
.. _ZeekControl documentation: https://github.com/zeek/zeekctl

==================
Zeek Cluster Setup
==================

.. TODO: integrate BoZ revisions

A *Zeek Cluster* is a set of systems jointly analyzing the traffic of
a network link in a coordinated fashion.  You can operate such a setup from
a central manager system easily using ZeekControl because it
hides much of the complexity of the multi-machine installation.

Cluster Architecture
====================

Zeek is not multithreaded, so once the limitations of a single processor core
are reached the only option currently is to spread the workload across many
cores, or even many physical computers. The cluster deployment scenario for
Zeek is the current solution to build these larger systems. The tools and
scripts that accompany Zeek provide the structure to easily manage many Zeek
processes examining packets and doing correlation activities but acting as
a singular, cohesive entity.  This document describes the Zeek cluster
architecture.  For information on how to configure a Zeek cluster,
see the documentation for `ZeekControl <https://github.com/zeek/zeekctl>`_.

Architecture
------------

The figure below illustrates the main components of a Zeek cluster.

.. image:: /images/deployment.png

For more specific information on the way Zeek processes are connected,
how they function, and how they communicate with each other, see the
:ref:`Broker Framework Documentation <broker-framework>`.

Tap
***
The tap is a mechanism that splits the packet stream in order to make a copy
available for inspection. Examples include the monitoring port on a switch
and an optical splitter on fiber networks.

Frontend
********
The frontend is a discrete hardware device or on-host technique that splits
traffic into many streams or flows. The Zeek binary does not do this job.
There are numerous ways to accomplish this task, some of which are described
below in `Frontend Options`_.

Manager
*******
The manager is a Zeek process that has two primary jobs.  It receives log
messages and notices from the rest of the nodes in the cluster using the Zeek
communications protocol (note that if you use a separate logger node, then the
logger receives all logs instead of the manager).  The result
is a single log instead of many discrete logs that you have to
combine in some manner with post-processing.
The manager also supports other functionality and analysis which
requires a centralized, global view of events or data.

Logger
******
A logger is an optional Zeek process that receives log messages from the
rest of the nodes in the cluster using the Zeek communications protocol.
The purpose of having a logger receive logs instead of the manager is
to reduce the load on the manager.  If no logger is needed, then the
manager will receive logs instead.

Proxy
*****
A proxy is a Zeek process that may be used to offload data storage or
any arbitrary workload.  A cluster may contain multiple proxy nodes.
The default scripts that come with Zeek make minimal use of proxies, so
a single one may be sufficient, but customized use of them to partition
data or workloads provides greater cluster scalability potential than
just doing similar tasks on a single, centralized Manager node.

Zeek processes acting as proxies don't tend to be extremely hard on CPU
or memory and users frequently run proxy processes on the same physical
host as the manager.

Worker
******
The worker is the Zeek process that sniffs network traffic and does protocol
analysis on the reassembled traffic streams.  Most of the work of an active
cluster takes place on the workers and as such, the workers typically
represent the bulk of the Zeek processes that are running in a cluster.
The fastest memory and CPU core speed you can afford is recommended
since all of the protocol parsing and most analysis will take place here.
There are no particular requirements for the disks in workers since almost all
logging is done remotely to the manager, and normally very little is written
to disk.

Frontend Options
----------------

There are many options for setting up a frontend flow distributor.  In many
cases it is beneficial to do multiple stages of flow distribution
on the network and on the host.

Discrete hardware flow balancers
********************************

cPacket
^^^^^^^

If you are monitoring one or more 10G physical interfaces, the recommended
solution is to use either a cFlow or cVu device from cPacket because they
are used successfully at a number of sites.  These devices will perform
layer-2 load balancing by rewriting the destination Ethernet MAC address
to cause each packet associated with a particular flow to have the same
destination MAC.  The packets can then be passed directly to a monitoring
host where each worker has a BPF filter to limit its visibility to only that
stream of flows, or onward to a commodity switch to split the traffic out to
multiple 1G interfaces for the workers.  This greatly reduces
costs since workers can use relatively inexpensive 1G interfaces.

OpenFlow Switches
^^^^^^^^^^^^^^^^^

We are currently exploring the use of OpenFlow based switches to do flow-based
load balancing directly on the switch, which greatly reduces frontend
costs for many users.  This document will be updated when we have more
information.

On host flow balancing
**********************

PF_RING
^^^^^^^

The PF_RING software for Linux has a "clustering" feature which will do
flow-based load balancing across a number of processes that are sniffing the
same interface.  This allows you to easily take advantage of multiple
cores in a single physical host because Zeek's main event loop is single
threaded and can't natively utilize all of the cores.  If you want to use
PF_RING, see the documentation on :ref:`how to configure Zeek with PF_RING
<pf-ring-config>`.

