Computer Networks

SIP (Session Initiation Protocol) is used to establish, modify, and terminate multimedia sessions like VoIP calls. It handles the signaling - setting up and tearing down connections - while the actual media flows separately.

RFC is a standard acronym in internet networking that stands for Request for Comments, which is a formal document drafted by the Internet Engineering Task Force (IETF) describing specifications.

SIP operates at the Application Layer (Layer 7) of the OSI model. It's a signaling protocol that uses TCP or UDP at the Transport layer to establish communication sessions between endpoints.

VoIP (Voice over Internet Protocol) transmits voice communications as digital data packets over IP networks instead of traditional circuit-switched telephone networks.

Historically, Cisco devices shipped with default credentials of username 'cisco' and password 'cisco' (or blank username with 'cisco' as password). This is well-documented though modern security best practices require immediate change of these defaults.

Windows systems default to TTL 128, while Linux/Unix systems typically use 64. The TTL (Time To Live) field prevents packets from circulating infinitely by decrementing at each router hop. When TTL reaches zero, the packet is discarded.

IP is a routed protocol (it carries the actual user data packets), while RIP is a routing protocol (it helps routers find paths and build routing tables). Routed protocols are payload; routing protocols are the control plane that determines how payloads are routed.

ipconfig is the Windows command to display IP configuration. ifconfig is used in Unix/Linux, ARP shows MAC address mappings, and ping tests connectivity. ipconfig shows IP address, subnet mask, and default gateway.

ARP stands for Address Resolution Protocol, which is a network protocol used to map IP addresses to MAC addresses in local area networks. It operates at Layer 2 of the OSI model and is essential for devices to communicate on the same network segment.

SSL/TLS for secure HTTP (HTTPS) uses port 443 by default. Port 80 is for standard HTTP, port 21 is for FTP, and port 23 is for Telnet. When you see https:// in a URL, the browser typically connects to port 443.

IPv6 routing is more efficient because the header has fewer and simpler fields compared to IPv4's variable options. This enables faster router processing decisions. Option A is incorrect (IPv6 header is 40 bytes vs IPv4's minimum 20), and options C/D are not technical reasons for routing efficiency.

IPv4's variable Options field has been replaced by extension headers in IPv6, which provide a more flexible and efficient mechanism for optional information. The Next Header field chains extension headers together, improving router efficiency by skipping irrelevant extensions.