neutron/releasenotes/notes/end-to-end-mtu-00345fc4282cb8fb.yaml
Kevin Benton 4df8d9a701 Make agent interface plugging utilize network MTU
This changes the 'plug' and 'plug_new' interfaces of the
LinuxInterfaceDriver to accept an MTU argument. It then
updates the dhcp agent and l3 agent to pass the MTU that
is set on the network that the port belongs to. This allows
it to take into account the overhead calculations that are
done for encapsulation types.

It's necessary for the L3 agent to have the MTU because it
must recognize when fragmentation is needed so it can fragment
or generate an ICMP error.

It's necessary for the DHCP agent to have the MTU so it doesn't
interfere when it plugs into a bridge with a larger than 1500
MTU (the bridge would reduce its MTU to match the agent).

If an operator sets 'network_device_mtu', the value of that
will be used instead to preserve previous behavior.

Closes-Bug: #1549470
Closes-Bug: #1542108
Closes-Bug: #1542475
DocImpact: Neutron agents now support arbitrary MTU
           configurations on each network (including
           jumbo frames). This is accomplished by checking
           the MTU value defined for each network on which
           it is wiring VIFs.
Co-Authored-By: Matt Kassawara <mkassawara@gmail.com>
Change-Id: Ic091fa78dfd133179c71cbc847bf955a06cb248a
2016-02-29 19:19:25 +00:00

21 lines
975 B
YAML

---
features:
- Use the value of the network 'mtu' attribute for the MTU
of virtual network interfaces such as veth pairs, patch
ports, and tap devices involving a particular network.
- Enable end-to-end support for arbitrary MTUs including
jumbo frames between instances and provider networks by
moving MTU disparities between flat or VLAN networks and
overlay networks from layer-2 devices to layer-3 devices
that support path MTU discovery (PMTUD).
upgrade:
- Does not change MTU for existing virtual network interfaces.
- Actions that create virtual network interfaces on an existing
network with the 'mtu' attribute containing a value greater
than zero could cause issues for network traffic traversing
existing and new virtual network interfaces.
fixes:
- Explicitly configure MTU of virtual network interfaces
rather than using default values or incorrect values that
do not account for overlay protocol overhead.