CCNA Completo | Leccion 5 | Capa de enlace de datos | Ethernet
Introduction to Data Link Layer and Ethernet LANs
Overview of the Data Link Layer
- The lesson focuses on the Data Link Layer (Layer 2 of the OSI model) and Ethernet-based Local Area Networks (LANs).
- Responsibilities of the Data Link Layer include accepting packets from Layer 3, encapsulating them into frames, controlling data transmission, exchanging frames between terminal devices, detecting errors, and rejecting damaged frames.
Standards and Organizations
- Various engineering organizations define standards for Layers 1 and 2; key players include ITU, ANSI, ISO, and IEEE.
- Differentiating network types can be complex; criteria such as size, geographical coverage, and equipment ownership help classify networks like LANs (private ownership connecting hosts within a company) versus WANs (telecommunication companies providing broader services).
IEEE Project 802
- Initiated in 1985 by IEEE to create standards for intercommunication among different manufacturers' equipment without replacing existing OSI or TCP/IP models.
- Ethernet is defined under IEEE standards 802.2 and 802.3 covering both physical and data link layers.
Early Ethernet Technologies
- Early Ethernet used bus topology or hubs with shared half-duplex transmission where only one device could send/receive at a time.
- CSMA/CD was employed to manage access in half-duplex environments by detecting collisions when multiple devices attempted simultaneous transmissions.
Modern Ethernet Technologies
- Current Ethernet networks utilize Layer 2 switches allowing full-duplex communication where multiple devices can transmit/receive simultaneously over dedicated media.
- MAC addresses identify physical origins/destinations in local network segments; they consist of 48 binary digits represented as hexadecimal for simplicity.
Representation of MAC Addresses
- Different manufacturers may represent MAC addresses variably (e.g., groups separated by colons or dots), but all must total twelve hexadecimal digits.
Additional Resources
- Links provided for further learning: tutorial on hexadecimal numbering system and a playlist of previous CCNA lessons.