EE450-U7-DataLinkLayer_Lecture-Nazarian-Summer10_1

EE450-U7-DataLinkLayer_Lecture-Nazarian-Summer10_1 - EE450...

Info iconThis preview shows pages 1–8. Sign up to view the full content.

View Full Document Right Arrow Icon
EE450 Computer Networks Data Link Layer Shahin Nazarian Summer 2010
Background image of page 1

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

View Full DocumentRight Arrow Icon
Shahin Nazarian/EE450/Summer 2010 Data Link Layer (DLL) – a Link to Link Protocol Every layer provides a set of services and provides it to the layer _____ it DLL (Layer 2) is a link-to-link basis (not end-to-end basis) protocol Receiver side needs to synch frame (to know where it starts where it ends.) Receiver is the other side of the link Physical layer transmits the bit and makes sure no duplicate or missing bit exists, but DLL handles the errors (caused by noise or signal attenuation) 2
Background image of page 2
Shahin Nazarian/EE450/Summer 2010 Where Is The Link Layer (LL) Implemented? LL is implemented in each and every node Much of LL controller’s functionality is implemented in hardware LL is implemented in “adaptor” (aka Network Interface Card or ____ card) E.g., Ethernet card (Intel’s 8254x controller), PCM-CIA card (plug-in to PC’s PCI card slot), 802.11 card (Atheros AR5006) Implements ___, Physical layer Attaches into node’s system buses LL is a combination of hardware, software, and firmware controller physical transmission cpu memory host bus (e.g., PCI) network adapter card (aka network Interface card) host schematic application transport network link link physical 3 Example: host link layer
Background image of page 3

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

View Full DocumentRight Arrow Icon
Shahin Nazarian/EE450/Summer 2010 Some DLL Services 4
Background image of page 4
Shahin Nazarian/EE450/Summer 2010 Error Control, Flow Control Error Control 1 st technique [simplest approach]: In case error is detected, receiver will drop the frame. so automatically packet is dropped as well 2 nd technique: Receiver will request from the sender (Note: not the end node, but the node on the other side of the link) to retransmit using ARQ 3 rd technique: Receiver is not only able to detect the error, but also to locate (i.e., correct) it Most of the networking applications use dropping and ARQ instead of this technique Flow Control A procedure that lets the receiver inform the sender to not overwhelm it by too many frames (so sender would slow down) 5
Background image of page 5

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

View Full DocumentRight Arrow Icon
Shahin Nazarian/EE450/Summer 2010 Point to Point DLC Protocols A B 6
Background image of page 6
PPP Data Link Control Packet framing (encapsulating into frame) is performed Only error _________ is performed, i.e., no error correction or error recovery If a frame is corrupted it is silently dropped; the upper -layer protocol needs to take care of the problems _________ control, i.e., the sender can send several frames one after another with no concern about overwhelming the receiver Lack of error control and sequence numbering may cause a packet to be received out of order Error recovery, flow control, and data re-ordering are relegated to ________ layers! A
Background image of page 7

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

View Full DocumentRight Arrow Icon
Image of page 8
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 09/27/2010 for the course EE 450 taught by Professor Zahid during the Summer '06 term at USC.

Page1 / 57

EE450-U7-DataLinkLayer_Lecture-Nazarian-Summer10_1 - EE450...

This preview shows document pages 1 - 8. Sign up to view the full document.

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