General Metrics

This article discusses general (i.e. flow) metrics used in Kentik queries.

Notes:
For general metric information, see About Metrics.
For non-flow metrics, see Non-flow Metrics.
For device-specific metrics, see Device-specific Metrics.
Filter and group-by dimensions are covered in Dimensions Reference (see Per-flow Metrics).
Metrics are used for Kentik portal query settings and the Query API.

About General Metrics

In Kentik, general metrics are transmitted via flow protocols like NetFlow or sFlow and aren’t tied to specific devices. Their availability in settings like the Metrics Pane of the Query sidebar in Data Explorer depends on the device category (Router or Host) and the specific device type (see Supported Device Types).

Metrics from All Devices

When a query includes traffic solely from data sources (see About Data Sources) in the "Routers" category, only the following metrics are available:

Metric in portal	Variations	Calculated as...	Derived from KDE column(s)
Bits per second	Sampled at: Ingress and Egress Ingress Egress	Average 95th Percentile 99th Percentile Max Total	in_bytes, out_bytes
Packets per second	Sampled at: Ingress and Egress Ingress Egress	Average 95th Percentile 99th Percentile Max Total	in_pkts, out_pkts
Flows per second	N.A.	Average 95th Percentile 99th Percentile Max Total	Based on rows per KDE main table
Source IPs	Unique Count Bitrate per IP	Average 95th Percentile 99th Percentile Max Total	inet_src_addr
Destination IPs	Unique Count Bitrate per IP	Average 95th Percentile 99th Percentile Max Total	inet_dst_addr
Unique Route Prefixes	Source Destination	Average 95th Percentile 99th Percentile Max Total	inet_src_route_prefix, inet_dst_route_prefix
Unique Ports	Source Destination	Average 95th Percentile 99th Percentile Max Total	inet_src_route_prefix, inet_dst_route_prefix
Unique ASNs	Source Destination Next Hop Destination	Average 95th Percentile 99th Percentile Max Total	src_as, dst_as, i_dst_nexthop_as_name
Unique Countries	Source Destination	Average 95th Percentile 99th Percentile Max Total	src_geo, dst_geo
Unique Regions	Source Destination	Average 95th Percentile 99th Percentile Max Total	src_geo_region, dst_geo_region
Unique Cities	Source Destination	Average 95th Percentile 99th Percentile Max Total	src_geo_city, dst_geo_city
Sample rate	Max Average	Average 95th Percentile 99th Percentile Max Total	sample_rate

Notes:
The “Total” metric is available only when the chart type is set to Table or Matrix (see Chart View Types).
Metrics labeled as "unique" are evaluated across all instances on queried devices within each individual time slice of the query's time range, but not between different time slices (see Table Time-slicing).

Host Traffic Metrics

When querying traffic that includes devices in the "Host" category (using Kentik’s host agent, see About the Universal Agent), the data from these hosts is stored in KDE.

Host Metrics by Protocol

The availability of a given metric varies by protocol:

Metric in portal	TCP	HTTP	DNS	Calculated as...	Derived from KDE column(s)
Retransmits	Per second Repeated per second Percent Percent Repeated	Repeated Retransmits Retransmitted Packets Out	N.A.	Average Percentile (95th or 98th) Max Total	retransmitted_out_pkts, repeated_retransmits, both_pkts (for %)
Out-of-order packets	Per second Percent	Per second (In)	N.A.	Average Percentile (95th or 98th) Max Total	ooorder_in_pkts, ooorder_out_pkts, both_pkts (for %)
Fragments	Per second Percent	Per second	Per second	Average Percentile (95th or 98th) Max Total	fragments, both_pkts (for %)
Zero Windows	Count Percent	Per second	N.A.	Average Percentile (95th or 98th) Max	zero_windows
Receive Window	N.A.	N.A.	N.A.	Average Percentile (95th or 98th) Max	receive_window
Latency	Client Server Application First Payload Exchange	Client Server Application FPEX	Application	Average Percentile (95th or 98th) Max	client_nw_latency_ms, server_nw_latency_ms, appl_latency_ms, fpex_latency_ms

Note: The “Total” metric is available only when the chart type is set to Table or Matrix (see Chart View Types).

