RFC 6302

RFC 6302: Logging Recommendations for Internet-Facing Servers 💖

• Authors: Alain Durand (Juniper Networks), Igor Gashinsky (Yahoo! Inc.), Donn Lee (Facebook, Inc.), and Scott Sheppard (ATT Labs) 👑
• Category: Best Current Practice, BCP 162 🌸
• Date: June 2011 🦋
• ISSN: 2070-1721 ✨
• Obsoletes/Updates: the title block doesn't list anything this one obsoletes or updates 🧚

Abstract ✨

okay so after IPv4 ran out and everyone started sharing addresses, this doc recommends that Internet-facing servers log the port number and accurate timestamps too, not just the incoming IP address 🔥

Status of This Memo 📜

This memo documents an Internet Best Current Practice.

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). Further information on BCPs is available in 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/rfc6302.

Copyright Notice 💅

Copyright (c) 2011 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 (http://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.

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1. Introduction ✨

bestie, the global IPv4 address free pool at IANA ran out in February 2011 🥲 Service providers are now going to have a hard time finding enough IPv4 global addresses to keep up with product and subscriber growth. There's a huge existing global infrastructure, both hardware and software, so vendors and service providers have to keep supporting IPv4 technologies for the foreseeable future 💜 As legacy applications and hardware get retired, the reliance on IPv4 will shrink, but that's a process that will take years, perhaps decades 🐢

So to keep legacy IPv4 support going, service providers will have basically no choice but to share IPv4 global addresses among multiple customers 🫶 The techniques for doing that are outside the scope of this document. All of them include some form of address translation/address sharing: NAT44 [RFC3022], NAT64 [RFC6146], or DS-Lite [DS-LITE].

The effects on the Internet of introducing those address sharing techniques have been documented in [RFC6269] 🌈

Address sharing techniques come with their own logging infrastructure to track the relation between which original IP address and source port(s) were associated with which user and external IPv4 address at any given point in time. In the past, to support abuse mitigation or public safety requests, knowing the external global IP address was enough to identify a subscriber of interest. With address sharing, just giving a service provider the external public address tied to a session is no longer enough to unambiguously identify customers 😭

Note: This document provides recommendations for Internet-facing servers logging incoming connections. It does not provide any recommendations about logging on carrier-grade NAT or other address sharing tools.

2. Recommendations 🎀

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].

It is RECOMMENDED as best current practice that Internet-facing servers logging incoming IP addresses from inbound IP traffic also log:

• The source port number. 🔥
• A timestamp, RECOMMENDED in UTC, accurate to the second, from a traceable time source (e.g., NTP [RFC5905]). ⏰
• The transport protocol (usually TCP or UDP) and destination port number, when the server application is defined to use multiple transports or multiple ports. 🧚

Discussion: okay the tea is that carrier-grade NATs can have different policies for recycling ports. Some implementations reuse ports almost immediately, and some wait several minutes before marking the port ready for reuse. So servers have no idea how fast ports will get reused, and that means they should log timestamps using a reasonably accurate clock 🕰️ At this point, the RECOMMENDED accuracy for timestamps is to the second or better. Timestamps in UTC are preferred over local time with a UTC-offset or time zone, because that extra info can get lost in the reporting chain 🙈

Examples of Internet-facing servers include, but are not limited to, web servers and email servers 💌

Although address sharing isn't foreseen in IPv6, the above recommendations apply to both IPv4 and IPv6, if only for consistency and code simplification reasons 🧠

Discussions about data-retention policies are out of scope for this document. Server security and transport security are important for protecting logs for Internet-facing systems. The operator of the Internet-facing server must consider the risks, including the data and services on the server, to determine the appropriate measures. Protecting logs is critical in incident investigations. If logs are tampered with, evidence could be destroyed 💀

The above recommendations also apply to devices such as load-balancers logging incoming connections on behalf of actual servers 🍓

The above recommendations apply to current logging practices. They do not require any changes in the way logging is performed, e.g., which packets are examined and logged. 💖

3. ISP Considerations 🌸

An ISP deploying IP address sharing techniques should also deploy a corresponding logging architecture to maintain records of the relation between a customer's identity and the IP/port resources utilized. However, recommendations on this topic are out of scope for this document 📚

4. Security Considerations 🚨

This one is seriously important, no cap. Without the source port number and accurate timestamp information, operators deploying any address sharing techniques will not be able to unambiguously identify customers when dealing with abuse or public safety queries. That's a real problem, and it's the whole reason this doc exists 😱

5. References 📚

5.1. Normative references

• [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997.

5.2. Informative references

• [DS-LITE] Durand, A., Droms, R., Woodyatt, J., and Y. Lee, "Dual-Stack Lite Broadband Deployments Following IPv4 Exhaustion", Work in Progress, May 2011.
• [RFC3022] Srisuresh, P. and K. Egevang, "Traditional IP Network Address Translator (Traditional NAT)", RFC 3022, January 2001.
• [RFC5905] Mills, D., Martin, J., Burbank, J., and W. Kasch, "Network Time Protocol Version 4: Protocol and Algorithms Specification", RFC 5905, June 2010.
• [RFC6146] Bagnulo, M., Matthews, P., and I. van Beijnum, "Stateful NAT64: Network Address and Protocol Translation from IPv6 Clients to IPv4 Servers", RFC 6146, April 2011.
• [RFC6269] Ford, M., Ed., Boucadair, M., Durand, A., Levis, P., and P. Roberts, "Issues with IP Address Sharing", RFC 6269, June 2011.

Authors' Addresses 🫶

Alain Durand
Juniper Networks
1194 North Mathilda Avenue
Sunnyvale, CA  94089-1206
USA

EMail: adurand@juniper.net


Igor Gashinsky
Yahoo! Inc.
45 West 18th St.
New York, NY  10011
USA

EMail: igor@yahoo-inc.com


Donn Lee
Facebook, Inc.
1601 S. California Ave.
Palo Alto, CA  94304
USA

EMail: donn@fb.com


Scott Sheppard
ATT Labs
575 Morosgo Ave, 4d57
Atlanta, GA  30324
USA

EMail: Scott.Sheppard@att.com