Transcript Slide 1

Managing Network connections
Networking Cables
Networking Cables
Network Cabling
Ethernet Topology
• Bus topology
– Connects each node in a line
– Has no central connection point
• Star topology
– Connects all nodes to a centralized hub
– More popular; easier to maintain
Ethernet Topology
Ethernet Using Star Topology
Ethernet Hub
Ethernet Using Star Bus Topology
Repeaters
• Devices that amplify signals on a network
• Help overcome limitations on the length of
cables that can be used
• Two kinds
– Amplifier repeater
– Signal-regenerating repeater (used by Ethernet)
Repeaters
Wireless LANs (WLANs)
• Make connections using a wireless NIC
• Communicate directly or connect to a LAN by way of
a wireless access point (AP)
• Popular where cables are difficult to install
• Slower than wired networks
• Security is an issue
• Standards
– 1999 IEEE 802.11b (Wi-Fi, AirPort)
– Bluetooth
WLANs
Token Ring
• Physical star; logical ring
• Transmits data at 4 Mbps or 16 Mbps
• Uses a centralized device called a MAU
(Multistation Access Unit)
• Less popular than Ethernet
Network Cards
FDDI
Token ring
Network Cards
Ethernet
Wireless
How NIC (Network Interface Card) Works
• Network card
– Sends and receives data to and from system bus in parallel
– Sends and receives data to and from network in series
– Uses a transceiver for signal conversion
• Network in use is transparent to applications
software using it
• Network nodes are identified by a MAC (Media
Access Control) address
Ethernet Combo Card
Considerations When Selecting a
Network Card
• Speed and type of network
• Type of cable (shielded twisted-pair, coaxial,
or fiber-optic) – except for wireless
connections
• Type of slot (PCI or ISA)
Segmenting a Network
• Decreases amount of traffic on overall
network
• Done through use of bridges and switches
– More intelligent than hubs; make decisions about
whether or not to allow traffic to pass, or where
to forward that traffic
– Use MAC addresses, which they store in routing
tables, to determine where to send packets
Bridges
Bridges and Switches
• Bridges
– Send broadcast messages; not
good for large networks
– Effective at separating highvolume areas on a LAN
– Work best when used to
connect LANs that usually do
not communicate outside
their immediate network
• Switches
– Send a packet only to network
segment for which it is
destined
Bridges and Switches
Bridges Compared with Switches
MAC Addresses
• Unique addresses that are permanently embedded
in a NIC and identify a device on a LAN
• Expressed as six pairs of hexadecimal numbers and
letters
• A local address
• Used at the lowest (physical) networking level for
NICs and other devices on the same network to
communicate
MAC and IP Addresses
• TCP/IP Overview
• Configuring TCP/IP Clients
• Using TCP/IP Utilities
27
Network Address Translation
• Uses a single public IP address to access the
Internet on behalf of all hosts on the network
using other IP addresses
• Proxy server sometimes does double duty as a
firewall
Proxy Server
Connecting Networks with Routers
• Responsible for data
traveling across
interconnected networks
• Use IP addresses to
determine path for packet
• Stateless devices
• Transmit data packet to a
remote network only if data
packet is a routable protocol
Using Routers to Connect Networks
Web browser in Chennai
Web server in Newyork
TCP/IP Overview
• Transmission Control Protocol/Internet
Protocol (TCP/IP) is an industry-standard suite
of protocols used on local area networks
(LANs) and wide area networks (WANs).
• Microsoft Windows supports TCP/IP.
32
Architectural Overview of the TCP/IP
33
The TCP/IP Protocols
• The TCP/IP protocols
– Provide networking connectivity support for
computers (called hosts) on LANs and WANs
– Follow a set of standards for how computers
communicate and how networks are
interconnected
– Follow the four-layer Department of Defense
(DOD) model
Application Layer
• Software programs gain access to the network
through the application layer.
• This layer maps roughly to the session,
presentation, and application layers of the
Open Systems Interconnection (OSI) model.
