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Path measurement: Difference between revisions
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#:This message box appears if flows have been identified for which not a single packet could be seen on both sides. Usually this means that there is some device in between both measurement points that modifies the packet. This can be WAN optimizer which rewrite TCP connection for improved network performance. Such setup is not supported. | #:This message box appears if flows have been identified for which not a single packet could be seen on both sides. Usually this means that there is some device in between both measurement points that modifies the packet. This can be WAN optimizer which rewrite TCP connection for improved network performance. Such setup is not supported. | ||
#: It can also mean that some other packet field is modified at some point in the network. One field that is known for modification is the IP identification field in the IPv4 header. For this case an additional option can be enabled to ignore this field. | #: It can also mean that some other packet field is modified at some point in the network. One field that is known for modification is the IP identification field in the IPv4 header. For this case an additional option can be enabled to ignore this field. | ||
# What does the note '''VLAN tag mismatch detected for matching packets on master and client''' means? | |||
#:This message indicates that matching packets have been seen on both devices but the used VLAN tag is different. Depending on the measurement setup, this may indicate an error as for connection matching the IP addresses, ports, and VLAN tags are used unless the option to ignore the VLAN tag is enabled. Therefore, the identical packets will be accounted for two different connections often resulting in shown packet loss. | |||
#: Often, the recommended solution is to enable the configuration option '''Ignore VLAN tags for connection matching'''. | |||
# What kind of packet information is used to determine latency and packet loss? | # What kind of packet information is used to determine latency and packet loss? | ||
#:Both measurement devices calculate checksums starting from the layer 3 packet data to compare packet information on both sides. This means for IPv4 and IPv6 traffic, the Ethernet header including possible VLAN tags is ignored. For non-IP traffic, the complete layer 2 packet is used so this traffic can only be analyzed in switched networks. | #:Both measurement devices calculate checksums starting from the layer 3 packet data to compare packet information on both sides. This means for IPv4 and IPv6 traffic, the Ethernet header including possible VLAN tags is ignored. For non-IP traffic, the complete layer 2 packet is used so this traffic can only be analyzed in switched networks. | ||