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Microsoft Windows Peer - to - Peer networking ❘ 1345<br />

In past releases of PNRP there was a third type of cloud, site local. This is no longer<br />

used <strong>and</strong> is not covered in this chapter.<br />

You can discover what clouds you are connected to with the following comm<strong>and</strong>:<br />

netsh p2p pnrp cloud show list<br />

A typical result is shown in Figure 45 - 5.<br />

figure 45-5<br />

Figure 45 - 5 shows that a single cloud is available, <strong>and</strong> that it is a link local cloud. You can tell this from<br />

both the name <strong>and</strong> the Scope value, which is 3 for link local clouds <strong>and</strong> 1 for global clouds. To connect to a<br />

global cloud you must have a global IPv6 address. The computer used to generate Figure 45 - 5 does not have<br />

one, which is why only a local cloud is available.<br />

Clouds may be in one of the following states:<br />

➤<br />

➤<br />

Active — If the state of a cloud is active , you can use it to publish <strong>and</strong> resolve peer names.<br />

Alone — If the peer you are querying the cloud from is not connected to any other peers, it will have<br />

a state of alone .<br />

➤ No Net — If the peer is not connected to a network, the cloud state may change from active to no net .<br />

➤<br />

➤<br />

Synchronizing — Clouds will be in the synchronizing state when the peer is connecting to them.<br />

This state will change to another state extremely quickly because this connection does not take long,<br />

so you will probably never see a cloud in this state.<br />

Virtual — The PNRP service connects to clouds only as required by peer name registration <strong>and</strong><br />

resolution. If a cloud connection has been inactive for more than 15 minutes it may enter the<br />

virtual state.<br />

If you experience network connectivity problems you should check your fi rewall in<br />

case it is preventing local network traffi c over the UDP ports 3540 or 1900. UDP<br />

port 3540 is used by PNRP, <strong>and</strong> UDP port 1900 is used by the Simple Service<br />

Discovery Protocol (SSDP), which in turn is used by the PNRP service (as well as<br />

UPnP devices).<br />

PnrP in Windows 7<br />

With Windows 7, PNRP makes use of a new component called the Distributed Routing Table (DRT).<br />

This component is responsible for determining the structure of the keys used by PNRP, the default implementation<br />

of which is the PNRP ID previously described. By using the DRT API it is possible to define an<br />

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