• The following TCP/IP utilities and services run
at the application layer:
– Hypertext Transfer Protocol (HTTP)
– File Transfer Protocol (FTP)
– Simple Mail Transfer Protocol (SMTP)
35
Application Layer (Cont.)
• TCP/IP utilities and services that run at the
application layer (Cont.):
– Telnet
– Domain Name System (DNS)
– Simple Network Management Protocol (SNMP)
• Microsoft TCP/IP provides two interfaces for
applications to use:
– WinSock
– Network Basic Input/Output System (NetBIOS)
36
Transport Layer
• Transport protocols
– Provide communication sessions between computers
– Define the type of transport service as
either
connection-oriented or connectionless datagramoriented
• This layer maps roughly to the transport layer in
the OSI model.
• The transport layer protocols are
– TCP: connection-oriented, reliable
– UDP: connectionless, no guarantee of packet delivery
37
Internet Layer
• The Internet layer protocols encapsulate
transport layer data into units called datagrams,
address them, and route them to their
destinations.
• This layer maps roughly to the network layer in
the OSI model.
• Windows implements three main protocols at
this layer:
– Internet Protocol (IP)
– Address Resolution Protocol (ARP)
– Internet Control Message Protocol (ICMP)
38
Link Layer
• This layer sends and receives frames, which
are packets of information transmitted on a
network as a single unit.
• The link layer is equivalent to the data-link and
physical layers of the OSI model.
• Two protocols often used for WAN
connections are part of the TCP/IP suite:
– Point-to-Point Protocol (PPP)
– Serial Line Internet Protocol (SLIP)
39
Transmission Control Protocol
• Transmission Control Protocol (TCP) is a
reliable, connection-oriented delivery service.
• TCP achieves reliability by using a system
called positive acknowledgment with
retransmission.
• Many Internet client applications, such as Web
browsers and FTP clients, rely on TCP to
transmit files.
• Virtually every application that transmits large
amounts of data over a network uses TCP.
40
User Datagram Protocol (UDP)
• Provides a connectionless datagram service that
does not guarantee delivery or correct
sequencing of delivered packets
• Used by applications that
– Do not require an acknowledgment of data receipt
– Usually transmit small amounts of data at one time
• Used by
– Broadcast transmissions
– Services and applications such as DNS, Dynamic Host
Configuration Protocol (DHCP), and SNMP
41
Internet Protocol
• Internet Protocol (IP) does the actual delivery
of datagrams.
• IP adds the following header fields to each
packet:



Source IP Address
Destination IP Address
Protocol


Checksum
Time to Live (TTL)
42
IP Addressing
• Every host on a TCP/IP network must have a
unique IP address (a 32-bit number that
identifies both the host and the network the
host is located on).
• IP addresses are expressed in dotted-decimal
format, such as 192.168.123.132.
• Each set of four dotted-decimal numbers
represents eight bits of the binary address.
– The addresses range from 00000000 to 11111111,
or, in decimal notation, from 0 to 255.
43
IP Addressing (Cont.)
• An IP address is accompanied by a subnet mask.
• The subnet mask, when compared to the IP address,
identifies the part of the IP address that is the network
identifier and the part that is the host identifier.
– The 1s identify network bits and the 0s identify host bits.
– In the subnet mask 255.255.0.0, the first 16 bits
(2 octets)
are the equivalent of all ones in binary form.
• The first two octets of the IP address are the network identifier.
• The last two octets represent the host identifier.
44
Why IP Address?
• To communicate on the Internet, a computer must use an IP
address that is registered with the Internet Assigned Numbers
Authority (IANA).
– In practice, you obtain a valid network address from your Internet
service provider (ISP), not directly from the IANA.
• The IANA assigns network identifiers only; the administrator
assigns a unique host identifier to each computer.
• There are three primary classes of network addresses: A, B,
and C.
– The actual class used is based on the size of the network.
– Each address class has a different default subnet mask.
45
IP Address Classes
46
IP Address Class Characteristics
• You can identify the class of an IP address by
looking at the value of its first octet.
• Because a Class A address uses only eight bits
for its network ID, only 126 possible Class A
addresses exist.
