TCP/IP Basics Flashcards
protocols
set of rules upon which software is developed
protocol suite
aggregation of protocols
protocol stack
software installed on a system that enables a specific protocol suite to function
IPv4
internet protocol version 4
IPv6
internet protocol version 6
ICMP
internet control message protocol
“is there a computer out there with the address of”
called automatically by apps for the most part
used by ping utility
RTT
round trip time (real transfer time)
time of response for a ping query
times out if connection is not available
destination & source addresses are part of the [blank]
TCP/IP Internet layer
OSI network layer
connection-oriented
ensure data arrives in good order (TCP)
connectionless
data arrival condition not important (UDP)
TCP handling of data
breaks data into segments
gives segments sequence number
verifies all segments were received
missing segments resent
port numbers
used by systems to determine which application needs to receive the data
1 - 65,535
HTTP port number
TCP 80
POP3 port number
TCP 110
flags
individual bits that give both sides detailed information about the state of the connection
checksum
checks TCP header for errors
UDP summary
packets do not contain extra confirmation components
lots of data needs to be delivered
integrity of data is not critical
systems are close - chance of problem minimal
VoIP - UDP much faster than TCP
2 network protocols that use UDP
DNS
DHCP
UDP datagrams get chopped into segments [T/F]
false
IP addressing in LANs
MAC broadcast traffic would not work in larger networks
IP addressing overcomes this hurdle
composition of IPv4 address
32-bit value
broken into 4 groups of 8 - separated by period
each group converted into decimal number between 0 & 255
naming standard used by IP addresses
dotted decimal notation
dotted octet numbering system
commands to display IP address
ipconfig /all - Windows
ifconfig - UNIX / Linux / OS X
network ID
shared numbers of IP addresses that identify a network
network ID & host ID of the following address:
202.120.10.5
network ID = 202.120.10
host ID = 5
why no computer can have an IP address ending in 0
reserved for the network ID
in order to interconnect LANs [blank] is required
router with IP address on the LAN it serves
default gateway
router interface
usually “1” on LAN side
routing table
instructions that tell the router what to do with incoming packets & where to send them
subnet mask
provides the ability to determine if the target computer is on the same network
0 translates to
00000000
255 translates to
11111111
ARP
address resolution protocol
how TCP/IP network determines the MAC address based on the destination IP address
method of monitoring devices connected to LAN
examine MAC addresses - look for any that are unfamiliar
exam term MAC address lookup table
source address table (SAT)
Cisco calls SATs MAC address tables
RARP
reverse address resolution protocol
long dead - reverse of ARP
may be incorrect answer
show current ARP table in Windows
cmd “arp -a”
delete entry in Windows ARP table
cmd “arp -d [IP address]”
subnet shorthand
/ [number of 1’s in subnet mask]
IANA
internet assigned numbers authority
tracks and disperses IP addresses on the Internet
RIR
regional internet registry
subgroups of IANA
distribute IP addresses to ISPs & major corporations
ARIN
american registry for internet numbers
RIR that covers north america
network blocks (blocks)
IANA passes out IP addresses in continuous chunks
class A
1st decimal value = 1 - 126
Addresses = 1.0.0.0 - 126.255.255.255
Hosts per Network ID = 16,277,214
class B
1st decimal value = 128 - 191
Addresses = 128.0.0.0 - 191.255.255.255
Hosts per Network ID = 65,534
class C
1st decimal value = 192 - 233
Addresses = 192.0.0.0 - 223.255.255.255
Hosts per Network ID = 254
class D
1st decimal value = 224 - 239
Addresses = 224.0.0.0 - 239.255.255.255
Hosts per Network ID = multicast
class E
1st decimal value = 240 - 254
Address = 240.0.0.0 - 254.255.255.255
Hosts per Network ID = experimental
classful
describes traditional class blocks
ICANN
international corporation for assigned names & numbers
manages IANA
broadcast
every computer on the LAN hears a message
unicast
1 computer sends a message directly to another
multicast
single computer sends a packet to a group of interested computers
often used when routers comunicate
i.e. streaming video conference
experimental addresses
addresses that are reserved & only used for occasional experimental reasons
determine class by 1st binary octet
A = 0 B = 10 C = 110 D = 1110 E = 1111
CIDR
classless inter-domain routing
dividing up a class of IP addresses into smaller groups
done by ISP before distributing IP addresses
benefits to subnetting
more efficient use of IP addresses
separation of networks for security
management of bandwidth utilization
determine number of available hosts
2^x
x = number of zeroes in subnet mask (binary)
always 32 digits in subnet - subtract the “/x” value from 32 to find the number of 0’s
calculating subnet masks
extend subnet extension until the necessary number of subnets have been created
moving subnet extension by 1 digit
results in a possible value of 1 or 0
produces 2 subnets
often create more subnets than needed
manual binary conversion to dotted decimal
128 - divide in half until you get to 1
place binary value under corresponding 8 digits
calculate sum of all values aligned with a 1
result is the dotted decimal value
manual dotted decimal to binary conversion
128 - divide in half until you get to 1
place decimal value over 128
decimal greater than number it is over - subtract and add a 1 below that number
less than - place 0 under number and move to next value
static address assignment
manually enter all IP information
dynamic address assignment
server program automatically passes out all IP information to systems as they boot up or connect to the a network
entering static IP information
Windows - IPv4 properties menu
OS X - Network Utility (System Preferences)
UNIX/Linux - Network Configuration or “ifconfig”
DCHP
dynamic host configuration protocol
automatically assigns IP address whenever a computer connects to the network
BOOTP
bootstrap protocol
former name for DCHP
DCHP port numbers
UDP 67 - DHCP servers
UDP 68 - DHCP clients
DCHP client
computer configured to use DHCP
DHCP process
client boots up - automatically sends out a DHCP discover packet via the broadcast address
DHCP server responds with DHCP offer
DHCP client sends out DHCP request (accepting offer)
DHCP server sends DHCP acknowledgement & lists the MAC address & IP information given to DHCP client in a database
DHCP scope
pool of IP addresses from which the DHCP server is configured to distribute IP addresses from
information passed out by DHCP server
“options”
default gateway, DNS server, network time server, etc.
DHCP reservations
DCHP configured to reserve IP addresses for specific machines
better to use static addressing in case DHCP server goes down
DCHP lease
fixed amount of time in which a client is assigned DHCP information
usually 5 - 8 days
near end of lease - client makes another discover message
unless another client has taken lease - server always hands out the same information
DHCP issues
client fails to get a DHCP address
gets IP address in the 169.254.0.0/16 network ID
zero-configuration networking (zeroconfig)
method of generating special 199.254.0.0/16 IP address
APIPA
automatic private IP addressing
Microsoft’s implementation of zeroconf
clients are designed to generate APIPA address automatically if they don’t receive response to DHCP discover message
APIPA limitation
cannot issue default gateway
will not be able to connect to the Internet
computer can’t connect to the internet
look for APIPA - DHCP problem
renew DHCP lease
manually renew DHCP lease
Windows - “ipconfig /release” + “ipconfig /renew”
Linux/OS X - “sudo ifconfig eth0 down’ + “sudo ifconfig etho0 up”
loopback address
127.0.0.1
tells device to send packets to itself
private IP addresses
- 0.0.0 - 10.255.255.255 (1 Class A network block)
- 16.0.0 - 172.31.255.255 (16 Class B network blocks)
- 168.0.0 - 192.168.255.255 (256 Class C network blocks)
* All other IP addresses are private*
