Basic Communications ModelStandards are needed at all Layers User Layer
Application Layer
Computer (Transport) Layer
Transmission Layer
Subnet Layer
1
2
3
Station A Station B
Transmission of Messages1. Within a Single Subnet, or
2. in Point-to-Point Links Between Subnets
4
1 2
InternettingStation A Station B
internet: collection of subnets such that any station on any subnet can communicate with any other station on any other subnet simply by giving the
internet address of the other station.
1
2
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Layering in Major Architectures
Basic Model
Application
Computer(Transport)
Internet
TCP/IP
Internet
IPX/SPX
Internet
Subnet(OSI)
OSI
Application (7)
Presentation (6)
Session (5)
Transport (4)
Network (3):Internet &
Subnet
Data Link (2)
Application Application
Transport:TCP, etc.
Complex:SPX, etc.
Physical (1)
Subnet(OSI)
Subnet(OSI)
LANs, MANs, & WANs
LAN– Local area network– Single office, building, campus– 10 Mbps to 100 Mbps to the desktop common– 1 Gbps coming
Will carry most traffic, because most traffic is local
PC Networking on a small LAN
Network InterfaceCard (NIC)
In each PC
Each client and server needs a NIC rather than a modem
LANs, MANs, & WANs
WAN– Wide area network– Intercity, international– 9,600 bps to 1 Mbps common to the desktop– Links with higher speed are usually shared
(multiplexed) by several desktops Emerged before LANs, due to high cost of long-
distance telephone charges
Microsoft Layered Network ArchitectureMicrosoft Layered Network Architecture
Network Interface Card
Network Adapter Card Drivers
NDIS Interface Streams
Streams
Transport Protocols
Transport Driver Interface
NetBIOS driver
Redirectors Servers WinSock driver
1. Physical
2. Data Link
3. Network
MAC
LLC
4. Transport
5. Session
6. Presentation
7. Application
Kernel Mode
User Mode
Some basic conceptsSome basic concepts
NDIS Interface: Network Driver Specification Interface, wraps NIC drivers and allow communication with multiple protocols, binds a NIC to a protocol.
Streams: multiple channels allowing broader bandwidth for data transfer, envelop the protocols.
Transport Driver Interface: allows software drivers (server, redirector, etc) to communicate with protocols.
Redirectors: software in WS that redirect network drives, printers requests to network I/O requests.
Servers: software that allows a device to accept requests from other devices.
Standard protocolsStandard protocols
NetBEUI - NetBIOS Extended User Interface, “native” Windows protocol, not routable.
TCP/IP - implemented through WinSock, routable, supports SNMP, DHCP, WINS.
NWLink (IPX/SPX) - used to connect to Novell NetWare, just a protocol, not access.
DLC - Data Link Control, used to connect to IBM mainframes and HP printers directly connected to a network (server).
Data Link Layer
Logical Link Control LayerLogical Link Control Layer
Media Access Control (MAC) LayerMedia Access Control (MAC) Layer
802.310Base-T
802.310Base-T
802.310Base-5
802.310Base-5
802.3Other
PhysicalLayer
802.3Other
PhysicalLayer
802.5Physical
Layer4 Mbps
802.5Physical
Layer4 Mbps
802.5Physical
Layer16 Mbps
802.5Physical
Layer16 Mbps
OtherPhysical
Layer
OtherPhysical
Layer
OSIData Link
Layer(Layer 2)
OSIPhysical
Layer(Layer 1)
OSI Data Link Layer is subdivided into two layers Media access control Logical link control
OSI Data Link Layer is subdivided into two layers Media access control Logical link control
LAN Using Ethernet 10Base-T
RJ-45 jacks10Base-T Hub (Multiport Repeater)
Unshielded Twisted Pair (UTP) Wiring(4-Pair Bundle)
PC
RJ-45Jack
NIC
NetworkInterface
Card
10Base-TUTP Wiring
Bundles:4 Pairs
EIACategory3, 4, or 5
NICs
Network Interface Cards
– Implement Physical Layer– Plug and Electrical Signaling
– Implements the Data Link Layer (data packaging, access control, etc.)
– LLC (802.2)
– MAC (802.3 MAC)
Wiring Unshielded Twisted Pair (UTP)
– Twisted several times per foot to reduce interference, T in 10Base- and Unshielded
– No protection except for plastic coating– Distance limitation: 100 meters (attenuation, distortion, noise and interference,
crosstalk) -- propagation
Categories of UTP Wiring– Category 5: The best. Good for 100 Mbps– Category 3 and 4: lower. May be OK for 100 Mbps
Wiring Plugs: RJ-45 Standard– Similar to home (RJ-11) jacks, but wider
CSMA/CD Media Access Control CD: Collision Detection
– If two stations transmit at once ….– Their signals collide, scrambling one another– Because each sender listens (senses the carrier),
both know that there has been a collision– Both stop and wait a random amount of time.
