Data Link Layer Issues2 Flashcards
What is ATM (Asynchronous Transfer Mode)?
ATM is a high-speed network technology that uses optical fibers and operates on SONET hardware. It employs fixed-size cells (53 octets) for efficient communication.
What is the structure of an ATM cell?
An ATM cell is 53 octets:
5 bytes: Header for control and routing.
48 bytes: Payload for user data.
How does ATM combine packet-switching and circuit-switching?
ATM uses virtual circuits, providing the efficiency of packet-switching with the reliability of circuit-switching by establishing a path before data transfer.
What are the types of virtual circuits in ATM networks?
Permanent Virtual Circuits (PVCs): Manually configured for long-term use.
Switched Virtual Circuits (SVCs): Created dynamically when needed.
What is the Virtual Circuit Identifier (VCI)?
A unique identifier used for efficient data routing once a virtual circuit is established.
What are ATM switches, and how are they efficient?
ATM switches route data without per-packet routing overhead.
Fixed-size cells enable optimized hardware-level transmission, eliminating buffering delays.
What is the ATM Adaptation Layer (AAL5)?
AAL5 abstracts hardware-specific constraints, supports up to 65,535-octet packets, ensures data integrity with CRC, and manages end-to-end data segmentation and reassembly.
What are the advantages of ATM networks?
High-speed transmission with reduced latency.
Reliable virtual circuits ensure packet order and prevent loss.
Hardware-level switching provides quick and efficient data transfer.
What are the drawbacks of ATM networks?
Incompatibility with existing technologies due to fixed cell size.
Differing addressing from TCP/IP systems.
Lack of native broadcasting and multicasting support.
What is TCP/IP tunneling in ATM?
A method to encapsulate TCP/IP packets in ATM cells, allowing internet-based applications to run over ATM networks.
How does ATM handle TCP/IP packets?
IP datagrams, including headers, are embedded in AAL5 logical packets, which are then transmitted via ATM cells and reassembled at the destination.
What are ATM service categories?
Constant Bit Rate (CBR): Fixed bandwidth for real-time applications.
Variable Bit Rate (VBR): Guaranteed minimum bandwidth with peaks (RT for streaming, NRT for downloads).
Available Bit Rate (ABR): Adaptive bandwidth with feedback for congestion.
Unspecified Bit Rate (UBR): Uses leftover bandwidth without guarantees.
What is LAN Emulation in ATM?
Emulated LANs (E-LANs) simulate LAN environments using ATM hardware, forwarding packets like Ethernet frames via AAL5.
What is Segmentation and Reassembly in ATM?
Large packets are divided into smaller cells for transmission and reassembled at the destination, enabling seamless data handling.
How does ATM ensure data integrity?
By using CRC (Cyclic Redundancy Check) for error detection and correction.
Why is ATM efficient in hardware implementation?
Most ATM functionalities are hardware-implemented, reducing software overhead and maximizing speed.
