Hi Wendy and Lyle, See below for comments.
BR G.Robert Chen ---------------------------------------------------------------------------------------------------------------------------------------- >>>> -----Original Message----- >>>> From: alto [mailto:[email protected]] On Behalf Of Wendy Roome >>>> Sent: Tuesday, September 15, 2015 10:09 PM >>>> To: [email protected] >>>> Subject: Re: [alto] Cost Maps, Endpoint Cost Maps and Coarse Grained >>>> Searches >>>> >>>> Lyle, >>>> >>>> Here is my opinion on Endpoint Cost Service (ECS) vs. Network Maps & Cost >>>> Maps (NM/CM): They are two different ways to present the same data. They >>>> are different viewports into the same data, if you will, with different >>>> levels of >>>> detail, and different performance and ease-of-use. >>>> >>>> To start, I believe most clients will prefer ECS. Clients really care >>>> about costs >>>> between endpoints; PIDs and Network Maps are irrelevant. For example, >>>> consider a Bittorrent peer which gets 50 new peers every 15 minutes or so. >>>> That ALTO client would prefer to send an ECS request to the ALTO server to >>>> rank those peers, rather than fetching full maps, converting endpoints to >>>> PIDs >>>> and looking up the costs between PIDs. >>>> >>>> For a client, ECS is simple & easy to use: the client does not have to >>>> maintain >>>> any maps, and the client gets the latest cost data. >>>> I agree on this. >>>> Now consider a busy Bittorrent tracker. It gets 10+ requests/second, and >>>> for >>>> each request, it must select 50 out of (say) 5,000 peers. If the tracker >>>> used ECS, >>>> it would have to send 10 ECS requests a second, each with 5,000 endpoints. >>>> That would add too much latency to the tracker response, and would >>>> overload the ALTO server. >>>> >>>> So a tracker client would prefer to download the full NM/CM and evaluate >>>> costs locally, without involving the ALTO server each time. That requires >>>> more >>>> programming effort, but is more efficient. >>>> >>>> Here is another piece of historical motivation that is not clear in the >>>> RFC: we expect ALTO Servers will be offered by network service providers. >>>> Some providers will be (understandably!) reluctant to publish a detailed >>>> breakdown of their internal network. The NM/CM model allows a service >>>> provider to control the level of detail it wants to make available to the >>>> outside >>>> world. >>>> >>>> Incidentally, the RFC says an ALTO Server MUST provide an NM/CM, while ECS >>>> is optional. Personally, I think that is a mistake. I think NM/CM should be >>>> optional, and ECS should be required. I agree on this >>>> So if you are writing a server, I recommend you build an internal cost map, >>>> with as high a level of detail as practical. Offer an ECS that uses that >>>> underlying detailed map. Then to satisfy the RFC, use some form of cluster >>>> analysis to partition the endpoints in the underlying map into >>>> (say) 100 to 200 PIDs, and offer a Network Map & Cost Map based on that >>>> partitioning. >>>> >>>> I hope that helps. >>>> >>>> - Wendy Roome >>>> >>>> >>>> >Date: Tue, 8 Sep 2015 20:53:37 -0500 >>>> >From: Lyle Bertz <[email protected]> >>>> >To: [email protected] >>>> >Subject: [alto] Cost Maps, Endpoint Cost Maps and Coarse Grained >>>> > Searches >>>> >Message-ID: >>>> > >>>> <CAC5bAiYH5N2tQpr3CEZn+eO8C9kYgWttyqNrwKKe=8kRKAfL4w@m >>>> ail.gmail.com> >>>> >Content-Type: text/plain; charset="utf-8" >>>> > >>>> >All, >>>> > >>>> >I am implementing an Erlang based ALTO server and had a couple of >>>> >questions based upon an observation of 7285. >>>> > >>>> >The Cost Map is assumed to be coarse grained and one cannot make a >>>> >determination about whether an endpoint cost measure is fine or coarse >>>> >per the RFC. >>>> > >>>> >If i am to search for a cost between two endpoints (1 source and 1 >>>> >destination) and 'miss' on the first endpoint map I am looking at the >>>> >other endpoint costs responses I may have available for an answer. In >>>> >such a case I can just look for the two endpoints and, if present, I >>>> >have a hit and I am good to go. >>>> > >>>> >However, if I am looking to Cost Maps the map dependency assumes that >>>> both >>>> >endpoints are members of the same map. This implies that only endpoint >>>> >cost maps can contain metrics between two endpoints that are not in the >>>> >same map. I find this interesting in that as a designer if you want all >>>> >data in Network Cost Maps you have to model the entire internet or you >>>> >can just rely on endpoint cost maps. >>>> > >>>> >What was the intent in this relationship? I like the open ended option >>>> >the endpoint cost maps provide but I am a bit reluctant to begin coding >>>> >something that may have not been an intentional feature in ALTO. >>>> > >>>> >Thanks. >>>> > >>>> >Lyle >>>> > >>>> >PS - Code for Erlang ALTO server (very Alpha) can be found at >>>> >https://github.com/lylebe/e__alto >>>> >-------------- next part -------------- An HTML attachment was >>>> >scrubbed... >>>> >URL: >>>> ><https://mailarchive.ietf.org/arch/browse/alto/attachments/20150908/d08 >>>> >924 >>>> >af/attachment.html> >>>> >>>> >>>> _______________________________________________ >>>> alto mailing list >>>> [email protected] >>>> https://www.ietf.org/mailman/listinfo/alto _______________________________________________ alto mailing list [email protected] https://www.ietf.org/mailman/listinfo/alto