47
Guidelines for IP Address Assignments
• There are several general guidelines for how to
assign IP addresses:
–
–
–
–
–
The first octet of the network ID cannot be 127.
The network and host ID bits cannot be all 1s.
The network and host ID bits cannot be all 0s.
The host ID for each computer must be unique.
A unique network ID is required for each network and
wide area connection.
– A registered network ID is required for connecting to
the Internet.
– All TCP/IP hosts require unique host IDs.
– Each host requires a subnet mask.
48
Using Private Addresses
• Workstations protected by firewalls and
computers that do not connect to the Internet
can use unregistered, private IP addresses.
• When building a private network, you should
use one of the special ranges of private IP
addresses, rather than assigning IP addresses
randomly.
49
IP Address Ranges for Private
Networks
Class
Network Addresses
A
10.0.0.0 through
10.255.255.255
B
172.16.0.0 through
172.31.255.255
C
192.168.0.0 through
192.168.255.255
50
Routing
• Routing is the process of choosing a path over
which to send packets, which is the primary
function of IP.
• A router (also called a gateway) is a device
that forwards packets from one physical
network to another.
• Routers match packet headers to a LAN
segment and choose the best path for the
packet, which optimizes network
performance.
51
Packet Routing Example
52
IP Routing
• To make routing decisions, the IP layer
consults a routing table, which consists of a
series of entries, called routes.
• On a computer running Windows, a routing
table is built automatically based on its TCP/IP
configuration.
• To view a routing table on a computer running
Windows, at a command prompt, type route
print, and then press Enter.
53
Cmd
C:\> route print
54
Static and Dynamic IP Routing
• Static routing can only use fixed routing tables.
• Static routers require building and updating routing
tables manually.
• Use the Route.exe command to add static entries to the
routing table.
• Dynamic routing
– Automatically updates routing tables
– Uses routing protocols, such as Routing Information Protocol
(RIP) and Open Shortest Path First (OSPF), to periodically
transmit the contents of their routing tables to the other routers
on the network
55
Installing TCP/IP
• The Windows Xp setup program automatically installs
TCP/IP if it detects a network interface adapter in the
computer.
• You need to manually install TCP/IP on a computer
running Windows Xp only if
– The default protocol selection was overridden during setup
– You have deleted it from a connection
• In Windows Xp, TCP/IP is implemented as a single
module called Internet Protocol (TCP/IP), which is
installed from the Network And Dial-Up Connections
application in Control Panel.
56
Installing TCP/IP (Cont.)
• To manually install TCP/IP:
1.
2.
3.
Log on using an administrator account.
Click Start, point to Settings, and then click
Network And Dial-Up Connections.
Right-click the Local Area Connection icon,
and then select Properties to display the Local
Area Connection Properties dialog box.
57
Installing TCP/IP (Cont.)
• To manually install TCP/IP (Cont.):
4. Click Install.
5. In the Select Network Component Type dialog
box, select Protocol, and then click Add.
6. In the Select Network Protocol dialog box, select
Internet Protocol (TCP/IP) in the Network
Protocol list, and then click OK.
7. Click Close.
58
Type the following commands in cmd
and write what it shows
Using Ipconfig.exe
• Use Ipconfig.exe to view the TCP/IP
configuration settings on a host, including IP
address, subnet mask, and default gateway.
– At the command prompt, type ipconfig or ipconfig
/all and then press Enter.
– Use the /all parameter to display more
information.
• Running Ipconfig is an easy way to view the IP
address and other parameters that the DHCP
server has assigned to your computer.
60
Using Ping
• Ping is a command-line utility that uses Echo Request
messages to determine if the TCP/IP stack of another
computer on the network is functioning normally.
• From a command prompt, type ping target (where
target is the IP address or the name [DNS or NetBIOS,
Example ping www.google.co.in] of the computer you
are trying to contact).
– A successful ping results in several reply messages from the
target computer.
– If the ping fails, one or both computers might have a
networking hardware or software problem.
– Example c:\> ping 192.168.1.2
61
Using Traceroute
• Tracert.exe, a variant of Ping, displays the path
that packets take to their destination.
