Physical Layer Protocols and Services:
L1 controls how data is placed on the media.
It has to encode bits into signals and Tx/Rx these signals across the physical media.
The delivery of frames across media requires.
Physical media and connectors.
A representation of bits – code.
Encoding of data and control information.
Tx and Rx circuitry on devices.
The purpose of L1 is to create the electrical, optical, or radio signal that reqresents the bits in each frame.
It also must retrieve signals from media, restore them to bit representations, and pass them to L2 as a complete frame.
The type of signal – depends on the type of media.
Copper = electrical pulses.
Fiber = patterns of light.
Wireless = patterns of radio transmissions.
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Tags: wan, 802.1q, guides, cisco, vlan, router
Data Link Layer
2 primary functions:
1. Prepares L3 packets for transmission.
2. Controls access to the physical media.
Accessing the media:
A L3 exchange may involve many L2 and media transitions.
At each hop, routers decapsulate and re-encapsulate frames to match the right media.
The L3 protocol is not aware of which media is used.
L2 includes many types of media and access methods (eg. how it is getting to the wire).
L2 protocols specify the frame type and how to get a frame on and off each medium (media access control method, MAC method).
Devices use adapters to connect to a network (eg. NIC)
The adapter manages the framing and media access control (generates the signal transition).
Routers have different physical interfaces that frame the data as suitable for each link.
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Tags: guides, vlan, router, wan, ip, switch
Bitmindframes cisco study guides
Why use wireless?
Networks are evolving to support people on the move
Many different infastructures (wired LAN, service providers) allow mobility.
Productivity is no longer restricted to a fixed work location or a defined time period.
WLAN’s reduce cost.
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Tags: vlan, vtp, wan, 802.1q, router, switch
