Merge "Add bgp speaker and route advertisement doc"
This commit is contained in:
Jenkins
Gerrit Code Review
commit
58e3e42894
@ -24,5 +24,144 @@
|
||||
|
||||
BGP Speaker
|
||||
===========
|
||||
BGP Speaker acts as a route server using BGP routing protocol. It advertises
|
||||
routes to the BGP peers which are added to the BGP Speaker. Now there is a
|
||||
framework that allows different `BGP drivers <../design/drivers.rst>`_
|
||||
to be plugged into a `dynamic routing agent <./dynamic-routing-agent.rst>`_.
|
||||
|
||||
TODO: Coming Soon
|
||||
Currently, BGP Speaker only advertises routes for a network to which it is associated.
|
||||
A BGP Speaker requires association with a "gateway" network to determine eligible routes.
|
||||
In Neutron, a "gateway" network connects Neutron routers to the upstream routers. An
|
||||
external network is best for being used as a gateway network. The association builds a
|
||||
list of all virtual routers with gateways on provider and self-service networks within
|
||||
the same address scope. Hence, the BGP speaker advertises self-service network prefixes
|
||||
with the corresponding router as the next-hop IP address.
|
||||
For details refer to `Route advertisement <./route-advertisement.rst>`_.
|
||||
|
||||
Address Scopes
|
||||
--------------
|
||||
`Address scopes <https://git.openstack.org/cgit/openstack/neutron/tree/doc/source/devref/address_scopes.rst>`_
|
||||
provide flexible control as well as decoupling of address overlap from tenancy,
|
||||
so this kind control can provide a routable domain, the domain has itself route
|
||||
and no overlap address, it means an address scope define "a L3 routing domain".
|
||||
|
||||
BGP Speaker will associate the external networks and advertise the tenant's
|
||||
networks routes. Those networks should reside in the same address scope.
|
||||
Neutron can route the tenant network directly without NAT. Then Neutron can
|
||||
host globally routable IPv4 and IPv6 tenant networks. For determining which
|
||||
tenant networks prefixes should be advertised, Neutron will identify all routers
|
||||
with gateway ports on the network which had been bounded with BGP Speaker,
|
||||
check the address scope of the subnets on all connected networks, then begin
|
||||
advertising nexthops for all tenant networks to routers on the bound network.
|
||||
|
||||
BGP Peer
|
||||
--------
|
||||
BGP peer defined in Neutron represents real BGP infrastructure such as
|
||||
routers, route reflectors and route servers. When a BGP peer is defined and
|
||||
associated with a BGP Speaker, Neutron will attempt to open a BGP peering
|
||||
session with the mentioned remote peer. It is this session, using which Neutron
|
||||
announces it's routes.
|
||||
|
||||
How to configure a remote peer
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
A remote peer can be real or virtual e.g. vRouters or real routers.
|
||||
The remote peer should be configured to handle peering with Neutron in passive
|
||||
mode. The peer needs to waits for the Neutron dynamic routing agent to
|
||||
initiate the peering session. Also, the remote peer can be configured in active
|
||||
mode, but it still can speak BGP until the complete initialization of BGP Speaker
|
||||
running on Neutron dynamic routing agent.
|
||||
|
||||
Configuring BGP Speaker:
|
||||
One needs to ensure below points for setting a BGP connection.
|
||||
|
||||
* Host running Neutron dynamic agent MUST connect to the external router.
|
||||
* BGP configuration on the router should be proper.
|
||||
|
||||
``bgp router-id XX.XX.XX.XX``
|
||||
This must be an IP address, the unique identifier of BGP routers actually
|
||||
and can be virtual. If one doesn't configure the router-id, it will be selected
|
||||
automatically as the highest IP address configured for the local interfaces.
|
||||
Just a suggestion, please make sure that it is the same as the ``peer_ip``
|
||||
which you configure in Neutron for distinguishing easily.
|
||||
``local_as``
|
||||
Autonomous System number can be same or different from the AS_id of external
|
||||
BGP router. AS_id will be same for iBGP and different for eBGP sessions.
|
||||
|
||||
Setting BGP peer:
|
||||
::
|
||||
|
||||
neighbor A.B.C.D remote-as AS_ID
|
||||
A.B.C.D is the host IP which run Neutron dynamic routing agent.
|
||||
|
||||
A Sample Quagga router configuration file forming BGP peering with Neutron:
|
||||
::
|
||||
|
||||
!
