08_LAN Design
Upcoming SlideShare
Loading in...5
×
 

08_LAN Design

on

  • 899 views

 

Statistics

Views

Total Views
899
Views on SlideShare
898
Embed Views
1

Actions

Likes
0
Downloads
37
Comments
0

1 Embed 1

http://www.slideshare.net 1

Accessibility

Categories

Upload Details

Uploaded via as Microsoft PowerPoint

Usage Rights

© All Rights Reserved

Report content

Flagged as inappropriate Flag as inappropriate
Flag as inappropriate

Select your reason for flagging this presentation as inappropriate.

Cancel
  • Full Name Full Name Comment goes here.
    Are you sure you want to
    Your message goes here
    Processing…
Post Comment
Edit your comment

08_LAN Design 08_LAN Design Presentation Transcript

  • Local Area Network Design
  • Contents
    • Components of a LAN
    • Cabling
    • Active Components
    • Ethernet Switching
    • Virtual LANs
    • Switched LAN Design
  • The Components of LAN
    • The cabling system : media
    • The active components :
    • * hub: distributes the bus capacity among equipment
    • * switch: gives dedicated bandwidth to the LAN
    • equipment and connections
    • * router: provides logical segmenting
    • The servers : provide shared resources for the hosts
    • The workstations : use the network resources
    • The network interface card+driver software : adapts
    • the equipment and the programs to the network
    • The networking software :
    • * Networked operating system, e.g. Windows2000
    • * Communication software: e.g. TCP/IP
  • The Structured LAN Cabling CD BD BD BD FD FD FD FD TO TO TO Horizontal cabling Vertical cabling Campus cabling CD Campus Distributor = aluejakamo BD Building Distributor = talojakamo FD Floor Distributor = kerrosjakamo TO (To Office) = työpiste
  • The Principles of Design Floor distributor patch panel equipment cable horizontal cabling equipment cable active component jack terminal equipment P 2 P 3 P 4 P 1
    • Cabling recommendations : twisted pair : 100 Ω UTP- or STP cable
    • fiber : MM-fiber (GK or GI)
    • Horizontal cabling:
    • Campus and vertical cabling
    Floor distributor Building distributor Campus distributor fiber panel fiber panel patch panel patch cable Equipment cable twisted pair fiber Campus cable A 1 A 4 A 1 A 1 A 2 A 3 Vertical cable
    • Cable recommendations :
    • - vertical cabling : GK –multimode fiber
    • Cat 5 twisted pair
    • - Campus cabling : GK-multimode fiber
    • SM-singlemode fiber
  • The Active Components
    • Functions of the active c omponents
      • the end equipment access
      • (hubs, switches)
      • extending the physical network
      • enhance the performance of the network (switches, routers)
      • interconnect different types of
      • networks (bridges, switches, routers, gateways)
    Application Presentation Session Transport Network Data Link Physical REPEATER BRIDGE ROUTER GATEWAY SWITCH
  • The Concentrator = Hub
    • Shared media operation : the incoming frames are copied to all
    • other ports
    • A hub is a repeater: the signals are regenerated
    • Maximum distance between hub and workstation is 100 m
    • (twisted pair), catchment area 210 m
    • Used as the ”backbone ” of small offices
    repeater MAU MAU MAU MAU
  • Characteristics of a hub network collision domain A
    • All the equipment in a hub network are in the same collision domain
    • - all traffic can be monitored from any port with an analyzer
    • - hubs may filter errored frames (runts, giants)
  • Bridge
    • If a hub-extension is not sufficient, the span of the LAN can be extended with a bridge
      • local bridge (adjacent LANs)
      • remote bridge (far away LANs)
    B another LAN, or remote bridge
    • Multiport bridge is a LAN switch
    B
  • The Operation of a bridge
    • Works on layer 2 of the OSI-model
    • - self-learning : MAC - addresses
    • LAN segmentation and traffic filtering
    • - the LAN is split into two collision domains
    • Transparent
    Collision domain 1 Collision domain 2 A B
  • Ethernet Switching
    • A switch is a multiport bridge, whose task is to switch frames
    • as fast as possible from the input port to the output port
    • - the idea is to provide wire-speed capacity to simultaneous
    • connections (10, 100 or 1000 Mbit/s)
    • - a switch needs to have a fast internal backplane bus and
    • efficient ASIC- circuits
    Bus 10 Gbit/s 1 2 3 4 5 6 7 8 12 10 10 …… 100
  • Benefits of Switching
    • The connections speeds increase (throughput)
    • Better security : unicast-traffic is confined to the ports of the
    • communicating parties
    10 MB/s 10 MB/s 10 MB/s 10 MB/s 10 MB/s 100 MB/s 100 MB/s
  • Basic Operation of an Ethernet Switch
    • The switch learns the layer 2 (MAC) addresses from each port ;
    • there can be several addresses (hub or another switch in a port)
    • The switch builds a MAC-address table based on the addresses it has
    • learned
    • Broadcast-messages are copied to every port
    • A switch has two operation modes: cut-through and store-and-forward
    • Higher speed can be used on trunk ports (between switches) or on
    • server ports (100 or 1000 Mbit/s)
    Port MAC-address 00:a0:24:d6;b7:c8 1 00:a0:24:12:d5:a1 2 00:a0:24:c1:e2:b6 3
  • Collision Domains in a Switch Network Broadcast domain Collision domain
    • Each switch port forms a collision domain (half-duplex, HD)
    • A switch does not limit the spreading of broadcast-messages
    • (unless virtual LANs are used)
    • A port can be set to full-duplex (FD) operation, where there are no
    • collisions
    A
  • Half Duplex and Full Duplex port HD : FD :
    • Benefits of bidirectional operation:
    • - the capacity increases (max about 20/200 Mbit/s)
    • maximum distance between equipment increases (only media
