SYSLOG YANG model
draft-ietf-netmod-syslog-model-06

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Document Type Active Internet-Draft (netmod WG)
Author Clyde Wildes 
Last updated 2016-02-22 (latest revision 2015-12-22)
Replaces draft-wildes-netmod-syslog-model
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NETMOD WG                                                   Clyde Wildes
Internet-Draft                                              Kiran Koushik
Intended status: Informational                          Cisco Systems Inc.
Expires: Jun 16, 2016                                       Dec 23, 2015
                                                           
                                                           

                             SYSLOG YANG model
                      draft-ietf-netmod-syslog-model-06

Abstract

   This document describes a data model for Syslog
   protocol which is used to convey event notification messages.

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
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on Jun 16, 2016.

Copyright Notice

   Copyright (c) 2015 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
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   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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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Definitions and Acronyms  . . . . . . . . . . . . . . . .   3
   2.  Problem Statement . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Design of the SYSLOG Model . .  . . . . . . . . . . . . . . .   3
     3.1.  SYSLOG Module . . . . . . . . . . . . . . . . . . . . . .   4
   4.  SYSLOG YANG Models  . . . . . . . . . . . . . . . . . . . . .   6
     4.1.  SYSLOG TYPES Module . . . . . . . . . . . . . . . . . . .   6
     4.2.  SYSLOG module . . . . . . . . . . . . . . . . . . . . . .  10
     4.3.  A SYSLOG Example  . . . . . . . . . . . . . . . . . . . .  18
   5.  Implementation Status . . . . . . . . . . . . . . . . . . . .  19
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  19
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  20
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  20
   9.  Change log [RFC Editor: Please remove]  . . . . . . . . . . .  20
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .  20
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  21

1.  Introduction

   Operating systems, processes and applications generate messages
   indicating their own status or the occurrence of events. These
   messages are useful for managing and/or debugging the network and its
   services. The BSD Syslog protocol is a widely adopted protocol that
   is used for transmission and processing of the messages.

   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. No
   acknowledgement of the receipt is made.

   Essentially, a Syslog process receives messages (from the kernel,
   processes, applications or other Syslog processes) and processes
   those. The processing involves logging to a local file, displaying on
   console, user terminal, and/or relaying to syslog processes on other
   machines. The processing is determined by the "facility" that
   originated the message and the "severity" assigned to the message by
   the facility.

   We are using definitions of Syslog protocol from [RFC5424] in this
   draft.

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1.1.  Definitions and Acronyms

   IP: Internet Protocol

   IPv4: Internet Protocol version 4

   IPv6: Internet Protocol version 6

   UDP: User Datagram Protocol

   VRF: Virtual Routing and Forwarding

2.  Problem Statement

   This document defines a YANG [RFC6020] configuration data model that
   may be used to monitor and control one or more syslog processes running
   on a system. YANG models can be used with network management 
   agents such as NETCONF [RFC6241] to install, manipulate, and delete 
   the configuration of network devices.

   This module makes use of the YANG "feature" construct which allows 
   implementations to support only those Syslog features that lie
   within their capabilities.

3.  Design of the SYSLOG Model

   The syslog model was designed by comparing various syslog features 
   implemented by various vendors' in different implementations.

   This draft addresses the common leafs between all vendors and creates
   a common model, which can be augmented with proprietary features, if 
   necessary. The base model is designed to be very simple for maximum 
   flexibility.

   Syslog consists of message producers, a group level suppression filter, 
   and message distributors. The following digram shows syslog messages 
   flowing from a message producer, through the group level suppression 
   filter, and if passed by the group filter to message distributors where 
   further suppression filtering can take place.

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   Message Producers  
    +-------------+  +-------------+  +-------------+  +-------------+
    |  Various    |  |     OS      |  |             |  |   Remote    |
    | Components  |  |   Kernel    |  | Line Cards  |  |   Servers   |
    +-------------+  +-------------+  +-------------+  +-------------+  

    +-------------+  +-------------+  +-------------+  +-------------+
    |    SNMP     |  |  Interface  |  |   Standby   |  |   Syslog    |
    |   Events    |  |   Events    |  |  Supervisor |  |   Itself    |
    +-------------+  +-------------+  +-------------+  +-------------+

    |                                                                |
    +----------------------------------------------------------------+
                 |
                 |
                 |
                 |
         +-----------+------------+--------------+
         |           |            |              |
         v           v            v              |
   Message Distributors                          |
  +----------+ +----------+ +----------+         |
  |          | | Log      | | Log      |         |
  |  Console | | Buffer(s)| | File(s)  |         |
  +----------+ +----------+ +----------+         |
                                   +-------------+-------------+
                                   |             |             |                                   
                                   v             v             v
                                    
                            +-------------+ +-----------+ +-----------+
                            |Remote       | |           | |User       |
                            |Collectors(s)| |Terminal(s)| |Sessions(s)|
                            +-------------+ +-----------+ +-----------+
 

  The leaves in the base syslog model correspond to the group level 
   suppression filter and each message distributor:

   - console
   - log buffer(s)
   - log file(s)
   - remote collector(s)
   - terminal(s)
   - user session(s).

