Avaya VoIP Monitoring Manager Reference Release 3.1 Manual de usuario descargar pdf (Pagina 91)

Avaya VoIP Monitoring Manager Reference

TTL Considerations

For a number of reasons, packets may not get delivered to their destination in a reasonable

length of time. For example, a combination of incorrect routing tables could cause a packet to

loop endlessly. A solution is to discard the packet after the packet has been forwarded a certain

number of times and send a message to the originator, who decides whether to resend the

packet.

The initial TTL value is set, usually by a system default, in a field of the IP packet header with a

value in the range 0 to 255. The original idea of TTL was that it would specify a certain time span

in seconds that, when exhausted, would cause the packet to be discarded.

Since each router is required to subtract at least one count from the TTL field, the count usually

indicates the number of router hops the packet has remaining before it must be discarded. Each

router that receives a packet subtracts one from the count in the TTL field. When the count

reaches zero, the router detecting it discards the packet and sends an Internet Control Message

Protocol (ICMP) message back to the originating host.

VoIP Monitoring Manager reports the TTL value detected by the endpoint for each RTP packet it

receives.

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Avaya VoIP Monitoring Manager Reference Release 3.1 Manual de usuario Pagina 91