J'ai trouvé la raison :
rphx a une IP 213.245.44.xxx Numericale (AS 21502) tandis que moi, j'ai une IP 79.83.168.xxx SFR (AS 15557)
Le trafic IN pour une IP Numericable (AS 21502) passe par le port TH2 de France-IX (40 Gb/s) ou le port PAR2 de France-IX (20 Gb/s)
Le trafic IN pour une IP SFR (AS 15557) passe par le port TH2 de France-IX (100 Gb/s)
Pour le trafic sortant, tous les abonnés câble, ceux avec IP SFR comme ceux avec IP Numericable, sortent par les interconnexion de Numericable (mais ce n'est pas dans ce sens que le trafic est chargé et risque de saturer)
Whois pour rphx : c'est Numericable
$ whois 213.245.44.0
% Information related to '213.245.40.0 - 213.245.47.255'
% Abuse contact for '213.245.40.0 - 213.245.47.255' is 'abuse@numericable.fr'
inetnum: 213.245.40.0 - 213.245.47.255
netname: FR-NCNUMERICABLE
descr: End-User NUMERICABLE
remarks: ***********************************
remarks: * Abuse e-mail: abuse@numericable.fr *
remarks: ***********************************
country: FR
admin-c: ANUM-RIPE
tech-c: TNUM-RIPE
status: ASSIGNED PA
mnt-by: SFR-MNT
created: 2015-10-12T10:31:04Z
last-modified: 2015-10-12T10:31:04Z
source: RIPE
role: Numericable Administrative Role Account
address: NUMERICABLE
address: 6 rue Albert Einstein
address: 77420 CHAMPS SUR MARNE
address: FRANCE
abuse-mailbox: abuse@numericable.fr
admin-c: FH1435-RIPE
admin-c: HL2711-RIPE
admin-c: BPI1202-RIPE
tech-c: TNUM-RIPE
nic-hdl: ANUM-RIPE
mnt-by: NUMERICABLE-MNT
created: 2007-11-26T13:03:58Z
last-modified: 2017-02-17T13:25:06Z
source: RIPE # Filtered
role: Numericable Technical Role Account
address: NUMERICABLE
address: 6 rue Albert Einstein
address: 77420 CHAMPS SUR MARNE
address: FRANCE
abuse-mailbox: abuse@numericable.fr
admin-c: ANUM-RIPE
tech-c: FH1435-RIPE
tech-c: HL2711-RIPE
tech-c: BPI1202-RIPE
nic-hdl: TNUM-RIPE
mnt-by: NUMERICABLE-MNT
created: 2007-11-26T13:10:34Z
last-modified: 2017-02-17T13:26:02Z
source: RIPE # Filtered
% Information related to '213.245.0.0/17AS21502'
route: 213.245.0.0/17
descr: NUMERICABLE
origin: AS21502
mnt-by: NUMERICABLE-MNT
created: 2010-04-26T16:26:23Z
last-modified: 2010-04-26T16:26:23Z
source: RIPE
Whois pour mon abonnement RED Câble : C'est SFR
$ whois 79.83.168.0
% Information related to '79.83.168.0 - 79.83.171.255'
% Abuse contact for '79.83.168.0 - 79.83.171.255' is 'abuse@gaoland.net'
inetnum: 79.83.168.0 - 79.83.171.255
netname: FR-NCNUMERICABLE
descr: Dynamic pools
remarks: ***********************************
remarks: * Abuse e-mail: abuse@numericable.fr*
remarks: ***********************************
country: FR
admin-c: ANUM-RIPE
tech-c: TNUM-RIPE
status: ASSIGNED PA
mnt-by: LDCOM-MNT
created: 2016-02-16T10:19:15Z
last-modified: 2016-02-16T10:19:15Z
source: RIPE
role: Numericable Administrative Role Account
address: NUMERICABLE
address: 6 rue Albert Einstein
address: 77420 CHAMPS SUR MARNE
address: FRANCE
abuse-mailbox: abuse@numericable.fr
admin-c: FH1435-RIPE
admin-c: HL2711-RIPE
admin-c: BPI1202-RIPE
tech-c: TNUM-RIPE
nic-hdl: ANUM-RIPE
mnt-by: NUMERICABLE-MNT
created: 2007-11-26T13:03:58Z
last-modified: 2017-02-17T13:25:06Z
source: RIPE # Filtered
role: Numericable Technical Role Account
address: NUMERICABLE
address: 6 rue Albert Einstein
address: 77420 CHAMPS SUR MARNE
address: FRANCE
abuse-mailbox: abuse@numericable.fr
admin-c: ANUM-RIPE
tech-c: FH1435-RIPE
tech-c: HL2711-RIPE
tech-c: BPI1202-RIPE
nic-hdl: TNUM-RIPE
mnt-by: NUMERICABLE-MNT
created: 2007-11-26T13:10:34Z
last-modified: 2017-02-17T13:26:02Z
source: RIPE # Filtered
% Information related to '79.80.0.0/12AS15557'
route: 79.80.0.0/12
descr: LDCOM-NET
origin: AS15557
mnt-by: LDCOM-MNT
created: 2007-08-08T09:53:38Z
last-modified: 2007-08-08T09:53:38Z
source: RIPE
Conclusion : SFR ne sature pas son port sur France-IX, mais Numericable sature un de ses deux ports (ou les deux) sur France-IX.