   Optional features are used to specified fields that are not present in 
   all vendor configurations.

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3.1.  SYSLOG Module

   A simplified graphical representation of the complete data tree is
   presented here.

   Each node is printed as:

   <status> <flags> <name> <opts> <type> <if-features>

   <status> is one of:
    +  for current
    x  for deprecated
    o  for obsolete

   <flags> is one of:
    rw  for configuration data
    ro  for non-configuration data
    -x  for rpcs
    -n  for notifications

   <name> is the name of the node
    (<name>) means that the node is a choice node
    :(<name>) means that the node is a case node

   If the node is augmented into the tree from another module, its
   name is printed as <prefix>:<name>.

   <opts> is one of:
    ?  for an optional leaf or choice
    !  for a presence container
    *  for a leaf-list or list
    [<keys>] for a list's keys

   <type> is the name of the type for leafs and leaf-lists

    If the type is a leafref, the type is printed as "-> TARGET", where
    TARGET is either the leafref path, with prefixed removed if possible.

   <if-features> is the list of features this node depends on, printed
    within curly brackets and a question mark "{...}?"

module: ietf-syslog
   +--rw syslog
      +--rw log-actions
         +--rw console!
         |  +--rw log-selector
         |     +--rw (selector-facility)
         |     |  +--:(no-log-facility)
         |     |  |  +--rw no-facilities?   empty
         |     |  +--:(log-facility)
         |     |     +--rw log-facility* [facility]
         |     |        +--rw facility             union
         |     |        +--rw severity             union
         |     |        +--rw severity-operator?   enumeration {selector-severity-operator-config}?
         |     +--rw pattern-match?   string {selector-match-processing-config}?
         +--rw buffer
         |  +--rw log-buffer* [name]
         |     +--rw name                    string
         |     +--rw log-selector
         |     |  +--rw (selector-facility)
         |     |  |  +--:(no-log-facility)
         |     |  |  |  +--rw no-facilities?   empty
         |     |  |  +--:(log-facility)
         |     |  |     +--rw log-facility* [facility]
         |     |  |        +--rw facility             union
         |     |  |        +--rw severity             union
         |     |  |        +--rw severity-operator?   enumeration {selector-severity-operator-config}?
         |     |  +--rw pattern-match?   string {selector-match-processing-config}?
         |     +--rw buffer-size-bytes?      uint64 {buffer-limit-bytes}?
         |     +--rw buffer-size-messages?   uint64 {buffer-limit-messages}?
         +--rw file
         |  +--rw log-file* [name]
         |     +--rw name               inet:uri
         |     +--rw log-selector
         |     |  +--rw (selector-facility)
         |     |  |  +--:(no-log-facility)
         |     |  |  |  +--rw no-facilities?   empty
         |     |  |  +--:(log-facility)
         |     |  |     +--rw log-facility* [facility]
         |     |  |        +--rw facility             union
         |     |  |        +--rw severity             union
         |     |  |        +--rw severity-operator?   enumeration {selector-severity-operator-config}?
         |     |  +--rw pattern-match?   string {selector-match-processing-config}?
         |     +--rw structured-data?   boolean {structured-data-config}?
         |     +--rw file-archive
         |        +--rw number-of-files?   uint32 {file-limit-size}?
         |        +--rw max-file-size?     uint64 {file-limit-size}?
         |        +--rw rollover?          uint32 {file-limit-duration}?
         |        +--rw retention?         uint16 {file-limit-duration}?
         +--rw remote
         |  +--rw destination* [name]
         |     +--rw name                    string
         |     +--rw (transport)
         |     |  +--:(tcp)
         |     |  |  +--rw tcp
         |     |  |     +--rw address?   inet:host
         |     |  |     +--rw port?      inet:port-number
         |     |  +--:(udp)
         |     |     +--rw udp
         |     |        +--rw address?   inet:host
         |     |        +--rw port?      inet:port-number
         |     +--rw log-selector
         |     |  +--rw (selector-facility)
         |     |  |  +--:(no-log-facility)
         |     |  |  |  +--rw no-facilities?   empty
         |     |  |  +--:(log-facility)
         |     |  |     +--rw log-facility* [facility]
         |     |  |        +--rw facility             union
         |     |  |        +--rw severity             union
         |     |  |        +--rw severity-operator?   enumeration {selector-severity-operator-config}?
         |     |  +--rw pattern-match?   string {selector-match-processing-config}?
         |     +--rw destination-facility?   identityref
         |     +--rw source-interface?       if:interface-ref
         |     +--rw syslog-sign! {signed-messages-config}?
         |        +--rw cert-initial-repeat    uint16
         |        +--rw cert-resend-delay      uint16
         |        +--rw cert-resend-count      uint16
         |        +--rw sig-max-delay          uint16
         |        +--rw sig-number-resends     uint16
         |        +--rw sig-resend-delay       uint16
         |        +--rw sig-resend-count       uint16
         +--rw terminal
         |  +--rw (terminal-scope)
         |     +--:(all-terminals)
         |     |  +--rw all-terminals
         |     |     +--rw log-selector
         |     |        +--rw (selector-facility)
         |     |        |  +--:(no-log-facility)
         |     |        |  |  +--rw no-facilities?   empty
         |     |        |  +--:(log-facility)
         |     |        |     +--rw log-facility* [facility]
         |     |        |        +--rw facility             union
         |     |        |        +--rw severity             union
         |     |        |        +--rw severity-operator?   enumeration {selector-severity-operator-config}?
         |     |        +--rw pattern-match?   string {selector-match-processing-config}?
         |     +--:(per-terminal) {terminal-facility-user-logging-config}?
         |        +--rw device-name* [dname]
         |           +--rw dname           string
         |           +--rw log-selector
         |              +--rw (selector-facility)
         |              |  +--:(no-log-facility)
         |              |  |  +--rw no-facilities?   empty
         |              |  +--:(log-facility)
         |              |     +--rw log-facility* [facility]
         |              |        +--rw facility             union
         |              |        +--rw severity             union
         |              |        +--rw severity-operator?   enumeration {selector-severity-operator-config}?
         |              +--rw pattern-match?   string {selector-match-processing-config}?
         +--rw session
            +--rw (user-scope)
               +--:(all-users)
               |  +--rw all-users
               |     +--rw log-selector
               |        +--rw (selector-facility)
               |        |  +--:(no-log-facility)
               |        |  |  +--rw no-facilities?   empty
               |        |  +--:(log-facility)
               |        |     +--rw log-facility* [facility]
               |        |        +--rw facility             union
               |        |        +--rw severity             union
               |        |        +--rw severity-operator?   enumeration {selector-severity-operator-config}?
               |        +--rw pattern-match?   string {selector-match-processing-config}?
               +--:(per-user) {session-facility-user-logging-config}?
                  +--rw user-name* [uname]
                     +--rw uname           string
                     +--rw log-selector
                        +--rw (selector-facility)
                        |  +--:(no-log-facility)
                        |  |  +--rw no-facilities?   empty
                        |  +--:(log-facility)
                        |     +--rw log-facility* [facility]
                        |        +--rw facility             union
                        |        +--rw severity             union
                        |        +--rw severity-operator?   enumeration {selector-severity-operator-config}?
                        +--rw pattern-match?   string {selector-match-processing-config}?

