Fabric Link Services

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R_CTL of request is 0x02, R_CTL of reply is 0x03. TYPE is 0x22

ELP Exchange Link Parameters switches exchange R_A_TOV, E_D_TOV, credits, MTU, etc. Following ELP LR is sent and responded to with LRR, then IDLE’s are exchanged. Sent from 0xFFFFFD (fabric controller) of one switch to the fabric controller of the neighbor switch. Responsible for exchanging parameters such as supported classes of service, FCTimers, and BB_Credits.

ESC Exchange Switch Capabilities selects a routing protocol (FSPF), also determines if we are talking to a Cisco switch.

Optional authentication happens between ESC and EFP. After this the ISL is ready to be used.

EPP Exchange Peer Parameters. Exchange trunk and VSAN lists. Cisco only.

EFP Exchange Fabric Parameters. Performs principal switch selection. Contains information about the principal switch and the list of assigned domains

DIA principal elected, upstream neighbor assigned domain ID

RDI used to request domain ID from principal switch


Domain ID Assignment
A switch that has been assigned a Domain ID sends to its neighbors a Domain ID Assigned SW_ILS (DIA).
A switch cannot request a Domain ID, until it has received a DIA on its upstream ISL port. Once it does receive a DIA, it then sends a Request Domain ID SW_ILS (RDI) on its upstream ISL port.
When the principal switch receives the RDI it responds with a Domain ID assignment in the response to the RDI.
When a non-principal switch receives an RDI, it relays it toward the principal switch. The same goes with the reply from the principal switch to the RDI, it is relayed to the originator of the RDI request.
Every time a principal switch assigns a Domain ID, it floods an EFP containing the new Domain ID list.
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