What is the maximum application payload size of a UDP datagram when carried directly in IPv4 without options?
The maximum IPv4 packet is 65,535 bytes. With a 20-byte IPv4 header and an 8-byte UDP header, the maximum UDP application payload is 65,535 - 20 - 8 = 65,507 bytes.
Which application layer protocol uses TCP port 21 for Control connection and TCP port 20 for Data transfer?
FTP out-of-band architecture uses port 21 for control commands and port 20 for active data transfers.
Which DNS resource record type maps a domain name alias to its canonical domain name?
CNAME (Canonical Name) maps an alias domain name to its true canonical domain name. 'A' maps to IPv4, 'AAAA' to IPv6, 'MX' to Mail Server.
Which HTTP header field can explicitly request that a TCP connection remain persistent across multiple HTTP requests?
The 'Connection: keep-alive' header explicitly requests a persistent connection. HTTP/1.1 connections are persistent by default unless closed or otherwise indicated.
What is the total round-trip time (RTT) required to retrieve a Web page containing 5 inline images using HTTP/1.0 without parallel TCP connections?
HTTP/1.0 is non-persistent. Each object requires 1 RTT for TCP handshake + 1 RTT for HTTP request/data = 2 RTT per object. Total objects = 1 HTML + 5 images = 6 objects * 2 RTT = 12 RTT.