GENWiki

Premier IT Outsourcing and Support Services within the UK

User Tools

Site Tools


rfc:rfc3164

Network Working Group C. Lonvick Request for Comments: 3164 Cisco Systems Category: Informational August 2001

                      The BSD syslog Protocol

Status of this Memo

 This memo provides information for the Internet community.  It does
 not specify an Internet standard of any kind.  Distribution of this
 memo is unlimited.

Copyright Notice

 Copyright (C) The Internet Society (2001).  All Rights Reserved.

Abstract

 This document describes the observed behavior of the syslog protocol.
 This protocol has been used for the transmission of event
 notification messages across networks for many years.  While this
 protocol was originally developed on the University of California
 Berkeley Software Distribution (BSD) TCP/IP system implementations,
 its value to operations and management has led it to be ported to
 many other operating systems as well as being embedded into many
 other networked devices.

Table of Contents

 1. Introduction....................................................2
 1.1 Events and Generated Messages..................................3
 1.2 Operations of the Message Receivers............................5
 2. Transport Layer Protocol........................................5
 3. Definitions and Architecture....................................5
 4. Packet Format and Contents......................................7
 4.1 syslog Message Parts...........................................8
 4.1.1 PRI Part.....................................................8
 4.1.2 HEADER Part of a syslog Packet..............................10
 4.1.3 MSG Part of a syslog Packet.................................11
 4.2 Original syslog Packets Generated by a Device.................12
 4.3 Relayed syslog Packets........................................12
 4.3.1 Valid PRI and TIMESTAMP.....................................13
 4.3.2 Valid PRI but no TIMESTAMP or invalid TIMESTAMP.............13
 4.3.3 No PRI or Unidentifiable PRI................................14
 5. Conventions....................................................14
 5.1 Dates and Times...............................................15
 5.2 Domain Name and Address.......................................15

Lonvick Informational [Page 1] RFC 3164 The BSD syslog Protocol August 2001

 5.3 Originating Process Information...............................15
 5.4 Examples......................................................16
 6. Security Considerations........................................18
 6.1 Packet Parameters.............................................19
 6.2 Message Authenticity..........................................19
 6.2.1 Authentication Problems.....................................19
 6.2.2 Message Forgery.............................................20
 6.3 Sequenced Delivery............................................20
 6.3.1 Single Source to a Destination..............................20
 6.3.2 Multiple Sources to a Destination...........................21
 6.3.3 Multiple Sources to Multiple Destinations...................21
 6.3.4 Replaying...................................................22
 6.4 Reliable Delivery.............................................22
 6.5 Message Integrity.............................................22
 6.6 Message Observation...........................................22
 6.7 Message Prioritization and Differentiation....................23
 6.8 Misconfiguration..............................................24
 6.9 Forwarding Loop...............................................24
 6.10 Load Considerations..........................................25
 7. IANA Considerations............................................25
 8. Conclusion and Other Efforts...................................25
 Acknowledgements..................................................26
 References........................................................27
 Author's Address..................................................28
 Full Copyright Statement..........................................29

1. Introduction

 Since the beginning, life has relied upon the transmission of
 messages.  For the self-aware organic unit, these messages can relay
 many different things.  The messages may signal danger, the presence
 of food or the other necessities of life, and many other things.  In
 many cases, these messages are informative to other units and require
 no acknowledgement.  As people interacted and created processes, this
 same principle was applied to societal communications.  As an
 example, severe weather warnings may be delivered through any number
 of channels - a siren blowing, warnings delivered over television and
 radio stations, and even through the use of flags on ships.  The
 expectation is that people hearing or seeing these warnings would
 realize their significance and take appropriate action.  In most
 cases, no responding acknowledgement of receipt of the warning is
 required or even desired.  Along these same lines, operating systems,
 processes and applications were written to send messages of their own
 status, or messages to indicate that certain events had occurred.
 These event messages generally had local significance to the machine
 operators.  As the operating systems, processes and applications grew
 ever more complex, systems were devised to categorize and log these
 diverse messages and allow the operations staff to more quickly

Lonvick Informational [Page 2] RFC 3164 The BSD syslog Protocol August 2001

 differentiate the notifications of problems from simple status
 messages.  The syslog process was one such system that has been
 widely accepted in many operating systems.  Flexibility was designed
 into this process so the operations staff have the ability to
 configure the destination of messages sent from the processes running
 on the device.  In one dimension, the events that were received by
 the syslog process could be logged to different files and also
 displayed on the console of the device.  In another dimension, the
 syslog process could be configured to forward the messages across a
 network to the syslog process on another machine. The syslog process
 had to be built network-aware for some modicum of scalability since
 it was known that the operators of multiple systems would not have
 the time to access each system to review the messages logged there.
 The syslog process running on the remote devices could therefore be
 configured to either add the message to a file, or to subsequently
 forward it to another machine.
 In its most simplistic terms, the syslog protocol provides a
 transport to allow a machine to send event notification messages
 across IP networks to event message collectors - also known as syslog
 servers.  Since each process, application and operating system was
 written somewhat independently, there is little uniformity to the
 content of syslog messages.  For this reason, no assumption is made
 upon the formatting or contents of the messages.  The protocol is
 simply designed to transport these event messages.  In all cases,
 there is one device that originates the message.  The syslog process
 on that machine may send the message to a collector.  No
 acknowledgement of the receipt is made.
 One of the fundamental tenets of the syslog protocol and process is
 its simplicity.  No stringent coordination is required between the
 transmitters and the receivers.  Indeed, the transmission of syslog
 messages may be started on a device without a receiver being
 configured, or even actually physically present.  Conversely, many
 devices will most likely be able to receive messages without explicit
 configuration or definitions.  This simplicity has greatly aided the
 acceptance and deployment of syslog.

1.1 Events and Generated Messages

 The writers of the operating systems, processes and applications have
 had total control over the circumstances that would generate any
 message.  In some cases, messages are generated to give status. These
 can be either at a certain period of time, or at some other interval
 such as the invocation or exit of a program.  In other cases, the
 messages may be generated due to a set of conditions being met.  In
 those cases, either a status message or a message containing an alarm
 of some type may be generated.  It was considered that the writers of

