IPFYI

High Latency to Specific Geographic Region

Intermediate Performance

Users in a specific geographic region report significantly higher latency compared to users in other regions, even though the target server appears healthy from your local network. The issue affects a subset of users consistently and suggests a routing or peering problem between the affected region and the origin server.

Symptoms

  • ⚠ Round-trip times (RTT) above 200ms for users in a specific country or continent
  • ⚠ Traceroute from the affected region shows unexpectedly long AS path or backhaul routing
  • ⚠ Other regions experience normal latency to the same server
  • ⚠ The problem persists regardless of time of day, ruling out congestion-only causes
  • ⚠ MTR reports consistent latency spike at a specific hop — often an IXP or transit link
  • ⚠ Users closer to the server geographically experience worse latency than distant users

Possible Root Causes

  • • Suboptimal BGP routing: traffic is being sent through a distant transit provider instead of a closer IXP or peering link
  • • Missing CDN or anycast coverage for the affected region, forcing all requests to a geographically distant origin
  • • Cold-potato routing by the upstream ISP or transit provider that does not optimize for user-facing latency
  • • No direct peering between the origin AS and the regional ISPs, forcing traffic through a distant third-party transit
  • • Geographic DNS steering not configured, causing users in the region to resolve to a far-away server

Diagnosis Steps

Step 1 — Baseline from multiple vantage points

Use a looking-glass or online traceroute tool from the affected region. Alternatively, run from a VPS in that region:

# From affected region VPS
mtr --report --report-cycles 20 --no-dns your-server.com
traceroute -n your-server.com

Step 2 — Identify the latency-introducing hop

# Run MTR in report mode to find the problematic AS hop
mtr --report --report-cycles 50 --aslookup your-server.com

# Measure RTT at each hop
ping -c 20 <hop-ip>

Look for a hop where latency jumps by more than 50ms. Note the AS number at that hop.

Step 3 — Identify the BGP path taken

# On a Linux server, check the route your traffic is using
ip route get <destination-ip>

# Query BGP routing tables from route servers (e.g., RIPE RIS)
curl -s "https://stat.ripe.net/data/bgp-state/data.json?resource=<your-server-ip>" | python3 -m json.tool

# Check which ASNs are in the path
whois -h whois.radb.net <hop-ip>

Step 4 — Compare routing with expected path

# Check RIPE RIS for AS path announcements to your prefix
curl -s "https://stat.ripe.net/data/routing-history/data.json?resource=<your-prefix>" | \
  python3 -c "import sys,json; d=json.load(sys.stdin); print(json.dumps(d['data']['by_origin'], indent=2))"

# Run traceroute from multiple global PoPs using tools like:
# https://lg.he.net (Hurricane Electric looking glass)
# https://network-tools.com/tracert/

Step 5 — Check CDN and anycast coverage

# If using a CDN, check which PoP users in the affected region are hitting
curl -sI https://your-domain.com | grep -i 'cf-ray\|x-served-by\|x-cache\|server-timing'

# Verify DNS resolution from the affected region resolves to a nearby CDN PoP
dig +short your-domain.com @8.8.8.8

Step 6 — Measure end-to-end bandwidth to rule out link saturation

# Run iperf3 test from the affected region toward your server
# (requires iperf3 server running on your origin)
iperf3 -c your-server.com -t 30 -P 4

# Check available bandwidth and packet loss
iperf3 -c your-server.com -t 30 --get-server-output

Solution

Option A — Deploy a CDN or anycast node in the affected region

Add a CDN PoP or reverse proxy in or near the affected region. Providers like Cloudflare, Fastly, or AWS CloudFront have edge nodes globally:

# After enabling CDN, verify the edge PoP from the affected region
curl -sI https://your-domain.com | grep -i 'cf-ray\|x-amz-cf-pop\|x-served-by'

Option B — Enable latency-based DNS routing (GeoDNS)

Configure your DNS provider to return different A records based on the client's geographic location:

; Example GeoDNS zonefile fragment
$ORIGIN example.com.
@ 60 IN A 203.0.113.10    ; default (US East)
; Asia-Pacific clients resolved to closer IP
@ 60 IN A 198.51.100.20   ; APAC origin

Use AWS Route 53 Latency Routing or Cloudflare Load Balancer with geographic steering.

Option C — Establish regional peering or upgrade transit

Contact your upstream provider and request a BGP community to prefer local peering:

# Check if your upstream supports BGP communities for path preference
# Example: prepend to de-prefer a slow transit path
# In your router config (Cisco IOS example):
# route-map SET-COMMUNITY permit 10
#   set community 65000:100 additive

Option D — Move or replicate origin infrastructure

If latency is a hard requirement, deploy a regional origin (app server + DB read replica) closer to the affected users.

Verification after fix

# Confirm improved RTT from the affected region
mtr --report --report-cycles 20 your-server.com

# Confirm CDN PoP changed
curl -sI https://your-domain.com | grep -i 'cf-ray\|server'

Prevention

  • Deploy a CDN with global anycast coverage from the start to serve static assets and cache dynamic responses near users
  • Use latency-based DNS routing (GeoDNS) to direct users to the nearest origin or edge node
  • Monitor p95/p99 latency per region using synthetic checks from global PoPs (e.g., Pingdom, Datadog Synthetics)
  • Establish BGP peering at regional IXPs to reduce reliance on expensive and potentially indirect transit paths
  • Set latency SLO alerts per geographic segment so regional degradation is detected before users notice

Related Protocols

TCP UDP ICMP BGP DNS HTTP HTTP2 HTTP3

Related Terms

latency anycast cdn bgp asn traceroute hop internet-exchange peering transit

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