Path MTU – AWS and GCP

Part 3: GCP Architecture Design Considerations

For GCP, it is worth mentioning how fragmentation is handled by the firewall as explained in Google Cloud documentation.

GCP firewall rules do not reassemble fragmented TCP packets. Consequently, a firewall rule applicable to the TCP protocol can only apply to the first fragment because it contains the TCP header. Firewall rules applicable to the TCP protocol do not apply to the subsequent TCP fragments.

This means we need to ensure that the MTU is small enough to allow IP packets traverse end-to-end without fragmentation; and large enough to ensure bandwidth and throughput are optimized. In GCP, this compromise is reached by setting MTU as 1460 bytes as seen in previous sections.


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