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<title>iSCSI network</title>
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<h3 id="rzahqnciscinetwork">iSCSI network</h3>
<p>This physical network connects Ethernet iSCSI adapters in the hosting i5/OS™ with Ethernet iSCSI adapters in the hosted system. It is typically
a simple, switched, Gigabit Ethernet network. Two kinds of traffic flow over
this connection: storage (SCSI) and virtual Ethernet (LAN).</p>
<p>On one side of the network is an iSCSI adapter or adapters controlled by i5/OS. Each iSCSI adapter has two IP addresses: one for SCSI and one for
LAN. You configure the IP addresses and other attributes of an adapter in
an i5/OS device description object known as the network server host adapter.
For more information, see <a href="scnwsh.htm#scnwsh">Network server host adapters</a>. Each iSCSI adapter controlled
by i5/OS needs its own object. Every iSCSI adapter contains a TCP/IP stack
implemented in hardware that is independent of the normal i5/OS TCP/IP stack.
When you vary on a network server host adapter, an iSCSI adapter controlled
by i5/OS uses the configured values. If you want different values to take
effect, you must change the configuration and vary on the server host adapter
again. The i5/OS TCP/IP stack is unaware of the IP addresses configured for the
iSCSI adapters.</p>
<p>On the other side of the network is an iSCSI adapter or adapters for the
hosted system. You configure the IP addresses and other attributes of these
adapters in an i5/OS object known as the remote system configuration.
For more information, see <a href="scrmtsys.htm#scrmtsys">Remote system configuration</a>. This configuration differs
from the i5/OS network server adapter object in several ways:</p>
<ul>
<li>You can configure an iSCSI adapter port in a hosted system with 1 or 2
IP addresses: SCSI, LAN, or both. There must be at least one SCSI and one
LAN IP address among all of the configured adapters.</li>
<li>Whenever you configure an IP address for an iSCSI adapter in a hosted
system, you must also configure the corresponding adapter MAC address. Each
adapter has a label that shows its MAC addresses. Be careful to configure
MAC addresses correctly.</li>
<li>You configure all of the iSCSI adapters for a hosted system in the same i5/OS remote system configuration object. When the integrated server is subsequently
varied on, the product automatically ensures that iSCSI adapters in the hosted
system are using values in the i5/OS remote system configuration. If you want
different values to take effect, you must change the configuration and vary
on the server again.</li>
<li>SCSI traffic uses the iSCSI adapter's hardware TCP/IP stack, but
LAN traffic uses the Windows TCP/IP stack. Consequently, the Windows TCP/IP
stack is unaware of the SCSI IP address, but is aware of the LAN IP address.</li></ul>
<a name="wq16"></a>
<div class="notelisttitle" id="wq16">Notes:</div>
<ol type="1">
<li>In i5/OS configuration objects, network interface information is labeled
as local or remote. These terms are relative to i5/OS. Local interface information is for
the i5/OS side. Remote interface information is for the Windows hosted system
side.</li>
<li>The network server host adapter and the remote system configuration define
IP address information for opposite sides of the iSCSI network. When connected
by a simple, switched network, the following rules apply:
<ul>
<li>The SCSI internet addresses in these two objects that are connected by
a switch must be in the same subnet. For example, with IP addresses of the
form a.b.x.y and 255.255.255.0 subnet masks, a.b.x must be the same value
for both objects.</li>
<li>The LAN internet addresses in these two objects that are connected by
a switch must be in the same subnet.</li>
<li>In the network server host adapter, the gateway elements can be any unassigned
IP address in any subnet if you don't have a gateway in your network.</li>
<li>In the remote system configuration, the gateway elements should be blank
if you don't have a gateway in your network.</li></ul></li>
</ol>
<p><span class="bold">DHCP and DHCP relay</span>
<br />There are several
methods for delivering boot information to the hosted system. The default
method of delivering IP and storage information to boot Windows uses an integrated
Dynamic Host Configuration Protocol (DHCP) server on i5/OS side of the
iSCSI network. Even with DHCP, the IP address may be considered static because
the DHCP server associates a single IP address with a MAC address. For more
information, see <a href="rzahqdisklessbootingoveriscsi.htm#rzahqdisklessbootingoveriscsi">Diskless booting over iSCSI</a>.</p>
<p>The integrated DHCP server is designed to coexist with any DHCP servers
that might also be on the iSCSI network.</p>
<p>If the iSCSI networks includes routers between the iSeries™ server and
the hosted system, and the boot information delivery method is DHCP, then
an appropriately configured DHCP relay agent, also known as a BOOTP relay
agent, is required in the network.</p>
<p><span class="bold">Performance and maximum transmission unit (MTU)</span>
<br />High
bandwidth and low latency is desirable for the iSCSI network. Virtual Ethernet
can take advantage of an MTU up to a 9000 byte 'jumbo' frame if the
network supports the larger MTU. This improves virtual Ethernet performance.</p>
<p><span class="bold">Managing i5/OS iSCSI adapter utilization</span>
<br />Paths
configured in the network server description control what storage traffic,
if any, and what virtual Ethernet traffic, if any, can flow over an i5/OS iSCSI adapter.
For more information, see <a href="rzahqmanageiscsihbausage.htm#rzahqmanageiscsihbausage">Manage iSCSI HBA usage</a>.</p>
<p>Multiple hosted systems can use an i5/OS iSCSI adapter simultaneously if multiple
network server descriptions use the same network server host adapter object.</p>
<p><span class="bold">Managing hosted system iSCSI adapter utilization</span>
<br />You
can configure an iSCSI adapter in a hosted system with a SCSI IP address,
a LAN IP address, or both kinds of IP addresses. The presence of a SCSI IP
address enables storage traffic, and the presence of a LAN IP address enables
virtual Ethernet traffic. Each Windows virtual Ethernet adapter is normally
automatically assigned to a physical iSCSI adapter. There is an option on
the advanced properties tab of each virtual Ethernet adapter that allows a
particular physical iSCSI adapter to be selected. See <a href="rzahqmanagiscshbaalocatwin.htm#rzahqmanagiscshbaalocatwin">Manage iSCSI HBA allocation at the Windows side of the iSCSI network</a>.</p>
<p>IBM® does not support the use of the iSCSI adapter as a general purpose
external network connection. For more information on external network connections,
see <a href="rzahqexternallan.htm#rzahqexternallan">External networks</a>.</p>
<p><span class="bold">Other considerations</span>
<br /></p>
<ul>
<li>The iSCSI network only uses Internet Protocol version 4.</li>
<li>The frame format is Ethernet version 2.</li>
<li>The iSCSI network does not support Network Address Translation.</li></ul>
<p><span class="bold">Security</span>
<br />There are several for securing
storage traffic and securing virtual Ethernet traffic. For more information,
see <a href="rzahqsecurity.htm#rzahqsecurity">Security concepts</a>.</p><img src="deltaend.gif" alt="End of change" />
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