Ketan,
Lots of thanks for a prompt and unambiguous response!

Regards,
Sasha

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________________________________
From: Ketan Talaulikar <[email protected]>
Sent: Wednesday, June 10, 2026 8:52:44 PM
To: Alexander Vainshtein <[email protected]>
Cc: [email protected] <[email protected]>; Jorge Rabadan (Nokia) 
<[email protected]>; Wen Lin <[email protected]>; BESS 
<[email protected]>
Subject: [EXTERNAL] Re: A question about Section 3.3 of RFC 9819

Hi Sasha, Yes, the ARG would be unusable in that case. I believe this was 
covered by the base RFC9252 which in turn leverage RFC8986 - 
seehttps://datatracker.ietf.org/doc/html/rfc9252#section-3.2.1<https://datatracker.ietf.org/doc/html/rfc9252#section-3.2.1>
 "As defined in [RFC8986], the sum of the Locator Block Length (LBL), Locator 
Node Length (LNL), F
[https://image-processing-service.us-4.mimecastcybergraph.com/v2/banners?e=gW9fWeGHc9G8ALkSkGqJlep93WtD-A_N7zr6HbFYTc4zvHmKlLHBgTvbx7AvMG2Y56RUVMup4jmf1BGvoQAU63RxRAWpdyphZv4AKWk64bcHIy4V2UB7DzmGBDgOSi4ELSrUKedZi0DGa8eSe3TRIbWRD1FWT2OHoOd4kk2hC-GfpCbzQV4K4mdXmWmINmm1NQNBS2YeEebQ0spllywFRTD7b3wyK8iACZ6B5oUxB1upeP3h7E8EUKvdDU9dPUkkIhDb0SZCiavO9vKBgm0IfhxZ7oy19LV45JuDj1jBfAX4QrGz-HHjaarhG6J4NoVqCSgSTIMAj-3BqPuTL5SV3Flx07ghOymWPOkg4_NcgEXAQsnzvEpOEdvsLxbaFA0eNDT4CnmJHylFTGH0l7xj7fuueHOv2B4_yiXgx8vSjV1Qsuk01LHeyb4X95-K]<https://report.mimecastcybergraph.com?magiclink=https%3A%2F%2Fapi.services.mimecast.com%2Foauth2%2Fauthorize%3Fresponse_type%3Dcode%26client_id%3Do20nRkVXf7VUVnANkXhoOwGytEwGN0YAlyeDJn7oBTGNl2kN%26state%3DeyJhbGciOiJSU0EtT0FFUC0yNTYiLCJlbmMiOiJBMjU2R0NNIn0.oW71pYdeVuMiJBw4u9wS5N03IJ-G0zqNr3AZdGHlUnNHTN4X30qh2lstYuqnGF5SyAUpFY_GEHRK2UFc1sSIrqmF39vvjj3NTIp32rkX0eJ5vSUsxez6laxRZdhVbAMtG-Ba8vvBKS_Ex5gdIfg5s_tpsNKMdEzP90RSvZWm_9NZleO_oUYW8x3mtldWnXd5Y6qRbH1uMt8Pi2EeMo7dhG_eUDkB7BfSaholcNryomSReY-GoZCVhu_s69kO2ZJyIAiHJtSSFGkHPYPfgQV7B-SH_FClA9XjcidvXPurfWnCYWXICTOeK1yl0xwl8-xFOFTSFRYuVRIShChzvjgZaQ.FGQBVLwrLHwycBh2.iMxSZ_hB5IgIQi-FOp-O21OcmazNS0HsDmfuFQkqpAS85KjmdzFsXKPI5WmYhV6HnPMFX3Sb5axG1US2EyKlNJYoSpE8hxnlTcANmjrzSZonMa1GYHeVGqtG4xCYO9OyxaJufh_fR2LNwsTlkR48hI1NumRzbrvC4iXL6w7eMrmzSTMvaLdLfKdJIrd1IGrbdpDb7IZHzm5BSaCRd0DhftVL3AiCLdx9mde3gQXzJRJ9XrKHHRRCpI1CH4Dm70L2qPW3jc1jxxIy54XCv8rQ8jUp4r4eCOF7anEEL021qSvnmf73zz51do160ICE7d_9WgG0lyzgVwPwbqprtMxUS0m6wAUjylqjVbXvqH8az1hvLLq0Gzsh2zyPPsRH2NfZDJu7c0TtliLKb6dUtvZJV2YaRUdbaCg9xG-85SbjyV6eAdAQ0fekX-ygvD-IH7SXEVi7njdcL0aESb2xai8_Yatj-GpOVM-PU9NCv_3x0Qk-p9i94YAfxQsWEXO94EaPim4bxRVjM_uo4-Muwx0bvKHfMDb2YaIdWZzgPmA_P-8iRCgrfXh1S4H-ZJg1EY0xjjXb-eH9BAX8MXilEiK6g6drfgDgRdCwmwbXHYPalQIoF7DFFvobfJ-5e05qQXwwB_i0NWeACK7Bu_TVmrydDFaI5RplvREpidQ3PX90xOju_SD_ttQBO1RKHSC4Ilj8sDuuQEUm_7Cj2lZZl-gFYeL7JW3uqLi0B5hx9Zp8reGLs75DdmKdOR0MVOCYLnwP0NsYwKtI4dr_XIT6dts7bmFhaKR_nAEIAjWccrcKjd8_ujX_k7USy_082vtER5L1bMQm.OXL_9hj55XghbNLDEZBAPQ%26redirect_uri%3Dhttps%3A%2F%2Freport.mimecastcybergraph.com%2Fcallback>
CGBANNERINDICATOR
Hi Sasha,

Yes, the ARG would be unusable in that case. I believe this was covered by the 
base RFC9252 which in turn leverage RFC8986 - see 
https://datatracker.ietf.org/doc/html/rfc9252#section-3.2.1<https://datatracker.ietf.org/doc/html/rfc9252#section-3.2.1>

"As defined in [RFC8986], the sum of the Locator Block Length (LBL), Locator 
Node Length (LNL), Function Length (FL), and Argument Length (AL) fields MUST 
be less than or equal to 128 and greater than the sum of Transposition Offset 
and Transposition Length."

Thanks,
Ketan


On Wed, Jun 10, 2026 at 6:45 PM Alexander Vainshtein 
<[email protected]<mailto:[email protected]>> wrote:
Hi all,
I have a question about Section 3.3 of RFC 
9819<https://datatracker.ietf.org/doc/html/rfc9819#section-3.3>.

To the best of my understanding, this section defines the way in which Locator 
and Function of a SRv6 SID carried in the EVPN IMET route are combined with the 
Argument of this SID (when applicable) carried in the per-ES Ethernet A-D route 
if the structures of SIDs described in these routes are not identical as 
following:

  *   LBL, LNL, and FL of the combined SID are taken from the SID structure 
carried in the IMET route
  *   AL of the combined SID is taken from the SID structure carried in the 
per-ES Ethernet A-D route
  *   All the bits in the SID after (LBL+LNL+FN+AL) MUST be set to zeroes.

Unless I have missed something, this section does not say how to handle the 
situation when LBL+LNL+FN+AL) exceeds 128.

My guess is this would be yet another case to declare the Argument as unusable.

What, if anything, did I miss?

Regards, and lots of thanks in advance,
Sasha




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