Lonvick Informational [Page 3] RFC 3164 The BSD syslog Protocol August 2001

 the operating systems, processes and applications would quantify
 their messages into one of several broad categories.  These broad
 categories generally consist of the facility that generated them,
 along with an indication of the severity of the message.  This was so
 that the operations staff could selectively filter the messages and
 be presented with the more important and time sensitive notifications
 quickly, while also having the ability to place status or informative
 messages in a file for later perusal.   Other options for displaying
 or storing messages have been seen to exist as well.
 Devices MUST be configured with rules for displaying and/or
 forwarding the event messages.  The rules that have been seen are
 generally very flexible.  An administrator may want to have all
 messages stored locally as well as to have all messages of a high
 severity forwarded to another device.  They may find it appropriate
 to also have messages from a particular facility sent to some or all
 of the users of the device and displayed on the system console.
 However the administrator decides to configure the disposition of the
 event messages, the process of having them sent to a syslog collector
 generally consists of deciding which facility messages and which
 severity levels will be forwarded, and then defining the remote
 receiver.  For example, an administrator may want all messages that
 are generated by the mail facility to be forwarded to one particular
 event message collector.  Then the administrator may want to have all
 kernel generated messages sent to a different syslog receiver while,
 at the same time, having the critically severe messages from the
 kernel also sent to a third receiver.  It may also be appropriate to
 have those messages displayed on the system console as well as being
 mailed to some appropriate people, while at the same time, being sent
 to a file on the local disk of the device.  Conversely, it may be
 appropriate to have messages from a locally defined process only
 displayed on the console but not saved or forwarded from the device.
 In any event, the rules for this will have to be generated on the
 device.  Since the administrators will then know which types of
 messages will be received on the collectors, they should then make
 appropriate rules on those syslog servers as well.
 The contents of a message have also been at the discretion of its
 creator.  It has been considered to be good form to write the
 messages so that they are informative to the person who may be
 reading them.  It has also been considered good practice to include a
 timestamp and some indication of the sending device and the process
 that originated it in the messages.  However, none of those are
 stringently required.
 It should be assumed that any process on any device might generate an
 event message.  This may include processes on machines that do not
 have any local storage - e.g., printers, routers, hubs, switches, and

Lonvick Informational [Page 4] RFC 3164 The BSD syslog Protocol August 2001

 diskless workstations.  In that case, it may be imperative that event
 messages are transported to a collector so that they may be recorded
 and hopefully viewed by an operator.

1.2 Operations of the Message Receivers

 It is beyond the scope of this document to specify how event messages
 should be processed when they are received.  Like the operations
 described in Section 1.1, they generally may be displayed to the
 appropriate people, saved onto disk, further forwarded, or any
 combination of these.  The rules for determining the disposition of
 received messages have been seen to be identical to the rules for
 determining the disposition of locally generated messages.
 As a very general rule, there are usually many devices sending
 messages to relatively fewer collectors.  This fan-in process allows
 an administrator to aggregate messages into relatively few
 repositories.

2. Transport Layer Protocol

 syslog uses the user datagram protocol (UDP) [1] as its underlying
 transport layer mechanism.  The UDP port that has been assigned to
 syslog is 514.  It is RECOMMENDED that the source port also be 514 to
 indicate that the message is from the syslog process of the sender,
 but there have been cases seen where valid syslog messages have come
 from a sender with a source port other than 514.  If the sender uses
 a source port other than 514 then it is RECOMMENDED and has been
 considered to be good form that subsequent messages are from a single
 consistent port.

3. Definitions and Architecture

 The following definitions will be used in this document.
       A machine that can generate a message will be called a
       "device".
       A machine that can receive the message and forward it to
       another machine will be called a "relay".
       A machine that receives the message and does not relay it to
       any other machines will be called a "collector".  This has been
       commonly known as a "syslog server".
       Any device or relay will be known as the "sender" when it sends
       a message.

Lonvick Informational [Page 5] RFC 3164 The BSD syslog Protocol August 2001

       Any relay or collector will be known as the "receiver" when it
       receives the message.
 The architecture of the devices may be summarized as follows:
       Senders send messages to relays or collectors with no knowledge
       of whether it is a collector or relay.
       Senders may be configured to send the same message to multiple
       receivers.
       Relays may send all or some of the messages that they receive
       to a subsequent relay or collector.  In the case where they do
       not forward all of their messages, they are acting as both a
       collector and a relay.  In the following diagram, these devices
       will be designated as relays.
       Relays may also generate their own messages and send them on to
       subsequent relays or collectors.  In that case it is acting as
       a device.  These devices will also be designated as a relay in
       the following diagram.
 The following architectures shown in Diagram 1 are valid while the
 first one has been known to be the most prevalent.  Other
 arrangements of these examples are also acceptable.  As noted above,
 in the following diagram relays may pass along all or some of the
 messages that they receive along with passing along messages that
 they internally generate.

Lonvick Informational [Page 6] RFC 3164 The BSD syslog Protocol August 2001

       +------+         +---------+
       |Device|---->----|Collector|
       +------+         +---------+
       +------+         +-----+         +---------+
       |Device|---->----|Relay|---->----|Collector|
       +------+         +-----+         +---------+
       +------+     +-----+            +-----+     +---------+
       |Device|-->--|Relay|-->--..-->--|Relay|-->--|Collector|
       +------+     +-----+            +-----+     +---------+
       +------+         +-----+         +---------+
       |Device|---->----|Relay|---->----|Collector|
       |      |-\       +-----+         +---------+
       +------+  \
                  \      +-----+         +---------+
                   \-->--|Relay|---->----|Collector|
                         +-----+         +---------+
       +------+         +---------+
       |Device|---->----|Collector|
       |      |-\       +---------+
       +------+  \
                  \      +-----+         +---------+
                   \-->--|Relay|---->----|Collector|
                         +-----+         +---------+
       +------+         +-----+            +---------+
       |Device|---->----|Relay|---->-------|Collector|
       |      |-\       +-----+         /--|         |
       +------+  \                     /   +---------+
                  \      +-----+      /
                   \-->--|Relay|-->--/
                         +-----+
         Diagram 1.  Some Possible syslog Architectures

4. Packet Format and Contents

 The payload of any IP packet that has a UDP destination port of 514
 MUST be treated as a syslog message.  There MAY be differences
 between the format of an originally transmitted syslog message and
 the format of a relayed message.  In essence, it is RECOMMENDED to
 transmit a syslog message in the format specified in this document,
 but it is not required.  If a relay is able to recognize the message
 as adhering to that format then it MUST retransmit the message
 without making any changes to it.  However, if a relay receives a

Lonvick Informational [Page 7] RFC 3164 The BSD syslog Protocol August 2001

 message but cannot discern the proper implementation of the format,
 it is REQUIRED to modify the message so that it conforms to that
 format before it retransmits it.  Section 4.1 will describe the
 RECOMMENDED format for syslog messages.  Section 4.2 will describe
 the requirements for originally transmitted messages and Section 4.3
 will describe the requirements for relayed messages.

4.1 syslog Message Parts

 The full format of a syslog message seen on the wire has three
 discernable parts.  The first part is called the PRI, the second part
 is the HEADER, and the third part is the MSG.  The total length of
 the packet MUST be 1024 bytes or less.  There is no minimum length of
 the syslog message although sending a syslog packet with no contents
 is worthless and SHOULD NOT be transmitted.

