Hi WG, It was suggested that we post this design ahead of the hackathon and WG meeting just in case there are comments and suggestions. Since one important focus of the WG is on addressing issues supporting real deployment, and this design arises in our target deployment at LHCONE, we feel that we should discuss this with the WG early.
In the context of deploying ALTO at LHCONE, one main issue is that LHCONE is a multi-domain network: see slide 3 ( https://indico.cern.ch/event/1110783/contributions/4688996/attachments/2417086/4136448/2022-03-29_ECapone_LHCONE_L3VPN.pdf). As a result, to fully implement the ALTO endpoint cost service (or cost map), we will need to represent the full path spanning multiple domains from the source to the destination. Requiring that each network on the path reveal its internals is not practical, so we need to extend the current ALTO protocol to represent the properties of, potentially multiple, not fully revealed paths. Here is the current openalto design: it introduces a new representation of paths. In particular, it allows the path from a src to a dst to be a directed acyclic graph: with the following components: * A set of nodes, where each node has both a type, and attributes, where the type can be - host: such as src/dst, with attributes such as IP address - AS: which is a group of nodes, i.e., subgraph, with attributes including ASN - router, with subtypes such as BGP-router, with attributes such as IP address * A set of links, where each link has a head and a tail; hence the types of links will be the unique combinations of head-type x tail type. A link can have its attributes as well. Now, some examples of this representation in the openalto deployment use case: - For the geo-distance ALTO cost derived from geo-ip: the src is a host and the dst is also a host, and the metric is the geo distance; - For CERN looking glass ALTO server, from a src host in CERN to a dst host in another network, say KIT, the src is a host, with two links, one for each of the two looking glass BGP routers from cern; each of these BGP routers links to its BGP peer, and each such BGP peer links to the next AS, in the AS-PATH exposed by CERN.The preceding representation is quite general. We are implementing this design for the coming Hackathon and will give more details in follow up emails and the WG meeting on Friday. Any comments or suggestions are greatly appreciated, since we may have time to adopt the suggestions in the hackathon. Thanks a lot. Lauren, Jensen and Richard
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