GEN:SID 1:398
Message ICMP Destination Unreachable Host Unreachable for Type of Service
Summary This event is generated when An ICMP Host Unreachable for Type of Server datagram is detected on the network.  
Impact Routers will generate this message when the requested TOS (Type of Service) is not permitted to transverse the network.  This could be an indication of an improperly configured routing device or a improperly configured host on the network.
Detailed Information This rule generates informational events about the network.  Large numbers of these messages on the network could indication routing problems, faulty routing devices, or improperly configured hosts.
Affected Systems  
Attack Scenarios None Known
Ease of Attack Numerous tools and scripts can generate these types of ICMP datagrams.
Corrective Action This rule detects informational network information, no corrective action is necessary.
Additional References None