TCP info VCL features
Variables that provide TCP information.
- client.socket.tcpi_advmss — The number of bytes advertised in the Maximum Segment Size (MSS) option to the client during connection establishment and therefore the maximum packet size that will be received from the client.
- client.socket.tcpi_bytes_acked — The number of bytes that have been sent to the client on the current connection for which TCP acknowledgments have also been received.
- client.socket.tcpi_bytes_received — The number of bytes that have been received from the client for which TCP acknowledgments have been generated.
- client.socket.tcpi_data_segs_in — The number of packets received from the client on this connection with a positive data length (e.g., pure control packets do not count).
- client.socket.tcpi_data_segs_out — The number of packets sent to the client on this connection with a positive data length (e.g., pure control packets do not count).
- client.socket.tcpi_delivery_rate — The recent effective delivery bandwidth of the connection towards the client in bytes per second.
- client.socket.tcpi_delta_retrans — The number of transmitted packets in the current connection that contained data being retransmitted measured between when this request started and now.
- client.socket.tcpi_last_data_sent — The number of milliseconds between now and the last time data was transmitted to the client on the current connection.
- client.socket.tcpi_max_pacing_rate — The maximum rate, expressed in bytes per second, that the TCP stack will use at any time for sending to the client while using the fq qdisc.
- client.socket.tcpi_min_rtt — The smallest round trip time (RTT) measurement observed on the current connection.
- client.socket.tcpi_notsent_bytes — The number of bytes queued for transmission in the socket buffer that have not yet been written at least once to the client.
- client.socket.tcpi_pacing_rate — The rate, expressed in bytes per second, at which the Fair Queuing queuing discipline (a.k.a., fq qdisc) - used as a default by Fastly - will attempt to evenly send data to the client when not restricted by either the congestion window or the availability of application data.
- client.socket.tcpi_pmtu — The number of bytes the TCP stack believes can be transmitted in one IP packet without fragmentation to the client.
- client.socket.tcpi_rcv_mss — The number of bytes that the kernel believes the client TCP stack is using for its maximum segment size (MSS)sending parameter.
- client.socket.tcpi_rcv_rtt — An estimate of time, in microseconds, that it would take the remote client to exhaust the currently advertised remote receive window (RWIN) if no userspace consumption of that data occurred.
- client.socket.tcpi_rcv_space — The number of received bytes that were transferred to userspace over the previous round trip time (RTT).
- client.socket.tcpi_rcv_ssthresh — The maximum number of bytes currently advertised as the TCP receive window (RWIN) to the client.
- client.socket.tcpi_reordering — The TCP stack's measure of the frequency of packet reordering experienced on the path to the client.
- client.socket.tcpi_rtt — The TCP stack's smoothed round trip time (RTT) estimate, in microseconds, for the current connection to the client.
- client.socket.tcpi_rttvar — The TCP stack's estimate of the smoothed mean deviation of the round trip time samples used in conjunction with the smoothed round trip time for loss detection.
- client.socket.tcpi_segs_in — The number of packets received from the client on this connection including packets containing only control data.
- client.socket.tcpi_segs_out — The number of packets sent to the client on this connection including packets containing only control data.
- client.socket.tcpi_snd_mss — The current maximum segment size (MSS), in bytes, used for transmitting packets in the current TCP connection to the client.
- client.socket.tcpi_snd_ssthresh — The TCP stack's current sending slow start threshold expressed in packets.
- client.socket.tcpi_snd_total_retrans — The number of packets in the current connection that contained data being retransmitted counted across the lifetime of the connection.