NETMOD WG                                                   Clyde Wildes
Internet-Draft                                             Cisco Systems
Intended status: Informational                    Agrahara Kiran Koushik
Expires: Sep 05, 2015                      Brocade Communication Systems
                                                           Mar 05, 2015


                             SYSLOG YANG model
                  draft-ietf-netmod-syslog-model-02

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 Sep 05, 2015.

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
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.



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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 [RFC3164] 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

   Group Level Suppression
    +------------------------------+
    | Filter by message facility   |
    | and message severity         |
    +------------------------------+
                 |
                 |
                 |
         +------------+------------+------------+-----------+
         |            |            |            |           |
         v            v            v            v           v
   Message Distributors
    +----------+ +----------+ +----------+  +----------+  +----------+
    |          | | Log      | | Log      |  |    User  |  |   Remote |
    |  Console | | Buffer   | | File(s)  |  | Terminals|  |   Servers|
    +----------+ +----------+ +----------+  +----------+  +----------+

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

   - console
   - log buffer
   - log file(s)
   - user terminals
   - remote server(s).

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

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3.1.  SYSLOG Module
module: ietf-syslog
   +--rw syslog
      +--rw global-logging-action {global-logging-action}?
      |  +--rw (logging-level-scope)?
      |  |  +--:(logging-facility-all)
      |  |  |  +--rw severity?                            syslogtypes:severity
      |  |  +--:(logging-facility-none)
      |  |  |  +--rw none?                                empty
      |  |  +--:(logging-facility)
      |  |     +--rw logging-facilities* [facility]
      |  |        +--rw facility    identityref
      |  |        +--rw severity?   syslogtypes:severity
      |  +--rw logging-advanced-level-processing {selector-advanced-level-processing-config}?
      |  |  +--rw select-message-severity?   enumeration
      |  +--rw logging-match-processing {selector-match-processing-config}?
      |     +--rw pattern-match?   string
      +--rw console-logging-action
      |  +--rw (logging-level-scope)?
      |  |  +--:(logging-facility-all)
      |  |  |  +--rw severity?                            syslogtypes:severity
      |  |  +--:(logging-facility-none)
      |  |  |  +--rw none?                                empty
      |  |  +--:(logging-facility)
      |  |     +--rw logging-facilities* [facility]
      |  |        +--rw facility    identityref
      |  |        +--rw severity?   syslogtypes:severity
      |  +--rw logging-advanced-level-processing {selector-advanced-level-processing-config}?
      |  |  +--rw select-message-severity?   enumeration
      |  +--rw logging-match-processing {selector-match-processing-config}?
      |     +--rw pattern-match?   string
      +--rw buffered-logging-action
      |  +--rw (logging-level-scope)?
      |  |  +--:(logging-facility-all)
      |  |  |  +--rw severity?                            syslogtypes:severity
      |  |  +--:(logging-facility-none)
      |  |  |  +--rw none?                                empty
      |  |  +--:(logging-facility)
      |  |     +--rw logging-facilities* [facility]
      |  |        +--rw facility    identityref
      |  |        +--rw severity?   syslogtypes:severity
      |  +--rw logging-advanced-level-processing {selector-advanced-level-processing-config}?
      |  |  +--rw select-message-severity?   enumeration
      |  +--rw logging-match-processing {selector-match-processing-config}?
      |  |  +--rw pattern-match?   string
      |  +--rw buffer-size?                         uint64
      +--rw file-logging-action
      |  +--rw logging-files* [file-name]
      |     +--rw file-name                            inet:uri
      |     +--rw (logging-level-scope)?
