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BEST CURRENT PRACTICE
Internet Engineering Task Force (IETF) A. Durand
Request for Comments: 6302 Juniper Networks
BCP: 162 I. Gashinsky
Category: Best Current Practice Yahoo! Inc.
ISSN: 2070-1721 D. Lee
Facebook, Inc.
S. Sheppard
ATT Labs
June 2011
Logging Recommendations for Internet-Facing Servers
Abstract
In the wake of IPv4 exhaustion and deployment of IP address sharing
techniques, this document recommends that Internet-facing servers log
port number and accurate timestamps in addition to 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.
Durand, et al. Best Current Practice [Page 1]
RFC 6302 Internet-Facing Server Logging June 2011
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Recommendations . . . . . . . . . . . . . . . . . . . . . . . . 3
3. ISP Considerations . . . . . . . . . . . . . . . . . . . . . . 4
4. Security Considerations . . . . . . . . . . . . . . . . . . . . 4
5. References . . . . . . . . . . . . . . . . . . . . . . . . . . 4
5.1. Normative references . . . . . . . . . . . . . . . . . . . 4
5.2. Informative references . . . . . . . . . . . . . . . . . . 4
1. Introduction
The global IPv4 address free pool at IANA was exhausted in February
2011. Service providers will now have a hard time finding enough
IPv4 global addresses to sustain product and subscriber growth. Due
to the huge existing global infrastructure, both hardware and
software, vendors, and service providers must continue to support
IPv4 technologies for the foreseeable future. As legacy applications
and hardware are retired, the reliance on IPv4 will diminish;
however, this is a process that will take years, perhaps decades.
To maintain legacy IPv4 address support, service providers will have
little choice but to share IPv4 global addresses among multiple
customers. Techniques to do so are outside of the scope of this
document. All include some form of address translation/address
sharing, being NAT44 [RFC3022], NAT64 [RFC6146] or DS-Lite [DS-LITE].
The effects on the Internet of the introduction of 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, the knowledge of the external global IP
address was enough to identify a subscriber of interest. With
address sharing technologies, only providing information about the
external public address associated with a session to a service
provider is no longer sufficient information 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.
Durand, et al. Best Current Practice [Page 2]
RFC 6302 Internet-Facing Server Logging June 2011
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:
o The source port number.
o A timestamp, RECOMMENDED in UTC, accurate to the second, from a
traceable time source (e.g., NTP [RFC5905]).
o 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: Carrier-grade NATs may have different policies to recycle
ports; some implementations may decide to reuse ports almost
immediately, some may wait several minutes before marking the port
ready for reuse. As a result, servers have no idea how fast the
ports will be reused and, thus, should log timestamps using a
reasonably accurate clock. At this point, the RECOMMENDED accuracy
for timestamps is to the second or better. Representation of
timestamps in UTC is preferred to local time with UTC-offset or time
zone, as this extra information can be lost in the reporting chain.
Examples of Internet-facing servers include, but are not limited to,
web servers and email servers.
Although the deployment of address sharing techniques is not 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
the protection of 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. The protection of 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.
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RFC 6302 Internet-Facing Server Logging June 2011
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
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 IP/port resources
utilized. However, recommendations on this topic are out of scope
for this document.
4. Security Considerations
In the absence of the source port number and accurate timestamp
information, operators deploying any address sharing techniques will
not be able to identify unambiguously customers when dealing with
abuse or public safety queries.
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.
Durand, et al. Best Current Practice [Page 4]
RFC 6302 Internet-Facing Server Logging 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
Durand, et al. Best Current Practice [Page 5]
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