• From a command prompt, type tracert target
(where target is the IP address or the name
[DNS or NetBIOS] of the target computer).
• Use Tracert.exe to isolate the location of a
network communications problem,
particularly when a router is suspected.
• Example C:\> tracert.exe 192.168.1.2
62
Using Pathping
• Pathping is a route tracing tool that
– Sends packets to each router on the way to a final destination
over a period of time
– Computes results based on the packets returned from each hop
• You can use Pathping.exe to isolate problems because it
shows the degree of packet loss at any given router or
link.
• From the command line, type pathping target (where
target is the IP address or the name [DNS or NetBIOS] of
the target computer).
• Example C:\> pathping.exe 192.168.1.2
63
Using Route.exe (Cont.)
• The ROUTE PRINT command displays the
current contents of the routing table.
• To create a new entry, use ROUTE ADD with
parameters that specify the values for the
entry.
• Example C:\> route.exe 192.168.1.2
64
Using Route.exe
• Use Route.exe to create, delete, or modify static routes in
a routing table on a computer running Windows 2000.
• Route.exe uses the following syntax:
ROUTE [-f] [-p][command[destination]
[MASK netmask] [gateway]
[METRIC
metric] [IF interface]]
• The Route.exe command variable takes one of four
values:


PRINT
ADD


DELETE
CHANGE
65
Using Arp.exe
• IP uses ARP to discover the hardware address that each
datagram is transmitted to.
• Resolved addresses are stored in an ARP cache.
• Use Arp.exe to view or change the contents of the ARP
cache.
• Arp.exe uses the following syntax:
ARP [-a {ipaddress}] [-n ipaddress] [s ipaddress hwaddress {interface}]
[-d ipaddress {interface}]
66
Using Netstat.exe
• Netstat.exe is a Windows 2000 command-line
utility that displays information about
– The current network connections of a computer
using TCP/IP
– The traffic generated by various TCP/IP protocols
• Netstat.exe uses the following syntax:
NETSTAT [interval] [-a]
protocol] [-n] [-e] [-r] [-s]
[-p
67
Using Nbtstat.exe
• Nbtstat.exe is a Windows 2000 command-line
utility that displays information about the
NetBIOS over TCP/IP connections used by
Windows 2000 when communicating with
other Windows computers on a TCP/IP LAN.
• Nbtstat.exe uses the following syntax:
NBTSTAT [-a name] [-A ipaddress]
[-c] [-n] [-r] [-R] [-s] [-S] [-RR]
• The parameters for Nbtstat.exe are casesensitive.
68
Using Nslookup.exe
• Nslookup.exe is a Windows 2000 commandline utility that enables you to generate DNS
request messages and transmit them to a
specific DNS server on the network.
• Nslookup.exe uses the following syntax:
NSLOOKUP DNSname DNSserver
– DNSname specifies the DNS name you want to
resolve.
– DNSserver specifies the DNS name (or IP address
of the DNS server) you want to query for the
name you want to resolve.
69
DNS – Domain Name System
Domain Names
• A domain name is the sequence of labels from a node to the root,
separated by dots (“.”s), read left to right
– The name space has a maximum depth of 127 levels
– Domain names are limited to 255 characters in length
• A node’s domain name identifies its position in the name space
""
edu
com
nominum
west
east
dakota
tornado
metainfo
www
berkeley
gov
nwu
int
mil
net
nato
army
uu
org
Subdomains
• One domain is a subdomain of another if its domain
name ends in the other’s domain name
– So sales.nominum.com is a subdomain of
• nominum.com & com
– nominum.com is a subdomain of com
Name Resolution
• Name resolution is the process by which resolvers
and name servers cooperate to find data in the name
space
• Closure mechanism for DNS?
– Starting point: the names and IP addresses of the name
servers for the root zone (the “root name servers”)
– The root name servers know about the top-level zones and
can tell name servers whom to contact for all TLDs
The Resolution Process
• Let’s look at the resolution process step-bystep:
annie.west.sprockets.com
ping www.nominum.com.
