Fibre Channel SAN

Fibre Channel SAN Notes from Brocade FC Protocol Training.

Fabric: term to describe a generic switching environment, it can consist of one or more interconnected switches (domains).

One Fibre Channel Switch = One Fabric Domain.
Maximum Domains = 239 in a single Fabric based on 24-bit addressing.
Principal Switch: Determine precedence between FC Swithced without adding a separate external. Fabric management software. it facilitates the initialization of the Fabric, and acts as controller of domains.

Switch Ports:
E_port – expansion port, connects 2 FC switches together to make a Fabric.
F_port – Fabric port where N_port attaches.
FL_port – Fabric loop port where NL_Port attaches.

Device Ports:
N_port – port designator for direct fabric attached devices.
NL_port – device that is attached to the loop (seldom used, support for old FC stuff).

FC_ID: 24 Bit Address Space: Dynamically assigned during login.
| Domain ID | Area ID | Node ID |
Domain ID = upper 8 bits, identifies the FC Switch
Area ID = middle 8 bits, identifies port number
Node ID = lower 8 bits, N_Port address

Unique Identification:
-Fixed 64bit value assigned by manufacturer.
-Used in mapping to upper layer protocols.
WWPN: uniquely identify a port (Port_Name).
WWNN: uniquely identify a node (Node_Name).

FC defines two types of login procedures:
Fabric Login (flogi) – After link established, N_Port sends flogi frames to the fabric and receive responses back.

N_Port Login (plogi) – Enable a N_port to communicate with another N_port. Once logged in, it will stay indefinitely.

FC transmits data in frames, defines variable length:
36 bytes of overhead
SOF – 4 bytes
Header – 24 bytes
CRC – 4 bytes
EOF – 4 bytes
Up to 2112 bytes of payload
Optional Header – up to 64 bytes
Data – up to 2048 bytes

FC Layers:
FC-4: Upper layer protocola interface – SCSI, IP, and so on roughly as transport layer in the OSI model.
FC-3: common Services
FC-2: Data delivery – Framing Protocol and Flow Control. Similer to layer 2 of OSI.
FC-1: Encoding – 8b/10b (1,2,4,9 Gb/s) and 64b/66b (10 Gb/s). Link Controls
FC-0: Physical Interface – Media Connectors and Cables.

FC starndards site: http://www.t11.org
FC-FS: Fibre Channel Framing and Signaling Interface
FC-LS: Fibre Channel Link Service
FC-GS: Fibre Channel General Services
FCP: Fibre Channel Protocol for SCSI

FC switches:
Brocade 4900: 4Gb FC
Cisco MDS 9216A: 2Gb and 4Gb FC
Cisco MDS 9222i: 4Gb FC and 1Gb Ethernet

Targets:
EMC Symmetrix
EMC Clariion CX4
IBM DS4700