Patton electronics 3095, Справочное руководство администратора, Страница: 101 / 200

ICMP Receive/Send Messages window 99
mDSL DACS Administrators’ Reference Guide 13 • ICMP
Total Sent [imcpOutMsgs]
Similar to icmpInMsgs, Total Sent represents the total number of ICMP messages which the 3095 has
attempted to send. This variable includes all ICMP messages counted by icmpOutErrors (see “w/Errors (icmp-
InErrors, icmpOutErrors)”).
w/Errors (icmpInErrors, icmpOutErrors)
The number of ICMP messages which the Model 3095 received/sent but having ICMP-specific errors (for
example, bad ICMP checksums, bad length, or non-routable errors).
Destinations Unreachable (IcmpInDestUnreachs, IcmpOutDestUnreachs)
The number of ICMP destination unreachable messages received/sent. For instance, if the information in a
gateway’s routing table determines that the network specified in a packet is unreachable, the gateway will send
back an ICMP message stating that the network is unreachable. The following conditions will send back an
unreachable message:
• The network is unreachable
• The host is unreachable
• The protocol is not available to the network
• The port on the host is unavailable. a specified source route failed
• A packet must be fragmented (that is, broken up into two or more packets) but the packet was sent anyway
with instructions not to be fragmented.
Times Exceeded (icmpInTimeExcds, icmpOutTimeExcds)
The number of ICMP time exceeded messages received/sent. Each time a packet passes through a gateway, that
gateway reduces the time-to-live (TTL) field by one. The default starting number is defined under the IP sec-
tion. If the gateway processing a packet finds that the TTL field is zero it will discard the packet and send the
ICMP time exceeded message. Time exceeded will also be incremented when a host which is reassembling a
fragmented packet cannot complete the reassembly due to missing packets within its time limit. In this case,
ICMP will discard the packet and send the time exceeded message.
Parameter Problems (icmpInParmProbs, icmpOutParmProbs)
The number of ICMP parameter problem messages received/sent. If while processing a packet, a gateway or
host finds a problem with one or more of the IP header parameters which prohibits further processing, the gat-
way or host will discard the packet and return an ICMP parameter problem message. One potential source of
this problem may be with incorrect or invalid arguments in an option. ICMP sends the parameter problems
message if the gateway or host has discarded the whole packet.
Source Quenchs (icmpInSrcQuenchs, icmpOutSrcQuenchs)
The number of ICMP source quench messages received/sent. A gateway will discard packets if it cannot allo-
cate the resources, such as buffer space, to process the packet. If a gateway discards the packet, it will send an
ICMP source quench message back to the sending device. A host may send this messages if packets arrive too
fast to be processed or if there is network congestion. The source quench message is a request to reduce the rate
at which the source is sending traffic. If the DACS receives a source quench, it will wait for acknowledgement
of all outstanding packets before sending more packets to the remote destination. Then it will begin sending
out packets at an increasing rate until the connection is restored to standard operating conditions.