Infrastructure de Communications – CR 4107Chapter 41 The Medium Access Control Sublayer Chapter 4

Infrastructure de Communications – CR 4107Chapter 42 The Channel Allocation Problem Static Channel Allocation in LANs and MANs Dynamic Channel Allocation in LANs and MANs

Infrastructure de Communications – CR 4107Chapter 43 Dynamic Channel Allocation in LANs and MANs Station Model. Single Channel Assumption. Collision Assumption. (a) Continuous Time. (b) Slotted Time. (a) Carrier Sense. (b) No Carrier Sense.

Infrastructure de Communications – CR 4107Chapter 44 Multiple Access Protocols ALOHA Carrier Sense Multiple Access Protocols Collision-Free Protocols Limited-Contention Protocols Wavelength Division Multiple Access Protocols Wireless LAN Protocols

Infrastructure de Communications – CR 4107Chapter 45 Pure ALOHA In pure ALOHA, frames are transmitted at completely arbitrary times.

Infrastructure de Communications – CR 4107Chapter 46 Pure ALOHA (2) Vulnerable period for the shaded frame.

Infrastructure de Communications – CR 4107Chapter 47 Pure ALOHA (3) Throughput versus offered traffic for ALOHA systems.

Infrastructure de Communications – CR 4107Chapter 48 Persistent and Nonpersistent CSMA Comparison of the channel utilization versus load for various random access protocols.

Infrastructure de Communications – CR 4107Chapter 49 CSMA with Collision Detection CSMA/CD can be in one of three states: contention, transmission, or idle.

Infrastructure de Communications – CR 4107Chapter 410 Collision-Free Protocols The basic bit-map protocol.

Infrastructure de Communications – CR 4107Chapter 411 Wireless LAN Protocols A wireless LAN. (a) A transmitting. (b) B transmitting.

Infrastructure de Communications – CR 4107Chapter 412 Ethernet Invented at XEROX by Dr. R. Metcalfe in 1975 Formal specifications published in 1980 by DEC-Intel- Xerox Became IEEE standard in adopted by ISO 10 Mbps Coaxial cable Updated to include new technologies Twisted pair 100 Mbps Fast Ethernet - IEEE 802.3U Gigabit Ethernet - IEEE 802.3Z Wireless versions

Infrastructure de Communications – CR 4107Chapter 413 Elements of the Ethernet System  Physical Medium  Medium Access Control (MAC)  Ethernet Frame Operation of Ethernet  No central control  Stations are connected to a shared medium  Ethernet signals are transmitted serially, one bit at a time, to every connected station  To send data a station listens to the channel and if it is idle it transmits its data in the form of an Ethernet frame.  Access to the medium is determined by the MAC CSMA/CD protocol

Infrastructure de Communications – CR 4107Chapter 414 CSMA/CD Protocol The Ethernet MAC is based on the Carrier Sense Multiple Access / Collision Detection protocol A station that wants to transmit Listens to the channel  If the channel is idle, it transmits its data  If the channel is busy it waits until it is free and then transmits its data. If two stations transmit at the same time we have a collision ---- Jam signal  Truncated binary exponential backoff algorithm n th re-transmission will be attempted with a delay between 0 and 2 n -1 time units (ex. 53  s) maximum of 16 attempts to re-transmit

Infrastructure de Communications – CR 4107Chapter 415 Collision detection Collision detections can take as long as 2t

Infrastructure de Communications – CR 4107Chapter 416 Ethernet MAC Sublayer Protocol Frame formats. (a) DIX Ethernet, (b) IEEE

Infrastructure de Communications – CR 4107Chapter 417 Ethernet Addresses Ethernet addresses (48 bits) are unique and controlled by IEEE  24 bit Organizationally Unique Identifier (OUI) by the IEEE  24 bit by the organization Multicast and Broadcast addresses  High order address bit is 1 for multicast and broadcast  A destination address of only 1s is accepted by all stations

