TCP Packets Retransmission Size Larger than 1460

Parent Previous Next

TCP Packets Retransmission Size Larger than 1460


Filter: (tcp.analysis.retransmission || tcp.analysis.out_of_order) and tcp.len > 1460


Statistic of retransmitted packets which tcp.len > 1460.


For Ethernet, the standard MTU is 1500 bytes (this is the payload size inside the Ethernet frame, not including headers).

Packet Size with MTU 1500


Ethernet Header: 14 bytes

IP Header: 20 bytes (IPv4, without options)

TCP Header: 20 bytes (without options)

Data (payload): Up to 1460 bytes (1500 − 20 − 20)



Common MTU Sizes



Technology / Protocol

Typical MTU (bytes)

Notes

Ethernet (standard)  

1500

Most common MTU on LANs.

Ethernet (with VLAN tag, 802.1Q)

1500 (payload) / 1522 (frame size)

VLAN tag adds 4 bytes but doesn’t change MTU.

Jumbo Frames

9000 (sometimes 9216)  

Used in data centers, storage (iSCSI, NFS). Must be supported end-to-end.

PPPoE

1492    

8-byte PPPoE header reduces MTU.

GRE Tunnel    

~1476

GRE adds 24 bytes overhead.

IPSec VPN (ESP in tunnel mode)

~1400–1430

Depends on encryption/auth overhead.

DSL (PPPoE/ATM)    

1492 or lower (e.g., 1454)  

Encapsulation overhead reduces MTU.

Wi-Fi (802.11)      

1500    

Same as Ethernet by default.

Loopback (localhost)  

65535

Typically max possible size.

IPv6 minimum link MTU  

1280

Required by standard, though most use 1500.




Please compare "TCP Packets Retransmission" and "TCP Packets Retransmission Size Larger than 1460" report.

Please verify path MTU between two endpoints if most of transmitted packets are with size larger than 1460.



How to verify path MTU:


Linux / macOS

Use ping with DF flag (-M do) and gradually increase size:


ping -M do -s 1472 <destination>

-M do → don’t fragment

www.traceinside.com