    • restriction)
  • The Switching Modes
    • The store-and-forward mode:
    • - the switch is a fast multiport bridge: the whole frame is copied to the
    • input buffer before switching decision
    • - frames with errors can be discarded
    • - networks of different types and speeds can be interconnected
    • - added delay (almost 100 μs )
    • The cut-through:
    • - bit by bit switching starts after reading the destination address
    • from the incoming frame
    • - small delay (in the order of 10 μs)
    • - frames with errors are forwarded
    BER threshold cut-through store-and-forward
  • The Performance of a Switch
    • Filtering rate : the ability to interpret the destination addresses
    • in the incoming frames within a specified time period
    • Forwarding rate : the ability to forward frames through the switch
    • within a specified time period
    preamble actual frame IFG = Interframe gap (0.96 μs at 100 M speed)
    • The theoretical maximum forwarding rates in Ethernet :
    Rate (Mbit/s Minimum frames Maximum frames 10 14880 812 100 148800 8120 1000 235000 81200 Minimum frame : 64 + 8 bytes Maximum : 1526 + 8 bytes
  • The Spanning Tree Protocol
    • A switch network can be pruned to be loopless by using the STP
    • protocol
    • The main functions of STP:
    • - loop detection and elimination
    • - media fault detection and reconfiguration
    • - fine tuning of parameters by manual configuration
  • The Spanning Tree Operation
    • The protocol sets the trunk ports of the switches to blocking or
    • forwarding state using 3 parameters:
    • - bridge identifier : switch priority and MAC-address
    • - path cost : each port has a cost value, which is usually inversely
    • proportional to the port speed
    • - port priority : each port has a default priority : lower value means
    • higher priority
    • The spanning tree information is transferred using periodical
    • BPDU-multicast frames (1 - 3 s period)
    • - distribution of topology information
    • - election of the root switch
    • - pruning the redundant links
  • Election of the Root Switch and Root Ports
    • The root switch will the switch with the lowest bridge identifier
    • value
    • - the default value is 32768
    • - the lowest MAC-address value will ”win”
    • The root port: it has the lowest cost path to the root bridge
    • - low cost is preferred
    Switch 1 (ROOT) Switch 2 Switch 3 Switch 4 Switch 5 10 20 10 10 40 10 30 20 10 10 R R R R
  • Election of the Designated Bridge and Port Switch 1 (ROOT) Switch 2 Switch 3 Switch 4 Switch 5 10 20 10 10 40 10 30 20 10 10 R R R R LAN segment A LAN segment B LAN segment C LAN segment D
    • After election of the root ports, the designated switch and the
    • designated port are chosen: the lowest cost from a certain LAN
    • segment to the root switch
    D D D D
    • The designated ports are set to forwarding state, the other ports
    • are set to blocking state (except root ports): loops have been eliminated
  • Virtual LANs
    • Virtual local area networks (VLANs) are logical LANs, which are
    • using the same physical LAN as a “platform”
    • Benefits of VLANs:
    • They make it easier to add, move, or change users in a network
    • (reduced cost of administration)
    • They enhance network security by means of logical segmentation
    • of users and groups
    • - They help to control the spreading of broadcast-messages
    • Effect of the number of broadcasts on the computer performance
    • Logical grouping of users based on services
    • Creating isolated broadcast domains not dependent on location
    • VLANs are created on switches
    • The traffic between VLANs should be minimized
    The Basic Ideas of VLANs Sales Engineering Logistics The traffic of different departments is logically separated Server of Sales and Engineering Server of Logistics Enterprise switch
    • VLANs can be created on basis of several parameters:
    • - Switch port
    • - MAC-address
    • - Protocol
    • - IP subnet
    • - Application
    • …… .
    VLAN types VLAN Components
    • Switches for logical segmentation
    • A protocol to separate the different VLANs on trunk lines
    • A server and a protocol for distributing the VLAN information
    • in a dynamic environment
    • VLAN management system
    • A router to forward the traffic between VLANs
  • Port based VLANs
    • A common VLAN-implementation in workgroup switches:
    • layer 1 VLAN
    • A port is configured statically to a VLAN
    • VLAN ports are location independent
    • An easy implementation
    Port 1 VLAN1 Port 2 VLAN3 Port 3 VLAN1 Port 4 VLAN2 Port 5 VLAN3
  • Routing Between VLANs Router VLAN1 = subnet 1 VLAN2 = subnet 2
    • Standard IEEE 802.1Q
    • The standard specifies the method how to tag the frames of different
    • VLANs on trunk lines
    • 12 bits are used for VLAN identification : 4094 VLANs
    DA SA P CFI VLANID Type data ... 12 bits 802.1Q P = priority CFI = Canonical Format Identifier VLANID = VLAN identification
  • Switched LAN Design
    • Basic concepts :
    LAN Core equipment Edge equipment uplink downlink 10/100 Mbit/s 100 Mbit/s 1 Gbit/s Servers End equipment Users Services
  • A very small LAN Basis of Design
    • Amount of traffic/user (Mbit/s)
    • Amount of traffic/server (Mbit/s)
    • Number of users (ports needed)
    • Need for routing
    • The nature of applications (bursty/flat)
    hub UTP
  • A small LAN
    • If the number users is in the order of 10-20: a switched LAN
    • - e.g. 12 - 24 port switch (10/100 Mbit/s)
    • - 20 - 40 workstations : a stackable switch (e.g. 48 ports)
  • Core switch Edge switch 1 Gbit/s 1 Gbit/s
    • E.g. 200 - 100 workstations
    • Fault tolerant fast trunk lines and server ports
    An Enterprise LAN