Comment 5 for bug 1566706

Reviewed: https://review.openstack.org/322787
Committed: https://git.openstack.org/cgit/openstack/neutron/commit/?id=bd8adf3ee004d8155686ec05c18b31c3b9359c80
Submitter: Jenkins
Branch: stable/mitaka

commit bd8adf3ee004d8155686ec05c18b31c3b9359c80
Author: Ihar Hrachyshka <email address hidden>
Date: Wed Apr 6 10:05:13 2016 +0200

    Fixed help messages for path_mtu and global_physnet_mtus options

    For path_mtu, make it clear it applies to tunnel typed tenant networks.
    Removed information about specific mechanisms used to advertise MTU
    values to instances because a) it duplicates the global_physnet_mtu
    option description; b) it is not complete now that we also advertise MTU
    via RAs. Finally, removed description for calculation details because
    they duplicate global_physnet_mtu description.

    While at it, fixed help text for global_physnet_mtus option not to refer
    to segment_mtu which was renamed into global_physnet_mtu lately.

    The cherry-pick differs from the master patch, as Mitaka still uses
    a default value of 1500 for path_mtu. Master uses 0. The effect is,
    that with Mitaka you have to override the default 1500 path_mtu
    value to use jumbo frames, while with master the default 0 value is
    being ignored. There it's sufficient to specify the global_physnet_mtu
    only.

    Change-Id: Ib0010206f08ec9a76b0e26e84cdb03c80755908d
    Related-Bug: #1566706
    (cherry picked from commit 403e5a07f51dee1efd335011cdd6b4454d1e7fde)