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Configuration Gigabit

24 réponses
Avatar
Sam
Bonjour,

Je viens de migrer ma passerelle de woody ( noyau 2.4) vers etch
(2.6.19-2 vanilla) suite à un crash disc.
J'en ai profité pour tout migrer en gigabit pas cher, mais il y a un
problème de débit que je ne comprends pas.

Configuration (2 dmz, 2 sorties Internet + Lan) :

WinXP --- Etch --- Sarge

Tests ftp :

1) WinXP (filezilla) --> Etch (vsftpd) = 28 Mo/s

2) Etch (wget) ---> Sarge (vsftpd) = 28 Mo/s

3) WinXP (filezilla) ---> Etch (vsftpd) = 13 Mo/s ????

Je ne comprends pas cette perte de débit en FORWARD.

Il n'y a pas de règles de Qos sur ces interfaces (seulement les 2
sorties Internet).

Je pense éventuellement aux règles iptables FORWARD (5 interfaces) qui
sont très longues, mais les règles en INPUT/OUTPUT sont longues aussi.

Une augmentation du mtu de 1500 à 5000 sur ces 2 interfaces n'a rien donné.
Auriez-vous une idée pour démarrer mes recherches ?

Merci d'avance.
Samuel.

4 réponses

1 2 3
Avatar
Nina Popravka
On Mon, 12 Mar 2007 11:46:03 +0100, Pascal Hambourg
wrote:

Est-ce que ça ne pourrait pas aussi venir d'une taille de fenêtre
d'émission ou de réception TCP insuffisante en regard du produit
débit*latence de la liaison ?


Oui, mais le problème de fenêtre serait aussi présent lors des
transferts bécane --> passerelle, non ?
--
Nina

Avatar
Pascal Hambourg

Est-ce que ça ne pourrait pas aussi venir d'une taille de fenêtre
d'émission ou de réception TCP insuffisante en regard du produit
débit*latence de la liaison ?


Oui, mais le problème de fenêtre serait aussi présent lors des
transferts bécane --> passerelle, non ?


Pas de façon aussi aiguë car la latence n'est pas la même :
- bécane <-> passerelle : 1 lien ethernet
- bécane <-> bécane : 2 liens ethernet + traversée de la passerelle


Avatar
Sam
Bonjour,


Est-ce que ça ne pourrait pas aussi venir d'une taille de fenêtre
d'émission ou de réception TCP insuffisante en regard du produit
débit*latence de la liaison ?




Comment je peux le vérifier ?

Outre le problème de débit, il y a aussi toutes les 5 ou 10 secondes une
micro-coupure de quelques dixièmes de seconde, en faisant un tcpdump sur
la passerelle, la coupure a l'air d'avoir toujours lieu lors d'un
changement de dialogue lan --> dmz2 :

13:33:27.499782 IP zoe.ingescom.com.36370 > samuel.ingescom.com.1258: .
ack 134843241 win 62780
13:33:27.499853 IP zoe.ingescom.com.36370 > samuel.ingescom.com.1258: .
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ack 135872513 win 62780
13:33:27.562017 IP samuel.ingescom.com.1258 > zoe.ingescom.com.36370: .
135872513:135873973(1460) ack 1 win 65535
13:33:27.562686 IP zoe.ingescom.com.36370 > samuel.ingescom.com.1258: .
ack 135875433 win 62780
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13:33:27.617810 IP samuel.ingescom.com.1258 > zoe.ingescom.com.36370: .
136183809:136185269(1460) ack 1 win 65535
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13:33:27.657491 IP zoe.ingescom.com.36370 > samuel.ingescom.com.1258: .
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^^^^^^^^^ : coupure de quelques dixièmes de seconde.

Oui, mais le problème de fenêtre serait aussi présent lors des
transferts bécane --> passerelle, non ?


Pas de façon aussi aiguë car la latence n'est pas la même :
- bécane <-> passerelle : 1 lien ethernet
- bécane <-> bécane : 2 liens ethernet + traversée de la passerelle


Pour éliminer la cause du client, j'ai essayé avec le même poste WinXP +
un autre client gigabit avec Live CD Ubuntu.
Et bien les deux clients se partagent les 15Mo/s de dispo en bande
passante vers le serveur Debian.

Merci.
Sam.



Avatar
Sam
Est-ce que ça ne pourrait pas aussi venir d'une taille de fenêtre
d'émission ou de réception TCP insuffisante en regard du produit
débit*latence de la liaison ?




Comment je peux le vérifier ?


J'ai trouvé une page http://kb.pert.geant2.net/PERTKB/LinuxOSSpecific
qui explique la configuration gigabit en modifiant :

net/core/rmem_defaulte536
net/core/wmem_defaulte536
net/core/rmem_maxƒ88608
net/core/wmem_maxƒ88608
net/ipv4/tcp_rmem="8192 65536 8388608"
net/ipv4/tcp_wmem="8192 87380 8388608"

J'ai adapté ça aux deux serveurs, mais ça ne change rien, même s'il est
étrange que ces valeurs soient très différentes sur Etch et Sarge.

Sam.




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