Use of BGP for Routing in Large-Scale Data Centers
RFC 7938
Internet Engineering Task Force (IETF) P. Lapukhov
Request for Comments: 7938 Facebook
Category: Informational A. Premji
ISSN: 2070-1721 Arista Networks
J. Mitchell, Ed.
August 2016
Use of BGP for Routing in Large-Scale Data Centers
Abstract
Some network operators build and operate data centers that support
over one hundred thousand servers. In this document, such data
centers are referred to as "large-scale" to differentiate them from
smaller infrastructures. Environments of this scale have a unique
set of network requirements with an emphasis on operational
simplicity and network stability. This document summarizes
operational experience in designing and operating large-scale data
centers using BGP as the only routing protocol. The intent is to
report on a proven and stable routing design that could be leveraged
by others in the industry.
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 7841.
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/rfc7938.
Lapukhov, et al. Informational [Page 1]
RFC 7938 BGP Routing in Data Centers August 2016
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Network Design Requirements . . . . . . . . . . . . . . . . . 4
2.1. Bandwidth and Traffic Patterns . . . . . . . . . . . . . 4
2.2. CAPEX Minimization . . . . . . . . . . . . . . . . . . . 4
2.3. OPEX Minimization . . . . . . . . . . . . . . . . . . . . 5
2.4. Traffic Engineering . . . . . . . . . . . . . . . . . . . 5
2.5. Summarized Requirements . . . . . . . . . . . . . . . . . 6
3. Data Center Topologies Overview . . . . . . . . . . . . . . . 6
3.1. Traditional DC Topology . . . . . . . . . . . . . . . . . 6
3.2. Clos Network Topology . . . . . . . . . . . . . . . . . . 7
3.2.1. Overview . . . . . . . . . . . . . . . . . . . . . . 7
3.2.2. Clos Topology Properties . . . . . . . . . . . . . . 8
3.2.3. Scaling the Clos Topology . . . . . . . . . . . . . . 9
3.2.4. Managing the Size of Clos Topology Tiers . . . . . . 10
4. Data Center Routing Overview . . . . . . . . . . . . . . . . 11
4.1. L2-Only Designs . . . . . . . . . . . . . . . . . . . . . 11
4.2. Hybrid L2/L3 Designs . . . . . . . . . . . . . . . . . . 12
4.3. L3-Only Designs . . . . . . . . . . . . . . . . . . . . . 12
5. Routing Protocol Design . . . . . . . . . . . . . . . . . . . 13
5.1. Choosing EBGP as the Routing Protocol . . . . . . . . . . 13
5.2. EBGP Configuration for Clos Topology . . . . . . . . . . 15
5.2.1. EBGP Configuration Guidelines and Example ASN Scheme 15
5.2.2. Private Use ASNs . . . . . . . . . . . . . . . . . . 16
5.2.3. Prefix Advertisement . . . . . . . . . . . . . . . . 17
5.2.4. External Connectivity . . . . . . . . . . . . . . . . 18
5.2.5. Route Summarization at the Edge . . . . . . . . . . . 19
6. ECMP Considerations . . . . . . . . . . . . . . . . . . . . . 20
6.1. Basic ECMP . . . . . . . . . . . . . . . . . . . . . . . 20
6.2. BGP ECMP over Multiple ASNs . . . . . . . . . . . . . . . 21
6.3. Weighted ECMP . . . . . . . . . . . . . . . . . . . . . . 21
6.4. Consistent Hashing . . . . . . . . . . . . . . . . . . . 22
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