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[67.169.103.239]) by smtp.gmail.com with ESMTPSA id b22sm12462028pff.173.2021.03.08.20.32.22 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Mon, 08 Mar 2021 20:32:23 -0800 (PST) Sender: Tony Li Content-Type: text/plain; charset=utf-8 Mime-Version: 1.0 (Mac OS X Mail 14.0 \(3654.40.0.2.32\)) From: Tony Li In-Reply-To: <018801d71499$9890feb0$c9b2fc10$@tsinghua.org.cn> Date: Mon, 8 Mar 2021 20:32:21 -0800 Cc: Aijun Wang , lsr , draft-wang-lsr-prefix-unreachable-annoucement , "Acee Lindem (acee)" , Gyan Mishra Content-Transfer-Encoding: quoted-printable Message-Id: References: <22FDE3EA-B5D1-4E4D-B698-1D79173E8637@tony.li> <6E0281D2-7755-499A-B084-CA8472949683@chinatelecom.cn> <018801d71499$9890feb0$c9b2fc10$@tsinghua.org.cn> To: Aijun Wang X-Mailer: Apple Mail (2.3654.40.0.2.32) Archived-At: Subject: Re: [Lsr] https://tools.ietf.org/html/draft-wang-lsr-prefix-unreachable-annoucement-05 X-BeenThere: lsr@ietf.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Link State Routing Working Group List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 09 Mar 2021 04:32:28 -0000 Hi Aijun, > Stuffing things in the IGP seems like a poor way of determining that = there=E2=80=99s a BGP failure. Wouldn=E2=80=99t BFD be a more = appropriate way of determining the loss of connectivity? Or aggressive = BGP keepalive timers? > [WAJ] For BFD, you need to configure between each pair of them to = track the connectivity. For BGP keeplive times, the duration is too = long. You have to configure BGP on both sides too. Most implementations do allow you to change the timers. >> The other side of BGP peer can quickly remove the BGP session when it = receives such PUA message which tell it the other peer is down now. = Other BGP peer protection procedures can then take effects on. >> The immediate notification of the failure prefix can certainly = accelerate the switchover of BGP control plane and also the service = traffic that such BGP session carries. >=20 >=20 > The IGP is a very poor way of delivering service liveness information. > [WAJ] why?=20 Because it=E2=80=99s not a service (un)availability protocol. It=E2=80=99s= a reachability and path computation function. That is it=E2=80=99s = role in the architecture. Asking it to do something else is a violation = of the architecture. Routing protocols are not transport protocols. Or dump trucks. Or = service advertisement protocols. > That seems 100% unnecessary as the longer prefix will attract the = traffic in the way that you want. > [WAJ] If the ABR advertises such detail prefix, it will certainly = attract the traffic. But here the PUA message is just to trigger the ABR = to advertise such detail prefix, or else, such ABR will still advertise = the summary address. You don=E2=80=99t need the PUA message. The ABR can see the loss of = topology and can realize that it=E2=80=99s the best path to the prefix = and can then advertise the explicit longer prefix in addition to the = normal summary. Tony