---
title: Client connection
summary: null
url: https://www.fastly.com/documentation/reference/vcl/variables/client-connection
---

> **IMPORTANT:** Use of the data exposed by these variables could, in some cases, introduce [ossification risk](https://www.fastly.com/blog/minimizing-ossification-risk-is-everyones-responsibility) to the internet.

- [client.as.name](https://www.fastly.com/documentation/reference/vcl/variables/client-connection/client-as-name/)
- [client.as.number](https://www.fastly.com/documentation/reference/vcl/variables/client-connection/client-as-number/)
- [client.identity](https://www.fastly.com/documentation/reference/vcl/variables/client-connection/client-identity/)
- [client.ip](https://www.fastly.com/documentation/reference/vcl/variables/client-connection/client-ip/)
- [client.port](https://www.fastly.com/documentation/reference/vcl/variables/client-connection/client-port/)
- [client.requests](https://www.fastly.com/documentation/reference/vcl/variables/client-connection/client-requests/)
- [client.socket.congestion_algorithm](https://www.fastly.com/documentation/reference/vcl/variables/client-connection/client-socket-congestion-algorithm/)
- [client.socket.cwnd](https://www.fastly.com/documentation/reference/vcl/variables/client-connection/client-socket-cwnd/)
- [client.socket.nexthop](https://www.fastly.com/documentation/reference/vcl/variables/client-connection/client-socket-nexthop/)
- [client.socket.pace](https://www.fastly.com/documentation/reference/vcl/variables/client-connection/client-socket-pace/)
- [client.socket.ploss](https://www.fastly.com/documentation/reference/vcl/variables/client-connection/client-socket-ploss/)
- [client.socket.tcp_info](https://www.fastly.com/documentation/reference/vcl/variables/client-connection/client-socket-tcp-info/)
- [client.socket.tcpi_advmss](https://www.fastly.com/documentation/reference/vcl/variables/client-connection/client-socket-tcpi-advmss/)
- [client.socket.tcpi_bytes_acked](https://www.fastly.com/documentation/reference/vcl/variables/client-connection/client-socket-tcpi-bytes-acked/)
- [client.socket.tcpi_bytes_received](https://www.fastly.com/documentation/reference/vcl/variables/client-connection/client-socket-tcpi-bytes-received/)
- [client.socket.tcpi_data_segs_in](https://www.fastly.com/documentation/reference/vcl/variables/client-connection/client-socket-tcpi-data-segs-in/)
- [client.socket.tcpi_data_segs_out](https://www.fastly.com/documentation/reference/vcl/variables/client-connection/client-socket-tcpi-data-segs-out/)
- [client.socket.tcpi_delivery_rate](https://www.fastly.com/documentation/reference/vcl/variables/client-connection/client-socket-tcpi-delivery-rate/)
- [client.socket.tcpi_delta_retrans](https://www.fastly.com/documentation/reference/vcl/variables/client-connection/client-socket-tcpi-delta-retrans/)
- [client.socket.tcpi_last_data_sent](https://www.fastly.com/documentation/reference/vcl/variables/client-connection/client-socket-tcpi-last-data-sent/)
- [client.socket.tcpi_max_pacing_rate](https://www.fastly.com/documentation/reference/vcl/variables/client-connection/client-socket-tcpi-max-pacing-rate/)
- [client.socket.tcpi_min_rtt](https://www.fastly.com/documentation/reference/vcl/variables/client-connection/client-socket-tcpi-min-rtt/)
- [client.socket.tcpi_notsent_bytes](https://www.fastly.com/documentation/reference/vcl/variables/client-connection/client-socket-tcpi-notsent-bytes/)
- [client.socket.tcpi_pacing_rate](https://www.fastly.com/documentation/reference/vcl/variables/client-connection/client-socket-tcpi-pacing-rate/)
- [client.socket.tcpi_pmtu](https://www.fastly.com/documentation/reference/vcl/variables/client-connection/client-socket-tcpi-pmtu/)
- [client.socket.tcpi_rcv_mss](https://www.fastly.com/documentation/reference/vcl/variables/client-connection/client-socket-tcpi-rcv-mss/)
- [client.socket.tcpi_rcv_rtt](https://www.fastly.com/documentation/reference/vcl/variables/client-connection/client-socket-tcpi-rcv-rtt/)
- [client.socket.tcpi_rcv_space](https://www.fastly.com/documentation/reference/vcl/variables/client-connection/client-socket-tcpi-rcv-space/)
