Transcript Chapter 2 Fundamental Network

Chapter 2
Fundamental Network
• Reviewing the core components of Microsoft
TCP/IP and other network protocols
• Fundamental concepts of Networking:
TCP/IP
DNS
DHCP
WINS
Network Protocols
• NetBEUI
• NWLink (IPX/SPX)
• TCP/IP
Network configuration on W2K3
• Click Start > Control Panel > Network
Connection
• Right-click the network interface
• Select Properties (see your installed network
services and protocols listed)
• Click the Install button to install additional
services and protocols.
• See page 10
NetBEUI
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Enhance User Interface protocols
Windows 95/98
Small office/home office (SOHO) scenarios
It is not routable
Limiting its communication to a single
network subnet
• It was not supported by XP,WinS2003
NWLink (IPX/SPX)
• Microsoft's implementation of Novell's IPX/SPX
protocol
• Its packages data to be compatible with client/server
services on NetWare Networks
• Be aware of some of the basic functionality of
IPX/SPX
- Frame type
- Internal network number
- External network number
Frame Type
• In IPX network indicate the mean by which
data is encapsulated in IPX packets
Frame type:
- Ethernet II
- 802.3
- 802.2
- SNAP
- Arcnet
Problems
• Window System can only integrate with one
frame type on an IPX network.
• Auto detection and first come first serve
Internal Network Number
• It is unique number assigned to all NetWare server
• It required on Windows servers in the following
situations:
- Win servers with tow or more NICs
- Win servers with a single NIC with 2 different IPX
frame type bound to it
- Run File and Print Services for NetWare on the Win
server
- If required by an IPX application on the Win server
• It is made up of eight hexadecimal characters
(00000001 to FFFFFFFE)
External Network Number
• It used to provide a unique logical identifier to
represent a single network segment.
• TCP/IP concepts:
- the INN = the host ID
- the ENN = the network ID
TCP/IP Basic
• Transmission Control Protocol/Internet Protocol
• Protocol Suite
– Referred to as “IP” or “TCP/IP”
– Subprotocols include TCP, IP, UDP, ARP
• Developed by US Department of Defense
– ARPANET (1960s)
• Internet precursor
• Advantages of TCP/IP
– Open nature
• Costs nothing to use
– Flexible
• Runs on virtually any platform
• Connects dissimilar operating systems and
devices
– Routable
• Transmissions carry Network layer
addressing information
• Suitable for large networks
The TCP/IP Model
• Four layers
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Application layer
Transport layer
Internet layer
Network access layer (or Link layer)
The TCP/IP model compared with the OSI model
The TCP/IP Core Protocols
• TCP/IP suite subprotocols
• Operate in Transport or Network layers of OSI
model
• Provide basic services to protocols in other
layers
• Most significant protocols in TCP/IP suite
– TCP
– IP
TCP (Transmission Control Protocol)
• Transport layer protocol
• Provides reliable data delivery services
– Connection-oriented subprotocol
• Establish connection before transmitting
• Uses sequencing and checksums
• Provides flow control
• TCP segment format
– Encapsulated by IP packet in Network layer
• Becomes IP packet’s “data”
A TCP segment
• Three segments establish connection
• Computer A issues message to Computer B
– Sends segment with SYN bit set
• SYN field: Random synchronize sequence number
• Computer B receives message
– Sends segment
• ACK field: sequence number Computer A sent plus
1
• SYN field: Computer B random number
• Computer A responds
– Sends segment
• ACK field: sequence number Computer B sent plus 1
• SYN field: Computer B random number
• FIN flag indicates transmission end
Establishing a TCP connection
IP (Internet Protocol)
• Network layer protocol
– How and where data delivered, including:
• Data’s source and destination addresses
• Enables TCP/IP to internetwork
– Traverse more than one LAN segment
• More than one network type through router
• Network layer data formed into packets
– IP packet
• Data envelope
• Contains information for routers to transfer data
between different LAN segments
• Two versions
– IPv4: unreliable, connectionless protocol
– IPv6
• Newer version of IPv6
– IP next generation
– Released in 1998
• Advantages of IPv6
– Provides billions of additional IP addresses
– Better security and prioritization provisions
An IPv4 packet
An IPv6 packet header
IPv4 Addressing
• Networks recognize two addresses
– Logical (Network layer)
– Physical (MAC, hardware) addresses
• IP protocol handles logical addressing
• Specific parameters
– Unique 32-bit number
• Divided into four octets (sets of eight bits)
separated by periods
• Example: 144.92.43.178
– Network class determined from first octet
Commonly used TCP/IP classes
• Class A devices
– Share same first octet (bits 0-7)
• Network ID
– Host: second through fourth octets (bits 8-31)
• Class B devices
– Share same first two octet (bits 0-15)
– Host: second through fourth octets (bits 16-31)
• Class C devices
– Share same first three octet (bits 0-23)
– Host: second through fourth octets (bits 24-31)
IPv4 addresses and their classes
• Class D, Class E rarely used (never assign)
– Class D: value between 224 and 239
• Multicasting
– Class E: value between 240 and 254
• Experimental use
• Eight bits have 256 combinations
– Networks use 1 through 254
– 0: reserved as placeholder
– 255: reserved for broadcast transmission
• Loop back address
– First octet equals 127 (127.0.0.1)
• Loopback test
– Attempting to connect to own machine
– Powerful troubleshooting tool
• Windows XP, Vista
– ipconfig command
• Unix, Linux
– ifconfig command
Binary and Dotted Decimal Notation
• Dotted decimal notation
– Common way of expressing IP addresses
– Decimal number between 0 and 255 represents
each octet
– Period (dot) separates each decimal
• Dotted decimal address has binary equivalent
– Convert each octet
– Remove decimal points
Decimal numbers to Binary
1. Find the largest number in conversion chart that is less than or
equal to the number you are working with (128, 64, 32, 8, and
so on) and place a 1 in its column.
