Complex sentence: Consider two ISPs, "A" and "B", which each have a presence in New York, connected by a fast link with latency 5 ms; and which each have a presence in London connected by a 5 ms link.
Split into simpler sentences: Consider two ISPs, "A" and "B". Each has a presence in New York, connected by a fast link with latency 5 ms--and each has a presence in London connected by a 5 ms link.