General attributes

Status: Development

The attributes described in this section are not specific to a particular operation but rather generic. They may be used in any Span they apply to. Particular operations may refer to or require some of these attributes.

Server, client and shared network attributes

These attributes may be used to describe the client and server in a connection-based network interaction where there is one side that initiates the connection (the client is the side that initiates the connection). This covers all TCP network interactions since TCP is connection-based and one side initiates the connection (an exception is made for peer-to-peer communication over TCP where the “user-facing” surface of the protocol / API does not expose a clear notion of client and server). This also covers UDP network interactions where one side initiates the interaction, e.g. QUIC (HTTP/3) and DNS.

In an ideal situation, not accounting for proxies, multiple IP addresses or host names, the server.* attributes are the same on the client and server.

Address and port attributes

For all IP-based protocols, the “address” should be just the IP-level address. Protocol-specific parts of an address are split into other attributes (when applicable) such as “port” attributes for TCP and UDP. If such transport-specific information is collected and the attribute name does not already uniquely identify the transport, then setting network.transport is especially encouraged.

Server attributes

Warning Attributes in this section are in use by the HTTP semantic conventions. Once the HTTP semantic conventions are declared stable, changes to the attributes in this section will only be allowed if they do not cause breaking changes to HTTP semantic conventions.

Attributes:

Key	Stability	Requirement Level	Value Type	Description	Example Values
server.address		Recommended	string	Server domain name if available without reverse DNS lookup; otherwise, IP address or Unix domain socket name. [1]	example.com; 10.1.2.80; /tmp/my.sock
server.port		Recommended	int	Server port number. [2]	80; 8080; 443

[1] server.address: When observed from the client side, and when communicating through an intermediary, server.address SHOULD represent the server address behind any intermediaries, for example proxies, if it’s available.

[2] server.port: When observed from the client side, and when communicating through an intermediary, server.port SHOULD represent the server port behind any intermediaries, for example proxies, if it’s available.

server.address and server.port represent logical server name and port. Semantic conventions that refer to these attributes SHOULD specify what these attributes mean in their context.

server.address

For IP-based communication, the name should be a DNS host name of the service. On client side it matches remote service name, on server side, it represents local service name as seen externally on clients.

When connecting to an URL https://example.com/foo, server.address matches "example.com" on both client and server side.

On client side, it’s usually passed in form of URL, connection string, host name, etc. Sometimes host name is only available to instrumentation as a string which may contain DNS name or IP address. server.address SHOULD be set to the available known hostname (e.g., "127.0.0.1" if connecting to an URL https://127.0.0.1/foo).

If only IP address is available, it should be populated on server.address. Reverse DNS lookup SHOULD NOT be used to obtain DNS name.

If network.transport is "pipe", the absolute path to the file representing it should be used as server.address. If there is no such file (e.g., anonymous pipe), the name should explicitly be set to the empty string to distinguish it from the case where the name is just unknown or not covered by the instrumentation.

For Unix domain socket, server.address attribute represents remote endpoint address on the client side and local endpoint address on the server side.

Client attributes

Warning Attributes in this section are in use by the HTTP semantic conventions. Once the HTTP semantic conventions are declared stable, changes to the attributes in this section will only be allowed if they do not cause breaking changes to HTTP semantic conventions.

Attributes:

Key	Stability	Requirement Level	Value Type	Description	Example Values
client.address		Recommended	string	Client address - domain name if available without reverse DNS lookup; otherwise, IP address or Unix domain socket name. [1]	client.example.com; 10.1.2.80; /tmp/my.sock
client.port		Recommended	int	Client port number. [2]	65123

[1] client.address: When observed from the server side, and when communicating through an intermediary, client.address SHOULD represent the client address behind any intermediaries, for example proxies, if it’s available.

[2] client.port: When observed from the server side, and when communicating through an intermediary, client.port SHOULD represent the client port behind any intermediaries, for example proxies, if it’s available.

