OSI and Network Devices

1
OSI and Network Devices
Application Presentation Session Transport Network
Data Link Physical
2
Repeaters

• Connectivity device that regenerates and
  amplifies an analog or digital signal

Repeater
3
Repeaters

• Repeaters simplest type of connectivity devices
  that regenerate a digital signal
• Operate in Physical layer
• Cannot improve or correct bad or erroneous signal
• Regenerate signal over entire segment
• One input port and one output port
• Suited only to bus topology networks

4
Repeater Operation
repeater
5
Hub repeater with more than one output port

• Multiple data ports
• Operate at Physical layer
• Uplink port allows connection to another hub or
  other connectivity device
• On Ethernet networks, can serve as central
  connection point of star or star-based hybrid
  topology
• On Token Ring networks, hubs are called
  Multistation Access Units (MAUs)

6
Hubs

• Multiport repeater containing one port that
  connects to a networks backbone and multiple
  ports that connect to a group of workstations

Detailed diagram of a hub
7
Hubs

• 3COM SuperStack 3 Baseline 24 port 10/100 Hub
• 373.99 (5 port 77.99)

8
Hubs

• Passive hubs
• Only repeats signal
• Active hubs
• Regenerates signal
• Intelligent hubs
• Possesses processing capabilities
• SNMP

9
Hubs in a network design
10
Standalone Hubs

• Serves a workgroup of computers that are
  separated from the rest of the network

Standalone hubs
11
Stackable Hubs

• Designed to be linked with other hubs in a single
  telecommunications closet

Rack-mounted stackable hubs
Stackable hubs
12
Modular Hubs andIntelligent Hubs

• Modular hub
• Provide a number of interface options within one
  chassis
• Intelligent hubs
• Also called managed hubs
• MIB (management information base)
• Collection of data used by management programs to
  analyze network performance

13
Installing a Hub

• As with NICs, the best way to ensure a hub is
  properly installed is to follow the
  manufacturers guidelines

Connecting a workstation to a hub
14
Choosing the Right Hub

• Performance
• Cost
• Size and growth
• Security
• Management benefits
• Reliability

15
Bridges

• Like a repeater, it has a single input and single
  output port
• Unlike a repeater, it can interpret the data it
  retransmits
• FibreBridge 1100D - Bridge 1,879.99 (1000Mbs)

Bridge
16
Bridge Operation

• Connect two network segments
• Analyze incoming frames
• Make decisions about where to direct them based
  on each frames MAC address
• Operate at Data Link layer
• Protocol independent
• Can move data more rapidly than traditional
  routers
• Extend Ethernet network without extending
  collision domain or segment
• Can be programmed to filter out certain types of
  frames

17
Bridges

• Filtering database
• Collection of data created and used by a bridge
  that correlates the MAC addresses of connected
  workstations with their locations
• Also known as a forwarding table

FIGURE 6-22 Bridges use of a filtering database
18
Bridges

• Transparent Bridging
• Method used on most Ethernet networks
• Source Route Bridging
• Method used on most Token Ring networks
• Translation Bridging
• Method that can connect Token Ring and Ethernet
  networks

19
Bridge Operation
Data Link layer
bridge
20
Switches

• Switches subdivide a network into smaller logical
  pieces
• Collision domain
• Portion of a LAN encompassing devices that may
  cause and detect collisions among their group

Example of LAN switches
21
Swtiches

• Subdivide network into smaller logical pieces
  (segments)
• Layer 2 standard switch
• Layer 3 router switch
• Layer 4 application switch
• Acts as multiport bridges
• Most have internal processor, OS, memory, and
  several ports
• Each port on switch acts like bridge
• Each connected device effectively receives own
  dedicated channel

22
Routing Switches

• Routing switch
• Another term for a Layer 3 and sometimes a Layer
  4 switch
• Hewlett-Packard Procurve routing switch 9308M
• 10/100/Gigabit managed modular switch with 8 open
  module slots for up to 64 Gigabit or 168 10/100
  ports or any combination
• 13,179.88

