IBM AIX 7.1 – Common Problem 113 – Diagnosis and Fix

📖 ~1 min read

Table of contents

1. Symptom & Impact
2. Environment & Reproduction
3. Root Cause Analysis
4. Quick Triage
5. Step-by-Step Diagnosis
6. Solution – Primary Fix
7. Solution – Alternative Approaches
8. Verification & Acceptance Criteria
9. Rollback Plan
10. Prevention & Hardening
11. Related Errors & Cross-Refs
12. References & Further Reading

Symptom & Impact

Transfers over WAN saturate well below link capacity on AIX 7.2.

Environment & Reproduction

High latency link with default TCP send/recv space settings.

Root Cause Analysis

Default tcp_sendspace and tcp_recvspace too small for the BDP.

Quick Triage

Capture iperf3 numbers and run no -a to inspect current values.

Step-by-Step Diagnosis

Confirm interface attributes with ifconfig en0 and entstat -d ent0.

Solution – Primary Fix

Raise values with no -p -o tcp_sendspace=262144 -o tcp_recvspace=262144.

Solution – Alternative Approaches

Enable rfc1323 with no -p -o rfc1323=1 if window scaling is required.

Verification & Acceptance Criteria

iperf3 shows expected throughput and netstat -s reports fewer retransmits.

Rollback Plan

Revert with no -d tcp_sendspace and no -d tcp_recvspace if regressions occur.

Prevention & Hardening

Standardize tuning per workload class and snapshot no -L for audits.

Related Errors & Cross-Refs

Pairs with tcp_drop and overflow counters in netstat -s.

Related tutorial: View the step-by-step tutorial for aix-7.1.

View all aix-7.1 tutorials on the Tutorials Hub →

Browse all common problems & solutions on the Tutorials Hub.

References & Further Reading

IBM Docs: ‘no’ command and TCP tunables on AIX 7.2.