Where slowness comes from.
WHAT DETERMINES PERCEIVED SPEED
- Bandwidth: how much can be carried
- Latency: how long a round trip takes
- Packet loss: what must be retransmitted
- Jitter: variation in latency
WHAT MATTERS MOST FOR WEB BROWSING
Latency, usually, since a page involves many round trips.
WHAT THAT MEANS
Adding bandwidth beyond a point does not make pages load faster.
WHERE CONGESTION OCCURS
The access link, at peak times Aggregation, where oversubscription bites Interconnection points, where capacity between networks is insufficient International capacity
WHAT CONGESTED INTERCONNECTION LOOKS LIKE
Good performance to some destinations and poor performance to others, at particular times.
WHY THAT IS FREQUENTLY MISDIAGNOSED
It appears as a general slowdown, but affects only paths crossing the congested link.
WHAT BUFFERBLOAT IS
Excessive buffering adding latency under load.
WHAT IT CAUSES
A connection that tests fast but feels slow when anything else is transferring.
WHAT ADDRESSES IT
Modern queue management on the access device.
WHAT TO MEASURE
Latency under load, not only idle speed.
