ITNW 1333 -- Microsoft Networking Essentials
Course Syllabus
 
 
 

Chapter 6

Network Communications & Protocols

 

Packets in Networks

  • Large data messages reformatted
  • Smaller, more manageable pieces
  • Packets or frames
  • Resending of packet errors
  • Network saturation
 

Packet Structure

  • Packet Header
    • Source address
    • Destination address
    • Data transmission alert signal
    • Clocking information
    • Synchronize transmission
  • Packet Data
    • Actual data being sent
    • Size varies
    • Depending on network type
    • As little as 512 bytes
    • Up to 4 K
  • Packet Trailer
    • Validation information
    • Cyclical redundancy check (CRC)
    • Number formed by sender
    • Verified by receiver
    • Request resend if not a match
 

Packet Creation

 
 
 

Understanding Packets

  • Header includes addresses (Both send & receive)
  • Adapters read all packets
  • Accept just those addressed to them
  • Broadcast packets go to all adapters
 

Protocols

  • Rules & procedures of networks
  • For communication among users
  • Must speak the same language
  • Agree on the rules of communication
 

Protocol Functions

  • Computers use many protocols
  • Each one provides communication
  • Different purposes & functions
  • Work at one or more layers
  • Sophisticated work at higher levels
 

Connectionless Protocols

  • Place the data on the network
  • Assume it will arrive
  • Faster
  • Not as reliable
  • Referred to as datagrams
 

Connection-Oriented Protocol

  • Connection is established
  • Data sent in orderly, slower fashion
  • Packet receipt is acknowledged
  • Resends error packets
  • Connection is terminated
 

Routable Packets

  • Routing data to multiple networks
  • Network layer of OSI model
  • Hardware called router
  • Effective in enterprise networks
  • TCP/IP & IPX/SPX are routable
 

Layered Architecture Protocols

 
 
 

Protocols

  • Addressing information
  • Routing information
  • Error Checking
  • Resend requests
  • Rules for communicating
  • Three main protocols
    • Network protocols
    • Transport protocols
    • Application protocols
 

Network protocols

  • IP internet protocol TCP/IP network
  • IPX internetwork packet exchange (Novell's protocol)
  • NWLink Microsoft's implementation of Novell's protocol
  • NetBEUI IBM & MS for NetBIOS
  • DDP delivery datagram protocol (AppleTalk data transport protocol)
  • DLC data link control
    • networked HP printers
    • IBM mainframes
 

Transport Protocols

  • TCP transmission control protocol
  • SPX sequenced packet exchange
  • NWLink MS implementation of SPX
  • ATP
 

Application protocols

  • SMTP simple mail transport protocol
  • FTP file transfer protocol
  • SNMP simple network management protocol
  • NCP NetWare core protocol
  • AFP AppleTalk file protocol
 
 

Common Protocols

  • NetBIOS/NetBEUI
  • NWLink (IPX/SPX)
  • TCP/IP
  • AppleTalk
  • DLC
  • XNS
  • DECNet
  • X.25
 

NWLink

  • Windows NT to connect to Novell
  • All computers use same frame type
  • ODI Open Data-Link Interface
  • IPX Internetwork Packet Exchange
  • RIP Routing Information Protocol
  • SPX Sequenced Packet Exchange
  • NCP NetWare Core Protocol
  • SAP Service Advertising Protocol
 

TCP/IP

  • ICMP internet Control message protocol
  • ARP Address Resolution Protocol
  • TCP Transmission Control Protocol
  • UDP user Datagram Protocol
  • DNS Domain Name System
  • FTP File Transfer Protocol
  • Telnet
  • SMTP Simple Mail transport Protocol
  • RIP Routing Information Protocol
  • OSPF Open Shortest Path First
 

IP Addressing

  • Addressing & routing in TCP/IP
  • Logical addresses 4 bytes long
  • Each byte, an octet, is represented by a decimal number from 0 to 255 separated by a period, for example: 183.24.206.18
  • First octet denotes class A, B, C
    • Class A: 1-126 = 16,387,064 hosts
    • Class B: 128-121 = 64,512 hosts
    • Class C: 192-223 = 254 hosts
  • Missing addresses for special services (127 is for loopback )
 

TCP/IP private addresses

  • InterNIC series for private networks
  • Class A: 10 - one class A address
  • Class B: 172.16 thru 172.31 - 16 class B addresses
  • Class C: 192.168.0 thru 192.168.256 -256 Class C addresses
 

CIDR

  • Classless Inter-Domain Routing
  • Class addressing stopped
  • Class C is 24 bit
  • InterNIC uses 26 bit
  • ISP can give 192.203.187.23 thru 192.203.187.26
 

Subnet Masks

  • IP address has two sections (Host ID & network)
  • For address: 153.92.100.10 with mask 255.255.0.0, Host ID is 100.10 and network is 153.92
  • Using the same address with mask 255.255.255.0, Host Id is 10 and network is 153.192.100
 

DHCP

  • Dynamic Host Configuration Protocol
  • Easier IP addressing
  • Server has a block of addresses
  • Server has a block of Subnet masks
  • Server leases address to client
 

AppleTalk

  • Defines physical transport in Apple Macintosh networks
  • Establishes a suite of protocols
  • AppleTalk Phase II outside networks
  • Divides Computers into zones rather than defining networks
 

Xerox Network Systems (XNS)

  • For use in Ethernet networks
  • Basis for IPX/SPX
  • Seldom found in networks today
 

DECNet

  • Digital Equipment Corporation
  • Digital Network Architecture (DNA)
  • Proprietary protocol digital networks
  • Complete routable suite
  • Phase IV is current iteration
 

X.25

  • Set of wide area protocols
  • Used in packet switching networks
  • Connect terminals to mainframes
  • Widely used in Europe
 
 

Access Methods

  • Two computers talk at once = collision
  • Rules to prevent collisions
  • When computer can access cable (data channel)
  • Channel access methods
  • All machines must use same method
 

Major Access Methods

  • Contention
  • Token-passing
  • Demand priority
  • Polling
 

Contention

  • Everyone talks at the same time
  • Data sent when available to send
  • More collisions
  • More retransmission
  • Network useless jumble of signals
 

CSMA/CD

  • Carrier-Sense Multiple Access with Collision Detection
  • Used by Ethernet
  • Computer listens to network
  • Sends if medium is clear of data
 

CSMA/CA

  • Carrier-Sense Multiple Access with Collision Avoidance
  • Listens, sends intent to transmit
  • Other clients hold transmissions
  • Creates traffic, slows network
  • Apple LocalTalk uses
 

Token Passing

  • Computer with token transmits
  • All computers have equal access
  • Time sensitive applications, banks
  • Computer must wait on token
  • More complicated & expensive
 

Demand Priority

  • Only 100VG-AnyLAN 100 MBPS
  • Star bus topology, Intelligent hubs
  • End node sends demand signal
  • Hub sends OK to transmit
  • Transmission priorities are set
 

Polling

  • Central controller, primary device
  • Each computer, secondary device
  • Primary queries secondary
  • Allows limited amount of data sent
  • Then next secondary has turn