Nortel VoIP Gateway, Configuration Manual

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Norstar VoIP Gateway Configuration Guide
Appendix D
Network performance utilities
There are two common network utilities, Ping and Traceroute. These utilities provide a method to
measure quality of service parameters. Other utilities used also find more information about VoIP
Gateway network performance.
This section also describes the Sniffer utility.
• Ping
• Traceroute
• Sniffer
Ping
Ping (Packet InterNet Groper) sends an ICMP (Internet Control Message Protocol) echo request
message to a host. It also expects an ICMP echo reply, which allows for the measurement of a
round trip time to a selected host. By sending repeated ICMP echo request messages, percent
packet loss for a route can be measured.
Traceroute
Traceroute uses the IP TTL (time-to-live) field to determine router hops to a specific IP address. A
router must not forward an IP packet with a TTL field of 0 or 1. Instead, a router discards the
packet and returns to the originating IP address an ICMP
time exceeded
message.
Traceroute sends an IP datagram with a TTL of 1 to the selected destination host. The first router
to handle the datagram sends back a
time exceeded
message. This message identifies the first
router on the route. Then Traceroute transmits a datagram with a TTL of 2.
Following, the second router on the route returns a
time exceeded
message until all hops are
identified. The Traceroute IP datagram has a UDP Port number not likely to be in use at the
destination (normally > 30,000). The destination returns a
port unreachable
ICMP packet.
The destination host is identified.
Traceroute
is used to measure round trip times to all hops along a route, identifying bottlenecks
in the network.
Note:
Because data network conditions can vary at different times, collect performance
data over at least a 24-hour time period.