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MTU & MSS Optimizer

Solve fragmentation and PMTUD black holing. Engineered for complex multi-encapsulation overlay networks (VXLAN, IPsec, GRE).

Ingress MTU

Typical: 1500 (Ethernet), 9000 (Jumbo)

Encapsulation Stack

EFFECTIVE MTU
1450
RECOMMENDED MSS
1410
TOTAL OVERHEAD
50B

Packet Segment Visualization

VXLAN
IP/TCP
PAYLOAD (1410 Bytes)
Engineering Recommendation

Configure TCP MSS Clamping on your tunnel endpoints to 1410. This ensures that TCP sessions negotiation stays within the effective MTU, preventing "black hole" routing where ICMP Fragmentation Needed packets are dropped by firewalls.

Partner in Accuracy

"You are our partner in accuracy. If you spot a discrepancy in calculations, a technical typo, or have a field insight to share, don't hesitate to reach out. Your expertise helps us maintain the highest standards of reliability."

Contributors are acknowledged in our technical updates.

Technical Standards & References

REF [RFC-879]
Jon Postel (1983)
The TCP Maximum Segment Size and Related Topics
“Defines the fundamental relationship between MTU and TCP MSS.”
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REF [RFC-1191]
J. Mogul, S. Deering (1990)
Path MTU Discovery
“The primary mechanism for dynamically discovering the minimum MTU along a network path.”
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REF [RFC-7348]
M. Mahalingam et al. (2014)
Virtual eXtensible Local Area Network (VXLAN)
“Specifies the 50-byte overhead required for VXLAN encapsulation.”
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Mathematical models derived from standard engineering protocols. Not for human safety critical systems without redundant validation.

Understanding MTU & Fragmentation

Maximum Transmission Unit (MTU) defines the largest packet size that can traverse a network path without fragmentation. In overlay networks with multiple encapsulation layers (VXLAN, IPsec, GRE), improper MTU configuration leads to silent packet drops and degraded performance.

Technical Standards & References

REF [RFC-1191]
J. Mogul, S. Deering (1990)
Path MTU Discovery
“The foundational standard for PMTUD and ICMP-driven MTU discovery.”
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REF [RFC-4821]
M. Mathis, J. Heffner (2007)
Packetization Layer Path MTU Discovery
“Modern alternative to ICMP-based PMTUD, often used in restricted environments.”
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REF [GRE-IPSEC]
Cisco Systems (2023)
IPsec Overhead and Fragmentation Analysis
“Detailed breakdown of header overheads for GRE, IPsec, and DMVPN tunnels.”
Mathematical models derived from standard engineering protocols. Not for human safety critical systems without redundant validation.

Related Engineering Resources

Partner in Accuracy

"You are our partner in accuracy. If you spot a discrepancy in calculations, a technical typo, or have a field insight to share, don't hesitate to reach out. Your expertise helps us maintain the highest standards of reliability."

Contributors are acknowledged in our technical updates.