4.1.1 PRI Part

 The PRI part MUST have three, four, or five characters and will be
 bound with angle brackets as the first and last characters.  The PRI
 part starts with a leading "<" ('less-than' character), followed by a
 number, which is followed by a ">" ('greater-than' character). The
 code set used in this part MUST be seven-bit ASCII in an eight-bit
 field as described in RFC 2234 [2].  These are the ASCII codes as
 defined in "USA Standard Code for Information Interchange" [3].  In
 this, the "<" character is defined as the Augmented Backus-Naur Form
 (ABNF) %d60, and the ">" character has ABNF value %d62.  The number
 contained within these angle brackets is known as the Priority value
 and represents both the Facility and Severity as described below.
 The Priority value consists of one, two, or three decimal integers
 (ABNF DIGITS) using values of %d48 (for "0") through %d57 (for "9").
 The Facilities and Severities of the messages are numerically coded
 with decimal values.  Some of the operating system daemons and
 processes have been assigned Facility values.  Processes and daemons
 that have not been explicitly assigned a Facility may use any of the
 "local use" facilities or they may use the "user-level" Facility.
 Those Facilities that have been designated are shown in the following
 table along with their numerical code values.
     Numerical             Facility
        Code
         0             kernel messages
         1             user-level messages
         2             mail system
         3             system daemons
         4             security/authorization messages (note 1)

Lonvick Informational [Page 8] RFC 3164 The BSD syslog Protocol August 2001

         5             messages generated internally by syslogd
         6             line printer subsystem
         7             network news subsystem
         8             UUCP subsystem
         9             clock daemon (note 2)
        10             security/authorization messages (note 1)
        11             FTP daemon
        12             NTP subsystem
        13             log audit (note 1)
        14             log alert (note 1)
        15             clock daemon (note 2)
        16             local use 0  (local0)
        17             local use 1  (local1)
        18             local use 2  (local2)
        19             local use 3  (local3)
        20             local use 4  (local4)
        21             local use 5  (local5)
        22             local use 6  (local6)
        23             local use 7  (local7)
         Table 1.  syslog Message Facilities
      Note 1 - Various operating systems have been found to utilize
         Facilities 4, 10, 13 and 14 for security/authorization,
         audit, and alert messages which seem to be similar.
      Note 2 - Various operating systems have been found to utilize
         both Facilities 9 and 15 for clock (cron/at) messages.
 Each message Priority also has a decimal Severity level indicator.
 These are described in the following table along with their numerical
 values.
      Numerical         Severity
        Code
         0       Emergency: system is unusable
         1       Alert: action must be taken immediately
         2       Critical: critical conditions
         3       Error: error conditions
         4       Warning: warning conditions
         5       Notice: normal but significant condition
         6       Informational: informational messages
         7       Debug: debug-level messages
         Table 2. syslog Message Severities

Lonvick Informational [Page 9] RFC 3164 The BSD syslog Protocol August 2001

 The Priority value is calculated by first multiplying the Facility
 number by 8 and then adding the numerical value of the Severity. For
 example, a kernel message (Facility=0) with a Severity of Emergency
 (Severity=0) would have a Priority value of 0.  Also, a "local use 4"
 message (Facility=20) with a Severity of Notice (Severity=5) would
 have a Priority value of 165.  In the PRI part of a syslog message,
 these values would be placed between the angle brackets as <0> and
 <165> respectively.  The only time a value of "0" will follow the "<"
 is for the Priority value of "0". Otherwise, leading "0"s MUST NOT be
 used.

4.1.2 HEADER Part of a syslog Packet

 The HEADER part contains a timestamp and an indication of the
 hostname or IP address of the device.  The HEADER part of the syslog
 packet MUST contain visible (printing) characters.  The code set used
 MUST also be seven-bit ASCII in an eight-bit field like that used in
 the PRI part.  In this code set, the only allowable characters are
 the ABNF VCHAR values (%d33-126) and spaces (SP value %d32).
 The HEADER contains two fields called the TIMESTAMP and the HOSTNAME.
 The TIMESTAMP will immediately follow the trailing ">" from the PRI
 part and single space characters MUST follow each of the TIMESTAMP
 and HOSTNAME fields.  HOSTNAME will contain the hostname, as it knows
 itself.  If it does not have a hostname, then it will contain its own
 IP address.  If a device has multiple IP addresses, it has usually
 been seen to use the IP address from which the message is
 transmitted.  An alternative to this behavior has also been seen.  In
 that case, a device may be configured to send all messages using a
 single source IP address regardless of the interface from which the
 message is sent.  This will provide a single consistent HOSTNAME for
 all messages sent from a device.
 The TIMESTAMP field is the local time and is in the format of "Mmm dd
 hh:mm:ss" (without the quote marks) where:
       Mmm is the English language abbreviation for the month of the
       year with the first character in uppercase and the other two
       characters in lowercase.  The following are the only acceptable
       values:
       Jan, Feb, Mar, Apr, May, Jun, Jul, Aug, Sep, Oct, Nov, Dec
       dd is the day of the month.  If the day of the month is less
       than 10, then it MUST be represented as a space and then the
       number.  For example, the 7th day of August would be
       represented as "Aug  7", with two spaces between the "g" and
       the "7".

Lonvick Informational [Page 10] RFC 3164 The BSD syslog Protocol August 2001

       hh:mm:ss is the local time.  The hour (hh) is represented in a
       24-hour format.  Valid entries are between 00 and 23,
       inclusive.  The minute (mm) and second (ss) entries are between
       00 and 59 inclusive.
 A single space character MUST follow the TIMESTAMP field.
 The HOSTNAME field will contain only the hostname, the IPv4 address,
 or the IPv6 address of the originator of the message.  The preferred
 value is the hostname.  If the hostname is used, the HOSTNAME field
 MUST contain the hostname of the device as specified in STD 13 [4].
 It should be noted that this MUST NOT contain any embedded spaces.
 The Domain Name MUST NOT be included in the HOSTNAME field.  If the
 IPv4 address is used, it MUST be shown as the dotted decimal notation
 as used in STD 13 [5].  If an IPv6 address is used, any valid
 representation used in RFC 2373 [6] MAY be used.  A single space
 character MUST also follow the HOSTNAME field.

4.1.3 MSG Part of a syslog Packet

 The MSG part will fill the remainder of the syslog packet.  This will
 usually contain some additional information of the process that
 generated the message, and then the text of the message.  There is no
 ending delimiter to this part.  The MSG part of the syslog packet
 MUST contain visible (printing) characters.  The code set
 traditionally and most often used has also been seven-bit ASCII in an
 eight-bit field like that used in the PRI and HEADER parts.  In this
 code set, the only allowable characters are the ABNF VCHAR values
 (%d33-126) and spaces (SP value %d32).  However, no indication of the
 code set used within the MSG is required, nor is it expected.  Other
 code sets MAY be used as long as the characters used in the MSG are
 exclusively visible characters and spaces similar to those described
 above.  The selection of a code set used in the MSG part SHOULD be
 made with thoughts of the intended receiver.  A message containing
 characters in a code set that cannot be viewed or understood by a
 recipient will yield no information of value to an operator or
 administrator looking at it.
 The MSG part has two fields known as the TAG field and the CONTENT
 field.  The value in the TAG field will be the name of the program or
 process that generated the message.  The CONTENT contains the details
 of the message.  This has traditionally been a freeform message that
 gives some detailed information of the event.  The TAG is a string of
 ABNF alphanumeric characters that MUST NOT exceed 32 characters.  Any
 non-alphanumeric character will terminate the TAG field and will be
 assumed to be the starting character of the CONTENT field.  Most
 commonly, the first character of the CONTENT field that signifies the

Lonvick Informational [Page 11] RFC 3164 The BSD syslog Protocol August 2001

 conclusion of the TAG field has been seen to be the left square
 bracket character ("["), a colon character (":"), or a space
 character.  This is explained in more detail in Section 5.3.