23
Switch

• Cisco Catalyst 2924M 24 port 10/100 Switch
• 1,599.99

24
Cut-Through Mode andStore and Forward Mode

• Cut-through mode
• Switching mode in which switch reads a frames
  header and decides where to forward the data
  before it receives the entire packet
• Advantage is speed
• Can detect runts, or packet fragments
• Store and forward mode
• Switching mode in which switch reads the entire
  data frame into its memory and checks it for
  accuracy before transmitting it
• Transmits data more accurately
• Slower than cut-through mode
• Can transfer data between segments running
  different transmission speeds

25
Creating VLANs with Switches

• Virtual LANs (VLANs) logically separate networks
  within networks
• Use switches to group a number of ports into a
  broadcast domain
• Combination of ports making up a Layer 2 segment
• In TCP/IP, referred to as a subnet
• VLANs created by properly configuring switchs
  software
• VLAN configuration requires careful planning

26
Using Switches to Create VLANs

• Virtual local area networks (VLANs)
• Means by which a switch can logically group a
  number of ports into a broadcast domain
• Broadcast domain
• Combination of ports that make up a Layer 2
  segment and must be connected to a Layer 3 device

Simple VLAN design
27
Higher-Layer Switches

• Switch capable of interpreting Layer 3 is called
  a Layer 3 switch or routing switches
• Switch capable of interpreting Layer 4 is called
  a Layer 4 switch or application switches
• Ability to interpret higher-layer data enables
  switches to perform advanced filtering,
  statistics keeping, and security functions

28
Routers

• Multiport device
• Can connect integrate LANs and WANs running at
  different transmission speeds and using a variety
  of protocols
• Multiport connectivity devices that direct data
  between nodes on a network
• Operate at Network layer
• Reads incoming packets logical addressing
  information
• Determines where to deliver packet
• Determines shortest path to that network
• Protocol-dependent

29
Router Features and Functions

• Modular router
• Router with multiple slots that can hold
  different interface cards or other devices

Typical routers Cisco 3661 - 8,149.99
30
Router Features and Functions

• Filter out broadcast transmission to alleviate
  network congestion
• Determine the best path for data to follow
• Reroute traffic
• Prevent certain types of traffic from getting to
  a network
• Support simultaneous local and remote activity
• Provide high network fault tolerance through
  redundant components
• Monitor network traffic and report statistics to
  a MIB
• Diagnose internal or other connectivity problems
  and trigger alarms
• Support simultaneous local and remote connectivity

31
Router Operation
Network layer
Data Link layer
router
32
Routers
Placement of routers on a LAN
33
Routing Protocols

• Means by which routers communicate with each
  other about network status
• Convergence time
• The time it takes for a router to recognize a
  best path in the event of a change or outage
• Bandwidth overhead
• Burden placed on an underlying network to support
  the routing protocol

34
Router Features and Functions

• Interior router directs data between nodes on
  autonomous LANs
• Exterior router directs data between nodes
  external to given autonomous LAN
• Border routers connect autonomous LAN with a WAN
• Static routing network administrator programs
  router to use specific paths between nodes
• Dynamic routing automatically calculates best
  path between two nodes
• Accumulates information in routing table

35
Routing Protocols

• Locates the best path. Best path refers to the
  most efficient route from one node on a network
  to another
• RIP (Routing Information Protocol) for IP and IPX
• Distance vector algorithm based on hop count
• Small networks with fewer than 15 routers
• OSPF (Open Shortest Path First) for IP
• Link state algorithm based on hop count and
  weighted area for congestion
• EIGRP (Enhanced Interior Gateway Routing
  Protocol) for IP, IPX, and AppleTalk
• BGP (Border Gateway Protocol) for IP
• Internet

36
Brouters - Bridge router

• Industry term used to describe routers that take
  on some characteristics of bridges
• Can forward non-routable protocols
• Connect multiple network types through one device
• Cisco 1600 1604
• Bridge/router 1,249.99

37
Gateways

• Combination of networking hardware and software
  that connects two dissimilar kinds of networks
  using different formatting, communications
  protocols, or architecture
• Repackage information to be read by another
  system
• Operates at multiple OSI Model layers
• E-mail gateway
• IBM host gateway
• Internet gateway
• LAN gateway
• Proxy server does processing on each data packet
  at the application level

38
Gateway

• CISCO PIX Firewall Gateway
• 3,649.99
• 256,000 connections
• 170 megabits per second (Mbps)