OSPF Flooding Reduction in MSDC
draft-xu-ospf-flooding-reduction-in-msdc-00
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| Author | Xiaohu Xu | ||
| Last updated | 2017-01-04 | ||
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draft-xu-ospf-flooding-reduction-in-msdc-00
Network Working Group X. Xu
Internet-Draft Huawei
Intended status: Standards Track January 4, 2017
Expires: July 8, 2017
OSPF Flooding Reduction in MSDC
draft-xu-ospf-flooding-reduction-in-msdc-00
Abstract
OSPF is commonly used as a underlay routing protocol for MSDC
(Massively Scalable Data Center) networks. This document proposes
some extensions to OSPF so as to reduce the OSPF flooding within MSDC
networks greatly. The reduction of the OSPF flooding is much
beneficial to improve the scalability of MSDC networks. These
modifications are applicable to both OSPFv2 and OSPFv3.
Status of This Memo
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provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on July 8, 2017.
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Copyright (c) 2017 IETF Trust and the persons identified as the
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include Simplified BSD License text as described in Section 4.e of
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 4
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Modifications to Current OSPF Behaviors . . . . . . . . . . . 4
3.1. OSPF Routers as Non-DRs . . . . . . . . . . . . . . . . . 4
3.2. Controllers as DR/BDR . . . . . . . . . . . . . . . . . . 5
4. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
6. Security Considerations . . . . . . . . . . . . . . . . . . . 5
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
7.1. Normative References . . . . . . . . . . . . . . . . . . 5
7.2. Informative References . . . . . . . . . . . . . . . . . 6
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction
OSPF is commonly used as a underlay routing protocol for Massively
Scalable Data Center (MSDC) networks. In addition, centrolized
controllers are becoming fundemental network elements in most MSDCs.
One or more controllers are usually connected to all routers within
the MSDC network via a Local Area Network (LAN) which is dedicated
for network management purpose (called management LAN), as shown in
Figure 1.
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+----------+ +----------+
|Controller| |Controller|
+----+-----+ +-----+----+
|DR |BDR
| |
| |
---+---------+---+----------+-----------+---+---------+-Management LAN
| | | | |
|Non-DR |Non-DR |Non-DR |Non-DR |Non-DR
| | | | |
| +---+--+ | +---+--+ |
| |Router| | |Router| |
| *------*- | /*---/--* |
| / \ -- | // / \ |
| / \ -- | // / \ |
| / \ --|// / \ |
| / \ /*- / \ |
| / \ // | -- / \ |
| / \ // | -- / \ |
| / /X | -- \ |
| / // \ | / -- \ |
| / // \ | / -- \ |
| / // \ | / -- \ |
| / // \ | / -- \ |
| / // \ | / -- \ |
| / // \ | / -- \ |
+-+- //* +\\+-/-+ +---\-++
|Router| |Router| |Router|
+------+ +------+ +------+
Figure 1
With the assistance of controllers acting as OSPF DR/BDR for the
management LAN, OSPF routers within the MSDC network don't need to
exchange any other type of OSPF packet than the OSPF Hello packet
among them. As specified in [RFC2328], these Hello packets are used
for the purpose of establishing and maintaining neighbor
relationships and ensuring bidirectional communication between OSPF
neighbors, and even the Designated Router (DR)/Backup Designated
Router (BDR) election purpose in the case where those OSPF routers
are connected to a broadcast network. In order to obtain the full
topology information (i.e., the fully synchronized link-state
database) of the MSDC's network, these OSPF routers would exchange
the link-state information with the controllers being elected as OSPF
DR/BDR for the management LAN instead.
