MACsec terminology

Figure 1 illustrates some of the main concepts used in MACsec for the static-CAK scenario.

Figure 1. MACsec concepts for static-CAK

Table 1 describes the MACsec terminology.

Table 1. MACsec terms
MACsec term	Description
CA: Connectivity Association	A security relationship, established and maintained by key agreement protocols (MKA), that comprises a fully-connected subset of the service access points in stations attached to a single LAN that are to be supported by MACsec.
MKA: MACsec Key Agreement Protocol	Control protocol between MACsec peers, which is used for peer aliveness and encryption key distribution. MACsec Key Agreement is responsible for discovering, authenticating, and authorizing the potential participants in a CA.
SecY: MAC Security Entity	Operates the MAC Security protocol within a system. Manages and identifies the SC and the corresponding active SA.
SC: Security Channel	SC provides a unidirectional point-to-point or point-to-multipoint communication. Each SC contains a succession of SAs and each SC has a different SAK.
SA: Security Association	In the cases of SR OS 2 SA per SC, each with a different SAK, each SC comprises a succession of SAs. Each SA is identified by the SC identifier, concatenated with a two-bit association number. The Secure Association Identifier (SAI), therefore created, allows the receiving SecY to identify the SA, and therefore the SAK used to decrypt and authenticate the received frame. The AN, and therefore the SAI, is only unique for the SAs that can be used or recorded by participating SecYs at any instant. MACsec Key Agreement is responsible for creating and distributing SAKs to each of the SecYs in a CA. This key creation and distribution is independent of the cryptographic operation of each of the SecYs. The decision to replace one SA with its successor is made by the SecY that transmits using the SC, after MACsec Key Agreement has informed it that all the other SecYs are prepared to receive using that SA. No notification, other than receipt of a secured frame with a different SAI is sent to the receiver. A SecY must always be capable of storing SAKs for two SAs for each inbound SC, and of swapping from one SA to another without notice. Certain LAN technologies can reorder frames of different priority, so reception of frames on a single SC can use interleaved SA.
SAK: Security Association Key	SAK is the encryption key used to encrypt the data path of MACsec.