Host Metrics Descriptions

The following descriptions apply to the host-only metrics listed in the table above:

Retransmits: Packets re-sent from source to destination, applicable to reliable protocols like TCP.
- Indicates network delivery issues affecting performance.
- Measured per second and as a percentage of all packets sent.
  Note: "Repeated" refers to packets retransmitted 3 or more times.
Out of order: Packets arriving out of sequence.
- High values suggest variability in delivery paths, impacting latency-sensitive traffic like real-time audio/video.
- Measured per second and as a percentage of all packets sent.
Fragments/second: Packets split into smaller packets for network delivery.
- Fragmentation can increase CPU load and cause retransmits if fragments arrive out-of-order.
- Measured per second and as a percentage of all packets sent.
Zero Windows: Count of TCP receive windows with a value of zero, indicating a full buffer.
Receive Window: Size of the TCP receive window.
Latency: Various measures include:
- RTT/2 client latency (derived): One-way latency from the client perspective. High values indicate network or server-side issues
- RTT/2 server latency (derived): One-way latency from the server perspective. High values indicate network or client-side issues.
- RTT/2 application latency (derived): Derived from request/response pairs at the application layer, indicating end-user experience latency. Effective for protocols with clear request/response pairings.
- First Payload Exchange Latency: Measures application response time when the protocol isn't understood or can’t be decoded (e.g., HTTPS, SQL). Excludes TCP setup, starting with the first packet sent and ending with the first packet returned.

Host Metrics KDE Columns

The following table shows the correspondence between the metrics described above and the columns of the Kentik Data Engine (KDE):

Metric in portal	Type: value column	Derived from KDE column(s)
Retransmits	bigint Native	retransmitted_out_pkts, repeated_retransmits, both_pkts (for %)
Out-of-order packets	bigint Native	ooorder_in_pkts, ooorder_out_pkts, both_pkts (for %)
Fragments	bigint Native	fragments, both_pkts (for %)
Zero Windows	bigint Native	zero_windows
Receive Window	bigint Native	receive_window
Latency	bigint Native	client_nw_latency_ms, server_nw_latency_ms, appl_latency_ms, fpex_latency_ms

Application Decodes Metrics

When using Kentik's software host agent for application decodes (see About Application Decodes), both dimensions and metrics are generated and stored in or derived from KDE columns. The metrics available for queries via the metric selector (see Metrics Dialog UI) include:

Metric in portal	Description	Type: value column
Connection Name	TCP connection ID.	bigint UDR
Application Latency	One-way network latency derived by examining request/response pairs at the application layer.	bigint UDR
FPEX Latency	Elapsed time from first packet sent to first packet returned.	bigint UDR

Note: For dimensions related to application decodes, see Application Decodes Dimensions.

Legacy Application Decodes Metrics

The "legacy" metrics in the table below are from older versions (<v1.3.0) of Kentik’s legacy host software agent, kprobe:

Metric in portal	Description	Type: value column	KDE name(s)
Connection ID	TCP connection ID. Note: Superseded by Connection Name.	bigint Native	connection_id
Application Latency (ms)	One-way network latency derived by examining request/response pairs at the application layer.	bigint Native	appl_latency_ms
First Payload Exchange Latency (ms)	Elapsed time from first packet sent to first packet returned. Note: Superseded by FPEX Latency.	bigint Native	fpex_latency_ms

Metric in portal

Description

Type:
value
column

KDE name(s)

Connection ID

TCP connection ID.

Note: Superseded by Connection Name.

bigint
Native

connection_id

Application Latency (ms)

One-way network latency derived by examining request/response pairs at the application layer.

bigint
Native

appl_latency_ms

First Payload Exchange Latency (ms)

Elapsed time from first packet sent to first packet returned.

Note: Superseded by FPEX Latency.

bigint
Native

fpex_latency_ms