|
||||
password zebra
|
||||
log file /var/log/quagga/bgpd.log
|
||||
!
|
||||
debug bgp events
|
||||
debug bgp keepalives
|
||||
debug bgp updates
|
||||
debug bgp fsm
|
||||
debug bgp filters
|
||||
!
|
||||
bgp multiple-instance
|
||||
!
|
||||
router bgp <BgpPeer remote_as> view test-as
|
||||
bgp router-id <quagga router IP address>
|
||||
neighbor <dr_agent IP address> remote-as <BgpSpeaker local_as>
|
||||
neighbor <dr_agent IP address> passive
|
||||
!
|
||||
line vty
|
||||
!
|
||||
|
||||
BGP Speaker Architecture
|
||||
------------------------
|
||||
Dynamic routing project saves BGP Speaker configuration as per the defined
|
||||
`_data model<https://git.openstack.org/cgit/openstack/neutron-dynamic-routing/tree/neutron_dynamic_routing/db/bgp_db.py#n85>`_.
|
||||
and pass on the configuration request to the dynamic routing agent for further processing.
|
||||
The implementation of a BGP Speaker is driver specific. During the driver interface
|
||||
initialization process, needed configurations are read from the configuration file
|
||||
and BGP Speaker object instance is created. For details refer to
|
||||
`BGP drivers <../design/drivers.rst>`_.
|
||||
|
||||
BGP Speaker Life Cycle
|
||||
~~~~~~~~~~~~~~~~~~~~~~
|
||||
Now we support RyuBgpDriver, BGP Speaker will be processed by Dragent. When
|
||||
associating a BGP Speaker with an active Dragent, the plugin will send an RPC
|
||||
message to the agent for calling driver in order to create a BGP Speaker instance.
|
||||
|
||||
In RyuBgpDriver, the created instance ``BGP Speaker`` will setup by router-id
|
||||
and ASN, then Ryu will setup new context with speaker configuration and listeners
|
||||
which monitor whether the related peers are alive.
|
||||
|
||||
Then the following operation could be done.
|
||||
|
||||
* Add peers to BGP Speaker
|
||||
When BGP Speaker is not associated with an active Dragent, there is no real speaker
|
||||
instance, so it will be still the db operation until the speaker is associated with
|
||||
dragent, and all the peers connection before will be setup by ``BGP Speaker``
|
||||
creation. If add peers into speaker which is running, Dragent will call driver
|
||||
to add peer dynamically. For RyuBgpDriver, it will register a new neighbor
|
||||
based on your peer configuration and try to establish a session with the peer.
|
||||
|
||||
* Delete peers from BGP Speaker
|
||||
The same logic with below, but it is reverse.
|
||||
|
||||
If you don't want use the specific BGP Speaker anymore, you can use CLI:
|
||||
``neutron bgp-speaker-delete <SPEAKER NAME/ID>``
|
||||
|
||||
BGP Plugin will find all the associated Dragent and send RPC ``bgp_speaker_remove_end``
|
||||
to make the Dragents to clean the ``BGP Speaker`` instances. This is the same
|
||||
with CLI:
|
||||
``neutron bgp-dragent-speaker-remove <DRAGENT ID> <SPEAKER NAME/ID>``
|
||||
BGP Plugin just send rpc ``bgp_speaker_remove_end`` to the specific Dragent.
|
||||
|
||||
Advertisement
|
||||
~~~~~~~~~~~~~
|
||||
For details refer to `Route Advertisement <./route-advertisement.rst>`_.
|
||||
|
||||
How to work
|
||||
-----------
|
||||
For details refer to `Testing <../others/testing.rst>`_.
|
||||
@ -24,5 +24,93 @@
|
||||
|
||||
Route Advertisement
|
||||
===================
|
||||
BGP
|
||||
---
|
||||
|
||||
TODO: Coming Soon
|
||||
This page discusses the behavior of BGP dynamic routing about how to advertise
|
||||
routes and show the routes details in the project.
|
||||
|
||||
BGP dynamic routing could advertise 3 classes of routes:
|
||||
|
||||
* Host routes for floating IP addresses hosted on non-DVR routers, as floatingip
|
||||
address set on the router namespace, it knows how to route the message to the
|
||||
correct way, so the next-hop should be the IP address of router gateway port.
