Applicability of the Babel Routing Protocol
RFC 8965
Document | Type | RFC - Informational (January 2021; No errata) | |
---|---|---|---|
Author | Juliusz Chroboczek | ||
Last updated | 2021-01-11 | ||
Replaces | draft-chroboczek-babel-applicability | ||
Stream | IETF | ||
Formats | plain text html xml pdf htmlized bibtex | ||
Reviews | |||
Stream | WG state | Submitted to IESG for Publication | |
Document shepherd | Donald Eastlake | ||
Shepherd write-up | Show (last changed 2018-12-25) | ||
IESG | IESG state | RFC 8965 (Informational) | |
Action Holders |
(None)
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||
Consensus Boilerplate | Yes | ||
Telechat date | |||
Responsible AD | Martin Vigoureux | ||
Send notices to | "Donald Eastlake" <d3e3e3@gmail.com> | ||
IANA | IANA review state | IANA OK - No Actions Needed | |
IANA action state | No IANA Actions |
Internet Engineering Task Force (IETF) J. Chroboczek Request for Comments: 8965 IRIF, University of Paris-Diderot Category: Informational January 2021 ISSN: 2070-1721 Applicability of the Babel Routing Protocol Abstract Babel is a routing protocol based on the distance-vector algorithm augmented with mechanisms for loop avoidance and starvation avoidance. This document describes a number of niches where Babel has been found to be useful and that are arguably not adequately served by more mature protocols. 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 candidates 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 https://www.rfc-editor.org/info/rfc8965. Copyright Notice Copyright (c) 2021 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 (https://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction and Background 1.1. Technical Overview of the Babel Protocol 2. Properties of the Babel Protocol 2.1. Simplicity and Implementability 2.2. Robustness 2.3. Extensibility 2.4. Limitations 3. Successful Deployments of Babel 3.1. Heterogeneous Networks 3.2. Large-Scale Overlay Networks 3.3. Pure Mesh Networks 3.4. Small Unmanaged Networks 4. Security Considerations 5. References 5.1. Normative References 5.2. Informative References Acknowledgments Author's Address 1. Introduction and Background Babel [RFC8966] is a routing protocol based on the familiar distance- vector algorithm (sometimes known as distributed Bellman-Ford) augmented with mechanisms for loop avoidance (there is no "counting to infinity") and starvation avoidance. This document describes a number of niches where Babel is useful and that are arguably not adequately served by more mature protocols such as OSPF [RFC5340] and IS-IS [RFC1195]. 1.1. Technical Overview of the Babel Protocol At its core, Babel is a distance-vector protocol based on the distributed Bellman-Ford algorithm, similar in principle to RIP [RFC2453] but with two important extensions: provisions for sensing of neighbour reachability, bidirectional reachability, and link quality, and support for multiple address families (e.g., IPv6 and IPv4) in a single protocol instance. Algorithms of this class are simple to understand and simple to implement, but unfortunately they do not work very well -- they suffer from "counting to infinity", a case of pathologically slow convergence in some topologies after a link failure. Babel uses a mechanism pioneered by the Enhanced Interior Gateway Routing Protocol (EIGRP) [DUAL] [RFC7868], known as "feasibility", which avoids routing loops and therefore makes counting to infinity impossible. Feasibility is a conservative mechanism, one that not only avoids all looping routes but also rejects some loop-free routes. Thus, it can lead to a situation known as "starvation", where a router rejects all routes to a given destination, even those that are loop-free. In order to recover from starvation, Babel uses a mechanism pioneered by the Destination-Sequenced Distance-Vector Routing Protocol (DSDV) [DSDV] and known as "sequenced routes". In Babel, this mechanism is generalised to deal with prefixes of arbitrary length and routes announced at multiple points in a single routing domain (DSDV was a pure mesh protocol, and only carried host routes). In DSDV, the sequenced routes algorithm is slow to react to a starvation episode. In Babel, starvation recovery is accelerated by using explicit requests (known as "seqno requests" in the protocol) that signal a starvation episode and cause a new sequenced route to be propagated in a timely manner. In the absence of packet loss,Show full document text