      |     |  +--:(logging-facility-all)
      |     |  |  +--rw severity?                            syslogtypes:severity
      |     |  +--:(logging-facility-none)
      |     |  |  +--rw none?                                empty
      |     |  +--:(logging-facility)
      |     |     +--rw logging-facilities* [facility]
      |     |        +--rw facility    identityref
      |     |        +--rw severity?   syslogtypes:severity
      |     +--rw logging-advanced-level-processing {selector-advanced-level-processing-config}?
      |     |  +--rw select-message-severity?   enumeration
      |     +--rw logging-match-processing {selector-match-processing-config}?
      |     |  +--rw pattern-match?   string
      |     +--rw file-logging-structured-data?        boolean {file-logging-structured-data}?
      |     +--rw file-logging-archive {file-logging-archive-config}?
      |        +--rw file-number?       uint32
      |        +--rw file-size?         uint64
      |        +--rw file-permission?   enumeration
      +--rw remote-logging-action
      |  +--rw remote-logging-destination* [destination]
      |     +--rw destination                          inet:host
      |     +--rw (logging-level-scope)?
      |     |  +--:(logging-facility-all)
      |     |  |  +--rw severity?                            syslogtypes:severity
      |     |  +--:(logging-facility-none)
      |     |  |  +--rw none?                                empty
      |     |  +--:(logging-facility)
      |     |     +--rw logging-facilities* [facility]
      |     |        +--rw facility    identityref
      |     |        +--rw severity?   syslogtypes:severity
      |     +--rw logging-advanced-level-processing {selector-advanced-level-processing-config}?
      |     |  +--rw select-message-severity?   enumeration
      |     +--rw logging-match-processing {selector-match-processing-config}?
      |     |  +--rw pattern-match?   string
      |     +--rw remote-logging-structured-data?      boolean {remote-logging-structured-data}?
      |     +--rw destination-port?                    inet:port-number
      |     +--rw destination-facility?                identityref
      |     +--rw source-interface?                    if:interface-ref
      |     +--rw vrf-name?                            string {remote-logging-use-vrf}?
      |     +--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-logging-action
         +--rw (user-scope)?
            +--:(all-users)
            |  +--rw all-users
            |     +--rw (logging-level-scope)?
            |     |  +--:(logging-facility-all)
            |     |  |  +--rw severity?                            syslogtypes:severity
            |     |  +--:(logging-facility-none)
            |     |  |  +--rw none?                                empty
            |     |  +--:(logging-facility)
            |     |     +--rw logging-facilities* [facility]
            |     |        +--rw facility    identityref
            |     |        +--rw severity?   syslogtypes:severity
            |     +--rw logging-advanced-level-processing {selector-advanced-level-processing-config}?
            |     |  +--rw select-message-severity?   enumeration
            |     +--rw logging-match-processing {selector-match-processing-config}?
            |        +--rw pattern-match?   string
            +--:(per-user) {terminal-facility-user-logging-config}?
               +--rw user-name* [uname]
                  +--rw uname                                string
                  +--rw (logging-level-scope)?
                  |  +--:(logging-facility-all)
                  |  |  +--rw severity?                            syslogtypes:severity
                  |  +--:(logging-facility-none)
                  |  |  +--rw none?                                empty
                  |  +--:(logging-facility)
                  |     +--rw logging-facilities* [facility]
                  |        +--rw facility    identityref
                  |        +--rw severity?   syslogtypes:severity
                  +--rw logging-advanced-level-processing {selector-advanced-level-processing-config}?
                  |  +--rw select-message-severity?   enumeration
                  +--rw logging-match-processing {selector-match-processing-config}?
                     +--rw pattern-match?   string


