METHODOLOGY

Introduction
Data obtained from the sampling is presented in near real-time generated reports which are formatted and presented for viewing on Global Crossing's Network Performance site. The data is also rolled up for the purposes of trending.

Measurements and Implementation
In general, measurements are taken based on a fixed number sample batch of ICMP propagation times. Our measurement methodology uses a polling and collection architecture that can be best described as a full mesh with distributed collector nodes collocated within our hubs. The polling engine for each node is a custom written Global Crossing application.

Latency and Packet Loss are the two significant measures of an Internet Service Provider's backbone performance. These measurements can be used to compare Global Crossing's IP backbone performance with other global providers.

DESCRIPTIONS OF PERFORMANCE MEASUREMENTS

In order for you to understand the performance measurements provided on this site, explanations are provided for the following performance measurements.

Latency
Latency is defined as the average end-to-end roundtrip delay in packet transmission between two IP hubs in the Global Crossing IP backbone network, measured in milliseconds (ms).

Latency can be the result of several different factors. To judge and compare IP backbone performance, one needs a measurement that is not influenced by latencies that are outside of the provider's control. Two factors that are within the ISP's control are routing and congestion.

IP backbone latency can be affected by:

• Transmission latency (the speed of the network circuits)
• Insertion latency (the rate at which routers can forward the packets)
• Queuing latency (the rate at which packets arrive at the router)
• Propagation latency (the time it takes for light to traverse the physical distance between source and destination)

Packet Loss
Packet loss is defined as the inability to deliver packets to their destination due to transmission errors or router overload while on the Global Crossing IP Backbone Network, expressed as a percentage (%) of the total number sent.

Looking Glass Utilities

Monthly Averages
Measurements for the previous calendar months round trip average latency and packet loss are also presented on the site.

• Router to Router Ping - allows you to collect real-time data statistics between any two Global Crossing nodes.
• Router to Host Ping - provides information about a round trip test between a selected Global Crossing node and a specified address or hostname.
• Traceroute - allows you to view all router hops encountered in between a Global Crossing node and a specified address or hostname.
• (Previous Month's) Average Latency - The monthly region or inter-region average round trip latency is the round trip latency averaged over the Global Crossing IP backbone and over all the measurements made in the previous calendar month.
• (Previous Month's) Average Packet Loss - The monthly network-wide average packet loss is the round trip packet loss averaged over the Global Crossing IP backbone and averaged over all the measurements made in the previous calendar month.
• (Current Month's) Average Latency - The monthly region or inter-region average round trip latency is the round trip latency averaged over the Global Crossing IP backbone and over all the measurements made in the current calendar month.
• (Current Month's) Average Packet Loss - The monthly network-wide average packet loss is the round trip packet loss averaged over the Global Crossing IP backbone and averaged over all the measurements made in the current calendar month.