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4.  SYSLOG YANG Models

4.1.  SYSLOG-TYPES module

<CODE BEGINS> file "ietf-syslog-types.yang"
module ietf-syslog-types {
  namespace "urn:ietf:params:xml:ns:yang:ietf-syslog-types";
  prefix syslogtypes;

  organization "IETF NETMOD (NETCONF Data Modeling Language) Working 
                Group";
  contact
    "WG Web:   <http://tools.ietf.org/wg/netmod/>
     WG List:  <mailto:netmod@ietf.org>
     
     WG Chair: Tom Nadeau
               <mailto:tnadeau@lucidvision.com>
     
     WG Chair: Kent Watsen
               <mailto:kwatsen@juniper.net>
     
     Editor:   Ladislav Lhotka
               <mailto:lhotka@nic.cz>";
  description
    "This module contains a collection of YANG type definitions for 
     SYSLOG.";

  revision 2015-11-09 {
    description
      "Initial Revision";
    reference
      "This model references RFC 5424 - The Syslog Protocol, 
       and RFC 5848 - Signed Syslog Messages.";
  }

  typedef severity {
    type enumeration {
      enum "emergency" {
        value 0;
        description
          "Emergency Level Msg";
      }
      enum "alert" {
        value 1;
        description
          "Alert Level Msg";
      }
      enum "critical" {
        value 2;
        description
          "Critical Level Msg";
      }
      enum "error" {
        value 3;
        description
          "Error Level Msg";
      }
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      enum "warning" {
        value 4;
        description
          "Warning Level Msg";
      }
      enum "notice" {
        value 5;
        description
          "Notification Level Msg";
      }
      enum "info" {
        value 6;
        description
          "Informational Level Msg";
      }
      enum "debug" {
        value 7;
        description
          "Debugging Level Msg";
      }
    }
    description
      "The definitions for Syslog message severity as per RFC 5424.";
  }

  identity syslog-facility {
    description
      "The base identity to represent syslog facilities";
  }

  identity kern {
    base syslog-facility;
    description
      "The facility for kernel messages as defined in RFC 5424.";
  }

  identity user {
    base syslog-facility;
    description
      "The facility for user-level messages as defined in RFC 5424.";
  }

  identity mail {
    base syslog-facility;
    description
      "The facility for the mail system as defined in RFC 5424.";
  }

  identity daemon {
    base syslog-facility;
    description
      "The facility for the system daemons as defined in RFC 5424.";
   }

  identity auth {
    base syslog-facility;
    description
      "The facility for security/authorization messages as defined 
       in RFC 5424.";
  }