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4.  SYSLOG YANG Models

4.1.  SYSLOG-TYPES module

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: Juergen Schoenwaelder
               <mailto:j.schoenwaelder@jacobs-university.de>

     WG Chair: Tom Nadeau
               <mailto:tnadeau@brocade.com>

     Editor:   Clyde Wildes
               <mailto:cwildes@cisco.com>

     Editor:   Agrahara Kiran Koushik
               <mailto:kkoushik@brocade.com>";
  description
    "This module contains a collection of YANG type definitions for
     SYSLOG.";

  revision 2015-03-05 {
     description
      "Initial Revision";
    reference
      "This model references RFC 5424 - The Syslog Protocol.";


  }

  typedef severity {
    type enumeration {
      enum "emergency" {
        value 0;
        description
          "Emergency Level Msg";
      }
      enum "alert" {
        value 1;
        description
          "Alert Level Msg";
      }

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      enum "critical" {
        value 2;
        description
          "Critical Level Msg";
      }
      enum "error" {
        value 3;
        description
          "Error Level Msg";
      }
      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.";
  }

  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.";
  }

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  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.";
   }

   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.";
  }
}

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4.2. SYSLOG module

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: David Kessens
               <mailto:david.kessens@nsn.com>

     WG Chair: Juergen Schoenwaelder
               <mailto:j.schoenwaelder@jacobs-university.de>

     Editor:   Clyde Wildes
               <mailto:cwildes@cisco.com>

     Editor:   Agrahara Kiran Koushik
               <mailto:kkoushik@brocade.com>";

  description
    "This module contains a collection of YANG definitions
     for Syslog configuration.";

  revision 2015-03-05 {
    description
      "Initial Revision";
    reference
      "This model references RFC 5424 - The Syslog Protocol,
       and RFC 5848 - Signed Syslog Messages.";
  }

  feature global-logging-action {
    description
      "This feature represents the ability to suppress log
       messages on the global level.";
  }

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

  feature remote-logging-structured-data {
    description
      "This feature represents the ability to deliver log
       messages to a remote server in structured-data format
       as per RFC 5424.";
  }

  feature file-logging-archive-config {
    description
      "This feature represents the ability to archive log files.";
  }

  feature remote-logging-use-vrf {
    description
      "This feature allows remote logging of messages to a
       particular VRF.";
  }

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

  feature selector-advanced-level-processing-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
       filter log messages.";
    leaf severity {
      type syslogtypes:severity;
      description
        "This leaf specifies the Syslog message severity.
         No value implies all severities.";
    }
  }

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  grouping syslog-selector {
    description
      "This grouping defines a Syslog selector which is used to
       filter log messages for the given action in which the
       selector appears. Choose one of the following:
         logging-facility-all <severity>
         logging-facility-none
         logging-facility [<facility> <severity>...]
       Additional severity comparison operations are available
       using the logging-advanced-level-processing container. If
       the logging-advanced-level-processing container is not
       present all messages of the specified severity and higher
       are logged according to the given action.";
    choice logging-level-scope {
      default logging-facility-all;
      description
        "This choice describes the option to specify all
         facilities, no facilities, or a specific facility.";
      case logging-facility-all {
        description
          "This case specifies all facilities will match when
           comparing the Syslog message facility.";
        uses syslog-severity;
      }
      case logging-facility-none {
        description
          "This case specifies no facilities will match when
           comparing the Syslog message facility. This is a method
           that can be used to turn an action off.";
        leaf none {
          type empty;
          description
          "This leaf specifies that no facilities participate in the
           filtering of Syslog messages for this action.";
        }
      }
      case logging-facility {
        description
          "This case specifies one or more specified facilities
           will match when comparing the Syslog message facility.";
        list logging-facilities {
          key "facility";
          description
            "This list describes a collection of Syslog facilities
             and severities.";
          leaf facility {
            type identityref {
              base syslogtypes:syslog-facility;
            }
            description
              "The leaf uniquely identifies a Syslog facility.";
          }
          uses syslog-severity;
        }
      }
    }

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    container logging-advanced-level-processing {
      if-feature selector-advanced-level-processing-config;
      description
        "This container describes the configuration parameters for
         advanced Syslog selector severity comparison.";
      leaf select-message-severity {
        type enumeration {
          enum equals-or-higher {
            description
              "All messages of the specified severity and higher are
               logged according to the given action";
          }
          enum equals {
            description
              "This leaf specifies all messages for the specified
               severity.";
          }
          enum not-equals {
            description
              "This leaf specifies all messages that are not for the
               specified severity.";
          }
        }
        default equals-or-higher;
        description
          "This leaf describes the option to specify how the
           severity comparison is performed.";
      }
    }
    container logging-match-processing {
      if-feature selector-match-processing-config;
      description
        "This container describes the configuration parameters for
         matching Syslog messages using a regular expression pattern
         match.";
      leaf pattern-match {
        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 global-logging-action {
      if-feature global-logging-action;
      description
        "This container describes the configuration parameters for
         global logging. Global logging represents the ability to
         perform global log message suppression.";
      uses syslog-selector;
    }

