White paper

2Q 2015

 

         

 

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How does the Accedian Performance Assurance Agent™ (PAA) compare to the monitoring capabilities of Cisco’s IP SLA?

Layer 2 vs. Layer 3 Accedian’s Network Performance Elements support both Layer 3 IP and Layer 2 Ethernet active SLA performance monitoring, whereas Cisco IP SLA only monitors at Layer 3.

Layer 2 testing is required to assess the performance of Carrier Ethernet services. Performance at Layer 2 cannot be extrapolated from Layer 3 measurements, just as you cannot assess download speed on a cable modem by checking radio frequency (RF) performance on the coaxial network.

The Accedian Networks Performance Assurance Agent™ (PAA) offers the capability to concurrently and independently measure QoS performance metrics at the IP and Ethernet layers, providing a complete view into network performance and the true customer experience. When delivering Ethernet using VPLS (Virtual Private LAN Service) / L2PT (Layer 2 Tunnelling Protocol, Cisco proprietary) over a routed (IP / MPLS) network, performance of both can be monitored at the same time.

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Test Setup Simplicity Simplifying real-world use, the PAA’s Layer 2 performance monitoring works directly within the customer VLAN without any IP level conflict or special test configuration.

By contrast, IP SLA requires that the operator assign an IP address in the customer’s VLAN (within their private address space) to enable testing. Assuming the customer permits this, it also means coordinating the configuration of each monitored end-point with their IT department to ensure a conflict-free address is assigned.

Standard vs. Proprietary Protocols All of Accedian’s Elements support the standard Layer 2 Y.1731 SLA performance monitoring (PM) protocol. This allows these units to interoperate with other equipment, including any network element conforming to the Y.1731 standard.

The PAA is also based on Y.1731, leveraging the available vendor-specific extensions to enable advanced functionality including multicast testing with integrated IGMP session performance measurement.

Hardware vs. Software-Based Network Element units from Accedian incorporate an advanced, hardware-based packet processing engine that provides up to three orders of magnitude more accuracy,

Tech Primer:  PAA vs. IP SLA

 

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  PAA vs. IP SLA • 2Q 2015

© 2015 Accedian Networks Inc. All rights reserved. Accedian Networks, the Accedian Networks logo, SkyLIGHT, AntMODULE, Vision EMS, Vision Suite, VisionMETRIX, Vision Collect, Vision Flow, Vision SP, V-NID, Plug & Go, R-FLO, Network State+, Traffic-Meter, FlowMETER & airMODULE are trademarks or registered trademarks of Accedian Networks Inc. All other company and product names may be trademarks of their respective companies. Accedian Networks may, from time to time, make changes to the products or specifications contained herein without notice. Some certifications may be pending final approval, please contact Accedian Networks for current certifications.     2

    Carrier-Grade

to the Core

Adding Accedian Network Element units to your network is a fail-safe choice. Designed and built from the ground-up, these premium in-line network elements ensure reliability is never impacted, only assured.

Unconditionally certified to MEF 9 & 14 standards, these units offer the full functionality required to provision, police & deliver Carrier Ethernet Virtual Circuits (EVCs). The units are also certified to NEBS Level 3, delivering performance & non-interference with other carrier-grade elements. Temperature hardening allows installation in outdoor cabinets and harsh environments.

With no moving parts or fans to fail and consuming only several watts, Network Element units feature a 52 year Mean Time Between Failures (MTBF) when evaluated by the Telcordia Reliability Prediction Procedure.

 

Certified Carrier-Grade

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precision and multi-flow measurement capacity than those conducted by Cisco’s IP SLA—implemented in software running on the same network processor responsible for switching, routing, aggregation, and other critical networking functions.

As a software implementation using a shared network processor, IP SLA measurement accuracy, precision and availability suffer under high-traffic load conditions—precisely the time when performance monitoring is most important. In addition, IP SLA measurements come from the router instead of an independent device, making it impossible for measurements to accurately account for egress side impairments due to the router itself.

By using a dedicated, all-hardware architecture, up to 100 concurrent PAA sessions can be maintained by any Accedian Network Element without introducing delay into live network traffic. Hardware-based time stamping applied directly “on the wire” provides microsecond vs. millisecond measurement precision and accuracy.

One-Way vs. Two Way Measurements Cisco's IP SLA can only measure round-trip latency, whereas the PAA can accurately measure both one-way delay and jitter at Layer 2 or 3. With asynchronous networks, traffic loading and directional application requirements, one-way measurements are increasingly specified in SLAs, and are invaluable for problem isolation and performance optimization.

A patent-pending synchronization technique allows remote Network Elements to sync

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their clocks and perform these measurements without requiring any external timing signal or GPS. This results in consistent, microsecond-level precision and accuracy compared to variable, millisecond-level results from IP SLA.

Measurement Frequency & Efficiency In addition to unrivalled precision, accuracy, and multi-flow monitoring density, Accedian’s Network Elements using PAA provide traffic statistics and PM metrics on a per-second basis. This highly granular measurement interval exposes micro-bursting, transient packet-loss, and other SLA-violating occurrences instead of burying them in multi-minute averages.

Measurement results can be retrieved from Elements using a number of methods, including a highly efficient, encrypted binary format pushed over TCP (to ensure they are received). This technique results in significantly less network overhead and telemetry bandwidth usage (200 bytes / minute / unit) than the SNMP-polling used by IP SLA, while providing significantly greater monitoring scalability.

Interoperability Cisco's IP SLA is specific only to Cisco routers. There is no interoperability with other vendors’ equipment. Accedian Networks’ Element units incorporate loopback functionality that can be controlled by a number of test and measurement solutions including most Ethernet / IP handheld test sets and JDSU’s QT-600 monitoring probes.

A failover bypass circuit ensures links never go down if a power outage occurs. Ensuring that’s a remote possibility, the units feature 3-way redundant power with instantaneous switching between twin 48VDC and AC-powered feeds.

Link redundancy is provided by 1+1 protected uplinks (optical or copper pairs) with ultra fast-failover, LAG & LACP support.

PAA, TWAMP & SOAM Complete, Standards-Based Performance Monitoring Accedian closely follows standards as they emerge, bringing best-in-class tools to communications service providers as soon as technology enables it. PAA™ is no exception. Based on a combination of Ethernet Service OAM (Y.1731, 802.3ah, 802.1ag), and Two-Way Active Measurement Protocol (TWAMP, RFC-5357), PAA fuses the best of each standard into a single technique.

Accedian solutions also support the complete implementation of native SOAM and TWAMP, with proven interoperability in over 350 multi-vendor networks worldwide.