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  identity syslog {
    base syslog-facility;
    description
      "The facility for messages generated internally by syslogd 
       facility as defined in RFC 5424.";
  }

  identity lpr {
    base syslog-facility;
    description
      "The facility for the line printer subsystem as defined in 
       RFC 5424.";
  }

  identity news {
    base syslog-facility;
    description
      "The facility for the network news subsystem as defined in 
       RFC 5424.";
  }

  identity uucp {
    base syslog-facility;
    description
      "The facility for the UUCP subsystem as defined in RFC 5424.";
  }

  identity cron {
    base syslog-facility;
    description
      "The facility for the clock daemon as defined in RFC 5424.";
  }

  identity authpriv {
    base syslog-facility;
    description
      "The facility for privileged security/authorization messages 
       as defined in RFC 5424.";
  }

  identity ftp {
    base syslog-facility;
    description
      "The facility for the FTP daemon as defined in RFC 5424.";
  }

  identity ntp {
    base syslog-facility;
    description
      "The facility for the NTP subsystem as defined in RFC 5424.";
  }

  identity audit {
    base syslog-facility;
    description
      "The facility for log audit messages as defined in RFC 5424.";
  }

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  identity console {
    base syslog-facility;
    description
      "The facility for log alert messages as defined in RFC 5424.";
  }

  identity cron2 {
    base syslog-facility;
    description
      "The facility for the second clock daemon as defined in 
       RFC 5424.";
  }

  identity local0 {
    base syslog-facility;
    description
      "The facility for local use 0 messages as defined in 
       RFC 5424.";
  }

  identity local1 {
    base syslog-facility;
    description
      "The facility for local use 1 messages as defined in 
       RFC 5424.";
  }

  identity local2 {
    base syslog-facility;
    description
      "The facility for local use 2 messages as defined in 
       RFC 5424.";
  }

  identity local3 {
    base syslog-facility;
    description
      "The facility for local use 3 messages as defined in 
       RFC 5424.";
  }

  identity local4 {
    base syslog-facility;
    description
      "The facility for local use 4 messages as defined in 
       RFC 5424.";
  }

  identity local5 {
    base syslog-facility;
    description
      "The facility for local use 5 messages as defined in 
       RFC 5424.";
  }

  identity local6 {
    base syslog-facility;
    description
      "The facility for local use 6 messages as defined in 
       RFC 5424.";
  }

  identity local7 {
    base syslog-facility;
    description
      "The facility for local use 7 messages as defined in 
       RFC 5424.";
  }
}

<CODE ENDS>

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4.2. SYSLOG module

<CODE BEGINS> file "ietf-syslog.yang"
module ietf-syslog {
  namespace "urn:ietf:params:xml:ns:yang:ietf-syslog";
  prefix syslog;

  import ietf-inet-types {
    prefix inet;
  }

  import ietf-interfaces {
    prefix if;
  }

  import ietf-syslog-types {
    prefix syslogtypes;
  }

  organization "IETF NETMOD (NETCONF Data Modeling Language) 
  Working Group";
  contact
    "WG Web:   <http://tools.ietf.org/wg/netmod/>
     WG List:  <mailto:netmod@ietf.org>
     
     WG Chair: Tom Nadeau
               <mailto:tnadeau@lucidvision.com>
     
     WG Chair: Kent Watsen
               <mailto:kwatsen@juniper.net>
     
     Editor:   Ladislav Lhotka
               <mailto:lhotka@nic.cz>";
  description
    "This module contains a collection of YANG definitions 
     for Syslog configuration.";

  revision 2015-11-09 {
    description
      "Initial Revision";
    reference
      "RFC 5424: The Syslog Protocol
       RFC 5848: Signed Syslog Messages";
  }

  feature buffer-limit-bytes {
    description
      "This feature indicates that local memory logging buffers
       are limited in size using a limit expressed in bytes.";
  }

  feature buffer-limit-messages {
    description
      "This feature indicates that local memory logging buffers
       are limited in size using a limit expressed in number
       of messages.";
  }

  feature structured-data-config {
    description
      "This feature represents the ability to log messages 
       in structured-data format as per RFC 5424.";
  }

