The negotiated Ethernet rate describes the local link's signalling capacity, not the guaranteed data rate of a stream. Protocol overhead, other network links and the remote source can reduce useful throughput. Read the number in context.
Check unexpected negotiation
A gigabit-capable pair connecting at a lower rate can justify checking cable quality, port specifications and supported settings. Do not force mismatched speed or duplex values without vendor guidance; automatic negotiation is the normal baseline for many devices.
Keep the wider path in view
A healthy gigabit link cannot exceed a slower internet service or unavailable media server. Equally, a stable lower-rate link can be sufficient for a particular stream. Compare actual demand rather than assuming that every video needs the largest rate.
Use the information diagnostically
Record the negotiated rate alongside playback symptoms and a known-cable comparison. That gives support a concrete local observation. A screenshot of the rate alone does not prove the service can sustain that speed end to end.