The Resolution Process
• The workstation annie asks its configured name
server, dakota, for www.nominum.com’s address
dakota.west.sprockets.com
What’s the IP address
of
www.nominum.com?
annie.west.sprockets.com
ping www.nominum.com.
The Resolution Process
• The name server dakota asks a root name server, m, for
www.nominum.com’s address
m.root-servers.net
dakota.west.sprockets.com
What’s the IP address
of
www.nominum.com?
annie.west.sprockets.com
ping www.nominum.com.
The Resolution Process
• The root server m refers dakota to the com name servers
• This type of response is called a “referral”
m.root-servers.net
dakota.west.sprockets.com
annie.west.sprockets.com
ping www.nominum.com.
Here’s a list of the
com name servers.
Ask one of them.
The Resolution Process
• The name server dakota asks a com name server,
f, for www.nominum.com’s address
What’s the IP address
of
www.nominum.com?
m.root-servers.net
dakota.west.sprockets.com
f.gtld-servers.net
annie.west.sprockets.com
ping www.nominum.com.
The Resolution Process
• The com name server f refers dakota to the
nominum.com name servers
Here’s a list of the
nominum.com
name servers.
Ask one of them.
m.root-servers.net
dakota.west.sprockets.com
f.gtld-servers.net
annie.west.sprockets.com
ping www.nominum.com.
The Resolution Process
• The name server dakota asks a nominum.com name server,
ns1.sanjose, for www.nominum.com’s address
What’s the IP address
of
www.nominum.com?
m.root-servers.net
dakota.west.sprockets.com
ns1.sanjose.nominum.net
f.gtld-servers.net
annie.west.sprockets.com
ping www.nominum.com.
The Resolution Process
• The nominum.com name server ns1.sanjose
responds with www.nominum.com’s address
m.root-servers.net
dakota.west.sprockets.com
Here’s the IP
address for
www.nominum.com
ns1.sanjose.nominum.net
f.gtld-servers.net
annie.west.sprockets.com
ping www.nominum.com.
The Resolution Process
• The name server dakota responds to annie with
www.nominum.com’s address
Here’s the IP
address for
www.nominum.com
m.root-servers.net
dakota.west.sprockets.com
ns1.sanjose.nominum.net
f.gtld-servers.net
annie.west.sprockets.com
ping www.nominum.com.
Resolution Process (Caching)
• After the previous query, the name server dakota now knows:
– The names and IP addresses of the com name servers
– The names and IP addresses of the nominum.com name
servers
– The IP address of www.nominum.com
• Let’s look at the resolution process again
annie.west.sprockets.com
ping ftp.nominum.com.
Resolution Process (Caching)
• The workstation annie asks its configured name
server, dakota, for ftp.nominum.com’s address
m.root-servers.net
dakota.west.sprockets.com
What’s the IP address
of ftp.nominum.com?
ns1.sanjose.nominum.net
f.gtld-servers.net
annie.west.sprockets.com
ping ftp.nominum.com.
Resolution Process (Caching)
• dakota has cached a NS record indicating ns1.sanjose is an
nominum.com name server, so it asks it for
ftp.nominum.com’s address
What’s the IP address
of ftp.nominum.com?
m.root-servers.net
dakota.west.sprockets.com
ns1.sanjose.nominum.net
f.gtld-servers.net
annie.west.sprockets.com
ping ftp.nominum.com.
Resolution Process (Caching)
• The nominum.com name server ns1.sanjose
responds with ftp.nominum.com’s address
m.root-servers.net
dakota.west.sprockets.com
Here’s the IP
address for
ftp.nominum.com
ns1.sanjose.nominum.net
f.gtld-servers.net
annie.west.sprockets.com
ping ftp.nominum.com.
Resolution Process (Caching)
• The name server dakota responds to annie with
ftp.nominum.com’s address
Here’s the IP
address for
ftp.nominum.com
m.root-servers.net
dakota.west.sprockets.com
ns1.sanjose.nominum.net
f.gtld-servers.net
annie.west.sprockets.com
ping ftp.nominum.com.
Try your own…
LEARN , LEAP , LEAD…