Random, malformed frames of data that are sent continuously by failed circuitry in a networking component. A network interface card (NIC) or other device that is jabbering generates a continuous stream of unwanted signals that can disrupt communication between other devices on the network. This is especially common on Ethernet networks, in which each device must compete for use of the line using the Carrier Sense Multiple Access with Collision Detection (CSMA/CD) contention protocol. When a NIC jabbers on an Ethernet network, all network communication might cease until the offending NIC is replaced. Other causes of jabbering on a network include a faulty NIC, loose cabling, or a poorly grounded cable (for shielded cabling).
The term “jabber” is also used in the Institute of Electrical and Electronic Engineers (IEEE) 802.3 specification for any frame of data that exceeds the maximum frame length for that specification. For Ethernet networks, the maximum frame length is 1518 bytes (18 bytes of overhead and 1500 bytes of payload). A frame longer than 1518 bytes is often called a “jabber frame.” Another name for jabbering is “long packet error.”
Jabbering can also occur in Fast Ethernet networks, in which a combination of 100BaseT4 and 100BaseTX cabling schemes are employed in one network. The continuously generated idle stream signal of the TX network can appear to the T4 network as jabber and can bring down the entire network. This should not be a problem if all network devices implement autonegotiation in an IEEE-compliant fashion. In addition, Fast Ethernet repeaters generally implement jabber control by automatically disconnecting any port that transmits information in streams longer than 40 Kb.
A frame shorter than 64 bytes on an Ethernet network is called a “runt frame.”