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adjust mss on S6720 HI serie

Created: Apr 15, 2020 01:35:09Latest reply: Apr 27, 2020 14:48:33 276 23 0 0
  Rewarded HiCoins: 1 (problem resolved)

Hi all, is there any way to change the tcp mss value of a passtrough tcp traffic. I had proveb with the global command tcp max-mss but it only change the mss of the traffic generated/recived by the switch.

Thanks! Mauro

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Created Apr 15, 2020 09:00:12 Helpful(0) Helpful(0)

For a AR router, there is a command "tcp adjust-mss" to restrict the MSS value. But I didn't find a correponding command in the S series switch documentation. I think there isn't a such command could statisfied your requirement.
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mauro83 Created Apr 15, 2020 14:08:46
Thanks, I´m in a problem.  
mauro83 Created Apr 17, 2020 22:11:06
This answer can not be the recomended, does not resolve nothing!!!!!  
Sapte Reply mauro83  Created Apr 30, 2020 14:43:33
yes there is an MTU command you can use to configure MTU-40=MSS
Please check my answer  
All Answers
sohaib.ansar MVE Created Apr 15, 2020 01:40:08 Helpful(0) Helpful(0)

Hi User,

When a TCP connection is set up between switch and other devices, TCP properties such as TCP connection for BGP need to be configured.

The following TCP properties can be configured on the switch:

  • SYN-Wait timer: When SYN packets are sent, the SYN-Wait timer is started. If no response packet is received after the SYN-Wait timer expires, the TCP connection is closed.

  • FIN-Wait timer: When the TCP connection status changes from FIN_WAIT_1 to FIN_WAIT_2, the FIN-Wait timer is started. If no response packet is received after the FIN-Wait timer expires, the TCP connection is closed.

  • Receive/send buffer size of connection-oriented socket.

  • Minimum Maximum Segment Size (MSS) value: Setting a minimum MSS value for a TCP connection defines the smallest TCP packet size, preventing DoS attacks caused by packets with small MSS values.

  • Maximum MSS value: Setting a maximum MSS value for a TCP connection defines the largest TCP packet size, allowing TCP packets to be successfully forwarded by intermediate devices when no MTU is available.

Procedure

  1. Run:


    system-view

    The system view is displayed.


  2. Run:


    tcp timer syn-timeout interval

    The SYN-Wait timer of TCP connections is configured.

    By default, the value of the TCP SYN-Wait timer is 75s.


  3. Run:


    tcp timer fin-timeout interval

    The FIN-WAIT timer of TCP connections is configured.

    By default, the value of the TCP FIN-Wait timer is 675s.


  4. Run:


    tcp window window-size

    The size of the receive or send buffer of a connection-oriented socket is configured.



    By default, the size of the receive or send buffer of a connection-oriented socket is 8k bytes.


  5. Run:


    tcp min-mss mss-value

    The minimum MSS value is configured for a TCP connection.

    By default, the minimum MSS value for a TCP connection is 216 bytes.


  6. Run:


    tcp max-mss mss-value

    The maximum MSS value is configured for a TCP connection.

    By default, the maximum MSS value is not configured for TCP connections.

https://support.huawei.com/enterprise/en/doc/EDOC1000088748?section=j00b

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mauro83 Created Apr 15, 2020 14:11:23
I did it, but only is usefull if the traffic is gerenerated or recived on the switch. In need to intercept flow of user connected to the switch and remark the mss. In other lines of Huawei’s routers it can be do on an interface by tcp adjust-mss command.
Thanks
Mauro  
mauro83 Created Apr 15, 2020 01:46:10 Helpful(0) Helpful(0)

I did it, but only is usefull if the traffic is gerenerated or recived on the switch. In need to intercept flow of user connected to the switch and remark the mss. In other lines of Huawei’s routers it can be do on an interface by tcp adjust-mss command.
Thanks
Mauro
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DDSN Admin Created Apr 15, 2020 01:53:59 Helpful(0) Helpful(0)

Hi user_3776214,

The MSS is an option defined in the TCP protocol and refers to the maximum length of TCP packets that can be received by a device. When setting up a TCP connection, the local and peer devices negotiate an MSS value to determine the maximum data length of TCP packets. If the length of TCP packets sent from the peer device exceeds the MSS value, the packets are fragmented.