XCollision
101010 001110
Ethernet 10Base-T LAN with Multiple Hubs
Hub 1
Hub 2 Hub 3
Hub 4
StationA
StationB
StationC
StationD
UTPWire
UTPWire UTP
Wire
UTPWire
UTP Wire
Daisy chain, no Loopsallowed!
Daisy chain, no Loopsallowed!
Maximum distancebetween farthest Stations is
4 Hubs/5 100 meter segments
Switches
Switch
StationA
StationB
StationC
StationD
Connection 1A-C
Connection 1A-C
Connection 2B-D
Connection 2B-D
With a switch, multiple stations may transmit simultaneously: no congestion as traffic grows.
Wireless LAN
BroadcastSignal
TransceiverTransmitting
TransceiverReceiving
ClusterTransceiver
Receiving
Antenna
Hub Controller
Wireless LAN
Wireless LAN with Access PointsWireless LAN with Access Points
WirelessNotebook
NIC
Access Point
IndustryStandard
CoffeeCup
To EthernetSwitch
Antenna(Fan) PC Card
Connector
802.11 Wireless LAN Speeds802.11 Wireless LAN Speeds
802.11 2 Mbps (rare)2.4 GHz band (limited in bandwidth)
802.11b 11 Mbps, 2.4 GHz3 channels/access point
802.11a 54 Mbps, 5 GHz (> bandwidth than 2.4 GHz)
11 channels/access point 802.11g 54 Mbps,
2.4 GHzlimited bandwidth
AddressAddressesesAddressAddresseses
Ethernet address (MAC address ) 48-bit unique addresses hard wired in NICs (280 trillion) 12 hex numbers, e.g. 00-A0-C9-9F-00-07 first three identify company, Intel in the example how to see: IPconfig, or System Information
IP address (number) 32-bit value, not hard coded (4 billion), assigned manually or by
DHCP four dotted quads, each quad a decimal from 0-255,
corresponding to eight bits, e.g. UBMAIL IP address is 198.202.0.25
to convert open Calculator select View, Scientific, decimal and type dotted quad decimal value, then select binary.
InternetinInternetinggInternetinInternetingg
Station A wants to send message to station D, but IP number is not in the same subnet -- no can do!
Sends the message to the default IP router -- default gateway All stations belonging to the same subnet share the first three dotted
quads. 204.52.128.67 and 204.52.128.147 are in the same subnet, while
198.202.0.25 is not.
A,B and C-Class NetworksA,B and C-Class NetworksA,B and C-Class NetworksA,B and C-Class Networks A-class networks
first 8 bits fixed, from 0-126 (only 127) very large companies like IBM, BBN, DEC,HP can assign 3 dotted quads - up to 16 million hosts
B-class networks first 16 bits fixed, first quad 128-191 and second 0-255 (16,384) Medium-sized companies like Microsoft, Exxon can assign 2 dotted quads - up to 65,535 hosts
C-class networks first 24 bits fixed, first quad 192-223, second and third 0-255
(2,097,152) can assign 1 dotted quad - up to 253 hosts, 0 is the subnet address.,
1 default router address, 255 broadcast address.
Sockets and WinSockSockets and WinSockSockets and WinSockSockets and WinSock Sockets are the basic TCP requirement Socket address
IP address of the receiver Port number of the receiving program (80,21,23) Type of port TCP or UDP
WinSock is an adaptation of sockets to the PC it now comes as part of the PC OSs it is an application programming interface
Internet Host NamesInternet Host NamesInternet Host NamesInternet Host Names Host names in Windows
HOSTS - a list of IP and names (each machine) DNS - a server with a common table of IP & names (use with
Windows 2000, together with Active Directory) WINS - Windows Internet Name Server
not DNS compatible (use only with NT/9x) can resolve IP addresses inside a Windows network good with dealing with NetBEUI names
FQDN Fully Qualified Domain Name name of a host like: machine.org.domain, e.g.
ubmail.ubalt.edu, with a DNS assignment to an IP
Setting static IP Setting static IP addressesaddressesSetting static IP Setting static IP addressesaddresses
Open Control Panel and select Network Connections Under LAN or High-Speed Internet select local area
connection, right-click and select properties select Internet Protocol (TCP/IP) and click on properties fill in IP number, Subnet Mask, Default Gateway and DNS
server click OK, close. Use ping to test your setup.
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