To further suppress the flooding of multicast OSPF packets originated
from OSPF routers over the management LAN, OSPF routers would not
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send multicast OSPF Hello packets over the management LAN. Insteads,
they just wait for OSPF Hello packets originated from the controllers
being elected as OSPF DR/BDR initially. Once OSPF DR/BDR for the
management LAN have been discovered, they start to send OSPF Hello
packets directly (as unicasts) to OSPF DR/BDR periodically. In
addition, OSPF routers would send other types of OSPF packets (e.g.,
Database Descriptor packet, Link State Request packet, Link State
Update packet, Link State Acknowledgment packet) to OSPF DR/BDR for
the management LAN as unicasts as well. In contrast, the controllers
being elected as OSPF DR/BDR would send OSPF packets as specified in
[RFC2328]. As a result, OSPF routers would not receive OSPF packets
from one another unless these OSPF packets are forwarded as unknown
unicasts over the management LAN. Through the above modifications to
the current OSPF router behaviors, the OSPF flooding is greatly
reduced which is much beneficial to improve the scalability of MSDC
networks. These modifications are applicable to both OSPFv2
[RFC2328] and OSPFv3 [RFC5340].
Furthermore, the mechanism for OSPF refresh and flooding reduction in
stable topologies as described in [RFC2328] could be considered as
well.
1.1. Requirements Language
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 RFC 2119 [RFC2119].
2. Terminology
This memo makes use of the terms defined in [RFC2328].
3. Modifications to Current OSPF Behaviors
3.1. OSPF Routers as Non-DRs
After the exchange of OSPF Hello packets among OSPF routers, the OSPF
neighbor relationship among them would transitions to and remains in
the TWO-WAY state. OSPF routers would originate Router-LSAs and
Network-LSAs as per [RFC2328]. However, these self-originated LSAs
need not to be exchanged directly among them anymore. Instead, these
LSAs just need to be sent solely to the controllers being elected as
OSPF DR/BDR for the management LAN.
To further reduce the flood of multicast OSPF packets over the
management LAN, OSPF routers SHOULD send OSPF packets as unicasts.
More specifically, OSPF routers SHOULD send unicast OSPF Hello
packets periodically to the controllers being elected as OSPF DR/BDR.
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In other words, OSPF routers would not send any OSPF Hello packet
over the management LAN until they have found OSPF DR/BDR for the
management LAN. Note that OSPF routers SHOULD NOT be elected as OSPF
DR/BDR for the management LAN (This is done by setting the Router
Priority of those OSPF routers to zero). As a result, OSPF routers
would not see each other over the management LAN. Furthermore, OSPF
routers SHOULD send all other types of OSPF packets than OSPF Hello
packets (i.e., Database Descriptor packet, Link State Request packet,
Link State Update packet, Link State Acknowledgment packet) to the
controllers being elected as OSPF DR/BDR as unicasts as well.
To advoid the data traffic from being forwarded across the management
LAN, the cost of all OSPF routers' interfaces to the management LAN
SHOULD be set to the maximum value.
3.2. Controllers as DR/BDR
The controllers being elected as OSPF DR/BDR would send OSPF packets
as multicasts or unicasts as per [RFC2328]. In addition, Link State
Acknowledgment packets are RECOMMENDED to be sent as unicasts if
possible.
4. Acknowledgements
TBD.
5. IANA Considerations
TBD.
6. Security Considerations
TBD.
7. References
7.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328,
DOI 10.17487/RFC2328, April 1998,
<http://www.rfc-editor.org/info/rfc2328>.
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[RFC5340] Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF
for IPv6", RFC 5340, DOI 10.17487/RFC5340, July 2008,
<http://www.rfc-editor.org/info/rfc5340>.
7.2. Informative References
[RFC4136] Pillay-Esnault, P., "OSPF Refresh and Flooding Reduction
in Stable Topologies", RFC 4136, DOI 10.17487/RFC4136,
July 2005, <http://www.rfc-editor.org/info/rfc4136>.
[RFC5838] Lindem, A., Ed., Mirtorabi, S., Roy, A., Barnes, M., and
R. Aggarwal, "Support of Address Families in OSPFv3",
RFC 5838, DOI 10.17487/RFC5838, April 2010,
<http://www.rfc-editor.org/info/rfc5838>.
Author's Address
Xiaohu Xu
Huawei
Email: xuxiaohu@huawei.com
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