Address Resolution Problems in Large Data Center Networks
RFC 6820
Internet Engineering Task Force (IETF) T. Narten
Request for Comments: 6820 IBM Corporation
Category: Informational M. Karir
ISSN: 2070-1721 Merit Network Inc.
I. Foo
Huawei Technologies
January 2013
Address Resolution Problems in Large Data Center Networks
Abstract
This document examines address resolution issues related to the
scaling of data centers with a very large number of hosts. The scope
of this document is relatively narrow, focusing on address resolution
(the Address Resolution Protocol (ARP) in IPv4 and Neighbor Discovery
(ND) in IPv6) within a data center.
Status of This Memo
This document is not an Internet Standards Track specification; it is
published for informational purposes.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Not all documents
approved by the IESG are a candidate for any level of Internet
Standard; see Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc6820.
Narten, et al. Informational [Page 1]
RFC 6820 ARMD-Problems January 2013
Copyright Notice
Copyright (c) 2013 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
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described in the Simplified BSD License.
Table of Contents
1. Introduction ....................................................3
2. Terminology .....................................................3
3. Background ......................................................4
4. Address Resolution in IPv4 ......................................6
5. Address Resolution in IPv6 ......................................7
6. Generalized Data Center Design ..................................7
6.1. Access Layer ...............................................8
6.2. Aggregation Layer ..........................................8
6.3. Core .......................................................9
6.4. L3/L2 Topological Variations ...............................9
6.4.1. L3 to Access Switches ...............................9
6.4.2. L3 to Aggregation Switches ..........................9
6.4.3. L3 in the Core Only ................................10
6.4.4. Overlays ...........................................10
6.5. Factors That Affect Data Center Design ....................11
6.5.1. Traffic Patterns ...................................11
6.5.2. Virtualization .....................................11
6.5.3. Summary ............................................12
7. Problem Itemization ............................................12
7.1. ARP Processing on Routers .................................12
7.2. IPv6 Neighbor Discovery ...................................14
7.3. MAC Address Table Size Limitations in Switches ............15
8. Summary ........................................................15
9. Acknowledgments ................................................16
10. Security Considerations .......................................16
11. Informative References ........................................16
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RFC 6820 ARMD-Problems January 2013
1. Introduction
This document examines issues related to the scaling of large data
centers. Specifically, this document focuses on address resolution
(ARP in IPv4 and Neighbor Discovery in IPv6) within the data center.
Although strictly speaking the scope of address resolution is
confined to a single L2 broadcast domain (i.e., ARP runs at the L2
layer below IP), the issue is complicated by routers having many
interfaces on which address resolution must be performed or with the
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