IBM Flex System V7000 Expansion Enclosure 4939H29 User Manual

Chapter 11. SAN Connections and Configuration 

Draft Document for Review January 29, 2013 12:52 pm

layer is used to integrate the data with the clock information required by serial 
transmission technologies.

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Framing and signaling protocol: FC-2

– Reliable communications result from Fibre Channel’s FC-2 framing and signaling 

protocol. FC-2 specifies a data transport mechanism that is independent of upper layer 
protocols.

The Upper layer includes two layers: FC-3 and FC-4.

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Common services: FC-3

– FC-3 defines functions that span multiple ports on a single-node or fabric. Functions 

that are currently supported include:

•

 Hunt Groups – A a set of associated N_Ports attached to a single node. This set is 
assigned an alias identifier that allows any frames containing the alias to be routed 
to any available N_Port within the set. This decreases latency in waiting for an 
N_Port to become available.

•

 Striping – Striping is used to multiply bandwidth, using multiple N_Ports in parallel 
to transmit a single information unit across multiple links.

•

Multicast – Multicast delivers a single transmission to multiple destination ports. 
This includes the ability to broadcast to all nodes or a subset of nodes.

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Upper layer protocol mapping (ULP): FC-4

– The highest layer, FC-4, provides the application-specific protocols. Fibre Channel is 

equally adept at transporting both network and channel information and allows both 
protocol types to be concurrently transported over the same physical interface.

A channel protocol example is Fibre Channel Protocol (FCP). This is used to transfer SCSI 
commands and data over Fibre Channel and is commonly used in FC SANs.

Fibre Channel combines the best characteristics of traditional I/O channels with those of 
computer networks:

– High performance for large data transfers by using simple transport protocols and 

extensive hardware assists

– Serial data transmission
– A physical interface with a low error rate definition
– Reliable transmission of data with the ability to guarantee or confirm error free delivery 

of the data

– Packaging data in packets (frames in Fibre Channel terminology)
– Flexibility in terms of the types of information which can be transported in frames (such 

as data, video and audio)

– Use of existing device oriented command sets, such as SCSI and FCP
– A vast expansion in the number of devices which can be addressed when compared to 

I/O interfaces — a theoretical maximum of more than 15 million ports

It is this high degree of flexibility, availability and scalability; the combination of multiple 
protocols at high speeds over long distances; and the broad acceptance of the Fibre Channel 
standards by vendors throughout the IT industry, which makes the Fibre Channel architecture 
ideal for the development of enterprise SANs.

For further information on Fibre Channel layers and SAN networking Introduction to Storage 
Area Networks and System Networking, SG24-5470