Netmap
^^^^^^

FreeBSD has an in-progress project named Netmap which will enable flow-based
load balancing as well.  When it becomes viable for real world use, this
document will be updated.

Click! Software Router
^^^^^^^^^^^^^^^^^^^^^^

Click! can be used for flow based load balancing with a simple configuration.
This solution is not recommended on
Linux due to Zeek's PF_RING support and only as a last resort on other
operating systems since it causes a lot of overhead due to context switching
back and forth between kernel and userland several times per packet.

.. _cluster-configuration:

Cluster Configuration
=====================

A *Zeek Cluster* is a set of systems jointly analyzing the traffic of
a network link in a coordinated fashion.  You can operate such a setup from
a central manager system easily using ZeekControl because it
hides much of the complexity of the multi-machine installation.

This section gives examples of how to setup common cluster configurations
using ZeekControl.  For a full reference on ZeekControl, see the
`ZeekControl documentation`_.

Preparing to Setup a Cluster
----------------------------

In this document we refer to the user account used to set up the cluster
as the "Zeek user".  When setting up a cluster the Zeek user must be set up
on all hosts, and this user must have ssh access from the manager to all
machines in the cluster, and it must work without being prompted for a
password/passphrase (for example, using ssh public key authentication).
Also, on the worker nodes this user must have access to the target
network interface in promiscuous mode.

Additional storage must be available on all hosts under the same path,
which we will call the cluster's prefix path.  We refer to this directory
as ``<prefix>``.  If you build Zeek from source, then ``<prefix>`` is
the directory specified with the ``--prefix`` configure option,
or ``/usr/local/zeek`` by default.  The Zeek user must be able to either
create this directory or, where it already exists, must have write
permission inside this directory on all hosts.

When trying to decide how to configure the Zeek nodes, keep in mind that
there can be multiple Zeek instances running on the same host.  For example,
it's possible to run a proxy and the manager on the same host.  However, it is
recommended to run workers on a different machine than the manager because
workers can consume a lot of CPU resources.  The maximum recommended
number of workers to run on a machine should be one or two less than
the number of CPU cores available on that machine.  Using a load-balancing
method (such as PF_RING) along with CPU pinning can decrease the load on
the worker machines.  Also, in order to reduce the load on the manager
process, it is recommended to have a logger in your configuration.  If a
logger is defined in your cluster configuration, then it will receive logs
instead of the manager process.

Basic Cluster Configuration
---------------------------

With all prerequisites in place, perform the following steps to setup
a Zeek cluster (do this as the Zeek user on the manager host only):

- Edit the ZeekControl configuration file, ``<prefix>/etc/zeekctl.cfg``,
  and change the value of any options to be more suitable for
  your environment.  You will most likely want to change the value of
  the ``MailTo`` and ``LogRotationInterval`` options.  A complete
  reference of all ZeekControl options can be found in the
  `ZeekControl documentation`_.

- Edit the ZeekControl node configuration file, ``<prefix>/etc/node.cfg``
  to define where logger, manager, proxies, and workers are to run.  For a
  cluster configuration, you must comment-out (or remove) the standalone node
  in that file, and either uncomment or add node entries for each node
  in your cluster (logger, manager, proxy, and workers).  For example, if you
  wanted to run five Zeek nodes (two workers, one proxy, a logger, and a
  manager) on a cluster consisting of three machines, your cluster
  configuration would look like this::

    [logger]
    type=logger
    host=10.0.0.10

    [manager]
    type=manager
    host=10.0.0.10

    [proxy-1]
    type=proxy
    host=10.0.0.10

    [worker-1]
    type=worker
    host=10.0.0.11
    interface=eth0

    [worker-2]
    type=worker
    host=10.0.0.12
    interface=eth0

  For a complete reference of all options that are allowed in the ``node.cfg``
  file, see the `ZeekControl documentation`_.

- Edit the network configuration file ``<prefix>/etc/networks.cfg``.  This
  file lists all of the networks which the cluster should consider as local
  to the monitored environment.

- Install Zeek on all machines in the cluster using ZeekControl::

    > zeekctl install

- See the `ZeekControl documentation`_
  for information on setting up a cron job on the manager host that can
  monitor the cluster.

.. _pf-ring-config:

PF_RING Cluster Configuration
-----------------------------

`PF_RING <http://www.ntop.org/products/pf_ring/>`_ allows speeding up the
packet capture process by installing a new type of socket in Linux systems.
It supports 10Gbit hardware packet filtering using standard network adapters,
and user-space DNA (Direct NIC Access) for fast packet capture/transmission.