Source and destination attributes

These attributes may be used to describe the sender and receiver of a network exchange/packet. These should be used when there is no client/server relationship between the two sides, or when that relationship is unknown. This covers low-level network interactions (e.g. packet tracing) where you don’t know if there was a connection or which side initiated it. This also covers unidirectional UDP flows and peer-to-peer communication where the “user-facing” surface of the protocol / API does not expose a clear notion of client and server.

Source

Attributes:

Key	Stability	Requirement Level	Value Type	Description	Example Values
source.address		Recommended	string	Source address - domain name if available without reverse DNS lookup; otherwise, IP address or Unix domain socket name. [1]	source.example.com; 10.1.2.80; /tmp/my.sock
source.port		Recommended	int	Source port number	3389; 2888

[1] source.address: When observed from the destination side, and when communicating through an intermediary, source.address SHOULD represent the source address behind any intermediaries, for example proxies, if it’s available.

Destination

Destination fields capture details about the receiver of a network exchange/packet.

Attributes:

Key	Stability	Requirement Level	Value Type	Description	Example Values
destination.address		Recommended	string	Destination address - domain name if available without reverse DNS lookup; otherwise, IP address or Unix domain socket name. [1]	destination.example.com; 10.1.2.80; /tmp/my.sock
destination.port		Recommended	int	Destination port number	3389; 2888

[1] destination.address: When observed from the source side, and when communicating through an intermediary, destination.address SHOULD represent the destination address behind any intermediaries, for example proxies, if it’s available.

Other network attributes

Warning Attributes in this section are in use by the HTTP semantic conventions. Once the HTTP semantic conventions are declared stable, changes to the attributes in this section will only be allowed if they do not cause breaking changes to HTTP semantic conventions.

Attributes:

Key	Stability	Requirement Level	Value Type	Description	Example Values
network.local.address		Recommended	string	Local address of the network connection - IP address or Unix domain socket name.	10.1.2.80; /tmp/my.sock
network.local.port		Recommended	int	Local port number of the network connection.	65123
network.peer.address		Recommended	string	Peer address of the network connection - IP address or Unix domain socket name.	10.1.2.80; /tmp/my.sock
network.peer.port		Recommended	int	Peer port number of the network connection.	65123
network.protocol.name		Recommended	string	OSI application layer or non-OSI equivalent. [1]	amqp; http; mqtt
network.protocol.version		Recommended	string	The actual version of the protocol used for network communication. [2]	1.1; 2
network.transport		Recommended	string	OSI transport layer or inter-process communication method. [3]	tcp; udp
network.type		Recommended	string	OSI network layer or non-OSI equivalent. [4]	ipv4; ipv6

[1] network.protocol.name: The value SHOULD be normalized to lowercase.

[2] network.protocol.version: If protocol version is subject to negotiation (for example using ALPN), this attribute SHOULD be set to the negotiated version. If the actual protocol version is not known, this attribute SHOULD NOT be set.

[3] network.transport: The value SHOULD be normalized to lowercase.

Consider always setting the transport when setting a port number, since a port number is ambiguous without knowing the transport. For example different processes could be listening on TCP port 12345 and UDP port 12345.

[4] network.type: The value SHOULD be normalized to lowercase.

network.transport has the following list of well-known values. If one of them applies, then the respective value MUST be used; otherwise, a custom value MAY be used.

Value	Description	Stability
pipe	Named or anonymous pipe.
quic	QUIC
tcp	TCP
udp	UDP
unix	Unix domain socket

network.type has the following list of well-known values. If one of them applies, then the respective value MUST be used; otherwise, a custom value MAY be used.

Value	Description	Stability
ipv4	IPv4
ipv6	IPv6

network.peer.* and network.local.* attributes

These attributes identify network peers that are directly connected to each other.

network.peer.address and network.local.address should be IP addresses, Unix domain socket names, or other addresses specific to network type.

Note: Specific structures and methods to obtain socket-level attributes are mentioned here only as examples. Instrumentations would usually use Socket API provided by their environment or sockets implementations.

