Increasing the MTU (Maximum Transmission Unit) size allows larger frames to be transmitted, reducing overhead and improving throughput - especially for large file transfers like backups.
A). QoS prioritizes traffic but doesn't reduce backup times directly.
B). SDN is a network management model, not a parameter change.
D). VXLAN encapsulates VLANs, not relevant to backup speeds.
E). TTL is for packet lifetime, not throughput.
References (CompTIA Network+ N10-009):
Domain: Network Infrastructure - MTU, jumbo frames, performance tuning.

Port 25 is associated with SMTP, which is traditionally used for Simple Mail Transfer Protocol traffic. In basic port-mapping questions for CompTIA Network+, SMTP on port 25 is commonly treated as the non- encrypted mail transport option. If the organization is migrating to encrypted mail protocols, closing port 25 can help deny non-encrypted SMTP access while allowing encrypted mail submission or web-based secure access to continue through other ports.
The CompTIA Network+ N10-009 objectives require candidates to recognize common protocols, port numbers, and their secure alternatives. Port 587 is commonly used for SMTP message submission with TLS support, so it should remain available when encrypted mail submission is required. Port 443 is HTTPS and may be used for secure webmail access. Port 22 is SSH, which is encrypted remote administration, not a mail protocol. Port 23 is Telnet, which is unencrypted, but it is not a mail protocol.
Because the question specifically asks about denying non-encrypted mail protocols, port 25 is the best answer among the listed options.

Border Gateway Protocol (BGP) is the primary protocol used to route traffic on the public internet. It allows ISPs and large networks to exchange routing information, making it an Exterior Gateway Protocol (EGP).
Breakdown of Options:
A). BGP - Correct answer. Used for internet routing and exchanges routing information between ISPs.
B). OSPF - An Interior Gateway Protocol (IGP) used for routing within an autonomous system (not the public internet).
C). EIGRP - Cisco's proprietary IGP, used within private networks, not the public internet.
D). RIP - An older distance-vector protocol, not scalable for the internet.
Reference:
CompTIA Network+ (N10-009) Official Study Guide - Domain 1.4: Explain routing technologies.
RFC 4271: Border Gateway Protocol 4 (BGP-4)

SFTP (Secure File Transfer Protocol) operates over port 22, using SSH (Secure Shell) encryption for secure file transfers.
Breakdown of Options:
A). 22 - Correct answer. SFTP runs over SSH (port 22) for secure file transfers.
B). 80 - Used for HTTP, not SFTP.
C). 443 - Used for HTTPS (secure web traffic).
D). 3389 - Used for RDP (Remote Desktop Protocol).
Reference:
CompTIA Network+ (N10-009) Official Study Guide - Domain 3.1: Compare and contrast network protocols.
RFC 4253: SSH Transport Layer Protocol