Re: [RTG-DIR] RtgDir Early review: draft-ietf-rtgwg-atn-bgp-12.txt
Mach Chen <mach.chen@huawei.com> Mon, 07 February 2022 10:01 UTC
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From: Mach Chen <mach.chen@huawei.com>
To: "Templin (US), Fred L" <Fred.L.Templin@boeing.com>, Mach Chen <mach.chen=40huawei.com@dmarc.ietf.org>, rtgwg-chairs <rtgwg-chairs@ietf.org>, "draft-ietf-rtgwg-atn-bgp.all@ietf.org" <draft-ietf-rtgwg-atn-bgp.all@ietf.org>
CC: "rtg-dir@ietf.org" <rtg-dir@ietf.org>, "rtgwg@ietf.org" <rtgwg@ietf.org>
Thread-Topic: RtgDir Early review: draft-ietf-rtgwg-atn-bgp-12.txt
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Date: Mon, 07 Feb 2022 10:01:26 +0000
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Subject: Re: [RTG-DIR] RtgDir Early review: draft-ietf-rtgwg-atn-bgp-12.txt
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Hi Fred, Some responses inline... > -----Original Message----- > From: rtg-dir [mailto:rtg-dir-bounces@ietf.org] On Behalf Of Templin (US), > Fred L > Sent: Tuesday, February 1, 2022 1:44 AM > To: Mach Chen <mach.chen=40huawei.com@dmarc.ietf.org>; rtgwg-chairs > <rtgwg-chairs@ietf.org>; draft-ietf-rtgwg-atn-bgp.all@ietf.org > Cc: rtg-dir@ietf.org; rtgwg@ietf.org > Subject: Re: [RTG-DIR] RtgDir Early review: draft-ietf-rtgwg-atn-bgp-12.txt > > Mach, thank you very much for this helpful pre-review and see below for > follow-up: > > Fred > > > -----Original Message----- > > From: rtgwg [mailto:rtgwg-bounces@ietf.org] On Behalf Of Mach Chen > > Sent: Friday, January 28, 2022 2:07 AM > > To: rtgwg-chairs <rtgwg-chairs@ietf.org>; > > draft-ietf-rtgwg-atn-bgp.all@ietf.org > > Cc: rtg-dir@ietf.org; rtgwg@ietf.org > > Subject: RtgDir Early review: draft-ietf-rtgwg-atn-bgp-12.txt > > > > Hello > > > > I have been selected to do a routing directorate “early” review of this > draft. > > https://datatracker.ietf.org/doc/ draft-ietf-rtgwg-atn-bgp-12/ > > > > The routing directorate will, on request from the working group chair, > > perform an “early” review of a draft before it is submitted for > > publication to the IESG. The early review can be performed at any time > during the draft’s lifetime as a working group document. The purpose of the > early review depends on the stage that the document has reached. > > > > As this document is going to be in working group last call, my focus > > for the review was to determine whether the document is ready to be > published. Please consider my comments along with the other working group > last call comments. > > > > For more information about the Routing Directorate, please see > > http://trac.tools.ietf.org/area/rtg/trac/wiki/RtgDir > > > > Document: draft-ietf-rtgwg-atn-bgp-12.txt > > Reviewer: Mach Chen > > Review Date: 2022/1/28 > > Intended Status: Informational > > > > Summary: > > > > This document is basically ready for publication, but has nits that should be > considered prior to being submitted to the IESG.. > > > > Comments: > > > > 1. Section 2, > > "OAL Autonomous System", no places in this document refer to the term, > if there is no use, it should be removed.. > > > > 2. Section 2, > > Core Autonomous System > > The "hub" autonomous system maintained by all c-ASBRs within > the > > same partition. > > I have difficult to understand the above definition, need some > > clarification text if the term is desired. BTW, I found that this term > > is only used for definition of "OAL Autonomous System", given that "OAL > Autonomous System" is not used in the document, the simplest solution is > to remove this term as well. > > The terms "OAL AS", "Core AS" and "Stub AS" are used throughout the > document and are needed to set the proper context. Would it help if I were > to add the abbreviations (OAL AS, Core AS and Stub AS) to the respective "* > Autonomous System" definitions? Yes, indeed. > > > 3. Section 3, > > "...The overlay does not > > interact with the underlying INET BGP routing systems, and only a > > small and unchanging set of MSPs are advertised externally instead of > > the full dynamically changing set of MNPs." > > > > The front part says that there is no interaction with the underlying > > INET BGP routing system, the second half say there may be some MSPs > advertised between the two, seems it's self-contradictory? > > How does this sound for a rewrite: > > "...The ATN/IPS routing system interacts with underlying INET BGP routing > systems only through the static advertisement of a small and unchanging set > of MSPs instead of the full dynamically changing set of MNPs." Looks good to me. > > > 4. Section 3, > > s/each s-ASBRs/each s-ASBR > > Agreed. > > > 5. Section 3, > > "Since the BGP instance does not > > connect with any INET BGP routing systems, the ASNs assigned need > not > > be coordinated with IANA and can in fact coincide with values that > > are assigned in other domains. The only requirement is that ASNs > > must not be duplicated within the ATN/IPS routing system