IS-IS Flooding Reduction in MSDC
draft-xu-isis-flooding-reduction-in-msdc-00
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| Document | Type | Active Internet-Draft (individual) | |
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| Author | Xiaohu Xu | ||
| Last updated | 2017-01-06 | ||
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draft-xu-isis-flooding-reduction-in-msdc-00
Network Working Group X. Xu
Internet-Draft Huawei
Intended status: Standards Track January 6, 2017
Expires: July 10, 2017
IS-IS Flooding Reduction in MSDC
draft-xu-isis-flooding-reduction-in-msdc-00
Abstract
IS-IS is commonly used as a underlay routing protocol for MSDC
(Massively Scalable Data Center) networks. This document proposes
some extensions to IS-IS so as to reduce the IS-IS flooding within
MSDC networks greatly. The reduction of the IS-IS flooding is much
beneficial to improve the scalability of MSDC networks.
Status of This Memo
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This Internet-Draft will expire on July 10, 2017.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 4
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Modifications to Current IS-IS Behaviors . . . . . . . . . . 4
3.1. IS-IS Routers as Non-DIS . . . . . . . . . . . . . . . . 4
3.2. Controllers as DIS . . . . . . . . . . . . . . . . . . . 5
4. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
6. Security Considerations . . . . . . . . . . . . . . . . . . . 5
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
7.1. Normative References . . . . . . . . . . . . . . . . . . 5
7.2. Informative References . . . . . . . . . . . . . . . . . 5
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction
IS-IS is commonly used as a underlay routing protocol for Massively
Scalable Data Center (MSDC) networks. In addition, centrolized
controllers are becoming fundamental 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|
+----+-----+ +-----+----+
|DIS |Candidate DIS
| |
| |
---+---------+---+----------+-----------+---+---------+-Management LAN
| | | | |
|Non-DIS |Non-DIS |Non-DIS |Non-DIS |Non-DIS
| | | | |
| +---+--+ | +---+--+ |
| |Router| | |Router| |
| *------*- | /*---/--* |
| / \ -- | // / \ |
| / \ -- | // / \ |
| / \ --|// / \ |
| / \ /*- / \ |
| / \ // | -- / \ |
| / \ // | -- / \ |
| / /X | -- \ |
| / // \ | / -- \ |
| / // \ | / -- \ |
| / // \ | / -- \ |
| / // \ | / -- \ |
| / // \ | / -- \ |
| / // \ | / -- \ |
+-+- //* +\\+-/-+ +---\-++
|Router| |Router| |Router|
+------+ +------+ +------+
Figure 1
With the assistance of a controller acting as IS-IS Designated
Intermediate System (DIS) for the management LAN, IS-IS routers
within the MSDC network don't need to exchange any IS-IS Protocl
Datagram Units (PDUs) other than Hello packets among them. In order
to obtain the full topology information (i.e., the fully synchronized
link-state database) of the MSDC's network, these IS-IS routers would
exchange the link-state information with the controller being elected
as IS-IS DIS for the management LAN instead.
To further suppress the flooding of multicast IS-IS PDUs originated
from IS-IS routers over the management LAN, IS-IS routers would not
send multicast IS-IS Hello packets over the management LAN.
Insteads, they just wait for IS-IS Hello packets originated from the
controller being elected as IS-IS DIS initially. Once an IS-IS DIS
for the management LAN has been discovered, they start to send IS-IS
Hello packets directly (as unicasts) to the IS-IS DIS periodically.
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In addition, IS-IS routers would send IS-IS PDUs to the IS-IS DIS for
the management LAN as unicasts as well. In contrast, the controller
being elected as IS-IS DIS would send IS-IS PDUs as before. As a
result, IS-IS routers would not receive IS-IS PDUs from one another
unless these IS-IS PDUs are forwarded as unknown unicasts over the
management LAN. Through the above modifications to the current IS-IS
router behaviors, the IS-IS flooding is greatly reduced which is much
beneficial to improve the scalability of MSDC networks.
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 [RFC1195].
3. Modifications to Current IS-IS Behaviors
3.1. IS-IS Routers as Non-DIS
After the bidirectional exchange of IS-IS Hello packets among IS-IS
routers, IS-IS routers would originate Link State PDUs (LSPs)
accordingly. However, these self-originated LSPs need not to be
exchanged directly among them anymore. Instead, these LSPs just need
to be sent solely to the controller being elected as IS-IS DIS for
the management LAN.
To further reduce the flood of multicast IS-IS PDUs over the
management LAN, IS-IS routers SHOULD send IS-IS PDUs as unicasts.
More specifically, IS-IS routers SHOULD send unicast IS-IS Hello
packets periodically to the controller being elected as IS-IS DIS.
In other words, IS-IS routers would not send any IS-IS Hello packet
over the management LAN until they have found an IS-IS DIS for the
management LAN. Note that IS-IS routers SHOULD NOT be elected as IS-
IS DIS for the management LAN (This is done by setting the DIS
Priority of those IS-IS routers to zero). As a result, IS-IS routers
would not see each other over the management LAN. In other word, IS-
IS routers would not establish adjacencies with one other.
Furthermore, IS-IS routers SHOULD send all the types of IS-IS PDUs to
the controller being elected as IS-IS DIS as unicasts as well.
To advoid the data traffic from being forwarded across the management
LAN, the cost of all IS-IS routers' interfaces to the management LAN
SHOULD be set to the maximum value.
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3.2. Controllers as DIS
The controller being elected as IS-IS DIS would send IS-IS PDUs as
multicasts or unicasts as before. And it SHOULD accept and process
those unicast IS-IS PDUs originated from IS-IS routers. Upon
receiving any new LSP from a given IS-IS router, the controller being
elected as DIS MUST flood it immediately to the management LAN for
two purposes: 1) implicitly acknowledging the receipt of that LSP; 2)
synchronizing that LSP to all the other IS-IS routers.
Futhermore, to decrease the frequency of advertising Complete
Sequence Number PDU (CSNP) on the controller being elected as DIS,
it's RECOMMENDED that IS-IS routers SHOULD send an explicit
acknowledgement with a Partial Sequence Number PDU (PSNP) upon
receiving a new LSP from the controller being elected as DIS.
4. Acknowledgements
TBD.
5. IANA Considerations
TBD.
6. Security Considerations
TBD.
7. References
7.1. Normative References
[RFC1195] Callon, R., "Use of OSI IS-IS for routing in TCP/IP and
dual environments", RFC 1195, DOI 10.17487/RFC1195,
December 1990, <http://www.rfc-editor.org/info/rfc1195>.
[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>.
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>.
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Author's Address
Xiaohu Xu
Huawei
Email: xuxiaohu@huawei.com
Xu Expires July 10, 2017 [Page 6]