Jumbo Frame Support on Dataplane Interfaces

ExoGENI Testbed supports jumbo frames on dataplane interfaces across sites. (Currently, all racks except UMass and WVN racks support jumbo frames. UMass and WVN interfaces will be configured in the following weeks.)

VMs are created with dataplane interfaces that have an MTU of 1500 bytes. Underneath bridges and physical interfaces along the path are configured for an MTU of 9000. Currently, neuca tools don’t have an option to setup MTU size. MTU size needs to be modified within inside the VM.

Screen Shot 2017-06-13 at 13.28.23

On node0:

root@Node0:~# ifconfig eth1
eth1      Link encap:Ethernet  HWaddr FA:16:3E:00:21:09  
          inet addr:172.16.0.1  Bcast:172.16.0.3  Mask:255.255.255.252
          inet6 addr: fe80::f816:3eff:fe00:2109/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:25 errors:0 dropped:0 overruns:0 frame:0
          TX packets:5 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:1922 (1.8 KiB)  TX bytes:378 (378.0 b)

root@Node0:~# ifconfig eth1 mtu 9000

On node1:

root@Node1:~# ifconfig eth1
eth1      Link encap:Ethernet  HWaddr FA:16:3E:00:16:BD  
          inet addr:172.16.0.2  Bcast:172.16.0.3  Mask:255.255.255.252
          inet6 addr: fe80::f816:3eff:fe00:16bd/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:7 errors:0 dropped:0 overruns:0 frame:0
          TX packets:5 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:530 (530.0 b)  TX bytes:398 (398.0 b)

root@Node1:~# ifconfig eth1 mtu 9000

Now, jumbo frames can be exchanged:

root@Node0:~# ping -M do -s 8972 -c 3 172.16.0.2
PING 172.16.0.2 (172.16.0.2) 8972(9000) bytes of data.
8980 bytes from 172.16.0.2: icmp_seq=1 ttl=64 time=114 ms
8980 bytes from 172.16.0.2: icmp_seq=2 ttl=64 time=56.9 ms
8980 bytes from 172.16.0.2: icmp_seq=3 ttl=64 time=56.7 ms

--- 172.16.0.2 ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2059ms
rtt min/avg/max/mdev = 56.732/76.150/114.798/27.329 ms

-M do : Prohibits fragmentation
-s : Sets packetsize. 8972 bytes (padding) + 20 bytes (TCP header) + 8 bytes (ICMP header) = 9000

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