Infrastructure de Communications – CR 4107Chapter 418 Higher level addresses Ethernet is a trucking system and can operate with different higher level protocols, like TCP/IP, AppleTalk, Novel etc. Higher level protocols have their own addressing schemes. They must find the right Ethernet address in order to communicate with each other. Example in TCP/IP : Address Resolution Protocol (ARP) Station A sends a broadcast requesting the Ethernet address the station B that has the specific IP address All stations receive the message Only the station with the requested IP address reply

Infrastructure de Communications – CR 4107Chapter 419 Ethernet Topology The total size of an Ethernet LAN is defined by the round trip propagation delay. All stations should by able to respond to signals within a specified amount of time. Ethernet segments can be connected at any physical topology (star, tree, bus...) as long as the timing restrictions are fulfilled. Repeaters A repeater is simply re-transmits the signal extending the overall size of the LAN Switching hubs Divides a set of Ethernet segments to multiple LANs  Packet switching

Infrastructure de Communications – CR 4107Chapter 420 Ethernet Cabling The most common kinds of Ethernet cabling.

Infrastructure de Communications – CR 4107Chapter 421 Ethernet Cabling (2) Three kinds of Ethernet cabling. (a) 10Base5, (b) 10Base2, (c) 10Base-T.

Infrastructure de Communications – CR 4107Chapter 422 Ethernet Cabling (3) Cable topologies. (a) Linear, (b) Spine, (c) Tree, (d) Segmented.

Infrastructure de Communications – CR 4107Chapter 423 Ethernet Cabling (4) (a) Binary encoding, (b) Manchester encoding, (c) Differential Manchester encoding.

Infrastructure de Communications – CR 4107Chapter 424 Ethernet Performance Efficiency of Ethernet at 10 Mbps with 512-bit slot times.

Infrastructure de Communications – CR 4107Chapter 425 Switched Ethernet A simple example of switched Ethernet.

Infrastructure de Communications – CR 4107Chapter 426 Fast Ethernet The original fast Ethernet cabling.

Infrastructure de Communications – CR 4107Chapter 427 Gigabit Ethernet (a) A two-station Ethernet. (b) A multistation Ethernet.

Infrastructure de Communications – CR 4107Chapter 428 Gigabit Ethernet (2) Gigabit Ethernet cabling.

Infrastructure de Communications – CR 4107Chapter 429 Ethernet problems Capture effect A station with high traffic load can capture the network for a considerable amount of time Security Packets are received by all stations

Infrastructure de Communications – CR 4107Chapter 430 IEEE 802.2: Logical Link Control (a) Position of LLC. (b) Protocol formats.

Infrastructure de Communications – CR 4107Chapter 431 Wireless LANs The Protocol Stack The Physical Layer The MAC Sublayer Protocol The Frame Structure Services

Infrastructure de Communications – CR 4107Chapter 432 The (WLAN) Protocol Stack Part of the protocol stack.

Infrastructure de Communications – CR 4107Chapter 433 The MAC Sublayer Protocol (a) The hidden station problem. (b) The exposed station problem.

Infrastructure de Communications – CR 4107Chapter 434 The MAC Sublayer Protocol The use of virtual channel sensing using CSMA/CA.

Infrastructure de Communications – CR 4107Chapter 435 The MAC Sublayer Protocol A fragment burst.

Infrastructure de Communications – CR 4107Chapter 436 The MAC Sublayer Protocol (4) Interframe spacing in

Infrastructure de Communications – CR 4107Chapter 437 The Frame Structure The data frame.

Infrastructure de Communications – CR 4107Chapter Services Association Disassociation Reassociation Distribution Integration Distribution Services

Infrastructure de Communications – CR 4107Chapter Services Authentication Deauthentication Privacy Data Delivery Intracell Services

Infrastructure de Communications – CR 4107Chapter 440 Broadband Wireless Comparison of and The Protocol Stack The Physical Layer The MAC Sublayer Protocol The Frame Structure

Infrastructure de Communications – CR 4107Chapter 441 The Protocol Stack The Protocol Stack.

