IBM TotalStorage DS300 Best Practices Manual page 33

Queries to an Internet Storage Name Server (iSNS)
The Internet Storage Name Server permits iSCSI targets to register with a
central point. The administrator can set up discovery domains so that when a
host iSCSI initiator queries the central control point for the locations of iSCSI
storage controllers, only the authorized controllers are reported. The iSNS server
can be located by one of the following techniques:
iSCSI initiators multicasting to the iSNS server
setting the iSNS server IP address in the DHCP server
setting the iSNS server IP address in the SLP server (see below)
setting the iSNS server IP address in the iSCSI initiator or target
Service Location Protocol (SLP)
The Service Location Protocol can be used to locate iSCSI target devices. SLP
operates with three agents:
User agent (UA) - works on the client (iSCSI initiator) to help establish contact
with a service (iSCSI target). It does this be retrieving information from
service agents (SA) or directory agents (DA).
Service agent (SA) - runs on the iSCSI target device to advertise the service
and its capabilities.
Directory agent (DA) - collects service advertisements from the iSCSI targets.
Starting iSCSI (iSCSI login)
The purpose of login is to establish a TCP connection for iSCSI to use. This
process authenticates the iSCSI end stations. The session parameters are set
and a security protocol association is created. A TCP connection is mapped to
an iSCSI session. iSCSI connections use layer 5 (session layer) of the OSI seven
layer reference model. See Figure 2-2.
Application
Presentation
Session
Transport
Network
Data Link
Physical
Figure 2-2 Seven layers of the OSI reference model
Chapter 2. iSCSI overview
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