Performance Sessions Overview

This article provides an overview of Skylight solution performance sessions to help you understand session types, including:

• TWAMP
• Ethernet OAM
• Echo
• 2xOnewWay
• NFV-PM

It also describes the uses and applicability of performance sessions.

Performance sessions allow for monitoring of the performance of services on your network by capturing a wide range of performance metrics.

In the Sessions page, you can set up various types of layer-2 and layer-3 sessions.

How Network Performance is Measured

• Streams of frames (or packets) are injected into the network under test.
• The streams are tiny with respect to bandwidth and frame rate.
• The streams mimic the services they are monitoring and are affected by the network in the same way as the real traffic when transported between the sender and the reflector.

System Components

• Skylight orchestrator: Controls all measurement and supervision activities
• Sender: Device that generates a stream of frames and sends them to a reflector device; it also receives the stream that is sent back by the reflector
• Reflector: Device that can reflect frames back to the sender in a session
• Analytics System: Northbound system for PM visualization and analysis
• OSS/NMS: Northbound system for alarms reporting

System Scalability

Skylight orchestrator

• Can manage up to 100 sensor elements (actuators)
• 52,000 sessions on a single virtual machine

Actuators

• Sensor control: Up to 4000 sessions
• Classic actuator: Up to 1000 sessions

Performance Session Types

• TWAMP Sessions (layer 3)
  • Support TWAMP Full and Light models
  • Compatible with standard TWAMP reflectors
  • Stateful or stateless reflectors
• Ethernet OAM Sessions (layer 2)
  • Compatible with devices capable of supporting:
    • ETH-LB: Ethernet Loopback Message
    • ETH-DM: Delay Measurement Message
    • ETH-VS: Vendor Specific Protocol
• Echo Sessions (layer 3)
  • Compatible with devices capable of supporting:
    • ICMP echo (ping)
    • UDP echo
• 2xOneWay Sessions
  • Accedian proprietary L3 performance session
  • Provides a superset of features compared to TWAMP
  • Designed for use with Accedian actuators or reflector agents
• NFV Sessions
  • Allow Skylight modules to act as senders
  • Based on Virtual Connection Endpoints (VCE)
  • Session types supporting NFV:
    • TWAMP
    • Echo (ICMP and UDP)
    • Ethernet OAM (ETH-DM, ETH-LB, ETH-VS)

TWAMP: Two-Way Active Measurement Protocol

• TWAMP (RFC-5357) is used to monitor performance on layer-3 networks.
• The full TWAMP model involves four components:
  • Session Sender: Generates TWAMP test packets and sends them to the reflector.
  • Session Reflector: Receives TWAMP test packets from the sender and reflects them back to the sender.
  • Control Client: Sets up, starts and stops the TWAMP test session, and collects statistics.
  • Server: Responds to the Control Client’s request for establishing, starting, or stopping a test session.
• The components typically reside on two devices:
  • Controller device: hosts the control client and the sender.
  • Responder device: hosts the control server and the reflector.
• TWAMP involves two protocols:
  • TWAMP-Control (TCP): Used to set up, start, and end test sessions.
  • TWAMP-Test (UDP): Defines the packet format used for performance measurement.
    

TWAMP Light

• Lightweight model designed to help in implementing TWAMP for entities acting as active responders to controllers.
  • Control Client, Server, and Session Sender components are implemented in the Controller.
  • Session Reflector is implemented in the Responder.
• TWAMP Light allows a simplified architecture.
  • The Responder simply acts as a test point over a network without the need for any negotiation protocol.
  • The TWAMP-Control protocol is simply replaced by the management plane.
  • The Session Reflector does not necessarily have knowledge of the session’s state.

