Chapter 7 Notes - Chapter 7 Data Link Layer Prepares...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
Chapter 7 – Data Link Layer Prepares network data for the physical network Accessing the Media Performs 2 basic services Allows the upper layers to access the media using techniques such as framing Controls how data is placed onto the media and is received from the media using techniques such as media access control and error detection Terms: Frame – Data Link Layer PDU Node – Layer 2 notion for network devices connected to a common medium (a device on a network) Media/Medium (physical) – physical means for the transfer of information between 2 nodes Network (physical) – 2 or more nodes connected to a common medium Data link layer protocols govern how to format a frame for use on different media Different protocols may be in use for different media Point-to-Point Protocol (PPP) Ethernet High-Level Data Link Control (HDLC) Frame Relay Asynchronous Transfer Mode (ATM) At each hop along the path An intermediary device accepts frames from one medium Decapsulates the frame and forwards the packets in a new frame Headers of each frame are formatted for the specific medium that it will cross Media access control method – technique used for getting frame on and off media Media access control methods described by DLL protocols define the processes by which network devices can access the network media and transmit frames in diverse network environments Creating a Frame DLL protocols require control info to enable the protocols to function. Info may tell: Which nodes are in communication with each other
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
When communication between individual nodes begins and when it ends Which errors occurred while the nodes communicated Which nodes will communicate next DLL frame includes: Data – packet from the network layer Header – contains control information (addressing) & is located at beginning of PDU Trailer – contains control info added to the end of the PDU When data travels on media, converted into bits. Field types include: Start and stop indicator fields – beginning & end limits of the frame Naming or addressing fields Type field – type of PDU contained in frame Quality – control fields Data field – frame payload (Network layer packet) DLL links the software and hardware layers Physical devices devoted to the DLL have both hardware and software components Data link sublayers Upper sublayer defines software processes that provide services to the Network layer protocols Lower defines the media access processes performed by the hardware 2 Common LAN sublayers Logical Link Control (LLC) Places info in the frame that identifies which Network layer protocol is being used for the frame Allows layer 3 protocols to utilize same network interface & media Media Access Control (MAC) Provides DLL addressing & delimiting of data according to physical signaling requirements of medium and type of DLL
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 04/29/2008 for the course ICTN 2154 taught by Professor Khoury during the Spring '08 term at East Carolina University .

Page1 / 9

Chapter 7 Notes - Chapter 7 Data Link Layer Prepares...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online