[ovs-discuss] how OVS working together with MTU ??

[Li, Chen]

Hi list,

I'm working under CentOS 6.4 + Openstack Havana + Openvswitch 1.10.0-1.el6

While ports have been created like:
ovs-vsctl show
d4c41787-8313-49a1-9fa8-1e34f7fa2086
    Bridge "br-eth4"
        Port "br-eth4"
            Interface "br-eth4"
                type: internal
        Port "phy-br-eth4"
            Interface "phy-br-eth4"
        Port "eth4"
            Interface "eth4"
    Bridge br-int
        Port br-int
            Interface br-int
                type: internal
        Port "qvobc57c061-99"
            tag: 1
            Interface "qvobc57c061-99"
        Port "int-br-eth4"
            Interface "int-br-eth4"
ovs_version: "1.10.0"

ip link |grep eth4
6: eth4: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP qlen 1000
54: br-eth4: <BROADCAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UNKNOWN
328: phy-br-eth4: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1504 qdisc pfifo_fast state UP qlen 1000
329: int-br-eth4: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1504 qdisc pfifo_fast state UP qlen 1000

ovs-ofctl dump-flows br-int
NXST_FLOW reply (xid=0x4):
cookie=0x0, duration=787.291s, table=0, n_packets=17099182, n_bytes=409367360073, idle_age=0, priority=3,in_port=1,vlan_tci=0x0000 actions=mod_vlan_vid:1,NORMAL
cookie=0x0, duration=908.918s, table=0, n_packets=170, n_bytes=10844, idle_age=10, priority=2,in_port=1 actions=drop
cookie=0x0, duration=909.944s, table=0, n_packets=15442515, n_bytes=1019231483, idle_age=0, priority=1 actions=NORMAL

ovs-ofctl dump-flows br-eth4
NXST_FLOW reply (xid=0x4):
cookie=0x0, duration=800.552s, table=0, n_packets=15975472, n_bytes=1054407237, idle_age=0, priority=4,in_port=1,dl_vlan=1 actions=strip_vlan,NORMAL
cookie=0x0, duration=922s, table=0, n_packets=9, n_bytes=694, idle_age=800, priority=2,in_port=1 actions=drop
cookie=0x0, duration=922.937s, table=0, n_packets=17883113, n_bytes=426539014687, idle_age=0, priority=1 actions=NORMAL

ovs-dpctl show
system at ovs-system:
        lookups: hit:618023724 missed:5279837 lost:121027
        flows: 6
        port 0: ovs-system (internal)
        port 1: br-int (internal)
        port 2: int-br-eth4
        port 3: phy-br-eth4
        port 4: qvobc57c061-99
        port 5: eth4
        port 8: br-eth4 (internal)

Then I run iperf test, and I get:

ovs-dpctl  dump-flows
in_port(3),eth(src=fa:16:3e:76:88:c0,dst=00:1b:21:a1:19:dc),eth_type(0x8100),vlan(vid=1,pcp=0),encap(eth_type(0x0800),ipv4(src=191.101.0.28,dst=191.101.100.254,proto=6,tos=0,ttl=64,frag=no),tcp(src=5001,dst=33032)), packets:4728341, bytes:312070578, used:0.000s, flags:., actions:pop_vlan,5
package size = 312070578 / 4728341 = 66

in_port(5),eth(src=00:1b:21:a1:19:dc,dst=fa:16:3e:76:88:c0),eth_type(0x0800),ipv4(src=191.101.100.254,dst=191.101.0.28,proto=6,tos=0,ttl=64,frag=no),tcp(src=33032,dst=5001), packets:5009744, bytes:120178504800, used:0.000s, flags:P., actions:3
package size = 120178504800/ 5009744 = 23989

in_port(2),eth(src=00:1b:21:a1:19:dc,dst=fa:16:3e:76:88:c0),eth_type(0x0800),ipv4(src=191.101.100.254,dst=191.101.0.28,proto=6,tos=0,ttl=64,frag=no),tcp(src=33032,dst=5001), packets:5009744, bytes:120178504800, used:0.000s, flags:P., actions:4
package size = 120178504800/ 5009744 = 23989

in_port(4),eth(src=fa:16:3e:76:88:c0,dst=00:1b:21:a1:19:dc),eth_type(0x0800),ipv4(src=191.101.0.28,dst=191.101.100.254,proto=6,tos=0,ttl=64,frag=no),tcp(src=5001,dst=33032), packets:4728343, bytes:312070710, used:0.000s, flags:., actions:push_vlan(vid=1,pcp=0),2
package size = 312070710/ 4728343 = 66


The question I have is :
Isn't  the device MTU restricted the max packages size ???
Why we still can observe such big packages ??


Thanks.
-chen
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://openvswitch.org/pipermail/ovs-discuss/attachments/20131114/2fd0bd96/attachment.html>