4556

IANA assigns TCP port 4556 to dtn-bundle, described as the DTN Bundle TCP convergence-layer protocol. RFC 9174 specifies TCPCLv4, which reliably carries Bundle Protocol version 7 bundles between adjacent DTN entities. The assignment identifies the service associated with the port; it does not show that a particular host runs it or establish whether it belongs on the public internet.

TCPCLv4 transports bundles as opaque data blocks and does not provide peer discovery or bundle routing logic. An implementation may listen passively for connections, but the RFC also allows entities to initiate sessions actively. The supplied evidence therefore does not establish a single expected audience or access policy for deployments.

The RFC describes security mechanisms including TLS and identifies risks such as data exposure, impersonation, denial of service, and transport-security stripping. It calls for TLS support, but a port assignment cannot establish whether a deployed service uses TLS or is securely configured. Restrict access according to the deployment's DTN peer and network policy.

Service

IANA assigns dtn-bundle to TCP port 4556, described as the DTN Bundle TCP convergence-layer protocol. [Confirmed]

Protocol

RFC 9174 specifies TCPCLv4 for reliable transport of BPv7 bundles between adjacent entities. [Confirmed]

Exposure

Unknown. The sources describe protocol behavior but do not establish the intended audience or a deployment's access policy. [Unknown]

Security

The RFC discusses TLS and threats including data leakage, impersonation, and denial of service; actual configuration is unknown. [Confirmed]

Service name

dtn-bundle [Confirmed] — https://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.csv

IANA description

DTN Bundle TCP CL Protocol [Confirmed] — https://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.csv

Protocol reference

RFC 9174

Protocol behavior

TCPCLv4 reliably transports BPv7 bundles between adjacent entities

Exposure policy

Unknown; protocol and registry evidence do not establish deployment audience

IANA assigns UDP port 4556 the service name dtn-bundle for the DTN Bundle UDP Convergence Layer Protocol. RFC 7122 recommends this port for carrying Bundle Protocol traffic over UDP. The assignment and protocol guidance do not show whether any particular host runs or exposes the service, so its public-internet suitability is Unknown.

RFC 7122 describes bundles carried directly in UDP datagrams and Licklider Transmission Protocol segments carried over datagrams. It discourages using the Bundle Protocol over a datagram convergence layer in IP networks when TCP convergence or LTP is feasible. For non-trivial UDP traffic outside an isolated network, implementations must provide congestion control consistent with RFC 5405.

The RFC also warns that receivers may process packets from unknown sources before discovering the DTN endpoint identity, creating a denial-of-service risk. It recommends authentication and, where possible, filtering packet origins. This is an Experimental document; it does not establish deployment, prevalence, or malware use.

Service

IANA registers dtn-bundle for UDP port 4556 as the DTN Bundle UDP Convergence Layer Protocol. [Confirmed] — https://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.csv

Exposure

Unknown; protocol guidance does not establish the intended audience for a particular service instance or justify public access. [Unknown] — https://www.rfc-editor.org/rfc/rfc7122.txt

Risk

RFC 7122 describes denial-of-service risk from high-rate datagrams and recommends authentication and source filtering where possible. [Confirmed] — https://www.rfc-editor.org/rfc/rfc7122.txt

Service name

dtn-bundle [Confirmed] — https://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.csv

Protocol guidance

UDP convergence layer for Bundle Protocol traffic; RFC 7122 says this use is generally discouraged in IP networks and recommends TCP convergence or LTP where possible

Registered description

DTN Bundle UDP CL Protocol [Confirmed] — https://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.csv

Congestion control

For non-trivial UDP traffic outside an isolated network, RFC 7122 requires congestion control consistent with RFC 5405 [Confirmed] — https://www.rfc-editor.org/rfc/rfc7122.txt

Deployment on a particular host

Unknown [Unknown] — https://www.rfc-editor.org/rfc/rfc7122.txt