- [client.socket.tcpi_rcv_ssthresh](https://www.fastly.com/documentation/reference/vcl/variables/client-connection/client-socket-tcpi-rcv-ssthresh/)
- [client.socket.tcpi_reordering](https://www.fastly.com/documentation/reference/vcl/variables/client-connection/client-socket-tcpi-reordering/)
- [client.socket.tcpi_rtt](https://www.fastly.com/documentation/reference/vcl/variables/client-connection/client-socket-tcpi-rtt/)
- [client.socket.tcpi_rttvar](https://www.fastly.com/documentation/reference/vcl/variables/client-connection/client-socket-tcpi-rttvar/)
- [client.socket.tcpi_segs_in](https://www.fastly.com/documentation/reference/vcl/variables/client-connection/client-socket-tcpi-segs-in/)
- [client.socket.tcpi_segs_out](https://www.fastly.com/documentation/reference/vcl/variables/client-connection/client-socket-tcpi-segs-out/)
- [client.socket.tcpi_snd_cwnd](https://www.fastly.com/documentation/reference/vcl/variables/client-connection/client-socket-tcpi-snd-cwnd/)
- [client.socket.tcpi_snd_mss](https://www.fastly.com/documentation/reference/vcl/variables/client-connection/client-socket-tcpi-snd-mss/)
- [client.socket.tcpi_snd_ssthresh](https://www.fastly.com/documentation/reference/vcl/variables/client-connection/client-socket-tcpi-snd-ssthresh/)
- [client.socket.tcpi_total_retrans](https://www.fastly.com/documentation/reference/vcl/variables/client-connection/client-socket-tcpi-total-retrans/)
- [fastly_info.edge.is_tls](https://www.fastly.com/documentation/reference/vcl/variables/client-connection/fastly-info-edge-is-tls/)
- [fastly_info.h2.stream_id](https://www.fastly.com/documentation/reference/vcl/variables/client-connection/fastly-info-h2-stream-id/)
- [fastly_info.is_h2](https://www.fastly.com/documentation/reference/vcl/variables/client-connection/fastly-info-is-h2/)
- [fastly_info.is_h3](https://www.fastly.com/documentation/reference/vcl/variables/client-connection/fastly-info-is-h3/)
- [quic.cc.cwnd](https://www.fastly.com/documentation/reference/vcl/variables/client-connection/quic-cc-cwnd/)
- [quic.cc.ssthresh](https://www.fastly.com/documentation/reference/vcl/variables/client-connection/quic-cc-ssthresh/)
- [quic.num_bytes.received](https://www.fastly.com/documentation/reference/vcl/variables/client-connection/quic-num-bytes-received/)
- [quic.num_bytes.sent](https://www.fastly.com/documentation/reference/vcl/variables/client-connection/quic-num-bytes-sent/)
- [quic.num_packets.ack_received](https://www.fastly.com/documentation/reference/vcl/variables/client-connection/quic-num-packets-ack-received/)
- [quic.num_packets.decryption_failed](https://www.fastly.com/documentation/reference/vcl/variables/client-connection/quic-num-packets-decryption-failed/)
- [quic.num_packets.late_acked](https://www.fastly.com/documentation/reference/vcl/variables/client-connection/quic-num-packets-late-acked/)
- [quic.num_packets.lost](https://www.fastly.com/documentation/reference/vcl/variables/client-connection/quic-num-packets-lost/)
- [quic.num_packets.received](https://www.fastly.com/documentation/reference/vcl/variables/client-connection/quic-num-packets-received/)
- [quic.num_packets.sent](https://www.fastly.com/documentation/reference/vcl/variables/client-connection/quic-num-packets-sent/)
- [quic.rtt.latest](https://www.fastly.com/documentation/reference/vcl/variables/client-connection/quic-rtt-latest/)
- [quic.rtt.minimum](https://www.fastly.com/documentation/reference/vcl/variables/client-connection/quic-rtt-minimum/)
- [quic.rtt.smoothed](https://www.fastly.com/documentation/reference/vcl/variables/client-connection/quic-rtt-smoothed/)
- [quic.rtt.variance](https://www.fastly.com/documentation/reference/vcl/variables/client-connection/quic-rtt-variance/)
- [req.is_ipv6](https://www.fastly.com/documentation/reference/vcl/variables/client-connection/req-is-ipv6/)
- [req.is_ssl](https://www.fastly.com/documentation/reference/vcl/variables/client-connection/req-is-ssl/)
- [req.protocol](https://www.fastly.com/documentation/reference/vcl/variables/client-connection/req-protocol/)