1. Run system-view

The system view is displayed.

2. Run wlan

The WLAN view is displayed.

3. Run traffic-profile name profile-name

A traffic profile is created, and the traffic profile view is displayed.

4. Run traffic-optimize tcp adjust-mss value

The MSS of TCP packets is configured in the traffic profile.

By default, the MSS of TCP packets in a traffic profile is not configured.

5. Run quit

Return to the WLAN view.

6. Run vap-profile name profile-name

The VAP profile view is displayed.

7. Run traffic-profile profile-name

The traffic profile is bound to the VAP profile.

By default, the traffic profile default is bound to a VAP profile.

I hope it helps!

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mauro83 Created Apr 15, 2020 01:58:37
Thanks, its work for all interfaces or only for wlan? I need to adjust the mss of client wired connected to the S6720.
Thanks  
user_3534491 Created Apr 15, 2020 09:00:12 Helpful(0) Helpful(0)

For a AR router, there is a command "tcp adjust-mss" to restrict the MSS value. But I didn't find a correponding command in the S series switch documentation. I think there isn't a such command could statisfied your requirement.
View more
  • x
  • convention:

mauro83 Created Apr 15, 2020 14:08:46
Thanks, I´m in a problem.  
mauro83 Created Apr 17, 2020 22:11:06
This answer can not be the recomended, does not resolve nothing!!!!!  
Sapte Reply mauro83  Created Apr 30, 2020 14:43:33
yes there is an MTU command you can use to configure MTU-40=MSS
Please check my answer  
chenhui Admin Created Apr 17, 2020 00:45:01 Helpful(0) Helpful(0)

@mauro83
What situation are you stuck in?
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mauro83 Created Apr 17, 2020 03:51:12
I need that the s6720 HI adjust the tcp mss of the tcp flow of clients connected to it. With the tcp max-mss the switch only adjust the mss of the traffic generated/recived by itself.  
mauro83 Created Apr 17, 2020 22:07:37 Helpful(0) Helpful(0)

Huawei does not have any serious answer to solve this problem? I can not believe it!
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Popeye_Wang Admin Created Apr 20, 2020 08:16:51 Helpful(0) Helpful(0)

Posted by mauro83 at 2020-04-17 22:07 Huawei does not have any serious answer to solve this problem? I can not believe it!
The modification of the TCP MSS takes effect only for the TCP connections created on the local device. If your switch works at Layer 2, it only forwards data frames and cannot modify TCP packets in the frames. The MTU/MSS can be modified only on the terminal or the Layer 3 device that forwards packets.
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mauro83 Created Apr 21, 2020 04:15:46
It’s working in layer 3, routing traffic of users.  
Steelblue Created Apr 24, 2020 11:10:13 Helpful(0) Helpful(0)

Try to use the MTU command on the interface.
MTU=MSS+40
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Sapte Created Apr 24, 2020 16:16:47 Helpful(0) Helpful(0)

hi @mauro83


You can see your problem solution in the below


1st - You should check MTU & MSS relationship


The MTU is the Maximum IP packet size for a given link. Packets bigger than the MTU is fragmented at the point where the lower MTU is found and reassembled further down the chain

MSS is Maximum TCP segment Size. Unlike MTU, packet exceeding MSS aren't fragmented, they're simply discarded. MSS is normally decided in the TCP three-way handshake, but some setup might yield path where the decided upon MSS is still too big, leading to dropped packets. The MSS isn't negotiated packet per packet, but for a complete TCP session, nor does it take into account TCP/IP headers

Also basic relationship between MSS & MTU is : MTU-40=MSS

TCP 20 and IP 20 bytes



2nd As a solution you can configure your MTU value for adjusting MSS value on a interface by considering this equation; MTU-40=MSS


Device : S6720

MTU Config in interface view


mtu

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Sapte Created Apr 27, 2020 15:35:27
hi @mauro83

this solves your problem fyi  
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