openstack/neutron
Code Issues Proposed changes

Revert "ML2: Configure path_mtu to default to 1500 bytes"

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This reverts commit 7a4633a9ca.

Revert to using 0 as the default value for path_mtu.

In most situations, underlying MTU does not differ for tunnel backed and
vlan/flat tenant networks, in which case the only configuration expected
from operators is setting global_physnet_mtu to the appropriate MTU
value as reflecting all data paths that tenant traffic may take between
nodes.

But with the non-zero value set for path_mtu, if an operator would like
to raise the global underlying MTU used by neutron to support Jumbo
frames, both global_physnet_mtu and path_mtu need a bump, which is not
ideal.

So switch back to using a zero value for path_mtu, effectively making it
not participating in MTU calculation, unless explicitly overridden.

Left the original release note intact since it reflects the state for
Mitaka.

Added a release note for the change.

Conflicts:
	neutron/plugins/ml2/config.py
	releasenotes/notes/1500-default-mtu-b0d6e4ab193b62a4.yaml

Change-Id: I97c4aa647efc85d7b6b45359e43e2a2ae2514a69
This commit is contained in:
Ihar Hrachyshka 2016-04-21 15:40:38 +02:00
parent 970fa5d37b
commit 38531ca59c
2 changed files with 10 additions and 2 deletions
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3
neutron/plugins/ml2/config.py
View File

@ -16,7 +16,6 @@
from oslo_config import cfg
from neutron._i18n import _
from neutron.common import constants
ml2_opts = [
cfg.ListOpt('type_drivers',
@ -40,7 +39,7 @@ ml2_opts = [
"entrypoints to be loaded from the "
"neutron.ml2.extension_drivers namespace. "
"For example: extension_drivers = port_security,qos")),
cfg.IntOpt('path_mtu', default=constants.DEFAULT_NETWORK_MTU,
cfg.IntOpt('path_mtu', default=0,
help=_('Maximum size of an IP packet (MTU) that can traverse '
'the underlying physical network infrastructure without '
'fragmentation. For instances using a '

9
releasenotes/notes/path-mtu-back-to-zero-e4f9e8bdd8317ad4.yaml Normal file
View File

@ -0,0 +1,9 @@
---
upgrade:
- In case you rely on the default ML2 path_mtu value of 1500 to cap MTU used
for new network resources, please set it explicitly in your ml2_conf.ini
file.
fixes:
- The default value for ML2 path_mtu option is changed from 1500 to 0,
effectively disabling its participation in network MTU calculation unless
it's overridden in the ml2_conf.ini configuration file.