CNAP AT VCC Semester 1 CHAPTER 7 Wael Yousif Connecting The Internet Generation

CNAP AT VCC  Content Token-ring. FDDI LAN. Ethernet and IEEE Layer 2 devices and effects on data flow.

CNAP AT VCC BASIC OF TOKEN-RING

CNAP AT VCC  Variants IBM developed the first Token Ring network in the 1970s. It is still IBM's primary LAN technology, and is second only to Ethernet (IEEE 802.3) in terms of LAN implementation.

CNAP AT VCC  Ring topology

CNAP AT VCC  Data passing When a station has information to transmit, it seizes the token and sends data frame to the next station. When frame reaches the destination station, the data is copied for processing. Frame continues to circle the ring until it returns to the sending station. Sending station removes the frame from the ring, verifies receipt, and releases the token.

CNAP AT VCC  Token-Ring frame format

CNAP AT VCC  Start delimiter and End delimiter Start delimiter. –Alert for the arrival of a token. End Delimiter –Completes the token or data/command frame. –Contains damage indicator. –Last of logical sequence.

CNAP AT VCC  Access control P: Priority bits T: Token bit M: Monitor bit R: Reservation bits P P P P P P T T M M R R R R R R

CNAP AT VCC  Priority and reservation bits B'000' Normal User Priority B'001' Normal User Priority B'010' Normal User Priority B'011' Normal User priority B'100' Bridge/Router B'101' Reserved IBM B'110' Reserved IBM B'111' Station Management

CNAP AT VCC  Priority management Using the priority field and the reservation field. Stations with a higher priority can reserve the token for the next network pass. Stations that raise a token's priority level must reinstate the previous priority after their transmission has been completed.

CNAP AT VCC  Frame control Only present in data/command frames. Indicates whether frame contains data or control information. If control, this byte specifies type of control information. Only present in data/command frames. Indicates whether frame contains data or control information. If control, this byte specifies type of control information.

CNAP AT VCC  Destination and Source addresses Universal Address. Local Administered Address. Broadcast Address Functional Address (0x0C XXXX) Universal Address. Local Administered Address. Broadcast Address Functional Address (0x0C XXXX)

CNAP AT VCC  Data Length limited by the maximum time a station may hold the token.

CNAP AT VCC  Frame checksum Frame Check Sequence. Source fills field with calculated value dependent on frame contents. Destination recalculates to check data integrity. Frame is discarded if damaged. Frame Check Sequence. Source fills field with calculated value dependent on frame contents. Destination recalculates to check data integrity. Frame is discarded if damaged.

CNAP AT VCC  Frame status Address recognized / frame copied indicator.

CNAP AT VCC  Management mechanisms Active Monitor –One station acts as centralized source of timing information for other stations. –Removes continuously circulating frames by set monitor bit to 1. –Start a token, when token have been lost. Beaconing –Detects and repairs network faults. –Initiates auto-reconfiguration.

CNAP AT VCC  Physical topology Physical topology : Star. Logical topology : Ring. IBM Token Ring network stations are connected to MSAU (Multi-Station Access Unit). Many MSAU can be wired together to form one large ring.

CNAP AT VCC  Multi-MSAU

CNAP AT VCC  Physical connection

CNAP AT VCC BASIC OF FDDI

CNAP AT VCC  Characteristics Fiber Distributed Data Interface. FDDI is popular as a campus backbone technology.  100 Mbps  Token passing  Dual-ring  Fiber Optic Cable  Total fiber length of 200Km

CNAP AT VCC  FDDI dual-ring (PR and SR)

CNAP AT VCC  Fiber-optic modes

CNAP AT VCC  FDDI Connections Class A: connect directly with PR – SR. –DAC: Dual Attachment Concentrator –DAS: Dual Attachment Station Class B: connect via FDDI concentrator. –SAS: Single Attachment Station

CNAP AT VCC  Operation mechanisms Connection Establishment –Station connect to neighbors to form the ring. –Negotiate the length of the link. Ring Initialization –Station claim the right to generate a token. Steady-state Operation –Token passing Ring Maintenance –Detects and repairs token or network faults.

CNAP AT VCC  FDDI topology

CNAP AT VCC ETHERNET AND IEEE 802.3

CNAP AT VCC  Ethernet introduction Ethernet is the most widely used local area network (LAN) technology. Ethernet was designed to carry data at high speeds for very limited distances. Ethernet is well suited to applications where a local communication medium must carry sporadic, occasionally heavy traffic at high peak data rates.

CNAP AT VCC  Datalink and Physical layers

CNAP AT VCC  Comparing Ethernet and IEEE Specify similar technologies. Broadcast network. Using CSMA/CD algorithm. Hardware implementation. Differences: –Ethernet provides services corresponding to physical and datalink layer. –IEEE specifies the physical layer and the channel-access portion of the data link layer but does not define a LLC protocol.

CNAP AT VCC  Ethernet family: 1000Base-SX-LX

CNAP AT VCC  Ethernet family: 1000Base-T

CNAP AT VCC  Ethernet family: 100Base-TX

CNAP AT VCC  Ethernet family: 10Base-T

CNAP AT VCC  Ethernet family

CNAP AT VCC  Ethernet frame format

CNAP AT VCC  Preamble Note that a frame is Ethernet or IEEE

CNAP AT VCC  Start of frame delimiter (SOF) The IEEE 802.3: synchronize the frame-reception portions of all stations on the LAN. Be explicitly specified in Ethernet. The IEEE 802.3: synchronize the frame-reception portions of all stations on the LAN. Be explicitly specified in Ethernet.