TWAMP Light Session

• The session takes place over a UDP connection set up between a sender and a reflector.
• Two directions:
  • Uplink: sender to reflector (sometimes referred to as P2R: Probe to Reflector)
  • Downlink: reflector to sender (sometimes referred to as R2P: Reflector to Probe)
• Sender can be:
  • Skylight sensor control local interface
  • Skylight sensor control remote interface (Skylight module configured for NFV-PM)
• Reflector can be:
  • Any device capable of reflecting standard TWAMP packets

TWAMP Metrics vs. Reflector Type

• TWAMP uses two techniques to measure delay and packet loss:
  • Packet sequence numbers (packet loss)
  • Timestamps (delay measurements)
• TWAMP reports:
  • Two-way delay metrics.
  • Can report one-way delay metrics if the endpoints are time-synchronized.
• Stateful reflector:
  • Capable of tracking packet sequence numbers.
  • Can support packet loss, reorder, and duplication measurements per direction (one-way).
• Stateless reflector:
  • Does not track packet sequence numbers.
  • Has no knowledge of the session state.
  • Can only support two-way packet loss measurements.

Ethernet OAM Sessions

• Used to monitor performance on layer-2 networks.
• Based on ITU-T Y.1731 and IEEE 802.1ag Ethernet OAM standards.
• Ethernet Loopback (ETH-LB) Session
  • Set up toward an OAM-enabled network device.
  • Measures and verifies bi-directional connectivity between the sender and the reflector (MEP to MEP/MIP).
  • Measures and reports two-way delay, two-way delay variation, frame loss, reordered and duplicate frames.
• Ethernet Delay Measurement (ETH-DM) Session
  • Set up toward an OAM-enabled network device.
  • Measures and verifies bi-directional connectivity between the sender and the reflector (MEP to MEP).
  • Measures and reports two-way delay, two-way delay variation, one-way delay for both directions.
  • Also measures and reports frame loss, reordered and duplicate frames.

• Ethernet Vendor Specific (ETH-VS) Session
  • Enhanced bidirectional measurement function for layer-2 networks.
  • Based on vendor-specific Y.1731 OAM PDU (ETH-VSP).
    • Supported with Accedian reflectors only:
    • Skylight sensor control
    • Classic actuator
  • Skylight performance elements
  • Measures and reports delay, delay variation, frame loss, jitter, and other metrics on one-way basis.

Echo Sessions

• Used to monitor performance on layer-3 networks.
• Based on IETF standards:
  • RFC 792: ICMP Echo
  • RFC 862: UDP Echo
• Used for continuous monitoring of bidirectional connectivity toward any regular IP-enabled network element such as a server, layer-3 CPE, managed Ethernet switch, router, etc.
• ICMP Echo Session
  • Measures and reports on bidirectional connectivity and round-trip metrics using the ICMP Echo protocol (ping).
• UDP Echo Session
  • Measures and reports on bidirectional connectivity and round-trip metrics using the UDP Echo protocol.

2xOneWay Sessions

• Accedian proprietary session used to monitor performance on layer-3 networks.
• Provides a superset of features compared to a standard TWAMP session.

A 2xOneWay session can be set up in two ways:

• Between two Accedian devices (actuators):
  • One device acts as the sender and the other as the reflector.
  • Supported encapsulation protocols: UDP, TCP, GRE, SCTP and ICMP.
• Between an Accedian sender device and an Accedian reflector agent:
  • The agent is embedded in a 3rd-party device (user-space reflector).
  • Supported encapsulation protocol: UDP.

NFV Sessions (NFV-PM)

• Skylight sensor control uses Network Function Virtualization (NFV) to allow Skylight modules to act as senders in performance monitoring sessions.
• Sensor control generates the packet stream and sends it to a module via an NFV tunnel.
• The module timestamps the packets and sends them to the reflector.
• The Virtual Connection Endpoint (VCE) is the mechanism that enables a Skylight module to act as a sender or reflector in a session.
• A VCE is a specialized interface that defines the NFV IP address and VLAN header for a Skylight module linked to sensor control
• VCEs can be used to support the following NFV-PM sessions:
  • NFV ECHO-ICMP and NFV ECHO-UDP (layer 3)
  • NFV ETH-DM, NFV ETH-LB and NFV ETH-VS (layer 2)
  • NFV TWAMP (layer 3)

Performance Sessions Uses and Applicability

Session Types vs. Products Capabilities

Session Types vs. Analytics System

Metric Types

OW (One-Way): Metric is available per direction
TW (Two-Way): Metric is available for round-trip