[ofa-general] How to Interpret MTU reported by "ibv_devinfo" vs "ifconfig ib0"

[Kumar, Amit H.]

Hello Everyone,

Why do we see a difference in the MTU reported here by: ibv_devinfo and "ifconfig ib0" How do we interpret them?


Also Is there a document where I can read in detail about IPoIB and applications that benefit from them.
In general I understand that Socket based applications can make use of IPoIB for a better bandwidth, thought NOT for a better transport latency.
In short I am trying to understand the difference and advantage, for an Application using "Ethernet NIC" vs "InfiniBand HCA(IPoIB enabled)", apart from knowing that there is no advantage in terms of transport latency.


Thank you!,
Amit

# ibv_devinfo
hca_id: mthca0
        fw_ver:                         1.2.0
        node_guid:                      0006:6a00:9800:e8e7
        sys_image_guid:                 0006:6a00:9800:e8e7
        vendor_id:                      0x066a
        vendor_part_id:                 25204
        hw_ver:                         0xA0
        board_id:                       MT_0230000001
        phys_port_cnt:                  1
                port:   1
                        state:                  PORT_ACTIVE (4)
                        max_mtu:                2048 (4)
                        active_mtu:             2048 (4)
                        sm_lid:                 2
                        port_lid:               29
                        port_lmc:               0x00



# ifconfig ib0
ib0       Link encap:InfiniBand  HWaddr 80:00:04:04:FE:80:00:00:00:00:00:00:00:00:00:00:00:00:00:00
          inet addr:172.25.44.250  Bcast:172.25.44.255  Mask:255.255.255.0
          inet6 addr: fe80::206:6a00:a000:e8e7/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:65520  Metric:1
          RX packets:138863 errors:0 dropped:0 overruns:0 frame:0
          TX packets:195994 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:256
          RX bytes:11000200 (10.4 MiB)  TX bytes:4321658633 (4.0 GiB)