Resilience & Diversity

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Introduction

On Demand connections are based on "unprotected" circuits, which are mesh protected across the Colt metro packet and long distance core network with an unprotected tail between the core network PoP serving the local access link and the customer premises (e.g. an enterprise office). This means that the majority of the service is protected - only the final mile tail is unprotected.

Circuits that are provided between key data centres are routed directly across Colt’s backbone network and are end-end protected by default (i.e. there is no unprotected tail). This also applies to cloud connections where the customer port is in a key data centre.

Circuits are presented on a single interface at the A and B end locations.

At locations that are on-net for Colt (i.e. connected directly to the Colt fibre network), diversity between a pair of On Demand ports can be provided. Diversity is available in all Colt countries in Europe and North America.

Diversity

In Demand ports can be provided with or without physical diversity. Where diversity is requested, the two ports in the diverse pair are provided across two separate fibre paths and equipment. Where requested, the ports can be provided in two physically separate PoP locations within the same building. The two ports in the diverse pair can also be provided in two physically separate buildings.

Diversity is a premium feature which attracts a higher charge on the 1st port in the dual port pair, and any Ethernet, Internet or Cloud connections that are attached to that port.

Customers can build their own topologies as required. For example, a pair of diverse access ports at an A end enterprise building, virtual cloud ports in physically separate cloud on-ramp locations and a pair of circuit connections between the access ports and cloud ports.

Port diversity is requested when a new port is ordered. There are four options:

  1. No Diversity - when a single port without diversity is required
  2. Diverse from existing port - where a new port is required that is diverse from an existing (live) port
  3. Diverse from new port (duplicate) – where two new ports are required, with identical settings (same location, same interface type)
  4. Diverse from new port (different) – where two new ports are required, with different settings (e.g. a different location or interface type)

Please note that diversity is not available on ports in offnet or hybrid on-net locations.

To enable diversity on Ethernet point to point services, port diversity is required at both the A and B end locations (i.e. two "diverse pairs" of ports).  Circuit connections requested between the diverse ports are delivered across Colt's mesh protected core network - so end-end diversity (via the access ports) & resilience (via the mesh protected core) is ultimately achieved.  

Under the Azure Expressroute hosted model, a single ExpressRoute Service Key enables dual/resilient connectivity into Microsoft Azure via Handover into Microsoft Azure dual interconnects (NNIs) at a single data centre PoP. Customers can then choose to request dual On Demand connections from Colt (and benefit from the default resilience offered by Microsoft) or request a single connection. 

Where dual circuit connections are required, they can be presented on On Demand access ports with physical diversity. This provides a high level of end-end resilience (diverse access ports, mesh protected circuits across the Colt core, dual NNIs into Microsoft).

Please note that a single On Demand Azure hosted cloud port supports either one or two circuit connections. A similar configuration can be supported for dedicated ports, based on two separate Azure dedicated cloud ports.  

The ExpressRoute Metro feature, which ensures the Microsoft NNIs used for handover are located in two physically separate data centres is also supported via On Demand.  

Hosted connectivity into Amazon Web Services is based on a single circuit connection by default. 

Customers who want to achieve maximum resilience can request two separate hosted OD cloud ports (at different AWS PoP locations), access ports with diversity and two separate circuit connections. The concept is similar to the Ethernet scenario described above, but here the two AWS PoPs replace the diverse OD access ports at the B end location.   

Connections into Google are based on a single circuit connection, provided with protection across the Colt core network and an unprotected access tail.

Under the On Demand offering, there are three resilience options for Google:

  • Standard single circuit configuration
  • Dual circuit configuration (99.9% Google SLA)
  • 2 x dual circuit configuration (99.99% Google SLA)

The options for the dual circuit configuration (equating to Google’s 99.9% SLA) are illustrated below. Both circuits need to connect to Google Cloud PoPs in the same city (e.g. London).

Note that the VLAN attachment (“pairing key”) should be assigned to Google Cloud PoPs in different zones (e.g. one VLAN attachment assigned to zone 1, the other in zone two).

 

The quad circuit configuration (equating to Google’s 99.99% SLA) is achieved by duplicating the dual circuit configuration.

Coming soon!

Dedicated Internet Access (DIA) connections are based on a single circuit connection by default, which is protected across the Colt core network. 

Similar to Ethernet On Demand services, DIA connections are delivered via an unprotected access tail in enterprise buildings and standard data centres and across a fully protected mesh into key data centres.

At the A end customer premises (data centre or enterprise office), DIA connections can be terminated on On Demand access ports which have diversity enabled - giving a high level of end-end resilience (the only common point of failure is the SAR router providing access to the internet).  SAR router diversity is planned as a future feature.   

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