4.2 Original syslog Packets Generated by a Device

 There are no set requirements on the contents of the syslog packet as
 it is originally sent from a device.  It should be reiterated here
 that the payload of any IP packet destined to UDP port 514 MUST be
 considered to be a valid syslog message.  It is, however, RECOMMENDED
 that the syslog packet have all of the parts described in Section 4.1
 - PRI, HEADER and MSG - as this enhances readability by the recipient
 and eliminates the need for a relay to modify the message.
 For implementers that do choose to construct syslog messages with the
 RECOMMENDED format, the following guidance is offered.
       If the originally formed message has a TIMESTAMP in the HEADER
       part, then it SHOULD be the local time of the device within its
       timezone.
       If the originally formed message has a HOSTNAME field, then it
       will contain the hostname as it knows itself.  If it does not
       have a hostname, then it will contain its own IP address.
       If the originally formed message has a TAG value, then that
       will be the name of the program or process that generated the
       message.

4.3 Relayed syslog Packets

 When a relay receives a packet, it will check for a valid PRI.  If
 the first character is not a less-than sign, the relay MUST assume
 that the packet does not contain a valid PRI.  If the 3rd, 4th, or
 5th character is not a right angle bracket character, the relay again
 MUST assume that the PRI was not included in the original message.
 If the relay does find a valid PRI part then it must check for a
 valid TIMESTAMP in the HEADER part.  From these rules, there will be
 three general cases of received messages.  Table 3 gives the general
 characteristics of these cases and lists the subsequent section of
 this document that describes the handling of that case.
            Case                                         Section
       Valid PRI and TIMESTAMP                            4.3.1
       Valid PRI but no TIMESTAMP or invalid TIMESTAMP    4.3.2
       No PRI or unidentifiable PRI                       4.3.3
            Table 3. Cases of Received syslog Messages

Lonvick Informational [Page 12] RFC 3164 The BSD syslog Protocol August 2001

4.3.1 Valid PRI and TIMESTAMP

 If the relay does find a valid PRI and a valid TIMESTAMP, then it
 will check its internal configuration.  Relays MUST be configured to
 forward syslog packets on the basis of their Priority value.  If the
 relay finds that it is configured to forward the received packet,
 then it MUST do so without making any changes to the packet.  To
 emphasize the point one more time, it is for this reason that it is
 RECOMMENDED that the syslog message originally transmitted adhere to
 the format described in Section 4.1.
 It should be noted here that the message receiver does not need to
 validate the time in the TIMESTAMP field.  The assumption may be made
 that a device whose date has not been correctly set will still have
 the ability to send valid syslog messages.  Additionally, the relay
 does not need to validate that the value in the HOSTNAME field
 matches the hostname or IP address of the device sending the message.
 A reason for this behavior may be found in Section 4.1.2.

4.3.2 Valid PRI but no TIMESTAMP or invalid TIMESTAMP

 If a relay does not find a valid TIMESTAMP in a received syslog
 packet, then it MUST add a TIMESTAMP and a space character
 immediately after the closing angle bracket of the PRI part.  It
 SHOULD additionally add a HOSTNAME and a space character after the
 TIMESTAMP.  These fields are described here and detailed in Section
 4.1.2.  The remainder of the received packet MUST be treated as the
 CONTENT field of the MSG and appended.  Since the relay would have no
 way to determine the originating process from the device that
 originated the message, the TAG value cannot be determined and will
 not be included.
 The TIMESTAMP will be the current local time of the relay.
 The HOSTNAME will be the name of the device, as it is known by the
 relay.  If the name cannot be determined, the IP address of the
 device will be used.
 If the relay adds a TIMESTAMP, or a TIMESTAMP and HOSTNAME, after the
 PRI part, then it MUST check that the total length of the packet is
 still 1024 bytes or less.  If the packet has been expanded beyond
 1024 bytes, then the relay MUST truncate the packet to be 1024 bytes.
 This may cause the loss of vital information from the end of the
 original packet.  It is for this reason that it is RECOMMENDED that
 the PRI and HEADER parts of originally generated syslog packets
 contain the values and fields documented in Section 4.1.

Lonvick Informational [Page 13] RFC 3164 The BSD syslog Protocol August 2001

4.3.3 No PRI or Unidentifiable PRI

 If the relay receives a syslog message without a PRI, or with an
 unidentifiable PRI, then it MUST insert a PRI with a Priority value
 of 13 as well as a TIMESTAMP as described in Section 4.3.2.  The
 relay SHOULD also insert a HOSTNAME as described in Section 4.3.2.
 The entire contents of the received packet will be treated as the
 CONTENT of the relayed MSG and appended.
 An example of an unidentifiable PRI would be "<00>", without the
 double quotes.  It may be that these are the first 4 characters of
 the message.  To continue this example, if a relay does receive a
 syslog message with the first four characters of "<00>", then it will
 consult its configuration.  If it is configured to forward syslog
 messages with a Priority value of 13 to another relay or collector,
 then it MUST modify the packet as described above.  The specifics of
 doing this, including the RECOMMENDED insertion of the HOSTNAME, are
 given below.
 Originally received message
   <00>...
 Relayed message
   <13>TIMESTAMP HOSTNAME <00>...
 If the relay adds a TIMESTAMP, or a TIMESTAMP and HOSTNAME, after the
 PRI part, then it MUST check that the total length of the packet is
 still 1024 bytes or less.  If the packet has been expanded beyond
 1024 bytes, then the relay MUST truncate the packet to be 1024 bytes.
 This may cause the loss of vital information from the end of the
 original packet.  It is for this reason that it is RECOMMENDED that
 the PRI and HEADER parts of originally generated syslog packets
 contain the values and fields documented in Section 4.1.

5. Conventions

 Although Section 4 of this document specifies all requirements for
 the syslog protocol format and contents, certain conventions have
 come about over time for the inclusion of additional information
 within the syslog message.  It must be plainly stated that these
 items are not mandated but may be considered by implementers for
 completeness and to give the recipient some additional clues of their
 origin and nature.