|
||||
* Host routes for floating IP addresses hosted on DVR routers. With DVR-enabled
|
||||
routers, the floating IP can be reached directly on the compute node hosting
|
||||
a given instance. As such, host routes for the floating IP address should
|
||||
advertise the FIP agent gateway on the compute node as the next-hop instead of
|
||||
the centralized router. This will keep inbound floating IP traffic from
|
||||
encountering the bottleneck of the centralized router.
|
||||
* Prefix routes for directly routable tenant networks with address scopes, the
|
||||
nexthop is the centralized router, the same for DVR and CVR. BGP dynamic
|
||||
routing could advertise tenant network prefixes to physical network
|
||||
devices(routers which support BGP protocol), called this
|
||||
``Prefixes advertisement``.
|
||||
|
||||
When distributed virtual routing (DVR) is enabled on a router, next-hops for
|
||||
floating IP's and fixed IP's are not advertised as being at the centralized
|
||||
router. Host routes with the next-hop set to the appropriate compute node
|
||||
are advertised.
|
||||
|
||||
Logical Model
|
||||
~~~~~~~~~~~~~
|
||||
::
|
||||
|
||||
+--------+ 1 N +---------------------+
|
||||
| Router |---------| BgpAdvertisedRoute |
|
||||
+--------+ +---------------------+
|
||||
| N
|
||||
|
|
||||
| 1
|
||||
+---------+ N N +------------+ N N +---------+
|
||||
| BgpPeer |-----------| BgpSpeaker |-----------| Network |
|
||||
+---------+ +------------+ +---------+
|
||||
| N
|
||||
|
|
||||
| 1
|
||||
+--------------+
|
||||
| AddressScope |
|
||||
+--------------+
|
||||
|
||||
.. note::
|
||||
A BGP Speaker only supports one address family to speak BGP. A dual-stack IPv4
|
||||
and IPv6 network needs two BGP Speakers to advertise the routes with BGP, one
|
||||
for IPv4 and the other for IPv6. So A network can have N number of BGP
|
||||
Speakers bound to it.
|
||||
|
||||
BgpAdvertisedRoute represents derived data. As the number of
|
||||
BgpAdvertisedRoutes can be quite large, storing in a database table is not
|
||||
feasible. BgpAdvertisedRoute information can be derived by joining data
|
||||
already available in the Neutron database. And now BGP dynamic routing project
|
||||
process the Bgpadvertiseroutes which should be advertised to external Router is
|
||||
basing on the exist Neutron DB tables.
|
||||
Neutron looks on each of the gateway network for any routers with a gateway port
|
||||
on that network. For each router identified, Neutron locates each floating IP
|
||||
and tenant network accessible through the router gateway port. Neutron then
|
||||
advertises each floating IP and tenant network with the IP address of the router
|
||||
gateway port as the next hop.
|
||||
|
||||
When BGP Plugin is started, it will register callbacks. All callbacks are used for
|
||||
processing Floating IP, Router Interface and Router Gateway creation or update, this
|
||||
functions listen the events of these resources for calling Dragent to change the
|
||||
advertisement routes.
|
||||
|
||||
Now we just focus on the resources which may cause route change, the following
|
||||
callbacks does this work.
|
||||
|
||||
* floatingip_update_callback
|
||||
This function listens to the Floating IP's AFTER_UPDATE event, it judges whether
|
||||
the associated router is changed, and changes the advertisement routes and nexthop
|
||||
based on that.
|
||||
* router_interface_callback
|
||||
This function listens to the tenants' network routes change, it listens to AFTER_CREATE
|
||||
and AFTER_DELETE events of Router Interface resource. It calls Dragent to advertise
|
||||
or stop the prefix routes after a interface attach into a router.
|
||||
* router_gateway_callback
|
||||
This function listens to the router gateway port creation or deletion. It also focuses
|
||||
on tenants' network routes change.
|
||||
|
||||
You could get the advertisement routes of specific BGP Speaker like:
|
||||
``neutron bgp-speaker-advertiseroute-list <created-bgp-speaker>``
|
||||
It does a complicated db query to generate the list of advertised routes.
|
||||
For more details refer to `route advertisement db lookup <https://git.openstack.org/cgit/openstack/neutron-dynamic-routing/tree/neutron_dynamic_routing/db/bgp_db.py#n462>`_
|
||||
|
||||
Loading…
Reference in New Issue
Block a user