Update to accommodate Jeff Haas's comment#40
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@mitradir @job @jhaas-pfrc Jeff requested consideration in the draft for rare AS partition scenarios, when AS loop detection may be disabled and the AS may accept its own routes with an AS loop from a provider and propagate to downstream customers. In these scenarios, operators may temporarily onboard a pre-designated emergency transit provider to bridge the isolated segments of AS. Jeff suggested we include some wording to say that operators must plan for these contingencies in advance while registering their ASPA.
Jeff requested consideration in the draft for rare AS partition scenarios, when AS loop detection may be disabled and the AS may accept its own routes with an AS loop from a provider and propagate to downstream customers. In these scenarios, operators may temporarily onboard a pre-designated emergency transit provider to bridge the isolated segments of AS. Jeff suggested we include some wording to say that operators must plan for these contingencies in advance while registering their ASPA. Added Sec. 6.6 for the above. Minor correction in Sec. 5.1 concerning AS prepend compression.
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This text addresses the point I've raised. Thanks for covering it. |
mitradir
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Let's discuss bellow comments
| <section title="Principles" anchor="principles"> | ||
| <t> | ||
| Let the sequence COMPRESSED_AS_PATH {AS(N), AS(N-1),..., AS(2), AS(1)} represent the AS_PATH in terms of unique ASNs, where AS(1) is the origin AS and AS(N) is the most recently added AS and neighbor of the receiving/verifying AS. | ||
| Let the sequence COMPRESSED_AS_PATH = {AS(N), AS(N-1),..., AS(2), AS(1)} represent the AS_PATH after collapsing consecutive duplicate ASNs, where AS(1) is the origin AS, AS(N) is the most recently added AS (and a neighbor of the receiving/verifying AS), and no two consecutive ASNs are equal. |
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I'm fine with the first change of the sentence, but the last part of the phrase looks like an overkill for me
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Perhaps:
Let the sequence COMPRESSED_AS_PATH = {AS(N), AS(N-1),..., AS(2), AS(1)} represent the AS_PATH after removing consecutive duplicate ASNs, where AS(1) is the origin AS, AS(N) is the most recently added AS, and a neighbor of the receiving/verifying AS.
| <section title="Partitioned AS" anchor="AS-part"> | ||
| <t> | ||
| In rare scenarios where an AS becomes internally partitioned, for example, due to a physical link failure, operators may temporarily onboard a pre-designated emergency transit provider to bridge the isolated segments. | ||
| To achieve this, the AS must override standard eBGP loop detection to accept its own routes via the emergency provider and it may propagate the routes (with loops) to its downstream customers. |
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Is there an assumption that there is a specific provider between two parts of the same network? I have seen such a scenario before in the wild, and to my understanding, there may be multiple ASs in the middle. If loop detection is turned off or relaxed, they just accept their own routes from other sources.
But the ASPA will also work in this case, no actions are needed except for registering providers, including emergency ones, and this was already stated in the document.
I can work on the wording of this section, but do we really need it if there is no specific processing and second thoughts?
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There can definitely be more than one provider involved.
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@mitradir @jhaas-pfrc
In the example in Section 6.6, there are two providers -- one regular (say Provider AS A) and another that is for emergency/backup (say Provider AS B). When the AS X in question is not partitioned, AS A serves all of AS X. When partitioned, AS X breaks into two disconnected parts -- Parts 1 and 2. Part 1 is still connected to and served by Provider AS A. The emergency Provider AS B is on-boarded to serve Part 2. So, when an ASBR in Part 2 receives Part 1's customers' routes from AS B, the routes contain both AS A and AS B in the path.
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It may be still be a regular provider, or a backup provider, or ASA ASB ASC ASA, where ASB and ASC are both providers of ASA, it doesn't change the situation. And doesn't require any additional guidance in terms of ASPA registration process.
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The sole necessary guidance is "if you're going to use loops as a feature, ASPA can break it if you don't have the necessary objects registered".
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@mitradir @job @jhaas-pfrc
Jeff requested consideration in the draft for rare AS partition scenarios, when AS loop detection may be disabled and the AS may accept its own routes with an AS loop from a provider and propagate to downstream customers. In these scenarios, operators may temporarily onboard a pre-designated emergency transit provider to bridge the isolated segments of AS. Jeff suggested we include some wording to say that operators must plan for these contingencies in advance while registering their ASPA.