Installing PF_RING
******************

1. Download and install PF_RING for your system following the instructions
   `here <http://www.ntop.org/get-started/download/#PF_RING>`_.  The following
   commands will install the PF_RING libraries and kernel module (replace
   the version number 5.6.2 in this example with the version that you
   downloaded)::

     cd /usr/src
     tar xvzf PF_RING-5.6.2.tar.gz
     cd PF_RING-5.6.2/userland/lib
     ./configure --prefix=/opt/pfring
     make install

     cd ../libpcap
     ./configure --prefix=/opt/pfring
     make install

     cd ../tcpdump-4.1.1
     ./configure --prefix=/opt/pfring
     make install

     cd ../../kernel
     make
     make install

     modprobe pf_ring enable_tx_capture=0 min_num_slots=32768

   Refer to the documentation for your Linux distribution on how to load the
   pf_ring module at boot time.  You will need to install the PF_RING
   library files and kernel module on all of the workers in your cluster.

2. Download the Zeek source code.

3. Configure and install Zeek using the following commands::

     ./configure --with-pcap=/opt/pfring
     make
     make install

4. Make sure Zeek is correctly linked to the PF_RING libpcap libraries::

     ldd /usr/local/zeek/bin/zeek | grep pcap
           libpcap.so.1 => /opt/pfring/lib/libpcap.so.1 (0x00007fa6d7d24000)

5. Configure ZeekControl to use PF_RING (explained below).

6. Run "zeekctl install" on the manager.  This command will install Zeek and
   required scripts to all machines in your cluster.

Using PF_RING
*************

In order to use PF_RING, you need to specify the correct configuration
options for your worker nodes in ZeekControl's node configuration file.
Edit the ``node.cfg`` file and specify ``lb_method=pf_ring`` for each of
your worker nodes.  Next, use the ``lb_procs`` node option to specify how
many Zeek processes you'd like that worker node to run, and optionally pin
those processes to certain CPU cores with the ``pin_cpus`` option (CPU
numbering starts at zero).  The correct ``pin_cpus`` setting to use is
dependent on your CPU architecture (Intel and AMD systems enumerate
processors in different ways).  Using the wrong ``pin_cpus`` setting
can cause poor performance.  Here is what a worker node entry should
look like when using PF_RING and CPU pinning::

   [worker-1]
   type=worker
   host=10.0.0.50
   interface=eth0
   lb_method=pf_ring
   lb_procs=10
   pin_cpus=2,3,4,5,6,7,8,9,10,11


Using PF_RING+DNA with symmetric RSS
************************************

You must have a PF_RING+DNA license in order to do this.  You can sniff
each packet only once.

1. Load the DNA NIC driver (i.e. ixgbe) on each worker host.

2. Run "ethtool -L dna0 combined 10" (this will establish 10 RSS queues
   on your NIC) on each worker host.  You must make sure that you set the
   number of RSS queues to the same as the number you specify for the
   lb_procs option in the node.cfg file.

3. On the manager, configure your worker(s) in node.cfg::

       [worker-1]
       type=worker
       host=10.0.0.50
       interface=dna0
       lb_method=pf_ring
       lb_procs=10


Using PF_RING+DNA with pfdnacluster_master
******************************************

You must have a PF_RING+DNA license and a libzero license in order to do
this.  You can load balance between multiple applications and sniff the
same packets multiple times with different tools.

1. Load the DNA NIC driver (i.e. ixgbe) on each worker host.

2. Run "ethtool -L dna0 1" (this will establish 1 RSS queues on your NIC)
   on each worker host.

3. Run the pfdnacluster_master command on each worker host.  For example::

       pfdnacluster_master -c 21 -i dna0 -n 10

   Make sure that your cluster ID (21 in this example) matches the interface
   name you specify in the node.cfg file.  Also make sure that the number
   of processes you're balancing across (10 in this example) matches
   the lb_procs option in the node.cfg file.

4. If you are load balancing to other processes, you can use the
   pfringfirstappinstance variable in zeekctl.cfg to set the first
   application instance that Zeek should use.  For example, if you are running
   pfdnacluster_master with "-n 10,4" you would set
   pfringfirstappinstance=4.  Unfortunately that's still a global setting
   in zeekctl.cfg at the moment but we may change that to something you can
   set in node.cfg eventually.

5. On the manager, configure your worker(s) in node.cfg::

       [worker-1]
       type=worker
       host=10.0.0.50
       interface=dnacluster:21
       lb_method=pf_ring
       lb_procs=10