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    container console-logging-action {
      description
        "This container describes the configuration parameters for
         console logging.";
      uses syslog-selector;
    }
    container buffered-logging-action {
      description
        "This container describes the configuration parameters for
         local memory buffer logging.";
      uses syslog-selector;
      leaf buffer-size {
        type uint64;
        description
          "This leaf describes the amount of memory that will be
           dedicated to local memory buffer logging. The default
           value varies by implementation.";
      }
    }
    container file-logging-action {
      description
        "This container describes the configuration parameters for
         file logging.";
      list logging-files {
        key "file-name";
        description
          "This list describes a collection of local logging
           files.";
        leaf file-name {
          type inet:uri;
          description
            "This leaf specifies the name of the log file.";
        }
        uses syslog-selector;
        leaf file-logging-structured-data {
          if-feature file-logging-structured-data;
          type boolean;
          default false;
          description
            "This leaf describes how log messages are written to the
             log file. If true, messages will be written in
             structured-data format; if false, messages will be
             written in standard message format.";
        }
        container file-logging-archive {
          if-feature file-logging-archive-config;
          description
            "This container describes the configuration parameters
             for log file archiving.";
          leaf file-number {
            type uint32;
            default 1;
            description
              "This leaf specifies the maximum number of log files
               retained.";
          }

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          leaf file-size {
            type uint64;
            default 262144;
            description
              "This leaf specifies the maximum log file size.";
          }
          leaf file-permission {
            type enumeration {
               enum world-readable {
                 value 1;
                 description
                   "This enum specifies that the log files
                    are readable by world.";
               }
               enum no-world-readable {
                 value 2;
                 description
                   "This enum specifies that the log files
                    are not readable by world.";
               }
            }
            default no-world-readable;
            description
              "This leaf describes who can read log files";
          }
        }
      }
    }
    container remote-logging-action {
      description
        "This container describes the configuration parameters for
         remote logging.";
      list remote-logging-destination {
        key "destination";
        description
          "This list describes a collection of remote logging
           destinations.";
        leaf destination {
          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.";
        }
        uses syslog-selector;
        leaf remote-logging-structured-data {
          if-feature remote-logging-structured-data;
          type boolean;
          default false;
          description
            "This leaf describes how log messages are sent to the
             remote server. If true, messages will be sent in
             structured-data format; if false, messages will be
             sent in standard message format.";
        }
        leaf destination-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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        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";
        }
        leaf vrf-name {
          if-feature remote-logging-use-vrf;
          type string;
          description
            "This leaf specifies the name of the virtual routing
             facility (VRF) that connects to the syslog server
             host. If not set, the default VRF will be used.";
        }
        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.";
          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-logging-action {
      description
        "This container describes the configuration parameters for
         the terminal logging configuration.";
      choice user-scope {
        default all-users;
        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 terminals";
        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 terminal-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.";

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            leaf uname {
              type string;
              description
                "This leaf uniquely describes a user name which is
                 the login name of the user whose terminal session
                 is to receive log messages.";
            }
            uses syslog-selector;
          }
        }
      }
    }
  }
}


4.3.  A SYSLOG Example

   Requirement:
   Enable global logging of two facilities:
     kern - severity critical(1)
     auth - severity error(3)

   Enable console logging of syslogs of severity
   critical(1)

   Here is the example syslog configuration xml:
   <rpc message-id="101" xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
     <edit-config>
       <target>
         <running/>
       </target>
       <config>
         <syslog xmlns="urn:ietf:params:xml:ns:yang:ietf-syslog">
           <global-logging-action>
             <logging-facilities>
               <facility>syslogtypes:kern</facility><severity>syslogtypes:critical</severity>
             </logging-facilities>
             <logging-facilities>
               <facility>syslogtypes:auth</facility><severity>syslogtypes:error</severity>
             </logging-facilities>
           </global-logging-action>
           <console-logging-action>
             <severity>syslogtypes:critical</severity>
           </console-logging-action>
         </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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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:global-logging-action   logging level cron 2
  syslog:console-logging-action  logging console 1
  syslog:file-logging-action     logging logfile mylog.log 2 4096
  syslog:terminal-logging-action logging monitor 2
  syslog:remote-logging-action  *logging server server.cisco.com 2
                                         facility user
                                         use-vrf management
                                *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 version 00 of this proposal:

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>
Chris Lonvick <lonvick@gmail.com>
Juergen Schoenwaelder <j.schoenwaelder@jacobs-university.de>
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

   [RFC3164]  Lonvick, C., "The BSD syslog Protocol", BCP 81, RFC 3164,
              August 2001.

   [RFC3688]  Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
              March 2204.

   [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
   Brocade Communications Systems

   Email: kkoushik@brocade.com

















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