When connecting using connect(2) (Linux or other POSIX systems / Windows) or bind(2)(Linux or other POSIX systems / Windows) with AF_INET address family, network.peer.address and network.peer.port represent sin_addr and sin_port fields of sockaddr_in structure.

network.peer.address and network.peer.port can be obtained by calling getpeername method (Linux or other POSIX systems / Windows).

network.local.address and network.local.port can be obtained by calling getsockname method (Linux or other POSIX systems / Windows).

Client/server examples using network.peer.*

Note that network.local.* attributes are not included in these examples since they are typically Opt-In.

Simple client/server example

Client/server example with reverse proxy

Client/server example with forward proxy

Network connection and carrier attributes

Attributes:

Key	Stability	Requirement Level	Value Type	Description	Example Values
network.carrier.icc		Recommended	string	The ISO 3166-1 alpha-2 2-character country code associated with the mobile carrier network.	DE
network.carrier.mcc		Recommended	string	The mobile carrier country code.	310
network.carrier.mnc		Recommended	string	The mobile carrier network code.	001
network.carrier.name		Recommended	string	The name of the mobile carrier.	sprint
network.connection.subtype		Recommended	string	This describes more details regarding the connection.type. It may be the type of cell technology connection, but it could be used for describing details about a wifi connection.	LTE
network.connection.type		Recommended	string	The internet connection type.	wifi

network.connection.subtype has the following list of well-known values. If one of them applies, then the respective value MUST be used; otherwise, a custom value MAY be used.

Value	Description	Stability
cdma	CDMA
cdma2000_1xrtt	CDMA2000 1XRTT
edge	EDGE
ehrpd	EHRPD
evdo_0	EVDO Rel. 0
evdo_a	EVDO Rev. A
evdo_b	EVDO Rev. B
gprs	GPRS
gsm	GSM
hsdpa	HSDPA
hspa	HSPA
hspap	HSPAP
hsupa	HSUPA
iden	IDEN
iwlan	IWLAN
lte	LTE
lte_ca	LTE CA
nr	5G NR (New Radio)
nrnsa	5G NRNSA (New Radio Non-Standalone)
td_scdma	TD-SCDMA
umts	UMTS

network.connection.type has the following list of well-known values. If one of them applies, then the respective value MUST be used; otherwise, a custom value MAY be used.

Value	Description	Stability
cell	cell
unavailable	unavailable
unknown	unknown
wifi	wifi
wired	wired

For Unix and pipe, since the connection goes over the file system instead of being directly to a known peer, server.address is the only attribute that usually makes sense (see description of server.address below).

General remote service attributes

This attribute may be used for any operation that accesses some remote service. Users can define what the name of a service is based on their particular semantics in their distributed system. Instrumentations SHOULD provide a way for users to configure this name.

Attributes:

Key	Stability	Requirement Level	Value Type	Description	Example Values
peer.service		Recommended	string	The service.name of the remote service. SHOULD be equal to the actual service.name resource attribute of the remote service if any. [1]	AuthTokenCache

[1] peer.service: Examples of peer.service that users may specify:

• A Redis cache of auth tokens as peer.service="AuthTokenCache".
• A gRPC service rpc.service="io.opentelemetry.AuthService" may be hosted in both a gateway, peer.service="ExternalApiService" and a backend, peer.service="AuthService".

General thread attributes

These attributes may be used for any operation to store information about a thread that started a span.

Attributes:

Key	Stability	Requirement Level	Value Type	Description	Example Values
thread.id		Recommended	int	Current “managed” thread ID (as opposed to OS thread ID). [1]	42
thread.name		Recommended	string	Current thread name. [2]	main

[1] thread.id: Examples of where the value can be extracted from:

[2] thread.name: Examples of where the value can be extracted from:

Source code attributes

Status: Release Candidate

Often a span is closely tied to a certain unit of code that is logically responsible for handling the operation that the span describes (usually the method that starts the span). For an HTTP server span, this would be the function that handles the incoming request, for example. The code attributes allow to report this unit of code and therefore to provide more context.