Computer Networks

ESS (Extended Service Set) is a wireless topology where multiple access points are connected to the same wired network and share the same SSID, enabling seamless roaming. IBSS (Independent Basic Service Set), also called ad hoc mode, is a peer-to-peer network between wireless devices without an access point. Ad hoc (C) is the same as IBSS. Only ESS (A) supports roaming between access points because stations can move between APs while maintaining connectivity to the same network.

When network services fail, in-band management access typically uses the Ethernet port. The console port (C) requires physical access and a console cable, which isn't always available. AUX (A) is a modem port for remote out-of-band access. Telnet (D) and SSH (E) are application-layer protocols that require network services to be functioning. If network services are down, you can't Telnet or SSH. The Ethernet port (B) is the correct answer because it provides in-band management access and doesn't depend on the failed network services - you can connect directly to the router's Ethernet interface for management.

WiMAX (Worldwide Interoperability for Microwave Access) is defined in IEEE 802.16 and provides broadband wireless access with speeds and quality comparable to DSL and cable. It offers last-mile broadband connectivity and can cover large geographic areas, making it an alternative to wired broadband connections.

The DTE physical layer are network nodes such as routers, servers and switches. DCEs are internetworking devices located normally with the telecom carrier. The connection between DTE and DCE can only be via physical cabling.

After a collision, CSMA/CD's backoff algorithm has each device wait a random amount of time before attempting to retransmit. The device whose random backoff timer expires first gets priority to transmit - there is no inherent priority based on MAC address, IP address, or timing of the collision itself. This randomized approach helps prevent repeated collisions by ensuring devices don't all retry simultaneously.

Switches increases the number of collisions domains in the network. Switches that are configured with VLANs will reduce the size of the collision domains by increasing the number of collision domains in a network, but making them smaller than that of one big, flat network.

Straight-through cables connect unlike devices: one end uses T568A pinout, the other uses T568B. Host-to-switch connections require straight-through cables because the host transmits on pins 1/2 and receives on 3/6, while the switch does the opposite (receives on 1/2, transmits on 3/6). Crossover cables are for like devices (switch-to-switch, router-to-router, host-to-host) or when connecting to router Ethernet ports that operate as host devices.

The Linksys WRT300N has a default IP address (typically 192.168.1.1) and requires an initial configuration via its web interface. To access this interface, your computer must be in the same IP subnet as the device (to enable IP communication) and connected via a direct cable (Ethernet) to one of the LAN ports. Console and AUX ports are Cisco-specific features not present on consumer devices like the WRT300N. A wireless connection cannot be used for initial configuration because the wireless radio is unconfigured until you access the setup interface.

The access method (how the physical wire is accessed)in an Ethernet network is Carrier Sense Multiple Access/Collision Detection (CSMA/CD). In a CSMA/CD network stations listen to check if the network is busy, if the network is free the station transmits data. When two stations listen, and both determine the network is not busy, and start sending the data simultaneously a collision occurs. When the collision is detected both stations will retransmit the data after a random wait time created by a backoff algorithm.

In Ethernet, when a collision occurs on a shared medium (like a hub), the jamming signal propagates throughout the collision domain. All hosts connected to the same physical segment receive and process this jam signal, which causes all transmitting stations to stop and back off using the exponential backoff algorithm. The exhibit shows hosts A, B, and C connected to the same collision domain (likely a shared hub), while D, E, and F are separated by a switch, bridge, or router boundary. Only hosts on the same collision domain receive the jamming signal.

ATM (Asynchronous Transfer Mode) uses fixed-size 53-byte cells, consisting of a 5-byte header and 48-byte payload. This small, fixed cell size was chosen to reduce jitter and ensure predictable latency for voice and video traffic. ATM can operate over both Switched Virtual Circuits (SVCs), which are set up on demand, and Permanent Virtual Circuits (PVCs), which are pre-configured. ISDN uses 64kbps channels, Frame Relay uses variable-length frames, and Metro Ethernet uses standard Ethernet frames (not 48-byte payloads).

VTP (VLAN Trunking Protocol) synchronizes VLAN configuration information across all switches in the same VTP domain. When you create, delete, or rename a VLAN on one VTP server switch, those changes are automatically propagated to all other switches in the domain. This greatly simplifies VLAN management on large switched networks. Option A is false because VTP supports both ISL and 802.1Q trunking. Option B is subjective - VTP actually reduces complexity by automating VLAN management. Option C is false - a switch can only belong to one VTP domain at a time.

Fiber-optic cable is most commonly used for backbone cabling runs because it supports high bandwidth over long distances without signal degradation. Backbone cabling connects entrance facilities, equipment rooms, and telecommunications closets. Horizontal, patch, and work area cables (B, C, D) are typically copper due to shorter distances and cost considerations.

Hardware addresses (MAC addresses) are used for Layer 2 communication to transmit frames between directly connected interfaces on the same local network segment. Option A is incorrect because packets (Layer 3) use IP addresses. Option C is incorrect because MAC addresses are burned into the NIC, not obtained from users. Option D is incorrect because remote communication requires IP addresses, not just MAC addresses.

Full duplex Ethernet communication is only possible when systems are connected to their own switch port