Infrastructure de Communications – CR 4107Chapter 442 The Physical Layer The transmission environment.

Infrastructure de Communications – CR 4107Chapter 443 The Physical Layer (2) Frames and time slots for time division duplexing.

Infrastructure de Communications – CR 4107Chapter 444 The MAC Sublayer Protocol Service Classes Constant bit rate service Real-time variable bit rate service Non-real-time variable bit rate service Best efforts service

Infrastructure de Communications – CR 4107Chapter 445 The Frame Structure (a) A generic frame. (b) A bandwidth request frame.

Infrastructure de Communications – CR 4107Chapter 446 Bluetooth Bluetooth Architecture Bluetooth Applications The Bluetooth Protocol Stack The Bluetooth Radio Layer The Bluetooth Baseband Layer The Bluetooth L2CAP Layer The Bluetooth Frame Structure

Infrastructure de Communications – CR 4107Chapter 447 Bluetooth Architecture Two piconets can be connected to form a scatternet.

Infrastructure de Communications – CR 4107Chapter 448 Bluetooth Applications The Bluetooth profiles.

Infrastructure de Communications – CR 4107Chapter 449 The Bluetooth Protocol Stack The version of the Bluetooth protocol architecture.

Infrastructure de Communications – CR 4107Chapter 450 The Bluetooth Frame Structure A typical Bluetooth data frame.

Infrastructure de Communications – CR 4107Chapter 451 Data Link Layer Switching Bridges from 802.x to 802.y Local Internetworking Spanning Tree Bridges Remote Bridges Repeaters, Hubs, Bridges, Switches, Routers, Gateways Virtual LANs

Infrastructure de Communications – CR 4107Chapter 452 Data Link Layer Switching Multiple LANs connected by a backbone to handle a total load higher than the capacity of a single LAN.

Infrastructure de Communications – CR 4107Chapter 453 Bridges from 802.x to 802.y Operation of a LAN bridge from to

Infrastructure de Communications – CR 4107Chapter 454 Bridges from 802.x to 802.y (2) The IEEE 802 frame formats. The drawing is not to scale.

Infrastructure de Communications – CR 4107Chapter 455 Local Internetworking A configuration with four LANs and two bridges.

Infrastructure de Communications – CR 4107Chapter 456 Spanning Tree Bridges Two parallel transparent bridges.

Infrastructure de Communications – CR 4107Chapter 457 Spanning Tree Bridges (2) (a) Interconnected LANs. (b) A spanning tree covering the LANs. The dotted lines are not part of the spanning tree.

Infrastructure de Communications – CR 4107Chapter 458 Remote Bridges Remote bridges can be used to interconnect distant LANs.

Infrastructure de Communications – CR 4107Chapter 459 Repeaters, Hubs, Bridges, Switches, Routers and Gateways (a) Which device is in which layer. (b) Frames, packets, and headers.

Infrastructure de Communications – CR 4107Chapter 460 Repeaters, Hubs, Bridges, Switches, Routers and Gateways (2) (a) A hub. (b) A bridge. (c) a switch.

Infrastructure de Communications – CR 4107Chapter 461 Virtual LANs A building with centralized wiring using hubs and a switch.

Infrastructure de Communications – CR 4107Chapter 462 Virtual LANs (2) (a) Four physical LANs organized into two VLANs, gray and white, by two bridges. (b) The same 15 machines organized into two VLANs by switches.

Infrastructure de Communications – CR 4107Chapter 463 The IEEE 802.1Q Standard Transition from legacy Ethernet to VLAN-aware Ethernet. The shaded symbols are VLAN aware. The empty ones are not.

Infrastructure de Communications – CR 4107Chapter 464 The IEEE 802.1Q Standard (2) The (legacy) and 802.1Q Ethernet frame formats.

Infrastructure de Communications – CR 4107Chapter 465 Summary Channel allocation methods and systems for a common channel.