Lonvick Informational [Page 14] RFC 3164 The BSD syslog Protocol August 2001

5.1 Dates and Times

 It has been found that some network administrators like to archive
 their syslog messages over long periods of time.  It has been seen
 that some original syslog messages contain a more explicit time stamp
 in which a 2 character or 4 character year field immediately follows
 the space terminating the TIMESTAMP.  This is not consistent with the
 original intent of the order and format of the fields.  If
 implementers wish to contain a more specific date and time stamp
 within the transmitted message, it should be within the CONTENT
 field.  Implementers may wish to utilize the ISO 8601 [7] date and
 time formats if they want to include more explicit date and time
 information.
 Additional methods to address this desire for long-term archiving
 have been proposed and some have been successfully implemented.  One
 such method is that the network administrators may choose to modify
 the messages stored on their collectors.  They may run a simple
 script to add the year, and any other information, to each stored
 record.  Alternatively, the script may replace the stored time with a
 format more appropriate for the needs of the network administrators.
 Another alternative has been to insert a record into the file that
 contains the current year.  By association then, all other records
 near that informative record should have been received in that same
 year.  Neither of these however, addresses the issue of associating a
 correct timezone with each record.

5.2 Domain Name and Address

 To readily identify the device that originated the message, it may be
 a good practice to include its fully qualified domain name (FQDN) and
 its IP address within the CONTENT field.  Traditionally, however,
 only the hostname has been included in the HOSTNAME field.

5.3 Originating Process Information

 It has also been considered to be a good practice to include some
 information about the process on the device that generated the
 message - if that concept exists.  This is usually the process name
 and process id (often known as the "pid") for robust operating
 systems.  The process name is commonly displayed in the TAG field.
 Quite often, additional information is included at the beginning of
 the CONTENT field.  The format of "TAG[pid]:" - without the quote
 marks - is common.  The left square bracket is used to terminate the
 TAG field in this case and is then the first character in the CONTENT
 field.  If the process id is immaterial, it may be left off.

Lonvick Informational [Page 15] RFC 3164 The BSD syslog Protocol August 2001

 In that case, a colon and a space character usually follow the TAG.
 This would be displayed as "TAG: " without the quotes.  In that case,
 the colon is the first character in the CONTENT field.

5.4 Examples

 As examples, these are valid messages as they may be observed on the
 wire between two devices.  In the following examples, each message
 has been indented, with line breaks inserted in this document for
 readability.
      Example 1
      <34>Oct 11 22:14:15 mymachine su: 'su root' failed for lonvick
      on /dev/pts/8
 This example shows an authentication error in an attempt to acquire
 additional privileges.  It also shows the command attempted and the
 user attempting it.  This was recorded as an original message from
 the device called mymachine.  A relay receiving this would not make
 any changes before sending it along as it contains a properly
 formatted PRI part and TIMESTAMP field in the HEADER part.  The TAG
 value in this example is the process "su".  The colon has terminated
 the TAG field and is the first character of the CONTENT field.  In
 this case, the process id (pid) would be considered transient and
 anyone looking at this syslog message would gain no useful
 information from knowing the pid.  It has not been included so the
 first two characters of the CONTENT field are the colon and a space
 character.
      Example 2
      Use the BFG!
 While this is a valid message, it has extraordinarily little useful
 information.  This message does not have any discernable PRI part. It
 does not contain a timestamp or any indication of the source of the
 message.  If this message is stored on paper or disk, subsequent
 review of the message will not yield anything of value.
 This example is obviously an original message from a device.  A relay
 MUST make changes to the message as described in Section 4.3 before
 forwarding it.  The resulting relayed message is shown below.
      <13>Feb  5 17:32:18 10.0.0.99 Use the BFG!

Lonvick Informational [Page 16] RFC 3164 The BSD syslog Protocol August 2001

 In this relayed message, the entire message has been treated as the
 CONTENT portion of the MSG part.  First, a valid PRI part has been
 added using the default priority value of 13.  Next, a TIMESTAMP has
 been added along with a HOSTNAME in the HEADER part.  Subsequent
 relays will not make any further changes to this message.  It should
 be noted in this example that the day of the month is less than 10.
 Since single digits in the date (5 in this case) are preceded by a
 space in the TIMESTAMP format, there are two spaces following the
 month in the TIMESTAMP before the day of the month.  Also, the relay
 appears to have no knowledge of the host name of the device sending
 the message so it has inserted the IPv4 address of the device into
 the HOSTNAME field.
      Example 3
       <165>Aug 24 05:34:00 CST 1987 mymachine myproc[10]: %% It's
       time to make the do-nuts.  %%  Ingredients: Mix=OK, Jelly=OK #
       Devices: Mixer=OK, Jelly_Injector=OK, Frier=OK # Transport:
       Conveyer1=OK, Conveyer2=OK # %%
 This message does have a valid PRI part with a Priority value
 indicating that it came from a locally defined facility (local4) with
 a severity of Notice.  The HEADER part has a proper TIMESTAMP field
 in the message.  A relay will not modify this message before sending
 it.  However, the HOSTNAME and TAG fields are not consistent with the
 definitions in Section 4.  The HOSTNAME field would be construed to
 be "CST" and the beginning of the MSG part would be "1987".
 It should be noted that the information contained in the CONTENT of
 this example is not telemetry data, nor is it supervisory control or
 data acquisition information.  Due to the security concerns listed in
 Section 6 of this document, information of that nature should
 probably not be conveyed across this protocol.
      Example 4
       <0>1990 Oct 22 10:52:01 TZ-6 scapegoat.dmz.example.org 10.1.2.3
       sched[0]: That's All Folks!
 This example has a lot of extraneous information throughout.  A human
 or sufficiently adaptable automated parser would be able to determine
 the date and time information as well as a fully qualified domain
 name (FQDN) [4] and IP address.  The information about the nature of
 the event is, however, limited.  Due to the indicated severity of the
 event, the process may not have been able to gather or send anything
 more informative.  It may have been fortunate to have generated and
 sent this message at all.

Lonvick Informational [Page 17] RFC 3164 The BSD syslog Protocol August 2001

 This example is obviously an original message from a device.  Since
 the first field in the HEADER part is not a TIMESTAMP in the format
 defined in Section 4.1.2, it MUST be modified by a relay.  A relay
 will add a TIMESTAMP and SHOULD add a HOSTNAME as follows and will
 treat the entire received packet after the PRI part from the original
 packet as the CONTENT field of the new packet.  The value used in the
 HOSTNAME field is only the hostname without the domain name as it is
 known by the relay.  A TAG value will not be added to the relayed
 packet.  While the inclusion of the domain name and IPv4 address in
 the original message is a noble endeavor, it is not consistent with
 the use of the field as described in Section 4.1.2.
       <0>Oct 22 10:52:12 scapegoat 1990 Oct 22 10:52:01 TZ-6
       scapegoat.dmz.example.org 10.1.2.3 sched[0]: That's All Folks!