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  feature file-limit-size {
    description
      "This feature indicates that file logging resources
       are managed using size and number limits.";
  }

  feature file-limit-duration {
    description
      "This feature indicates that file logging resources
       are managed using time based limits.";
  }

  feature terminal-facility-user-logging-config {
    description
      "This feature represents the ability to adjust 
       log message settings for individual terminal
       devices.";
  }

  feature session-facility-user-logging-config {
    description
      "This feature represents the ability to adjust 
       log message settings for individual user sessions.";
  }

  feature selector-severity-operator-config {
    description
      "This feature represents the ability to select messages 
       using the additional operators equal to, or not equal to 
       when comparing the Syslog message severity.";
  }

  feature selector-match-processing-config {
    description
      "This feature represents the ability to select messages based
       on a Posix 1003.2 regular expression pattern match.";
  }

  feature signed-messages-config {
    description
      "This feature represents the ability to configure signed 
       syslog messages according to RFC 5848.";
  }

  grouping syslog-severity {
    description
      "This grouping defines the Syslog severity which is used to 
       select log messages.";
    leaf severity {
      type union {
        type syslogtypes:severity;
        type enumeration {
          enum all {
            value -1;
            description
              "This enum describes the case where all severities 
               are requested.";
          }
          enum none {
            value -2;
            description
              "This enum describes the case where no severities 
               are requested.";
          }
        }
      }
      mandatory true;
      description
        "This leaf specifies the Syslog message severity. When 
         severity is specified, the default severity comparison 
         is all messages of the specified severity and greater are 
         logged. 'all' is a special case which means all severities
         are requested. 'none' is a special case which means that
         no severity selection should occur.";
    }

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    leaf severity-operator {
      if-feature selector-severity-operator-config;
      type enumeration {
        enum equals-or-higher {
          description
            "This enum specifies all messages of the specified 
             severity and higher are logged according to the 
             given log-action";
        }
        enum equals {
          description
            "This enum specifies all messages that are for 
             the specified severity are logged according to the 
             given log-action";
        }
        enum not-equals {
          description
            "This enum specifies all messages that are not for 
             the specified severity are logged according to the 
             given log-action";
        }
      }
      default equals-or-higher;
      description
        "This leaf describes the option to specify how the 
         severity comparison is performed.";
    }
  }

  grouping syslog-selector {
    description
      "This grouping defines a Syslog selector which is used to 
       select log messages for the log-action (buffer, file, 
       etc). Choose one of the following:
         no-log-facility
         log-facility [<facility> <severity>...]";
    container log-selector {
      description
        "This container describes the log selector parameters 
         for Syslog.";
      choice selector-facility {
        mandatory true;
        description
          "This choice describes the option to specify no 
           facilities, or a specific facility which can be
           all for all facilities.";
        case no-log-facility {
          description
            "This case specifies no facilities will match when 
             comparing the Syslog message facility. This is a 
             method that can be used to effectively disable a 
             particular log-action (buffer, file, etc).";
          leaf no-facilities {
            type empty;
            description
            "This leaf specifies that no facilities are selected 
             for this log-action.";
          }
        }

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        case log-facility {
          description
            "This case specifies one or more specified facilities 
             will match when comparing the Syslog message facility.";
          list log-facility {
            key facility;
            description
              "This list describes a collection of Syslog 
               facilities and severities.";
            leaf facility {
              type union {
                type identityref {
                  base syslogtypes:syslog-facility;
                }
                type enumeration {
                  enum all {
                    description
                      "This enum describes the case where all 
                       facilities are requested.";
                  }
                }
              }
              description
                "The leaf uniquely identifies a Syslog facility.";
            }
            uses syslog-severity;
          }
        }
      }
      leaf pattern-match {
        if-feature selector-match-processing-config;
        type string;
        description
          "This leaf desribes a Posix 1003.2 regular expression 
           string that can be used to select a Syslog message for 
           logging. The match is performed on the RFC 5424 
           SYSLOG-MSG field.";
      }
    }
  }

  container syslog {
    description
      "This container describes the configuration parameters for 
       Syslog.";
    container log-actions {
      description
        "This container describes the log-action parameters 
         for Syslog.";
      container console {
        presence "Enables logging console configuration";
        description
          "This container describes the configuration parameters for 
           console logging.";
        uses syslog-selector;
      }

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      container buffer {
        description
          "This container describes the configuration parameters for 
           local memory buffer logging. The buffer is circular in 
           nature, so newer messages overwrite older messages after 
           the buffer is filled.";
        list log-buffer {
          key name;
          description
            "This list describes a collection of local logging
             memory buffers.";
          leaf name {
            type string;
            description
              "This leaf specifies the name of the log buffer.";
          }
          uses syslog-selector;
          leaf buffer-size-bytes {
            if-feature buffer-limit-bytes;
            type uint64;
            units "bytes";
            description
              "This leaf configures the amount of memory 
               (in bytes) that will be dedicated to the local 
               memory logging buffer.  The default value varies 
               by implementation.";
          }
          leaf buffer-size-messages {
            if-feature buffer-limit-messages;
            type uint64;
            units "log messages";
            description
              "This leaf configures the amount number of log 
               messages that can be stored in the local memory 
               logging buffer.  The default value varies by 
               implementation.";
          }
        }
      }
      container file {
        description
          "This container describes the configuration parameters for 
           file logging.";
        list log-file {
          key "name";
          description
            "This list describes a collection of local logging 
             files.";
          leaf name {
            type inet:uri;
            description
              "This leaf specifies the name of the log file which 
               MUST use the uri scheme file:.";
          }

