QUOTE(nonamer @ Jun 21 2024, 07:56 AM)
if telco does not show mpls routing, do u think ttl is enabled in their mpls network?
Sorry man, I think my brain is having some problem. I still don't quite get your question.
If your question is "Is the hop count accurate if your telco don't use MPLS?"
The answer is most probably not. When your packet crosses to another AS, that AS might very well use MPLS / SRv6 in their network. This is a common deployment pattern used by a lot of service provider called "BGP-Free Core".
The implementation can be straight MPLS, Control-plane using MPLS with data-plane using SRv6, or straight SRv6, but the concept is still the same, with the same implication.
If your question is "Telco use MPLS routing, but you do not know if you are crossing a MPLS segment, which TTL is used?"
MPLS header has a TTL field. If it crosses the MPLS segment, the TTL field in the MPLS packet will be reduced. But your packet is never processed because it is the payload inside the MPLS packet.
Once the packet exit the MPLS tunnel, then processing of your packet from subsequent routing decision will reduce the TTL from your packet. Of course this also applies when the packet leave your device because MPLS tunnel don't exist in your home network.
QUOTE(Oltromen Ripot @ Jun 21 2024, 11:35 AM)
i'm interrupting here. i've never dealt with MPLS before.
but what i understand is every gateway router passed along will reduce TTL inside packet by 1. else stale packet will never age and will never get removed. imagine packets from the original 1970s network still bouncing around because TTL never reach 0.
it make sense that a packet outside whatever-kind-of-tunnel will get TTL reduced as it hops by each gateway router.
it also makes sense for a packet inside whatever-kind-of-tunnel get not get modified by MITM gateway routers in-between, but only by the ingress and egress devices of that the tunnel.
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website is generally at application leyer. OSI 7.
unless the webserver is built ground up to access and retrieve the test packets all the way from layer 3 where TTL is, it is correct to assume that whatever hop information is unreliable and at best only a guess. plus, on an IP network, back-to-back packets don't have to travel on same route to same destination. you can see the effect by repeating traceroutes again and again to distant targets.
Hello there, great to see you chime in. What you said is correct. Layer 3 packet don't carry routing information. You are also correct about routing being asymmetric on the Internet so whatever information gather from Layer 3 then becomes irrelevant..