6. Security Considerations

 An odor may be considered to be a message that does not require any
 acknowledgement.  People tend to avoid bad odors but are drawn to
 odors that they associate with good food.  The acknowledgement of the
 receipt of the odor or scent is not required and indeed it may be the
 height of discretion to totally ignore some odors.  On the other
 hand, it is usually considered good civility to acknowledge the
 prowess of the cook merely from the ambiance wafting from the
 kitchen.  Similarly, various species have been found to utilize odors
 to attract mates.  One species of moth uses this scent to find each
 other.  However, it has been found that bolas spiders can mimic the
 odor of the female moths of this species.  This scent will then
 attract male moths, which will follow it with the expectation of
 finding a mate.  Instead, when they arrive at the source of the
 scent, they will be eaten [8].  This is a case of a false message
 being sent out with inimical intent.
 In its local use, the syslog process places event notification
 messages into files on that system.  This relies upon the integrity
 of the system for the protection of the messages.  The subsequent
 configuration of the syslog process to use the syslog protocol to
 transport the messages to a remote collector was an extension of the
 delivery of event notification messages and it exhibits the same
 trust of the network.  There are several security consequences of the
 fundamental simplicity of syslog and there are some concerns about
 the applicability of this protocol in situations that require robust
 delivery.  Along the lines of the analogy, computer event messages
 may be sent accidentally, erroneously and even maliciously. At the
 time of this writing, however, there have not been any reports of any
 networked device consuming any other device.

Lonvick Informational [Page 18] RFC 3164 The BSD syslog Protocol August 2001

6.1 Packet Parameters

 As was described above, the message length MUST NOT exceed 1024
 bytes.  Attacks have seen where syslog messages are sent to a
 receiver that have message lengths greater than 1024 bytes.  In some
 older versions of syslog, the receipt of syslog packets that had a
 message greater than 1024 bytes caused problems.  syslog message
 receivers must not malfunction upon the receipt of packets where the
 message length is greater than 1024 bytes.  Various behaviors have
 been seen on receivers that do receive messages greater than 1024
 bytes.  Some have been seen to log the entire contents of the
 message, while others have been seen to log only portions of the
 message.  Still others have been known to discard the message
 altogether.  Devices MUST NOT retransmit messages whose received
 length exceeds 1024 bytes.
 Similarly, the receiver must rigidly enforce the correctness of the
 message body.  syslog collectors must not malfunction if received
 messages do not have the less-than and greater-than characters around
 a valid Priority value.  They MUST treat these messages as the
 unformatted CONTENT as was described in Section 4.3.3 if they relay
 it.
 Also, received messages must contain printable text in the message as
 was described throughout Section 4.  Devices must not malfunction if
 they receive a message containing characters other than the
 characters described above.

6.2 Message Authenticity

 The syslog delivery mechanism does not strongly associate the message
 with the message sender.  The receiver of that packet will not be
 able to ascertain that the message was indeed sent from the reported
 sender, or if the packet was sent from another device.  It should be
 noted here that the message receiver does not need to verify that the
 HOSTNAME in the HEADER part match the name of the IP address
 contained in the Source Address field of the IP packet.

6.2.1 Authentication Problems

 One possible consequence of this behavior is that a misconfigured
 machine may send syslog messages to a collector representing itself
 as another machine.  The administrative staff may become confused
 that the status of the supposed sender of the messages may not be
 accurately reflected in the received messages.  The administrators
 may not be able to readily discern that there are two or more
 machines representing themselves as the same machine.

Lonvick Informational [Page 19] RFC 3164 The BSD syslog Protocol August 2001

 It should also be noted that some cases of filling the HOSTNAME field
 in the HEADER part might only have local significance and that may
 only be ephemeral.  If the device had obtained an IP address from a
 DHCP pool, then any association between an identifier and an actual
 source would not always hold true.  The inclusion of a fully
 qualified domain name in the CONTENT may give the administrators the
 best chance of identifying the source of each message if it can
 always be associated with an IP address or if it can always be
 associated with a unique machine.

6.2.2 Message Forgery

 Malicious exploits of this behavior have also been noted.  An
 attacker may transmit syslog messages (either from the machine from
 which the messages are purportedly sent or from any other machine) to
 a collector.  In one case, an attacker may hide the true nature of an
 attack amidst many other messages.  As an example, an attacker may
 start generating forged messages indicating a problem on some
 machine.  This may get the attention of the system administrators who
 will spend their time investigating the alleged problem.  During this
 time, the attacker may be able to compromise a different machine, or
 a different process on the same machine.  Additionally, an attacker
 may generate false syslog messages to give untrue indications of
 status or of events.  As an example, an attacker may stop a critical
 process on a machine, which may generate a notification of exit.  The
 attacker may subsequently generate a forged notification that the
 process had been restarted.  The system administrators may accept
 that misinformation and not verify that the process had indeed been
 restarted.

6.3 Sequenced Delivery

 As a general rule, the forensics of a network anomaly rely upon
 reconstructing the sequence of events.  In a perfect world, the
 messages would be received on the syslog collector in the order of
 their generation from the other devices and anyone looking at these
 records would have an accurate picture of the sequence of events.
 Unfortunately, the syslog process and protocol do not ensure ordered
 delivery.  This section details some of the problems that may be
 encountered from this.

6.3.1 Single Source to a Destination

 The syslog records are usually presented (placed in a file, displayed
 on the console, etc.) in the order in which they are received.  This
 is not always in accordance with the sequence in which they were
 generated.  As they are transported across an IP network, some out of
 order receipt should be expected.  This may lead to some confusion as

Lonvick Informational [Page 20] RFC 3164 The BSD syslog Protocol August 2001

 messages may be received that would indicate that a process has
 stopped before it was started.  This may be somewhat rectified if the
 originating process had timestamped or numbered each of the messages
 before transmission.  In this, the sending device should utilize an
 authoritative time source.  It should be remembered, however, that
 not all devices are capable of receiving time updates, and not all
 devices can timestamp their messages.

6.3.2 Multiple Sources to a Destination

 In syslog, there is no concept of unified event numbering.  Single
 devices are free to include a sequence number within the CONTENT but
 that can hardly be coordinated between multiple devices.  In such
 cases, multiple devices may report that each one is sending message
 number one.  Again, this may be rectified somewhat if the sending
 devices utilize a timestamp from an authoritative source in their
 messages.  As has been noted, however, even messages from a single
 device to a single collector may be received out of order.  This
 situation is compounded when there are several devices configured to
 send their syslog messages to a single collector.  Messages from one
 device may be delayed so the collector receives messages from another
 device first even though the messages from the first device were
 generated before the messages from the second.  If there is no
 timestamp or coordinated sequence number, then the messages may be
 presented in the order in which they were received which may give an
 inaccurate view of the sequence of actual events.

6.3.3 Multiple Sources to Multiple Destinations

 The plethora of configuration options available to the network
 administrators may further skew the perception of the order of
 events.  It is possible to configure a group of devices to send the
 status messages -or other informative messages- to one collector,
 while sending messages of relatively higher importance to another
 collector.  Additionally, the messages may be sent to different files
 on the same collector.  If the messages do not contain timestamps
 from the source, it may be difficult to order the messages if they
 are kept in different places.  An administrator may not be able to
 determine if a record in one file occurred before or after a record
 in a different file.  This may be somewhat alleviated by placing
 marking messages with a timestamp into all destination files.  If
 these have coordinated timestamps, then there will be some indication
 of the time of receipt of the individual messages.