itself." > > Why not just use the private ASNs? It will avoid potential conflicts with the > Internet ASNs. > > Indeed. When this text was written, I was working under the limiting > assumption that only 1023 16-bit AS numbers were reserved for private use > which is far fewer than may be needed in some large deployments. > But, I did not know about RFC6996 which reserves 94,967,295 32-bit AS > numbers for private use which would seem to satisfy most deployments. > So, the proposed resolution is to cite RFC6996 and recommend (but not > mandate) private use 32-bit AS numbers. The reason to "not mandate" > is that enormous deployments could theoretically exhaust even the 32-bit > private AS number space. OK. > > > 6. Section 3, para 5, > > "Each c-ASBR configures a black-hole route for each of its MSPs. By > > black-holing the MSPs, the c-ASBR will maintain forwarding table > > entries only for the MNP-ULAs that are currently active, and packets > > destined to all other MNP-ULAs will correctly incur ICMPv6 > > Destination Unreachable messages [RFC4443] due to the black hole > > route." > > In my understanding, the black-hole route will cause the packets > > (without matching a specific MNP-ULA) to be dropped silently, and no > > ICMPv6 Destination Unreachable message will be incurred. Seems that the > black-hole route does not satisfy your requirement. > > This may require a bit more explanation. The requirement is for a c-ASBR that > lacks a MNP route matching a packet's destination address to drop the > packet and return an ICMPv6 Destination Unreachable. However, if there > were no black-hole MSP route, the packet could escape from the domain via > a less-specific route (e.g., "default") where it might be again injected back > into the overlay routing system and kicked back out by a default route ad > infinitum. So, black-holing the MSPs seems to be necessary, but how to make > the behavior of "drop and send ICMP" > based on matching the MSP is the question. Any suggestions? Unless there are some scenarios that require the c-ASBR to install a default. In my understanding, the c-ASBR does not have to maintain any default route, only the s-ASBR does. With this, the c-ASBR will drop the packet without matching a MNP and an ICMPv6 Destination Unreachable will be generated accordingly. Or maybe: "Each c-ASBR configures a black-hole route for each of its MSPs. By black-holing the MSPs, the c-ASBR will maintain forwarding table entries only for the MNP-ULAs that are currently active, and packets destined to all other MNP-ULAs will silently be dropped due to the black hole route, and a corresponding log will be recorded for this event." > > > 6. Section 4, para 6 > > "The s-ASBR's stub AS therefore > > consists of the set of all of its active Clients (i.e., the stub AS > > is a logical construct and not a physical construct)." > > From the BGP point of view, an AS is consisted of the routers that are > > running BGP protocol, the Clients are actually outside the AS and not > belong to the AS, unless the Clients or Proxy servers peer with the s-ASBR. > > OK, thanks for this. How does this look for a rewrite: > > "The s-ASBR's stub AS is therefore used only to advertise the set of MNPs of > all its active Clients and not to peer with other BGP routers (i.e., the stub AS > is a logical construct and not a physical one)." Maybe this? "The s-ASBR's stub AS is therefore used only to advertise the set of MNPs of all its active Clients and not to peer with other BGP routers, the stub AS is a logical construct and not a physical one." > > > 7. Section 5, > > In Figure 4/5, is the P/S a s-ASBR? If so, it's better to add some > > text to make it clearer. If not, how does P/S-1 know a packet should be sent > directly to P/S-2 instead to s-ASBR1? > > Yes, all P/S's are also s-ASBRs and serve a subset of the Clients in the system. > However, each Client 'A' that uses P/S 'B' as its s-ASBR could also have links > that connect through P/S's 'C', 'D', 'E', etc. Then, from the perspective of 'A', > only 'B' is the s-ASBR and all others are simple P/S's which coordinate with > the s-ASBR on 'A's behalf. > > The name "Proxy/Server" is intentionally chosen to show this duality of > function - the "P/S" in some instances acts as a simple Proxy and in other > instances acts as a Server (i.e., as a s-ASBR). > > I will see if I can add some text throughout the document that would make > this point clearer. Great! Best regards, Mach > > > Best regards, > > Mach > > _______________________________________________ > > rtgwg mailing list > > rtgwg@ietf.org > > https://www.ietf.org/mailman/listinfo/rtgwg
- [RTG-DIR] RtgDir Early review: draft-ietf-rtgwg-a… Mach Chen
- Re: [RTG-DIR] RtgDir Early review: draft-ietf-rtg… Templin (US), Fred L
- Re: [RTG-DIR] RtgDir Early review: draft-ietf-rtg… Mach Chen
- Re: [RTG-DIR] RtgDir Early review: draft-ietf-rtg… Templin (US), Fred L
- Re: [RTG-DIR] RtgDir Early review: draft-ietf-rtg… Mach Chen