2. Subtract the number from the marked column from the
number you started with.
3. Find the largest number in the conversion chart that is less
than or equal to the number that you were left with after
step1, and place a 1 in its column.
4. Subtract the number from the marked column from the
number you were left with after step 2.
5. Repeat steps 3 and 4 until you reach 0; then place a 0 in all
column that do not have a 1. That is your binary number.
Subnet Mask
• 32-bit number identifying a device’s subnet
• Combines with device IP address
• Informs network about segment, network
where device attached
• Four octets (32 bits)
– Expressed in binary or dotted decimal notation
• Assigned same way as IP addresses
– Manually or automatically (via DHCP)
Default subnet masks
IPv6 Addressing
• Composed of 128 bits
• Eight 16-bit fields
• Typically represented in hexadecimal numbers
– Separated by a colon
– Example:
FE22:00FF:002D:0000:0000:0000:3012:CCE3
• Abbreviations for multiple fields with zero values
– 00FF can be abbreviated FF
– 0000 can be abbreviated 0
• Multicast address
– Used for transmitting data to many different
devices simultaneously
• Anycast address
– Represents any one interface from a group of
interfaces
• Modern devices and operating systems can use
both IPv4 and IPv6
Assigning IP Addresses
• Government-sponsored organizations
– Dole out IP addresses
– IANA, ICANN, RIRs
• Companies, individuals
– Obtain IP addresses from ISPs
• Every network node must have unique IP
address
– Error message otherwise
• Static IP address
– Manually assigned
– To change: modify client workstation TCP/IP
properties
– Human error causes duplicates
• Dynamic IP address
– Assigned automatically
– Most common method
• Dynamic Host Configuration Protocol (DHCP)
IP Address Structure
• It divided into 2 parts
- Host ID
- Network ID
Example: Network ID
Host ID
10.8.32.8 = 00001010|00001000.00100000.00000110
255.0.0.0 = 11111111|00000000.00000000.00000000
Network ID = 10.0.0
Host ID = x.8.32.6
= 10.8.32.6
Nonroutable IP Address
• Internal Network Address:
10.0.0.0 to 10.255.255.255
169.254.0.0 to 169.254.255.255
172.16.0.0 to 172.31.255.255
192.168.0.0 to 192.168.255.255
TCP/IP in a Routed Environment
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Using Router to connect to the Internet
Router has its own IP address and subnet mask
Router is used to sent IP packets
Router uses its routing table
routing table is a cross-reference table that
stores information on how to get to IP
networks
• Default Gateway
- the same network ID and subnet mask
- send data beyond their local subnet
- Any computer its default gateway is where it
sends all packets that don’t have the
network ID of their local subnet.
- where it goes, where do I sent it?
NetBIOS Name V.S. FQDNs
• Both give you the ability to associate a friendly
name with a network object
• Difference is how you see the name written
• NetBIOS name is a simple name used to
represent a system but is limited in size to 15
characters.
