===============================
Software releases and upgrades
===============================

SD-WAN receives constant improvements and bugfixes. This
section describes our release processes and provides recommendations for
successful upgrade projects.

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Release procedure
------------------

We release new versions of SD-WAN four to six times per year
using the following procedure.

Development and test
---------------------

New software is subject to a suite of automated and manual tests that
verify it works as planned. When all the features expected in a release
are completed, it goes to the release candidate phase.

Release candidate
------------------

Software is released to a small number of partners. This is known as the
release candidate (RC) period. Management servers, aggregators, and
bonders are upgraded according to our recommendations in `Effective
upgrades <effective-upgrades.html>`__. Any bugs found during the
RC period are fixed before the general release. The RC period is usually
about four weeks long.

General release
----------------

The new release is announced to all partners.

Management server upgrades
---------------------------

The SD-WAN vendor upgrades all management servers. In the
release announcement, we propose a maintenance window for the upgrade.
Partners can contact us to give a different maintenance window. Since
customer traffic does not go through the management server, end-users
are not affected by this upgrade. In most cases, management, monitoring,
and aggregator failover are interrupted for 5-10 minutes during the
upgrade.

Bonder, aggregator, & private WAN router upgrades
---------------------------------------------------

After the management server is upgraded, partners can perform node
upgrades. Please review the `Effective
upgrades <effective-upgrades.html>`__ document and design an
upgrade procedure based on those recommendations.

If bugs are found after the general release, they are usually fixed in a
patch release.

Version compatibility
----------------------

Management servers, bonders, aggregators, and private WAN routers are upgraded
independently.
This allows each host to be upgraded at an appropriate time for the
site's end-users, but requires managing compatibility between different
software versions.

There is full compatibility between Debian releases and architectures.
For example, a 64-bit Debian 7 (Wheezy) bonder works fine on a 32-bit
Debian 6 (Squeeze) aggregator.

Please read `Deprecation policy <deprecation-policy.html>`__ to
find when support was dropped certain SD-WAN versions.

Management server & node compatibility
---------------------------------------

Management servers are compatible with nodes running software of the the
same version or some earlier versions. For example, a 2015.1 management
server is compatible with nodes running 2015.1, 2014.4, and some earlier
versions. To manage this compatibility issue, node software upgrades are
not made available to a partner until the partner's management server is
upgraded. Node upgrades are not released to all partners at once—the
upgraded node software is issued to each partner one-by-one as their
management servers are upgraded.

Bonder, aggregator, & private WAN router compatibility
------------------------------------------------------

Aggregators are compatible with bonders running software of
the the same version or some earlier versions. For example, a 2015.1
aggregator is compatible with nodes running 2015.1, 2014.4, and some
earlier versions. It is the partner's responsibility to manage this
compatibility issue by upgrading aggregators before bonders and by not
assigning upgraded bonders to aggregators that have not yet been
upgraded. For bonds with a secondary aggregator, the secondary
aggregator must also run the same or later version as the bonder.

Similarly, private WAN routers are compatible with aggregators running software
of the same version or some earlier version.