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          uses syslog-selector;
          leaf structured-data {
            if-feature structured-data-config;
            type boolean;
            default false;
            description
              "This leaf describes how log messages are written to 
               the log file. If true, messages will be written 
               with one or more STRUCTURED-DATA elements as per 
               RFC5424; if false, messages will be written with 
               STRUCTURED-DATA = NILVALUE.";
          }
          container file-archive {
            description
              "This container describes the configuration 
               parameters for log file archiving.";
            leaf number-of-files {
              if-feature file-limit-size;
              type uint32;
              description
                "This leaf specifies the maximum number of log 
                 files retained. Specify 1 for implementations 
                 that only support one log file.";
            }
            leaf max-file-size {
              if-feature file-limit-size;
              type uint64;
              units "megabytes";
              description
                "This leaf specifies the maximum log file size.";
            }
            leaf rollover {
              if-feature file-limit-duration;
              type uint32;
              units "minutes";
              description
                "This leaf specifies the length of time that log 
                 events should be written to a specific log file. 
                 Log events that arrive after the rollover period 
                 cause the current log file to be closed and a new 
                 log file to be opened.";
            }
            leaf retention {
              if-feature file-limit-duration;
              type uint16;
              units "hours";
              description
                "This leaf specifies the length of time that 
                 completed/closed log event files should be stored 
                 in the file system before they are deleted.";
            }
          }
        }
      }

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      container remote {
        description
          "This container describes the configuration parameters for 
           remote logging.";
        list destination {
          key "name";
          description
            "This list describes a collection of remote logging 
             destinations.";
          leaf name {
            type string;
            description
              "An arbitrary name for the endpoint to connect to.";
          }
          choice transport {
            mandatory true;
            description
              "This choice describes the transport option.";
            case tcp {
              container tcp {
                description
                  "This container describes the TCP transport
                   options.";
                leaf address {
                  type inet:host;
                  description
                    "The leaf uniquely specifies the address of 
                     the remote host. One of the following must 
                     be specified: an ipv4 address, an ipv6 
                     address, or a host name.";
                }
                leaf port {
                  type inet:port-number;
                  default 514;
                  description
                    "This leaf specifies the port number used to 
                     deliver messages to the remote server.";
                }
              }
            }
            case udp {
              container udp {
                description
                  "This container describes the UDP transport
                   options.";
                leaf address {
                  type inet:host;
                  description
                    "The leaf uniquely specifies the address of 
                     the remote host. One of the following must be 
                     specified: an ipv4 address, an ipv6 address, 
                     or a host name.";
                }
                leaf port {
                  type inet:port-number;
                  default 514;
                  description
                    "This leaf specifies the port number used to 
                     deliver messages to the remote server.";
                }
              }
            }
          }

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          uses syslog-selector;
          leaf destination-facility {
            type identityref {
              base syslogtypes:syslog-facility;
            }
            default syslogtypes:local7;
            description
              "This leaf specifies the facility used in messages 
               delivered to the remote server.";
          }
          leaf source-interface {
            type if:interface-ref;
            description
              "This leaf sets the source interface for the remote 
               Syslog server. Either the interface name or the 
               interface IP address can be specified. If not set, 
               messages sent to a remote syslog server will 
               contain the IP address of the interface the syslog 
               message uses to exit the network element";
          }
          container syslog-sign {
            if-feature signed-messages-config;
            presence
              "If present, syslog-sign is activated.";
            description
              "This container describes the configuration 
               parameters for signed syslog messages as described 
               by RFC 5848.";
            reference
              "RFC 5848: Signed Syslog Messages";
            leaf cert-initial-repeat {
              type uint16;
              mandatory true;
              description
              "This leaf specifies the number of times each 
               Certificate Block should be sent before the first 
               message is sent.";
            }
            leaf cert-resend-delay {
              type uint16;
              mandatory true;
              description
                "This leaf specifies the maximum time delay in 
                 seconds until resending the Certificate Block.";
            }
            leaf cert-resend-count {
              type uint16;
              mandatory true;
              description
                "This leaf specifies the maximum number of other 
                 syslog messages to send until resending the 
                 Certificate Block.";
            }
            leaf sig-max-delay {
              type uint16;
              mandatory true;
              description
                "This leaf specifies when to generate a new 
                 Signature Block. If this many seconds have 
                 elapsed since the message with the first message 
                 number of the Signature Block was sent, a new 
                 Signature Block should be generated.";
            }

