Describing the Benefits of Network Telemetry¶

Introduction to Network Telemetry¶

Network Telemetry¶

The technologies that are used in order to collection information from devices and then consume that information.

Model-Based Telemetry

Network telemetry that uses some sort of data model to share the information.

What’s the benefit?

Less resource intensive
Gather as much information for analysis
Used for SLAs and compliance
Determine how to shape traffic
Root cause analysis
Accurate prediction models

Network Telemetry Compoents

Data source and object
Data generation and processing
Encoding and exporting
Storage, analysis and querying
Data configuration and subscription

Information That Makes up Network Telemetry¶

Management Plane Protocols¶

Traditional protocols not sufficient
- SNMP too infrequent & small scope
- Syslog not standardized
NETCONF/RESTCONF using YANG
gNMI

Control Plane Protocols¶

BGP Monitoring Protocol (BMP)

Data Plane Protocols¶

NetFlow
Advanced Visibility and Control (AVC)

Intro to Data Models and YANG¶

Data Model¶

The explicit instructions of the structure, syntax or semantics of the data. Other systems will use the model in order to properly access the data.

Attributes of a Good Data Model¶

Accurate
Clear
Efficient
Simple
Limited in scope

YANG¶

Is made up of different modules that are used for a specific purpose
Multiple YANG modules make up a YANG Model
YANG is used to agree on how to interact with the data

Example Cisco Switch YANG Model

802.1X Module
AAA Module
ACL Module

container timeout {
  description
    "Various Timeouts";
  leaf auth-period {
    description
      "Timeout for authenticator reply";
    type uint16;

  leaf tx-period {
    description
      "Timeout for supplicant retries";
    type uint16;
  }
}

container password {
  description
    "Set the authentication password";
    leaf secret {
      type string;
  }
}

Container to define dot1x timeouts
Descriptions can be used to aid in understanding Leafs represent attributes that CAN be configured
Type specifies the data value that is expected. In this case it is an integer
tx-period leaf is used to define the timeout period for the supplicant
Expecting an integer “dotlx timeout tx-period 10”
Separate container to define passwords secret leaf is used to define the password
expecting a string data type as the value

Intro to NETCONF, RESTCONF, and gRPC¶

NETCONF¶

NETCONF uses SSH protocol, usually port 830
NETCONF uses XML to encode the data

Example XML sent to device

<rpc message-id ="2">
  <edit-config>
    <target>
        <running/>
    </target>
    <config>
      <timeouts xmlms="dotix YANG module location">
        <tx-period>10</tx-period>
      </timeouts>
    </config>
  </edit-config>
</rpc>

Example device reply

<rpc-reply message-id ="2">
  </ok>
</rpc-reply>

RESTCONF¶

RESTCONF uses REST principles and HTTP methods: GET, PUT, POST, PATCH & DELETE

Example XML sent to device

HTTP PUT restconf/api/running/dot1x
"data": {
  "timeouts": [
    {
      "tx-period": "10"
    }
  ]
}

Example device reply

HTTP 201 CREATED

gRPC and gNMI¶

gNMI is a subset of Google’s gRPC to transfer YANG modeled data.
Can use JSON or protobuf to encode the data

Dial-In vs Dial-Out¶

Doesn’t describe how the subscription information flows

Dial-Out

Network device would initiate session with management server
Statically configured to connect to each server
Network device would reestablish connection if it was lost

Dial-In

Management server initiates session with network device
Method is dynamic for the networking device, no config needed
Management server would be responsible for reestablishing connection