Internet DRAFT - draft-adubey-bfd-service-redundancy
draft-adubey-bfd-service-redundancy
BFD Workgroup S. Boutros, Ed.
Internet-Draft Ciena
Intended status: Standards Track A. Dubey
Expires: July 27, 2020 VMware
R. Rahman
Cisco
January 24, 2020
Service Redundancy using BFD
draft-adubey-bfd-service-redundancy-03
Abstract
In a data center, when multiple routing/service nodes are providing
single active redundancy for a set of L2, L3 and/or L4-L7 services.
Both non-revertive and revertive fail over modes are required for the
services. This draft describes a method to achieve the non-revertive
and revertive fail over modes for services using Bidirectional
Forwarding Detection (BFD).
Status of This Memo
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This Internet-Draft will expire on July 27, 2020.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
2. Solution Overview . . . . . . . . . . . . . . . . . . . . . . 3
2.1. Node failover . . . . . . . . . . . . . . . . . . . . . . 3
2.2. Per service failover for non-revertive services . . . . . 4
3. Security Considerations . . . . . . . . . . . . . . . . . . . 5
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
5. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 5
6. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
6.1. Normative References . . . . . . . . . . . . . . . . . . 5
6.2. Informative References . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction
This document describes how can a group of service/routing nodes in a
data center providing single active redundancy for multiple L2/L3
and/or L4/L7 services, can use BFD protocol to support non-revertive
as well as revertive fail over mode.
Typically, BFD is used between the group of service nodes to verify
the connectivity as well as the aliveness of the service nodes. The
assignment of which node in the group is the primary designated
forwarder for a given service can be determined using a centralized
or distributed control plane.
The use of BFD will be to communicate the set of services that are
being currently active on a given service node to the other service
nodes. On a given node failure, for a given service the backup node
will take over. If the service was configured to have a non-
revertive fail over mode, then the backup node should continue to
perform the service forwarding even after the primary node recovers
and comes back up. In order to do that, the backup node MUST inform
the primary node that it is currently active for the service. This
is achieved through the extension we are proposing to the BFD
protocol as will be described in the following sections.
It is to be noted that for revertive fail over mode of operation, the
primary node should be able to take over the active role from the
backup node when the primary node goes back to an operational state.
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This can be as well communicated using the BFD session establishment
between the primary node and the backup node.
1.1. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
2. Solution Overview
+----------+
|Controller|
+----------+
// | \
// | \
// | \
+-------+ +-------+ +-------+
|Node1 |-BFD-|Node2 |-BFD-|Node3 |
+-------+ +-------+ +-------+
|--------------BFD--------|
Figure 1: Solution Overview
Figure 1 shows 3 routing nodes using BFD to implement the single
active redundancy for revertive and non-revertive services. More
than 3 routing nodes can be used.
Multiple L2/L3 and/or L4/L7 services are offered in a data center by
a set of routing/service nodes providing single active redundancy.
The provisioning of the services can be done using a centralized
control plane implemented in a controller or using a distributed
dynamic control plane.
2.1. Node failover
An implementation MAY choose to support only node failover and not a
per service failover. A node can be primary or backup for a given
service. On a primary node failure, all non-revertive and revertive
services will become active on the backup node.
In figure 1, lets assume that Node1 is the primary node for a set A
of non-revertive services with node2 as backup, and another set B of
non-revertive services with Node3 as backup. As well, Node1 is
primary for a set C of revertive services with Node2 as backup and,
another set D of revertive services with Node3 as backup.
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If Node1 fails, Node2 and Node3 will set a new diag code in the BFD
control packet. This diag code will inform Node1 that both Node2 and
Node3 didn't fail, and Node1 MUST NOT activate the non-revertive set
of services A and B respectively, when it comes back up. The BFD
control packet with the new diag code will be sent after the BFD
session came up for at least twice the detection multiplier count.
Therefore, Node1 upon receiving the BFD control packet with the new
diag code, MUST NOT attempt to activate the non-revertive services,
but remain in standby state for the non-revertive services until the
Node2 or Node3 that took over fails.
Revertive services are assumed to revert back to the primary node
Node1, after the node recovers. Once the BFD session comes up
between the primary and backup nodes, the backup node should stop
forwarding for any revertive services. A node MUST start forwarding
all revertive services for which it is configured as a primary once
the BFD session comes up with the corresponding backup nodes. A node
MUST stop forwarding for revertive services for which it is a backup
once the BFD session comes up with the corresponding primary.
2.2. Per service failover for non-revertive services
An implementation MAY choose to support per service failover for non-
revertive services. For example, in figure1, some non-revertive
services could be active on Node1 while some non-revertive services
could be active on Node2 or Node3 for better load balancing of
services traffic. In this mode, every L2/L3 and/or L4/L7 non-
revertive service will be identified by a unique ID known across the
routing/service nodes providing the services.
A bitmap will be used to represent the non-revertive services, where
each non-revertive service is represented by one bit in the bitmap.
All the service nodes MUST have the same mapping of the bit position
to the non-revertive service unique ID. The bitmap position and the
unique service ID could be maintained by a network controller.
A node that is assigned as backup for a given non-revertive service
node will take over as active in either of the following cases: 1)
The node assigned as primary for this service failed. 2) This
specific service failed on the primary node for this service.
In case 1, the BFD session will go down since it is a node failure.
In case 2, BFD session between the nodes will remain up. In either
scenarios, the node assigned as secondary will become active for the
non-revertive service. In case 1, the secondary node will set the
new diag code in the BFD control packets once the BFD session is
established. The new diag code will be set in the BFD control
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packets for at least twice the detection multiplier count. In case
2, this diag code will be set in the next BFD control packets sent
after the node takes over as Active for a given non-revertive
service. If there is at least one non-revertive service for which
this node is not active AND at least 1 non-revertive service for
which it is active, the node will also send the bitmap in the BFD
control packets payload. The bits identifying the active non-
revertive services will be set in this bitmap. The new diag code and
the optional bitmap payload will be sent in the BFD control packets
for at least twice the detection multiplier count.
Therefore, if a node receives a BFD control packet with the new diag
code set but no payload in the BFD control packet, this means that it
MUST NOT activate all non-revertive services for which this node is
primary. Whereas, if a payload is present in the BFD control packet
that has the new diag code set, the receiving node MUST NOT activate
the non-revertive services indicated by the set bits in the bitmap.
Per service failover is not applicable to revertive services. They
will behave the same way as described in section 2.1
3. Security Considerations
This document does not introduce any additional security constraints.
4. IANA Considerations
IANA is requested to assign a new diag code from the "BFD Diagnostic
Codes"
Value BFD Diagnostic Code Name
----- ------------------------------------------------
0xNN Out-lived and optional BitMap BFD control packet
payload for non-revertive services.
5. Acknowledgments
6. References
6.1. Normative References
[RFC5880] Katz, D. and D. Ward, "Bidirectional Forwarding Detection
(BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010,
<https://www.rfc-editor.org/info/rfc5880>.
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6.2. Informative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
Authors' Addresses
Sami Boutros (editor)
Ciena
USA
Email: sboutros@ciena.com
Ankur Dubey
VMware
USA
Email: adubey@vmware.com
Reshad Rahman
Cisco
USA
Email: rrahman@cisco.com
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