Internet Shadow Service

Nextgen Group’s Internet Shadow Service provides a backup internet connection for service continuity in the event of failure or interruption in the primary link.


For service continuity Nextgen Internet Shadow services provide a backup connection to a primary Nextgen Group Internet service in the event of failure or interruption in the primary link.

We offer:

  • Cost effective alternative to a standard standby service
  • No usage charges when used in a failover mode of operation
  • Can be used with Nextgen Group’s Corporate Internet or Wholesale Internet Transit services
  • Availability on diverse fibre, microwave or SHDSL

Speed and site delivery

Internet Shadow Service can be ordered at a speed equal to or less than the primary service and may be delivered to the primary or an alternative site.

Service availability and failover

Both Nextgen Group’s primary and shadow Internet links are provisioned as always-on to ensure services are available in a ‘customer managed’ failover mode of operation.
The Nextgen Group Shadow Internet Service is commissioned over a permanently active alternative access link from the customer premises to Nextgen Group’s backbone. Border Gateway Protocol (BGP) is required on primary and shadow links and Multi-Exit Discriminators (MEDs) are used to re-route traffic in an outage situation.

Redundant link options

Customers may select from a range of access types to deliver an Internet Shadow Service with a level of route and electronic diversity that compliments the specific characteristics of the primary service access link. Access solution options for Internet Shadow Service includes:

• Nextgen Group’s fibre on a geographically or electronically diverse route

• Nextgen Group supplied fibre from the network or another carrier

• Alternative technology including microwave, SHDSL or high capacity bonded DSL

As part of the sales process, Nextgen Group will discuss the level of redundancy and diversity of access that can be provided to customer sites, on a case by case basis.

Usage charges

Usage fees for Internet Shadow Service are chargeable only if the service is used in situations other than as defined as non-chargeable usage.

Non-chargeable use

Shadow Internet service is offered for use by the customer, without usage charges, in situations of either:

1. Alternative service

‘Alternative service’ usage is where only one of the primary or secondary services is used above ‘test and keep alive traffic’ levels at any given time.

Alternative service use includes instances where the primary service is not available for use. These situations may include customer router failures, cable cuts, electronic faults in the access network and scheduled outages.

2. Test and keep alive traffic

Low usage levels are allowed on the shadow link in support of routine keep-alive and reasonable link availability testing. Any traffic profile where the 98th percentile utilisation of both the upstream and downstream directions is at or below 100kb/s will not incur excess usage charges. This allows for reasonable keep alive and testing traffic, and for example would support:
• Routine short bursts of less than 6 seconds every 5 minutes,


• A 20 minute throughput test every day at the full service rate.

Invoicing process

In the event of Internet Shadow Service usage levels above the permitted ‘test and keep alive traffic’ thresholds, usage charges will apply against the shadow service. We will only invoice you if our analysis reveals that the primary service was simultaneously operational at levels above ‘test and keep alive traffic’ thresholds.

98th percentile measurement

Statistics collected by Nextgen Group will be taken as evidence of actual usage. The measure of traffic utilisation is defined as the number of Ethernet frame bytes traversing the user network interface, as a percentage of the nominal service rate.

To calculate the 98th percentile, the average utilisation is measured every five minutes (8928 samples for a 31 day calendar month). The samples for each direction are sorted into ascending order and the 98th per cent largest sample (that is, sample number 8750 in the ordered list for a 31 day month) is the 98th percentile utilisation. The 98th percentile utilisation for the shadow service is calculated independently in each direction, and the larger of the two values is used as the 98th percentile utilisation for invoicing.

Negotiated test window

As a part of the service acceptance process, a test window period of up to 3 working days is available to customers for pre-production shadow and primary link testing. Traffic flow during the test window must be limited to pre-agreed levels is both down and up directions.

Internet Shadow Service provides protection against the possibility of failures in the access environment. These failures can be attributed, for example, to a cable cut, fault in the Nextgen Group NTU at the customer site or customer router ports.

Designed for use as a standby alternative, rather than an additional service, Nextgen Group’s Internet Shadow Service provides a lower cost redundancy solution compared to a standalone duplicate service.

The Nextgen Group Internet Shadow Service is priced with a low monthly recurring fee and incurs no usage charges when used as a failover alternative to the associated primary service. Shadow services are not available without a corresponding primary service. They can be used with Nextgen Group Corporate Internet or Nextgen Group Wholesale Internet Transit products.