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            leaf sig-number-resends {
              type uint16;
              mandatory true;
              description
                "This leaf specifies the number of times a 
                 Signature Block is resent. (It is recommended to 
                 select a value of greater than 0 in particular 
                 when the UDP transport [RFC5426] is used.).";
            }
            leaf sig-resend-delay {
              type uint16;
              mandatory true;
              description
                "This leaf specifies when to send the next 
                 Signature Block transmission based on time. If 
                 this many seconds have elapsed since the previous 
                 sending of this Signature Block, resend it.";
            }
            leaf sig-resend-count {
              type uint16;
              mandatory true;
              description
                "This leaf specifies when to send the next 
                 Signature Block transmission based on a count. 
                 If this many other syslog messages have been sent 
                 since the previous sending of this Signature 
                 Block, resend it.";
            }
          }
        }
      }
      container terminal {
        description
          "This container describes the configuration parameters for 
           the terminal logging configuration.";
        choice terminal-scope {
          mandatory true;
          description
            "This choice describes the option to specify all 
             terminals or a specific terminal. The all terminals 
             case implies that messages will be sent to all 
             sessions on that terminal";
          case all-terminals {
            description
              "This case specifies all terminals.";
            container all-terminals {
              description
                "This container describes the configuration 
                 parameters for all terminals.";
              uses syslog-selector;
            }
          }
          case per-terminal {
            if-feature terminal-facility-user-logging-config;
            description
              "This case specifies one or more terminals.";
            list device-name {
              key "dname";
              description
                "This list describes a collection of device names.";
              leaf dname {
                type string;
                description
                  "This leaf uniquely describes a device name which 
                   is the device to receive log messages.";
              }
              uses syslog-selector;
            }
          }
        }
      }
      container session {
        description
          "This container describes the configuration parameters for 
           session logging configuration.";
        choice user-scope {
          mandatory true;
          description
            "This choice describes the option to specify all users 
             or a specific user. The all users case implies that
             messages will be sent to all sessions";
          case all-users {
            description
              "This case specifies all users.";
            container all-users {
              description
                "This container describes the configuration 
                 parameters for all users.";
              uses syslog-selector;
            }
          }
          case per-user {
            if-feature session-facility-user-logging-config;
            description
              "This case specifies a specific user.";
            list user-name {
              key "uname";
              description
                "This list describes a collection of user names.";
              leaf uname {
                type string;
                description
                  "This leaf uniquely describes a user name which 
                   is the login name of the user whose session 
                   is to receive log messages.";
              }
              uses syslog-selector;
            }
          }
        }
      }
    }
  }
}

<CODE ENDS>

4.3.  A SYSLOG Example

   Requirement:
   Enable console logging of syslogs of severity critical
  
   Here is the example syslog configuration xml:
   <rpc message-id="101" xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
     <edit-config>
       <target>
         <candidate/>
       </target>
       <config xmlns:xc="urn:ietf:params:xml:ns:netconf:base:1.0">
         <syslog xmlns="urn:ietf:params:xml:ns:yang:ietf-syslog"
                 xmlns:syslog="urn:ietf:params:xml:ns:yang:ietf-syslog">
           <log-actions>
             <console>
               <log-selector>
                 <log-facility>
                   <facility>all</facility>
                   <severity>critical</severity>
                 </log-facility>
               </log-selector>
             </console>
           </log-actions>
         </syslog>
       </config>
     </edit-config>
   </rpc>

   <?xml version="1.0" encoding="UTF-8"?>
   <rpc-reply message-id="101" xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
     <ok/>
   </rpc-reply>

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   Enable remote logging of syslogs to udp destination 1.1.1.1
   for facility auth, severity error

   <rpc message-id="101" xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
     <edit-config>
       <target>
         <candidate/>
       </target>
       <config xmlns:xc="urn:ietf:params:xml:ns:netconf:base:1.0">
         <syslog xmlns="urn:ietf:params:xml:ns:yang:ietf-syslog"
                 xmlns:syslog="urn:ietf:params:xml:ns:yang:ietf-syslog">
           <log-actions>
             <remote>
               <destination>
                 <name>remote1</name>
                 <udp>
                   <address>1.1.1.1</address>
                 </udp>
                 <log-selector>
                   <log-facility>
                     <facility xmlns:syslogtypes=
                       "urn:ietf:params:xml:ns:yang:ietf-syslog-types">
                       syslogtypes:auth</facility>
                     <severity>error</severity>
                   </log-facility>
                 </log-selector>
               </destination>
             </remote>
           </log-actions>
         </syslog>
       </config>
     </edit-config>
   </rpc>

   <?xml version="1.0" encoding="UTF-8"?>
   <rpc-reply message-id="101" xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
   <ok/>
   </rpc-reply>

5.  Implementation Status

  [Note to RFC Editor: Please remove this section before publication.]
  
