HopTrace: Visual Traceroute for Android

When a website is slow or unreachable, the problem could be anywhere between your phone and the server. Traceroute narrows it down by measuring the network path hop by hop. HopTrace is an Android app that runs traceroute and displays the results visually, making it easy to spot where latency spikes or packet loss occurs.

How Traceroute Works

Traceroute exploits the IP TTL (Time to Live) field. Every IP packet has a TTL that decrements at each router. When TTL reaches zero, the router drops the packet and sends back an ICMP "Time Exceeded" message. Traceroute sends packets with increasing TTL values — TTL=1, TTL=2, TTL=3, and so on. Each router along the path responds when its TTL reaches zero, revealing its IP address and the round-trip time to that point.

The result is a map of the path: your packet goes through your home router, your ISP's edge router, a transit network, several backbone routers, and finally the destination's network before reaching the server.

Reading HopTrace Output

Each row in the traceroute output is a hop — one router in the path. The columns show:

• Hop number — the TTL at which this router responded
• IP address — the router's address (private IPs like 192.168.x.x are your local network)
• Hostname — reverse DNS lookup on the IP (often reveals the ISP or organisation)
• RTT (Round Trip Time) — how long the packet took to reach that router and come back, in milliseconds
• Packet loss — the percentage of probes that got no response from this hop

What to Look For

Latency spikes: if RTT jumps significantly at a particular hop, the bottleneck is likely at or just before that point. A jump from 20ms to 120ms at a transit router suggests congestion or a slow international link.

Asterisks (***): some routers don't respond to ICMP probes — they're configured to silently drop them. This doesn't necessarily mean a problem; the packet may still pass through. If the hops after the *** are responsive, the silent hop is just rate-limiting ICMP.

Packet loss at the final hop: if the destination has high packet loss but intermediate hops don't, the server itself may be overloaded or blocking ICMP.

Latency Graph

HopTrace's live latency graph shows RTT over time for each hop. This is useful for distinguishing intermittent problems (spikes that come and go) from consistent degradation (RTT slowly climbing). A router that shows occasional high RTT is rate-limiting ICMP — not actually congested. Consistent high RTT or loss is the more meaningful signal.

Download HopTrace from Google Play — free network path tracing for Android.