COIN H. Singh
Internet-Draft MNK Labs and Consulting
Intended status: Informational M-J. Montpetit
Expires: April 3, 2021 Concordia Univeristy
September 30, 2020
Use of P4 Programs in IETF Specifications
draft-hsingh-coinrg-p4use-00
Abstract
The IETF specifies several algorithms operating in the data plane of
a network node, including liveliness detection, congestion control,
network measurement, security, and load balancing. Such algorithms
are commonly specified using English or flow charts. As an
alternative, this document proposes that P4 programs can be used to
specify some data plane algorithms. P4 is a programming language
created in 2014 to program the data plane of network nodes such as
switches, routers, smartNICs, and generic compute targets.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
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Internet-Drafts are draft documents valid for a maximum of six months
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on April 3, 2021.
Copyright Notice
Copyright (c) 2020 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
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to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
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described in the Simplified BSD License.
Table of Contents
1. Requirements Language . . . . . . . . . . . . . . . . . . . . 2
2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
3. Example Use . . . . . . . . . . . . . . . . . . . . . . . . . 2
4. Summary of P4 . . . . . . . . . . . . . . . . . . . . . . . . 4
5. Security Considerations . . . . . . . . . . . . . . . . . . . 4
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 4
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 4
8.1. Normative References . . . . . . . . . . . . . . . . . . 4
8.2. Informative References . . . . . . . . . . . . . . . . . 5
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 5
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. Introduction
Research papers for data plane algorithms already use P4 programs to
specify algorithms. The MIT Domino compiler [MIT-Domino] which
synthesizes hardware logic also outputs a P4 program. For example,
the HULA [HULA] data plane congestion control algorithm includes P4
programming logic in the paper.
In another section, this document shows an example for how textual
description and flow chart of an algorithm could be augmented or
replaced by a P4 program. Lastly, This document presents a summary
of the P4 programming language.
3. Example Use
An IETF document in [I-D.chen-nvo3-load-banlancing] discusses the
flowlet algorithm for load balancing. The draft includes description
of algorithm in section 4.1 and a state machine diagram in section 5.
Further, if other tables are used in conjunction with the flowlet
table, in what sequence does one invoke the tables? Specifying the
algorithm of the draft as a P4 program is appropriate. Open source
P4 compiler (p4c) already includes a P4 program which implements the
flowlet algorithm. See
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https://github.com/p4lang/p4c/blob/master/testdata/p4_16_samples/
flowlet_switching-bmv2.p4
The program uses five tables and the ingress control block shows in
what order are the tables invoked. The flowlet algorithm exists in
the lookup_flow_map and update_flowlet_id P4 actions. The program
uses P4 registers to maintain state. The IETF draft uses timers.
The P4 code uses timestamps since P4 does not support timer yet. A
rudimentary timer in a P4 program can use arithmetic to determine
whether it is an even/odd minute based on data plane clock used for
timestamping packets.
A portion of the P4 program listed above is shown below. The portion
shows two P4 actions which implement the flowlet algorithm.
action lookup_flowlet_map() {
hash(meta.ingress_metadata.flowlet_map_index,
HashAlgorithm.crc16,
(bit<13>)0, { hdr.ipv4.srcAddr, hdr.ipv4.dstAddr,
hdr.ipv4.protocol, hdr.tcp.srcPort,
hdr.tcp.dstPort }, (bit<26>)13);
flowlet_id.read(meta.ingress_metadata.flowlet_id,
(bit<32>)meta.ingress_metadata.flowlet_map_index);
meta.ingress_metadata.flow_ipg =
(bit<32>)standard_metadata.ingress_global_timestamp;
flowlet_lasttime.read(
meta.ingress_metadata.flowlet_lasttime,
(bit<32>)meta.ingress_metadata.flowlet_map_index);
meta.ingress_metadata.flow_ipg =
meta.ingress_metadata.flow_ipg -
meta.ingress_metadata.flowlet_lasttime;
flowlet_lasttime.write(
(bit<32>)meta.ingress_metadata.flowlet_map_index,
(bit<32>)standard_metadata.ingress_global_timestamp);
}
action update_flowlet_id() {
meta.ingress_metadata.flowlet_id =
meta.ingress_metadata.flowlet_id + 16w1;
flowlet_id.write(
(bit<32>)meta.ingress_metadata.flowlet_map_index,
(bit<16>)meta.ingress_metadata.flowlet_id);
}
Figure 1: Two P4 actions implement the flowlet algorithm
The ingress control block invokes table lookup using 'table.apply()'.
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apply {
@atomic {
flowlet.apply();
if (meta.ingress_metadata.flow_ipg > 32w50000)
new_flowlet.apply();
}
ecmp_group.apply();
ecmp_nhop.apply();
forward.apply();
}
Figure 2: Code shows order of invocation for table lookup
4. Summary of P4
First, https://p4.org is a great resource to start with. The website
includes specifications, pointers to P4 tutorials, p4c, the P4
mailer, P4 Slack Channel, and other details to P4 events, blogs. etc.
The README.md file at https://github.com/p4lan/p4c/ includes details
on how to compile a P4 program. P4 started with a P4-14 version in
2014. Since, May 2017, a new version in P4-16 and compiler are
available. A list of hardware targets to use for P4 programming is
available here: https://github.com/hesingh/p4-info
5. Security Considerations
Use IPSec [RFC4301].
6. IANA Considerations
None.
7. Acknowledgements
Thanks (in alphabetical order by first name) to Nick McKeown for
encouraging this work.
8. References
8.1. Normative References
[I-D.chen-nvo3-load-banlancing]
Chen, H., "Load balancing without packet reordering in
NVO3", draft-chen-nvo3-load-banlancing-00 (work in
progress), October 2014.
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[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC4301] Kent, S. and K. Seo, "Security Architecture for the
Internet Protocol", RFC 4301, DOI 10.17487/RFC4301,
December 2005, <https://www.rfc-editor.org/info/rfc4301>.
8.2. Informative References
[HULA] Katta, N., Hira, M., Kim, C., Sivaraman, A., and J.
Rexford, "HULA: Scalable Load Balancing Using Programmable
Data Planes", March 2016,
<https://dl.acm.org/doi/pdf/10.1145/2890955.2890968>.
[MIT-Domino]
Sivaraman, A., Cheung, A., Budiu, M., Kim, C., Alizadeh,
M., Balakrishnan, H., Varghese, G., McKeown, N., and S.
Licking, "Packet Transactions: High-level Programming for
Line-Rate Switches", January 2016,
<http://web.mit.edu/domino/>.
Authors' Addresses
Hemant Singh
MNK Labs and Consulting
7 Caldwell Drive
Westford, MA 01886
USA
Phone: +1 978 692 2340
Email: hemant@mnkcg.com
URI: https://mnkcg.com/
Marie-Jose Montpetit
Concordia Univeristy
1455 Boulevard de Maisonneuve O
Montreal, Quebec 01886
Canada
Email: marie@mjmontpetit.com
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