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Traceroute and Request time out

Why do i receive request time out in the middle of a traceroute.. what does that means

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Accepted Solutions
Hall of Fame Super Silver

Re: Traceroute and Request time out

Meenakshi

I believe that a different explanation is more likely the cause of your issue. If your source IP address is not permitted at certain hops as suggested by Jong, then how does the traffic get past those hops without being dropped?

To explain what is happening we should start by reviewing how traceroute works. Traceroute sends packets to find the path through the network to the destination. Traceroute manipulates the TTL of the packet. The first set of probe packets has TTL set to 1. And so at the first hop the TTL expires, the first hop router discards the packet and generates an ICMP error message. This ICMP error message is what identifies the address of the first hop. Traceroute receives the ICMP error or if it does not receive the ICMP error message then Traceroute has a timeout. Then traceroute increments the TTL and sends packets with TTL of 2. The packet gets to the second hop where it expires and the second hop generates an ICMP error message. The error message identifies the second hop in the path. Traceroute continues to increment the TTL and to look for the ICMP error messages to identify the hop until the packet reaches the destination or until the traceroute gets to the max number of hops.

If some hops along the path do not send the ICMP error message then this is what generates the timeout in traceroute. Some providers configure their routers to not generate the ICMP error message because of a security concern and the desire to not provide identifying information about their public routers. I believe that this is a much more likely reason for some timeouts along the way in your traceroute.

HTH

Rick

4 REPLIES
New Member

Re: Traceroute and Request time out

If the traceroute's completed. It could be your source ip address is not permitted on that particular hops to send/received ICMP packets.

Regards,

Jong

Hall of Fame Super Silver

Re: Traceroute and Request time out

Meenakshi

I believe that a different explanation is more likely the cause of your issue. If your source IP address is not permitted at certain hops as suggested by Jong, then how does the traffic get past those hops without being dropped?

To explain what is happening we should start by reviewing how traceroute works. Traceroute sends packets to find the path through the network to the destination. Traceroute manipulates the TTL of the packet. The first set of probe packets has TTL set to 1. And so at the first hop the TTL expires, the first hop router discards the packet and generates an ICMP error message. This ICMP error message is what identifies the address of the first hop. Traceroute receives the ICMP error or if it does not receive the ICMP error message then Traceroute has a timeout. Then traceroute increments the TTL and sends packets with TTL of 2. The packet gets to the second hop where it expires and the second hop generates an ICMP error message. The error message identifies the second hop in the path. Traceroute continues to increment the TTL and to look for the ICMP error messages to identify the hop until the packet reaches the destination or until the traceroute gets to the max number of hops.

If some hops along the path do not send the ICMP error message then this is what generates the timeout in traceroute. Some providers configure their routers to not generate the ICMP error message because of a security concern and the desire to not provide identifying information about their public routers. I believe that this is a much more likely reason for some timeouts along the way in your traceroute.

HTH

Rick

New Member

Re: Traceroute and Request time out

Your explanation is exact…thanks..

New Member

Re: Traceroute and Request time out

Hi Rick,

Good explanation.Thanks.

By the way In regular business world how can we get these ISP related issues(Ex:Request time outs) get sorted?

If we assume we have a packet loss at "19th Hop" when sending packets from "Comapany A" router to "Company B" router ;

1.Is that Company A need to contact the ISP and report the failure ?

2.What is the procedure to inform them ? Some of the ISPs are in  different countries and it will be difficult to find at least their technical support email addresses or the Contact numbers ?

3.Can we escalate the issue to Comapny A's ISP provider ?

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