CCNA Completo | Leccion 3 | Capa física: cobre

Introduction to Physical Layer and Copper Transmission

Overview of the Lesson

• The tutorial continues with CCNA training, focusing on Lesson 3 about the Physical Layer and copper transmission media.

• A hybrid model of five layers is introduced, combining TCP/IP application and transport layers with OSI's network, data link, and physical layers.

Functions of the Physical Layer

• The Physical Layer is responsible for transporting bits by encoding complete frames into signals transmitted through a medium.

• It involves creating electrical, optical, or radio signals that represent frame bits for transmission.

Standards Organizations Involved in Physical Layer

Key Organizations

• Various international and national organizations set standards for the Physical Layer including ISO, TIA/EIA, ITU, ANSI.

• Regulatory authorities like FCC (USA) and ETSI (EU) also play significant roles in establishing these standards.

Understanding Bandwidth

Definition and Measurement

• Bandwidth refers to a medium's capacity to transport data; it measures how much data can flow from source to destination over time.

• Common units include kilobits per second (kbps), megabits per second (Mbps), or gigabits per second (Gbps).

Common Misconceptions

• There is confusion between bandwidth and bit travel speed; they are not synonymous.

Copper Cabling in Networking

Characteristics of UTP Cables

• Copper cabling is prevalent in networks today; data travels as electrical impulses over twisted pairs of wires.

• UTP cables consist of four color-coded twisted pairs designed to reduce interference known as crosstalk.

Noise Interference Issues

• Any unwanted electrical signal in cables is considered noise which threatens information integrity.

• External sources like electromagnetic interference (EMI) and radio frequency interference (RFI), along with internal noise sources can distort signals.

Crosstalk Phenomenon

Explanation of Crosstalk

• Crosstalk occurs when an electric field induces voltage in nearby wire pairs during signal transmission.

• Twisting wire pairs helps cancel out this electric field effect significantly reducing crosstalk impact.

Cable Categories and Standards

IEEE Classification System

• IEEE defines cable characteristics based on performance; higher category cables support greater bandwidth capacities.

Minimum Cable Standards

• Category 5e: Minimum acceptable standard for existing buildings at 1 Gbps over 100 meters.

• Category 6: Recommended minimum for new installations.

• Category 6a: Supports up to 10 Gbps over the same distance typically used for server connections.

Correct Wiring Practices

Pin Configuration Importance

• Hosts transmit on pins 1 & 2 while receiving on pins 3 & 6. Switches do the opposite.

• Straight-through cables connect corresponding pins directly ensuring proper communication between devices.

Cross-over Cable Usage

Crossover Cables and Their Relevance

Uso de cables crossover

• Ejemplos de uso de cables crossover incluyen la conexión directa entre dos PCs y la conexión entre routers.

• Actualmente, los cables crossover se consideran obsoletos debido a que muchos dispositivos pueden detectar automáticamente el tipo de conexión necesaria.

• Esta capacidad de detección automática se denomina Auto-MDIX, lo que permite una mayor flexibilidad en las conexiones.

• Se proporciona un enlace a una lista de reproducción con vídeos relacionados al curso CCNA Completo para aquellos interesados en profundizar más en el tema.