Exam 350-401 topic 1 question 70 discussion

The TCP Maximum Segment Size (TCP MSS) defines the maximum amount of data that a host is willing to accept in a single TCP/IP datagram. This TCP/IP datagram might be fragmented at the IP layer. The MSS value is sent as a TCP header option only in TCP SYN segments. Each side of a TCP connection reports its MSS value to the other side. Contrary to popular belief, the MSS value is not negotiated between hosts. The sending host is required to limit the size of data in a single TCP segment to a value less than or equal to the MSS reported by the receiving host. TCP MSS takes care of fragmentation at the two endpoints of a TCP connection, but it does not handle the case where there is a smaller MTU link in the middle between these two endpoints. PMTUD was developed in order to avoid fragmentation in the path between the endpoints. It is used to dynamically determine the lowest MTU along the path from a packet’s source to its destination.

MSS is the TCP setting that can be tuned to minimise fragmentation. MTU is the IP setting that can minimise fragmentation. The question asks for the TCP setting

The TCP Maximum Segment Size (MSS) defines the largest segment of application data that a device can send in a single TCP packet, excluding TCP and IP headers. When using GRE/IP tunnels, the encapsulation adds extra headers, which reduces the available space for the payload. Tuning the MSS ensures that the TCP payload size fits within the tunnel's effective MTU after accounting for the added headers, minimizing the risk of fragmentation. While MTU determines the largest packet size a network can handle without fragmentation, the TCP MSS specifically tunes the payload size to avoid exceeding the MTU in the context of encapsulated traffic.

A is correct

This is really confusing. but after reading in the following link, it A for sure. https://networkdirection.net/articles/network-theory/mtu-and-mss/

The problem is the ambiguity. If we are tuning the configuration on the networking device (i.e., Switch or Router), then we're tuning the MTU, right? And if it's on the Host side, the host automatically tunes the MSS value. Correct me if I'm wrong, please.

MSS is maximum segment size where the packet can be adjusted to make it less chance of being fragmented

are we ignoring the fact that this is in reference to GRE/IP tunnel? What must we take into account when creating a GRE tunnel to avoid/minimize fragmentation? we have to take into account the extra header added to the packet, its why it is recommended to modify the MTU to 1476 as best practice. Because of this MTU is the best answer.

The answer is B because according to Cisco, the value of the MSS field is determined by the MTU configuration on the host. The default MSS value for a PC is 1500 bytes. https://www.bing.com/ck/a?!&&p=f2cac0a3083b6063JmltdHM9MTY3NzcxNTIwMCZpZ3VpZD0wNGRlYjE4NS0yZWYyLTZmZWQtMjQ3Yi1hM2VmMmYxMjZlNWEmaW5zaWQ9NTU0Mg&ptn=3&hsh=3&fclid=04deb185-2ef2-6fed-247b-a3ef2f126e5a&psq=tcp+mss&u=a1aHR0cHM6Ly93d3cuY2lzY28uY29tL2MvZW4vdXMvdGQvZG9jcy9zd2l0Y2hlcy9sYW4vY2F0YWx5c3Q5MzAwL3NvZnR3YXJlL3JlbGVhc2UvMTYtMTEvY29uZmlndXJhdGlvbl9ndWlkZS9pcC9iXzE2MTFfaXBfOTMwMF9jZy9jb25maWd1cmluZ190Y3BfbXNzX2FkanVzdG1lbnQuaHRtbCM6fjp0ZXh0PVRoZSUyMHZhbHVlJTIwb2YlMjB0aGUlMjBNU1MlMjBmaWVsZA&ntb=1

A is correct

TCP Maximum Segment Size Acomplish This.

voting. provided answer is correct

https://www.cisco.com/c/en/us/support/docs/ip/generic-routing-encapsulation-gre/25885-pmtud-ipfrag.html#anc3 A. MSS