Network Nightmares! How TCP really works: MTU vs MSS

Network Nightmares! How TCP really works: MTU vs MSS

Wireshark TCP Deep Dive continues: You need to understand this – whats the difference between Maximum Transmission Unit (MTU) vs Maximum Segment Size (MSS).

// MENU //
00:00 ▶️ Coming Up
00:25 ▶️ Intro
00:32 ▶️ Chris introduction
00:47 ▶️ Topic: Maximum Segment Size (MSS)
01:27 ▶️ Explaining Maximum Transmission Unit (MTU)
08:42 ▶️ Interface layout
10:25 ▶️ David Bombal “War Story”
12:00 ▶️ Wireshark demo
13:26 ▶️ Increasing the MTU on your device for larger connections
16:27 ▶️ Difference between MTU and MSS
19:36 ▶️ Wireshark demo (cont’d)
24:58 ▶️ Using Path MTU Discovery
27:02 ▶️ Ping and Wireshark demo
33:32 ▶️ Cool trick for Mac system
35:08 ▶️ TCP/MSS Clamping
38:21 ▶️ Chris Greer “War Story”
51:09 ▶️ What happens if you can’t capture a server
55:08 ▶️ MSS Adjustment commands
56:55 ▶️ Tunnel Path MTU Discovery
57:40 ▶️ Figuring out 1432
01:02:52 ▶️ Conclusion
01:04:48 ▶️ “Cool features” in Wireshark

Previous video: https://youtu.be/rmFX1V49K8U

// Wireshark PCAP files //
MTU PCAP: https://github.com/packetpioneer/youtube/blob/main/PMTUD.pcapng
War Story PCAP Client: https://github.com/packetpioneer/youtube/blob/main/slowfile-clientside.pcapng
War Story PCAP Server: https://github.com/packetpioneer/youtube/blob/main/slowfile-serverside.pcapng
Special “Thumbs Up” and “Subscribe” PCAP: https://github.com/packetpioneer/youtube/blob/main/tcp-streamexport.pcapng

// VLAD SOCIAL //
Twitter: https://twitter.com/Packet_vlad
PMTUD Blog: http://www.packettrain.net/2016/09/21/pmtud-or-not/
Thanks Vladimir Gerasimov!

// GOOD READING //
Network Implications of PMTUD: https://www.ipspace.net/kb/Internet/PMTUD/30-network-implications.html
Path MTU Discovery: https://www.ipspace.net/kb/Internet/PMTUD/20-mtu-discovery.html
Resolve IPv4 Fragmentation, MTU, MSS, and PMTUD Issues with GRE and IPsec: https://www.ipspace.net/kb/Internet/PMTUD/20-mtu-discovery.html
Configuring TCP MSS Adjustment: https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst3650/software/release/16-9/configuration_guide/ip/b_169_ip_3650_cg/configuring_tcp_mss_adjustment.pdf
Ethernet MTU and TCP MSS Adjustment Concept for PPPoE Connections: https://www.cisco.com/c/en/us/support/docs/ip/transmission-control-protocol-tcp/200932-Ethernet-MTU-and-TCP-MSS-Adjustment-Conc.html

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// David SOCIAL //

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// Chris SOCIAL //
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