@ietf.org > https://www.ietf.org/mailman/listinfo/p2pi > _______________________________________________ > p2pi mailing list > p2pi@ietf.org > https://www.ietf.org/mailman/listinfo/p2pi _______________________________________________ p2pi mailing list p2pi@ietf.org https://www.ietf.org/mailman/listinfo/p2pi
- Re: [p2pi] ALTO Information Export Service Laird Popkin
- Re: [p2pi] ALTO Information Export Service stefano previdi
- Re: [p2pi] ALTO Information Export Service John Leslie
- [p2pi] ALTO Information Export Service Stanislav Shalunov
- Re: [p2pi] ALTO Information Export Service John Leslie
- Re: [p2pi] ALTO Information Export Service Woundy, Richard
- Re: [p2pi] ALTO Information Export Service Reinaldo Penno
- Re: [p2pi] ALTO Information Export Service Salman Abdul Baset
- Re: [p2pi] ALTO Information Export Service Reinaldo Penno
- Re: [p2pi] ALTO Information Export Service stefano previdi
- Re: [p2pi] ALTO Information Export Service Laird Popkin
- Re: [p2pi] ALTO Information Export Service Reinaldo Penno
- Re: [p2pi] ALTO Information Export Service John Leslie
- Re: [p2pi] ALTO Information Export Service Laird Popkin