• FQDN is typically <computer
name>.<domain name>.<domain extension>
NetBOIS Naming Rules
• The names can’t begin with a number
• The names can be no larger than 15 characters
• The name can use the characters A-Z, a-z, 0-9,
hyphens, and is not case sensitive
• The name can have spaces (a space counts as
on character)
FQDN Naming Rules
• The name can begin with anumber
• The name can be no larger than 255 characters
(domain controllers are limited to 155
characters)
• The name can us the characters A-Z, a-z, 0-9,
hyphens, and is not case sensitive
• The names cannot have spaces
• Portions of the name are separated by periods
(www.microsoft.com)
Name Resolution Methods
There are several ways on a network for a name to
become associated with an IP address
• Domain Name Service – The server that resolves
FQDNs to IP address
• Windows Internet Naming Service – The server that
resolves NetBIOS names to IP address
• LMHosts file – The file stored locally on every
computer that maps IP addresses to NetBIOS names
• Broadcast – A way for your computer to shout out to
the network. (It only work on the subnet connected to
the system)
Name Resolution with DNS
• DNS is a TCP/IP service that is used to map IP
address to FQDNs or vice versa
• Win 2K and newer systems try to resolve the name to
an IP address in the following order:
1. Resolver cache and Hosts file
2. DNS
3. NetBIOS cache
4. WINS
5. Broadcast
6. LMHosts
1. Resolver cache and Hosts file
• Its own resolver cache which is where the local
computer stores its previously queried FQDN
to IP address mappings
• Run ipconfig/displaydns to display
• Run ipconfig/flushdns to clear
• Wins system cache positive entries for the
Time to Live (TTL)value provided to them by
the authoritative DNS server that answered the
request, but never longer than 24 hours
• Negative entries are cached for 5 minutes
• Both entries values can be changed by editing
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControl
Set\Services\DNSCache\Parameters Registry key
• Change the maximum lifetime for positively cached
entries by create the DWORD value
MaxCacheEntryTtlLimit and set its value to the
desired maximum second
• Change the duration that negatively cached queries ar
e kept in the cache, create the DWORD value
NegativeCacheTime and set its value to the number of
seconds that your system to maintain negative name
resolution queries
Host File
• The contents of its Host file are automatically loaded
into the resolver cache when a system boots
• Your alter and save a Host file, it is automatically
reloaded into the resolver cache
• A client’s own local “mini DNS server”
• Manually configure or deploy the Host file to every
system where you would like to have th FQDN-to-IP
address mappings
• %systemroot%\system32\drivers\etc folder
(C:\Windows\system32\drivers\etc by default)
• Notepad to view and edit
2.DNS Query Types
• The client will perform a recursive query to its
primary DNS server
– A recursive query: it is a request for IP address
resolution of the entire FQDN.
• Not answer: it may make several iterative
queries to root-level name servers.
– An iterative query: it is a request to resolve only a
portion of an FQDN
3. NetBIOS Cache
• it will check in NetBIOS cache for any records
that match the host portion of the FQDN
• NetBIOS cache is equivalent of the DNS
resolver cache.
• Only different in that it show NetBIOS nameto-IP address mappings as opposed to FQDNto-IP address mappings
• Run nbtstat –c to view it
4. WINS
• It is used to resolve NetBIOS names to IP
address
• It was devised as a way to map IP addresses to
NetBIOS names
• The client simply sends the request directly to
the WINS server
• Broadcasts
• The method depends on the type of NetBIOS
client that the system is configured
NetBIOS client can be configured to use any one
of following NetBIOS name resolution modes:
- B-node (Broadcast node)
- P-node (Peer node)
- M-node (Mixed node): combination of B- and
P-node, broadcast => queries a NetBIOS name
server
- H-node (Hybrid node): combination of B- and
P-node, queries a NetBIOS name server =>
checks in its LMHosts file => broadcast
DHCP
• Dynamic Host Configuration Protocol
• It allows clients and server on your network to
automatically obtain an IP address from a DHCP
server
• Operations:
DHCP lease
DHCP scope
Reservation
DHCP options
DHCP relay agent
Automatic Private IP Addressing
DHCP Lease
• Network adapters are identified by 48-bit Media
Access Control (MAC) address
• MAC address are expressed in hexadecimal
MAC address = 00-03-2F-01-D0-1B
• DHCP servers only lease IP addresses to DHCP
clients
• A client is connected to the network, at the 50% point
of its DHCP lease duration it will automatically to
contact DHCP server and renew its lease
DHCP Scope
• DHCP address allocations and leases are configured
in DHCP scopes
• Defining a range of IP address
• Other Settings: Subnet mask, IP address exclusions,
IP address reservations, and DHCP options
• The IP address range is specified at the time a DHCP
scope is created and cannot be changed
• When configured, all IP addresses in the defined
exclusion rang will not be handed out by the DHCP
server
Reservation
• Same IP address for DHCP clients
• Must know the MAC address of the computer
• A mapping on the DHCP server of an IP
address to a MAC address
• Exclude the range of IP addresses from the
DHCP lease
DHCP Options
• It allow you to automatically provide clients with
much more than an IP address and a subnet mask
• It can automatically assign the following to DHCP
clients:
– Default gatway
– DNS server(s)
– DNS domain name
– WINS server(s)
– WINS node type
DHCP Relay Agent
• The problem with broadcasts is that router will drop them
• The router is RFC1542 compliant and has BOOTP forwarding
enabled, the router will forward DHCP Discover packets
• Not RFC1542 compliant, DHCP server on a single subnet,
client on multiple subnets to obtain IP address leases from the
server
- Buy newer RFC1542-complient routers
- configure a Win server running Routing and Remote
Access service as DHCP relay agent
• DHCP relay agent weren’t present => Microsoft invented
APIPA
Automatic Private IP Address
• It is in Windows 2000 or higher
• Client cannot contact a DHCP server gives
itself its own IP address
• Class B address in the 168.254.0.1 to
169.254.255.254 range with subnet mask of
255.255.0.0
• The feature allows you to automatically set up
a TCP/IP network by plugging the computer
into a hub or switch