- [tls.client.certificate.dn](https://www.fastly.com/documentation/reference/vcl/variables/client-connection/tls-client-certificate-dn/)
- [tls.client.certificate.is_cert_bad](https://www.fastly.com/documentation/reference/vcl/variables/client-connection/tls-client-certificate-is-cert-bad/)
- [tls.client.certificate.is_cert_expired](https://www.fastly.com/documentation/reference/vcl/variables/client-connection/tls-client-certificate-is-cert-expired/)
- [tls.client.certificate.is_cert_missing](https://www.fastly.com/documentation/reference/vcl/variables/client-connection/tls-client-certificate-is-cert-missing/)
- [tls.client.certificate.is_cert_unknown](https://www.fastly.com/documentation/reference/vcl/variables/client-connection/tls-client-certificate-is-cert-unknown/)
- [tls.client.certificate.is_unknown_ca](https://www.fastly.com/documentation/reference/vcl/variables/client-connection/tls-client-certificate-is-unknown-ca/)
- [tls.client.certificate.is_verified](https://www.fastly.com/documentation/reference/vcl/variables/client-connection/tls-client-certificate-is-verified/)
- [tls.client.certificate.issuer_dn](https://www.fastly.com/documentation/reference/vcl/variables/client-connection/tls-client-certificate-issuer-dn/)
- [tls.client.certificate.not_after](https://www.fastly.com/documentation/reference/vcl/variables/client-connection/tls-client-certificate-not-after/)
- [tls.client.certificate.not_before](https://www.fastly.com/documentation/reference/vcl/variables/client-connection/tls-client-certificate-not-before/)
- [tls.client.certificate.raw_certificate_b64](https://www.fastly.com/documentation/reference/vcl/variables/client-connection/tls-client-certificate-raw-certificate-b64/)
- [tls.client.certificate.serial_number](https://www.fastly.com/documentation/reference/vcl/variables/client-connection/tls-client-certificate-serial-number/)
- [tls.client.cipher](https://www.fastly.com/documentation/reference/vcl/variables/client-connection/tls-client-cipher/)
- [tls.client.ciphers_list](https://www.fastly.com/documentation/reference/vcl/variables/client-connection/tls-client-ciphers-list/)
- [tls.client.ciphers_list_sha](https://www.fastly.com/documentation/reference/vcl/variables/client-connection/tls-client-ciphers-list-sha/)
- [tls.client.ciphers_list_txt](https://www.fastly.com/documentation/reference/vcl/variables/client-connection/tls-client-ciphers-list-txt/)
- [tls.client.ciphers_sha](https://www.fastly.com/documentation/reference/vcl/variables/client-connection/tls-client-ciphers-sha/)
- [tls.client.handshake_sent_bytes](https://www.fastly.com/documentation/reference/vcl/variables/client-connection/tls-client-handshake-sent-bytes/)
- [tls.client.iana_chosen_cipher_id](https://www.fastly.com/documentation/reference/vcl/variables/client-connection/tls-client-iana-chosen-cipher-id/)
- [tls.client.ja3_md5](https://www.fastly.com/documentation/reference/vcl/variables/client-connection/tls-client-ja3-md5/)
- [tls.client.ja4](https://www.fastly.com/documentation/reference/vcl/variables/client-connection/tls-client-ja4/)
- [tls.client.protocol](https://www.fastly.com/documentation/reference/vcl/variables/client-connection/tls-client-protocol/)
- [tls.client.servername](https://www.fastly.com/documentation/reference/vcl/variables/client-connection/tls-client-servername/)
- [tls.client.tlsexts_list](https://www.fastly.com/documentation/reference/vcl/variables/client-connection/tls-client-tlsexts-list/)
- [tls.client.tlsexts_list_sha](https://www.fastly.com/documentation/reference/vcl/variables/client-connection/tls-client-tlsexts-list-sha/)
- [tls.client.tlsexts_list_txt](https://www.fastly.com/documentation/reference/vcl/variables/client-connection/tls-client-tlsexts-list-txt/)
- [tls.client.tlsexts_sha](https://www.fastly.com/documentation/reference/vcl/variables/client-connection/tls-client-tlsexts-sha/)
- [transport.bw_estimate](https://www.fastly.com/documentation/reference/vcl/variables/client-connection/transport-bw-estimate/)
- [transport.type](https://www.fastly.com/documentation/reference/vcl/variables/client-connection/transport-type/)