CNAP AT VCC  Source and destination addresses MAC addresses. Unicast. Multicast (D) Broadcast (D) MAC addresses. Unicast. Multicast (D) Broadcast (D)

CNAP AT VCC  Type (Ethernet) Specifies the upper-layer protocol to receive the data after Ethernet processing is completed

CNAP AT VCC  Length (IEEE 802.3) The length indicates the number of bytes of data that follows this field

CNAP AT VCC  Data (Ethernet) the data contained in the frame is sent to an upper-layer protocol

CNAP AT VCC  Data (IEEE 802.3) Data send to LLC layer, including LLC header and upper-layer data

CNAP AT VCC  Frame check sequence (FCS) This sequence contains a 4 byte CRC value that is created by the sender and is recalculated by the receiver to check for damaged frames

CNAP AT VCC  Media Access Control (MAC) Shared-media broadcast technology. Ethernet’s MAC performs three functions: 1.transmitting and receiving data packets 2.decoding data packets and checking them for valid addresses before passing them to the upper layers of the OSI model 3.detecting errors within data packets or on the network

CNAP AT VCC  Broadcast technology MAC

CNAP AT VCC  Broadcast address FF-FF-FF-FF-FF-FF

CNAP AT VCC  CSMA/CD When a station wishes to transmit, it checks the network to determine whether another station is transmitting. If network is free, the station proceeds with the transmission. While sending, the station monitors the network to ensure that no other station is transmitting. If a transmitting node recognizes a collision, it transmits a jam signal so that all other nodes recognize collision. All transmitting nodes then stop sending for a backoff time (randomly n - 1 of 51.2  s).

CNAP AT VCC  CSMA/CD (cont.)

CNAP AT VCC  CSMA/CD Algorithm

CNAP AT VCC  Ethernet star topology

CNAP AT VCC  Ethernet star topology (cont.)

CNAP AT VCC  TIA/EIA-568-A HC Standard

CNAP AT VCC  TIA/EIA-568-A: Distance limit

CNAP AT VCC LAYER 2 DEVICES AND EFFECTS ON DATAFLOW

CNAP AT VCC  Layer 2 Devices NIC (Network Interface Card) –Connect your computer with network. –Provide MAC addresses to each connection. –Implement CSMA/CD algorithm. Bridge –Forward or filter frame by MAC address. Switch –Multi-port bridge.

CNAP AT VCC  NIC

CNAP AT VCC  NIC (cont.) Provides ports for network connection. When selecting a network card, consider: 1.Type of network: Ethernet Token Ring FDDI 2.Type of media Twisted-pair Coaxial Fiber-optic 3.Type of system bus PCI ISA

CNAP AT VCC  NIC: Layer 2 functions Logical link control (LLC): communicates with upper layers in the computer Naming: provides a unique MAC address identifier Framing: part of the encapsulation process, packaging the bits for transport Media Access Control (MAC): provides structured access to shared access media Signaling: creates signals and interface with the media

CNAP AT VCC  Bridge Connects network segments. Make intelligent decisions about whether to pass signals on to the next segment. Improve network performance by eliminating unnecessary traffic and minimizing the chances of collisions. Divides traffic into segments and filters traffic based on MAC address. Often pass frames b/w networks operating under different Layer 2 protocols.

CNAP AT VCC  Bridge (cont.)

CNAP AT VCC  Bridge (cont.): Filter

CNAP AT VCC  Bridge (cont.): Forward

CNAP AT VCC  LAN Switch Switches connect LAN segments. LAN switches are considered multi-port bridges with no collision domain. Use a MAC table to determine the segment on which a frame needs to be transmitted. Switches often replace shared hubs and work with existing cable infrastructures. Higher speeds than bridges. Support new functionality, such as VLAN.

CNAP AT VCC  LAN Switch (cont.)

CNAP AT VCC  LAN Switch: MAC table

CNAP AT VCC  LAN Switch: Micro-segmentation

CNAP AT VCC  Benefits of LAN Switch No collision domain, because of micro- segmentation. Low latency levels and a high rate of speed for frame forwarding Increases the bandwidth available on a network Is performed in hardware instead of in software, it is significantly faster. BUT: All hosts connected to the switch are still in the same broadcast domain.

CNAP AT VCC  Why segment LANs? Isolate traffic between segments. Achieve more bandwidth per user by creating smaller collision domains. LANs are segmented by devices like bridges, switches, and routers. Extend the effective length of a LAN, permitting the attachment of distant stations.

CNAP AT VCC  Segmentation with bridges

CNAP AT VCC  Segmentation with bridges (cont.) Bridges increase the latency (delay) in a network by 10-30%. A bridge is considered a store-and- forward device because it must receive the entire frame and compute the cyclic redundancy check (CRC) before forwarding can take place. The time it takes to perform these tasks can slow network transmissions, thus causing delay.

CNAP AT VCC  Segmentation with switches

CNAP AT VCC  Segmentation with switches (cont.) Allows a LAN topology to work faster and more efficiently. Uses bandwidth so efficiently, the available bandwidth can reach to 100%. Ease bandwidth shortages and network bottlenecks (such as client-server). A computer connected directly to an Ethernet switch is its own collision domain and accesses the full 10Mbps.

CNAP AT VCC  Segmentation with routers

CNAP AT VCC  Segmentation with routers (cont.) Routers operates at the network layer Routers bases all of its forwarding decisions on the Layer 3 protocol address. Routers ability to make exact determinations of where to send the data packet. Router operate with a higher rate of latency.

CNAP AT VCC  Teaching topology

CNAP AT VCC  Basic 10BaseT troubleshooting

CNAP AT VCC