  This section records the status of known implementations of the Syslog
  YANG model at the time of posting of this Internet-Draft.

  Cisco Systems, Inc. has implemented the proposed IETF Syslog model
  for the Nexus 7000 NXOS OS as a prototype, together with an
  augmentation model for operating system specific Syslog configuration
  features.

  Five leaves were implemented in the base IETF model and three leaves
  were implemented in the Cisco specific augmentation model as follows:

      Leaf XPATH                   Sample NXOS CLI Command(s)

  syslog:log-actions/console     logging console 1
  syslog:log-actions/file        logging logfile mylog.log 2 4096
  syslog:log-actions/terminal    logging monitor 2
  syslog:log-actions/remote     *logging server server.cisco.com 2
                                         facility user
                                *logging source-interface loopback 0
  cisco-syslog:logging-timestamp-config  logging timestamp milli-seconds
  cisco-syslog:origin-id-cfg  logging origin-id string abcdef
  cisco-syslog:module-logging logging module 1

  *The "logging server" and "logging source-interface" commands were
  combined into one base model leaf.

  The description of implementations in this section is intended to assist
  the IETF in its decision processes in progressing drafts to RFCs.

6.  Security Considerations

   The YANG module defined in this memo is designed to be accessed via
   the NETCONF protocol [RFC6241] [RFC6241].  The lowest NETCONF layer
   is the secure transport layer and the mandatory-to-implement secure
   transport is SSH [RFC6242] [RFC6242].  The NETCONF access control
   model [RFC6536] [RFC6536] provides the means to restrict access for
   particular NETCONF users to a pre-configured subset of all available
   NETCONF protocol operations and content.

   There are a number of data nodes defined in the YANG module which are
   writable/creatable/deletable (i.e., config true, which is the
   default).  These data nodes may be considered sensitive or vulnerable
   in some network environments.  Write operations (e.g., <edit-config>)
   to these data nodes without proper protection can have a negative
   effect on network operations.

   TBD: List specific Subtrees and data nodes and their sensitivity/
   vulnerability.

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7.  IANA Considerations

   This document registers a URI in the IETF XML registry [RFC3688]
   [RFC3688].  Following the format in RFC 3688, the following
   registration is requested to be made:

   URI: urn:ietf:params:xml:ns:yang:syslog

   Registrant Contact: The IESG.

   XML: N/A, the requested URI is an XML namespace.

   This document registers a YANG module in the YANG Module Names
   registry [RFC6020].

   name: syslog namespace: urn:ietf:params:xml:ns:yang:syslog
   prefix: syslog reference: RFC XXXX

8.  Acknowledgements

The authors wish to thank the following who commented on versions 01 through 05 
of this proposal:
 
Martin Bjorklund <mbjorklu@cisco.com>
Jim Gibson <gibson@cisco.com>
Jeffrey Haas <jhaas@pfrc.org>
John Heasley <heas@shrubbery.net>
Giles Heron <giheron@cisco.com>
Lisa Huang <yihuan@cisco.com>
Jeffrey K Lange <jeffrey.K.lange@ge.com>
Jan Lindblad <jlindbla@cisco.com>
Chris Lonvick <lonvick@gmail.com>
Juergen Schoenwaelder <j.schoenwaelder@jacobs-university.de>
Jason Sterne <jason.sterne@alcatel-lucent.com>
Peter Van Horne <petervh@cisco.com>
Bert Wijnen <bertietf@bwijnen.net>
Aleksandr Zhdankin <azhdanki@cisco.com>

9.  Change log [RFC Editor: Please remove]

10. References

   [RFC5424]  Gerhards, R., "The Syslog Protocol", BCP 78, RFC 5424,
              March 2009.

   [RFC3688]  Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
              March 2004.

   [RFC6020]  Bjorklund, M., "YANG - A Data Modeling Language for the
              Network Configuration Protocol (NETCONF)", RFC 6020,
              October 2010.

   [RFC6241]  Enns, R., Bjorklund, M., Schoenwaelder, J., and A.
              Bierman, "Network Configuration Protocol (NETCONF)", RFC
              6241, June 2011.

   [RFC6242]  Wasserman, M., "Using the NETCONF Protocol over Secure
              Shell (SSH)", RFC 6242, June 2011.

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   [RFC6536]  Bierman, A. and M. Bjorklund, "Network Configuration
              Protocol (NETCONF) Access Control Model", RFC 6536, March
              2012.

Authors' Addresses

   Clyde Wildes
   Cisco Systems Inc.
   Email: cwildes@cisco.com

   Kiran Agrahara Sreenivasa
   Cisco Systems, Inc.
   Email: kkoushik@cisco.com

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