We’ve been adding some more peering sessions to improve our network redundancy. We already had direct peering with every significant UK ISP, we’ve now enhanced this so that one peering session terminates at one of the Telehouse sites, and the second terminates at one of the Telecity or Equinix sites. Each peering session is on a different London Internet Exchange (LINX) network which are physically separate from each other, and where possible we’ve preferred peering sessions that remain within a single building.
We have equal capacity on both networks at LINX, so unlike many ISPs with a single peering port or unequal capacity, in the event of a severe failure (e.g. a whole network or data centre) we just automatically migrate our traffic to our other peering link, rather than falling back to burst bandwidth with our transit providers. We feel that’s a risky strategy because failures are likely to be correlated, lots of ISPs will fall back to transit all at the same time in a badly planned and uncoordinated fashion which could cause a huge traffic spike upstream.
We light our own fibre ring around our core Docklands data centres, and have full transit and peering at both of our core POPs, with dual routers in each, and can offer full or partial transit at any of our data centres.