Lonvick Informational [Page 21] RFC 3164 The BSD syslog Protocol August 2001

6.3.4 Replaying

 Without any sequence indication or timestamp, messages may be
 recorded and replayed at a later time.  An attacker may record a set
 of messages that indicate normal activity of a machine.  At a later
 time, that attacker may remove that machine from the network and
 replay the syslog messages to the collector.  Even with a TIMESTAMP
 field in the HEADER part, an attacker may record the packets and
 could simply modify them to reflect the current time before
 retransmitting them.  The administrators may find nothing unusual in
 the received messages and their receipt would falsely indicate normal
 activity of the machine.

6.4 Reliable Delivery

 As there is no mechanism within either the syslog process or the
 protocol to ensure delivery, and since the underlying transport is
 UDP, some messages may be lost.  They may either be dropped through
 network congestion, or they may be maliciously intercepted and
 discarded.  The consequences of the drop of one or more syslog
 messages cannot be determined.  If the messages are simple status
 updates, then their non-receipt may either not be noticed, or it may
 cause an annoyance for the system operators.  On the other hand, if
 the messages are more critical, then the administrators may not
 become aware of a developing and potentially serious problem.
 Messages may also be intercepted and discarded by an attacker as a
 way to hide unauthorized activities.

6.5 Message Integrity

 Besides being discarded, syslog messages may be damaged in transit,
 or an attacker may maliciously modify them.  In the case of a packet
 containing a syslog message being damaged, there are various
 mechanisms built into the link layer as well as into the IP [9] and
 UDP protocols which may detect the damage.  An intermediary router
 may discard a damaged IP packet [10].  Damage to a UDP packet may be
 detected by the receiving UDP module, which may silently discard it.
 In any case, the original contents of the message will not be
 delivered to the collector.  Additionally, if an attacker is
 positioned between the sender and collector of syslog messages, they
 may be able to intercept and modify those messages while in-transit
 to hide unauthorized activities.

6.6 Message Observation

 While there are no strict guidelines pertaining to the event message
 format, most syslog messages are generated in human readable form
 with the assumption that capable administrators should be able to

Lonvick Informational [Page 22] RFC 3164 The BSD syslog Protocol August 2001

 read them and understand their meaning.  Neither the syslog protocol
 nor the syslog application have mechanisms to provide confidentiality
 of the messages in transit.  In most cases passing clear-text
 messages is a benefit to the operations staff if they are sniffing
 the packets off of the wire.  The operations staff may be able to
 read the messages and associate them with other events seen from
 other packets crossing the wire to track down and correct problems.
 Unfortunately, an attacker may also be able to observe the human-
 readable contents of syslog messages.  The attacker may then use the
 knowledge gained from those messages to compromise a machine or do
 other damage.

6.7 Message Prioritization and Differentiation

 While the processes that create the messages may signify the
 importance of the events through the use of the message Priority
 value, there is no distinct association between this value and the
 importance of delivery of the packet.  As an example of this,
 consider an application that generates two event messages.  The first
 is a normal status message but the second could be an important
 message denoting a problem with the process.  This second message
 would have an appropriately higher Severity value associated with the
 importance of that event.  If the operators had configured that both
 of these messages be transported to a syslog collector then they
 would, in turn, be given to UDP for transmission.  Under normal
 conditions, no distinction would be made between them and they would
 be transmitted in their order.
 Again, under normal circumstances, the receiver would accept syslog
 messages as they are received.  If many devices are transmitting
 normal status messages, but one is transmitting an important event
 message, there is no inherent mechanism within the syslog protocol to
 prioritize the important message over the other messages.
 On a case-by-case basis, device operators may find some way to
 associate the different levels with the quality of service
 identifiers.  As an example, the operators may elect to define some
 linkage between syslog messages that have a specific Priority value
 with a specific value to be used in the IPv4 Precedence field [9],
 the IPv6 Traffic Class octet [11], or the Differentiated Services
 field [12].  In the above example, the operators may have the ability
 to associate the status message with normal delivery while
 associating the message indicating a problem with a high reliability,
 low latency queue as it goes through the network.  This would have
 the affect of prioritizing the essential messages before the normal
 status messages.  Even with this hop-by-hop prioritization, this
 queuing mechanism could still lead to head of line blocking on the
 transmitting device as well as buffer starvation on the receiving

Lonvick Informational [Page 23] RFC 3164 The BSD syslog Protocol August 2001

 device if there are many near-simultaneous messages being sent or
 received.  This behavior is not unique to syslog but is endemic to
 all operations that transmit messages serially.
 There are security concerns for this behavior.  Head of line blocking
 of the transmission of important event messages may relegate the
 conveyance of important messages behind less important messages.  If
 the queue is cleared appropriately, this may only add seconds to the
 transmission of the important message.  On the other hand, if the
 queue is not cleared, then important messages may not be transmitted.
 Also at the receiving side, if the syslog receiver is suffering from
 buffer starvation due to large numbers of messages being received
 near-simultaneously, important messages may be dropped
 indiscriminately along with other messages.  While these are problems
 with the devices and their capacities, the protocol security concern
 is that there is no prioritization of the relatively more important
 messages over the less important messages.

6.8 Misconfiguration

 Since there is no control information distributed about any messages
 or configurations, it is wholly the responsibility of the network
 administrator to ensure that the messages are actually going to the
 intended recipient.  Cases have been noted where devices were
 inadvertently configured to send syslog messages to the wrong
 receiver.  In many cases, the inadvertent receiver may not be
 configured to receive syslog messages and it will probably discard
 them.  In certain other cases, the receipt of syslog messages has
 been known to cause problems for the unintended recipient [13].  If
 messages are not going to the intended recipient, then they cannot be
 reviewed or processed.

6.9 Forwarding Loop

 As it is shown in Figure 1, machines may be configured to relay
 syslog messages to subsequent relays before reaching a collector. In
 one particular case, an administrator found that he had mistakenly
 configured two relays to forward messages with certain Priority
 values to each other.  When either of these machines either received
 or generated that type of message, it would forward it to the other
 relay.  That relay would, in turn, forward it back.  This cycle did
 cause degradation to the intervening network as well as to the
 processing availability on the two devices.  Network administrators
 must take care to not cause such a death spiral.

Lonvick Informational [Page 24] RFC 3164 The BSD syslog Protocol August 2001

6.10 Load Considerations

 Network administrators must take the time to estimate the appropriate
 size of the syslog receivers.  An attacker may perform a Denial of
 Service attack by filling the disk of the collector with false
 messages.  Placing the records in a circular file may alleviate this
 but that has the consequence of not ensuring that an administrator
 will be able to review the records in the future. Along this line, a
 receiver or collector must have a network interface capable of
 receiving all messages sent to it.
 Administrators and network planners must also critically review the
 network paths between the devices, the relays, and the collectors.
 Generated syslog messages should not overwhelm any of the network
 links.

