IBM Tape Solutions for Storage Area Networks and FICON

8 IBM Tape Solutions for Storage Area Networks and FICON

򐂰 Introduction to Storage Area Networks, SG24-5470

򐂰 Designing an IBM Storage Area Network, SG24-5758

򐂰 IBM SAN Survival Guide, SG24-6143

1.4.1 Fibre Channel

Today, Fibre Channel is well established in the open systems environment as the underlining

architecture of the SAN. Fibre Channel is a technology standard that allows data to be

transferred from one network node to another at very high speed. Current implementations

transfer data at 100 MB/sec or 200 MB/sec. However, 400 MB/sec data rates have already

been tested, and products for 1 GB/s are being planned. This standard is backed by a

consortium of leading vendors and is accredited by the American National Standards Institute

(ANSI).

Fibre Channel is structured with independent layers, as are other networking protocols. There

are five layers, where 0 is the lowest layer. The physical layers are 0 to 2. These layers carry

the physical attributes of the network and transport the data created by the higher level

protocols, such as SCSI, TCP/IP, or FICON.

As you can see in Figure 1-4, these protocols can use the two top layers (the session and

transport layers) to move data segments. These segments are then rolled into a packet,

which in turn, are rolled into a frame. The originator creates the frame and sends it to the

destination, which unravels the frame back to a segment. The SCSI protocol is extended to

SCSI-3 to allow the protocol to travel across the Fibre Channel hardware layers.

Figure 1-4 Fibre Channel protocol layers

1.4.2 SAN topologies

Fibre Channel-based networks support three types of topologies:

򐂰 Point-to-point

򐂰 Loop (arbitrated)

򐂰 Switched

These can be implemented separately or interconnected to form a

fabric. The fabric can also

be extended to cover even greater distances. Currently, the distance limitation for

Note: The spelling of the word fibre in Fibre Channel. This is done because the

interconnections between nodes are not necessarily based on fiber optics, but can also be

based on copper cables.

Fibre Channel

physical layers

0 Physical Layer

2 Network Layer

4 Session Layer

3 Transport Layer

1 Data Link Layer

TCP/IP, SCSI, ...

SegmentTH

PacketNH

FrameDLH