• State Resolved
  • Locked Locked
  • Replies 6 replies
  • Subscribers 98 subscribers
  • Views 1006 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

MTU limit

Oleg Shakhov
Prodigy 90 points
Other Parts Discussed in Thread: DM388

Hello.
I use the debug board TMDXEVM437X.

And faced with such a problem.When you try to increase the MTU more standard in 1500, displaying the error.

root@am437x-evm:~# ifconfig
eth0      Link encap:Ethernet  HWaddr 35:B3:F3:38:41:7A
          inet addr:192.168.0.159  Bcast:192.168.0.255  Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:128 errors:0 dropped:0 overruns:0 frame:0
          TX packets:34 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:9969 (9.7 KiB)  TX bytes:2533 (2.4 KiB)
          Interrupt:72

lo        Link encap:Local Loopback
          inet addr:127.0.0.1  Mask:255.0.0.0
          UP LOOPBACK RUNNING  MTU:65536  Metric:1
          RX packets:113 errors:0 dropped:0 overruns:0 frame:0
          TX packets:113 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:238220 (232.6 KiB)  TX bytes:238220 (232.6 KiB)

root@am437x-evm:~# ifconfig eth0 mtu 9000 up
ifconfig: SIOCSIFMTU: Invalid argument
root@am437x-evm:~# ifconfig eth0 mtu 1500 up
root@am437x-evm:~# ifconfig eth0 mtu 2000 up
ifconfig: SIOCSIFMTU: Invalid argument
root@am437x-evm:~# ifconfig eth0 mtu 1000 up
root@am437x-evm:~# ifconfig
eth0      Link encap:Ethernet  HWaddr 35:B3:F3:38:41:7A
          inet addr:192.168.0.159  Bcast:192.168.0.255  Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST  MTU:1000  Metric:1
          RX packets:744 errors:0 dropped:0 overruns:0 frame:0
          TX packets:248 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:47717 (46.5 KiB)  TX bytes:16391 (16.0 KiB)
          Interrupt:72

lo        Link encap:Local Loopback
          inet addr:127.0.0.1  Mask:255.0.0.0
          UP LOOPBACK RUNNING  MTU:65536  Metric:1
          RX packets:113 errors:0 dropped:0 overruns:0 frame:0
          TX packets:113 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:238220 (232.6 KiB)  TX bytes:238220 (232.6 KiB)

root@am437x-evm:~#


As I understand this is due to the limitations of the hardware of the network.
Please tell me how to solve my problem.

Thank you all.

  • 0
    TI__Guru**** 393215 points

    Hi Oleg,

    I will ask the SW team to check if/what MTU is supported.

  • 0 in reply to Biser Gatchev-XID
    Prodigy 90 points
    Hi Biser,

    Tell me please, what they will say.
    I have worked with DaVinci IPNC_DM388_IMX185 there had no such problems. Although the source code relating to the same kind of MTU.
    I use SDK am437x-evm-sdk-src-07.01.00.00.

    Best Regards
    Oleg
  • 0 in reply to Oleg Shakhov
    TI__Expert 4475 points
    Hi Oleg,
    I'll give you some passage for MTU:
    "The MTUs in this section are given as the maximum size of an IP packet that can be transmitted without fragmentation - including IP headers but excluding headers from lower levels in the protocol stack. Nearly all IP over Ethernet implementations use the Ethernet V2 frame format where MTU = 1500.

    en.wikipedia.org/.../Maximum_transmission_unit

    For more details check standard (IEEE 802.3x-1997)

    In order to allow packets using Ethernet v2 framing and packets using the IEEE 802.3 framing to be used on the same Ethernet segment, a unifying standard (IEEE 802.3x-1997) was introduced that required that EtherType values be greater than or equal to 1536 (0x0600). That value was chosen because the maximum length (MTU) of the data field of an Ethernet 802.3 frame was 1500 bytes (0x05DC). Thus, values of 1500 (0x05DC) and below for this field indicate that the field is used as the size of the payload of the Ethernet Frame while values of 1536 and above indicate that the field is used to represent EtherType. The interpretation of values 1501–1535, inclusive, is undefined."
    BR
    Ivan
  • 0 in reply to Ivan Matrakov
    Prodigy 90 points
    Hi Ivan,

    "Most Ethernet LANs use an MTU of 1500 bytes (modern LANs can use Jumbo frames, allowing for an MTU up to 9000 bytes)..."

    You want to say that in DaVinci modern network and it is possible to set the MTU of 9000? And Sitara not support Jumbo frames? It seemed to me that all modern Gigabit adapters support it.

    Best Regards
    Oleg
  • 0 in reply to Oleg Shakhov
    TI__Expert 4475 points
    Hi Oleg,

    Yes, but this is the comments what I found:
    "The size of the payload of non-standard jumbo frames, typically ~9000
    Bytes long, falls within the range used by EtherType, creating a conflict.
    The proposition to resolve this conflict was to substitute the special
    EtherType 0x8870 when a length would otherwise be used."

    BR
    Ivan
  • 0 in reply to Ivan Matrakov
    Prodigy 90 points
    Hi Ivan,

    Thank you Ivan.
    Another question. What kind of speed can really provide TMDXEVM437X? I have so far are measured iperf 120-130 MByte per second. On 4M package when measured 60 seconds.

    Best Regards
    Oleg