7. IANA Considerations

 The syslog protocol has been assigned UDP port 514.  This port
 assignment will be maintained by IANA exclusively for this protocol.
 The syslog protocol provides for the definition of named attributes
 to indicate the Severity of each message and the Facility that
 generated the message as described in Section 4.  The name space
 identifiers for these attributes are defined as numbers.  The
 protocol does not define the specific assignment of the name space
 for these numbers; the application developer or system vendor is
 allowed to define the attribute, its semantics, and the associated
 numbers.  This name space will not be controlled to prevent
 collisions as systems are expected to use the same attributes,
 semantics and associated numbers to describe events that are deemed
 similar even between heterogeneous devices.

8. Conclusion and Other Efforts

 The syslog protocol may be effectively used to transport event
 notification messages across a network.  In all cases, it is
 important that the syslog message receiver embody the principle of
 "be liberal in what you accept".  It is highly recommended that the
 network operators who choose to use this understand the
 characteristics of the protocol and its security implications.
 There have been attempts in the past to standardize the format of the
 syslog message.  The most notable attempt culminated in a BOF at the
 Fortieth Internet Engineering Task Force meeting in 1997.  This was
 the Universal Logging Protocol (ulp) BOF and the minutes of their
 meeting are on-line at the IETF Proceedings web site [14].

Lonvick Informational [Page 25] RFC 3164 The BSD syslog Protocol August 2001

 Many good thoughts came from that effort and interested implementers
 may want to find some of the notes or papers produced from that
 effort.
 At the time of this writing, efforts are underway to allow the usage
 of international character sets in applications that have been
 traditionally thought of as being text-only.  The HOSTNAME and
 TIMESTAMP fields described above are representative of this.  Also,
 the entire CONTENT field has traditionally been printing characters
 and spaces in the code set known as US-ASCII.  It is hoped that the
 proponents of these internationalization efforts will find a suitable
 way to allow the use of international character sets within syslog
 messages without being disruptive.  It should also be hoped that
 implementers will allow for the future acceptance of additional code
 sets and that they may make appropriate plans.  Again, it must be
 cautioned that the simplicity of the existing system has been a
 tremendous value to its acceptance.  Anything that lessens that
 simplicity may diminish that value.

Acknowledgements

 The following people provided content feedback during the writing of
 this document:
       Jon Knight <J.P.Knight@lboro.ac.uk>
       Magosanyi Arpad <mag@bunuel.tii.matav.hu>
       Balazs Scheidler <bazsi@balabit.hu>
       Jon Callas <jon@counterpane.com>
       Eliot Lear <lear@cisco.com>
       Petter Reinholdtsen <pere@hungry.com>
       Darren Reed <darrenr@reed.wattle.id.au>
       Alfonso De Gregorio <dira@speedcom.it>
       Eric Allman <eric@sendmail.com>
       Andrew Ross <andrew@kiwi-enterprises.com>
       George Maslyar <george.maslyar@primark.com>
       Albert Mietus <albert@ons-huis.net>
       Russ Allbery <rra@stanford.edu>
       Titus D. Winters <titus@cs.hmc.edu>
       Edwin P. Boon <Edwin.Boon@consul.com>
       Jeroen M. Mostert <Jeroen.Mostert@consul.com>
 Eric Allman is the original inventor and author of the syslog daemon
 and protocol.  The author of this memo and the community at large
 would like to express their appreciation for this work and for the
 usefulness that it has provided over the years.

Lonvick Informational [Page 26] RFC 3164 The BSD syslog Protocol August 2001

 A large amount of additional information about this de-facto standard
 operating system feature may usually be found in the syslog.conf file
 as well as in the man pages for syslog.conf, syslog, syslogd, and
 logger, of many Unix and Unix-like devices.

References

 1  Postel, J., "User Datagram Protocol", STD 6, RFC 768, August 1980.
 2  Crocker, D. and P. Overell, "Augmented BNF for Syntax
    Specifications: ABNF", RFC 2234, November 1997.
 3  USA Standard Code for Information Interchange, USASI X3.4-1968
 4  Mockapetris, P., "Domain Names - Concepts and Facilities", STD 13,
    RFC 1034, November 1987.
 5  Mockapetris, P., "Domain names - Implementation and
    Specification", STD 13, RFC 1035, November 1987.
 6  Hinden, R. and S. Deering, "IP Version 6 Addressing Architecture",
    RFC 2373, July 1998.
 7  Data elements and interchange formats - Information exchange -
    Representation of dates and times, International Organization for
    Standardization, Reference number ISO 8601 : 1988 (E), 1988
 8  Stowe, M., et al, "Chemical Mimicry: Bolas Spiders Emit Components
    of Moth Prey Species Sex Pheromones", Science, 1987
 9  Postel, J., "Internet Protocol", STD 5, RFC 791, September 1981.
 10 Baker, F., "Requirements for IP Version 4 Routers", RFC 1812, June
    1995.
 11 Deering, S. and R. Hinden, "Internet Protocol, Version 6 (IPv6)
    Specification", RFC 2460, December 1998.
 12 Nichols, K., Blake, S., Baker, F. and D. Black, "Definition of the
    Differentiated Services Field (DS Field) in the IPv4 and IPv6
    Headers", RFC 2474, December 1998.
 13 Cisco Systems Product Security Incident Response Team (PSIRT),
    "Field Notice: Cisco IOS(r) Syslog Crash", January 11, 1999
    http://www.cisco.com/warp/public/707/advisory.html

Lonvick Informational [Page 27] RFC 3164 The BSD syslog Protocol August 2001

 14 Walker, D., IETF Secretariat, "Proceedings of the Fortieth
    Internet Engineering Task Force, Washington, DC, USA, December 8-
    12, 1997
    http://www.ietf.org/proceedings/97dec/index.html

Author's Address

 Chris Lonvick
 Cisco Systems
 12515 Research Blvd.
 Austin, TX, USA
 Phone:  +1.512.378.1182
 EMail:  clonvick@cisco.com

Lonvick Informational [Page 28] RFC 3164 The BSD syslog Protocol August 2001

Full Copyright Statement

 Copyright (C) The Internet Society (2001).  All Rights Reserved.
 This document and translations of it may be copied and furnished to
 others, and derivative works that comment on or otherwise explain it
 or assist in its implementation may be prepared, copied, published
 and distributed, in whole or in part, without restriction of any
 kind, provided that the above copyright notice and this paragraph are
 included on all such copies and derivative works.  However, this
 document itself may not be modified in any way, such as by removing
 the copyright notice or references to the Internet Society or other
 Internet organizations, except as needed for the purpose of
 developing Internet standards in which case the procedures for
 copyrights defined in the Internet Standards process must be
 followed, or as required to translate it into languages other than
 English.
 The limited permissions granted above are perpetual and will not be
 revoked by the Internet Society or its successors or assigns.
 This document and the information contained herein is provided on an
 "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
 TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
 BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
 HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
 MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Acknowledgement

 Funding for the RFC Editor function is currently provided by the
 Internet Society.

Lonvick Informational [Page 29]

/data/webs/external/dokuwiki/data/pages/rfc/rfc3164.txt · Last modified: 2001/08/27 18:04 by 127.0.0.1

Donate Powered by PHP Valid HTML5 Valid CSS Driven by DokuWiki