120 terms

Internet Protocols & TCP/IP

Introduction to Internet: Chapter 2
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DoD Model
Process/Application layer, Host-to-Host layer, Internet layer, Network Access layer
Process/Application layer
Application, Presentation, and Session layers
Host-to-Host layer
Transport layer
Internet layer
Network layer
Network Access layer
Data Link and Physical layers
Process/Application Layer Protocols
Telnet, FTP, TFTP, NFS, SMTP, LDP, X Window, SNMP, DNS, DHCP/BootP
Telnet
terminal emulation - allows a user on a remote client machine, called the Telnet client, to access the resources of another machine, the Telnet server
File Transfer Protocol (FTP)
file transfer between 2 machines, a protocol and a program, accesses directories and files, uses Telnet for login, cannot execute remote programs
Trivial File Transfer Protocol (TFTP)
stripped-down version of FTP, no directory-browsing abilities, uses smaller blocks of data, no authentication
Network File System (NFS)
allows two different types of file systems to interoperate
Simple Mail Transfer Protocol (SMTP)
uses a spooled, or queued, method of mail delivery, used to send mail (POP3 is used to receive mail)
Line Printer Daemon (LPD)
designed for printer sharing, along with the Line Printer (LPR) program, allows print jobs to be spooled and sent to the network's printers using TCP/IP
X Window
to allow a program, called a client, to run on one computer and have it display things through a window server on another computer
Simple Network Management Protocol (SNMP)
collects and manipulates network information,
Baseline
a report delimiting the operational traits of a healthy network
Trap
Alerts sent by SNMP agents
Domain Name Service (DNS)
resolves hostnames/fully qualified domain name (FQDN)
Dynamic Host Configuration Protocol (DHCP)
provides an IP Address, Subnet Mask, Domain Name, Default Gateway, DNS, WINS
Bootstrap Protocol (BootP)
gives an IP address to a host but the host's hardware address must be entered manually in a BootP table; used to send 'diskless workstations' their boot image
DHCP
connectionless, uses User Datagram Protocol (UDP)
Host-to-Host Layer Protocols
Transmission Control Protocol (TCP) & User Datagram Protocol (UDP)
TCP
segments and sequences information, waits for acknowledgments over the virtual circuit
TCP
full-duplex, connection-oriented, reliable, and accurate
TCP
lots of overhead
TCP Header
Source Port, Destination Port, Sequence Number, Acknowledgment Number, Header Number, Reserved, Code Bits, Window, Checksum, Urgent, Options, Data
Source port
The port number of the application on the host sending the data
Destination port
The port number of the application requested on the destination host
Sequence number
Puts the data back in the correct order or retransmits missing or damaged data, a process called sequencing
Acknowledgment number
Defines which TCP octet is expected next
Header length
The number of 32-bit words in the TCP header. This indicates where the data begins.
Reserved
Always set to zero
Code bits
Control functions used to set up and terminate a session
Window
The window size the sender is willing to accept, in octets
Checksum
cyclic redundancy check (CRC) checks the header and data fields
Urgent
The urgent pointer points to the sequence number of the octet following the urgent data
Options
May be 0 or a multiple of 32 bits
Data
Handed down to the TCP protocol at the Transport layer
UDP
fast, connectionless, unreliable
UDP Segment
Source Port, Destination Port, Length, Checksum, Data
Port Numbers below 1024
considered well-known port numbers dynamically assigned by the source host
Port Numbers 1024 and above
used by the upper layers to set up sessions with other hosts, used by TCP to use as source and destination addresses
Port 23
Telnet, TCP
Port 25
SMTP, TCP
Port 80
HTTP, TCP
Port 21
FTP, TCP
Port 53
DNS, TCP & UDP
Port 443
HTTPS, TCP
Port 161
SNMP, UDP
Port 69
TFTP, UDP
Port 110
POP3, UDP
Port 119
News, UDP
Internet Layer Protocols
Internet Protocol (IP), Internet Control Message Protocol (ICMP), Address Resolution Protocol (ARP), Reverse Address Resolution Protocol (RARP), Proxy ARP
Internet Protocol (IP)
decides where a packet is to be sent next, choosing the best path using a routing table
IP Header
Version, Header Length, Priority & Type, Total Length, Identification, Flags, Fragment Offset, Time to Live, Protocol, Header Checksum, Source IP, Destination IP, Options, Data
Version
IP Version number
Header Length
HLEN in 32-bit words
Priority & Type
how the datagram should be handled
Total Length
Length of of the packet
Identification
Unique IP-packet value
Flags
Specifies whether fragmentation should occur
Fragment offset
Provides fragmentation and reassembly if the packet is too large to put in a frame
Time to Live
Kills packets when time expires
Protocol
Port of upper-layer protocol (TCP is port 6 or UDP is port 17 [hex])
Header checksum
Cyclic redundancy check (CRC) on header only
Source IP
IP address of sending station
Destination IP
32-bit IP address of the station this packet is destined for
Options
Used for network testing, debugging, security, and more
Data
Upper-layer data
Internet Protocol (IP)
the Internet layer; the other protocols found here merely exist to support it
Port 6 (hex)
TCP
Port 17 (hex)
UDP
Internet Control Message Protocol (ICMP)
management protocol and messaging service provider for IP
Internet Control Message Protocol (ICMP)
They can provide hosts with information about network problems
Internet Control Message Protocol (ICMP)
They are encapsulated within IP datagrams
ICMP events and messages
Destination Unreachable, Buffer Full, Hops, Ping, Traceroute,
Destination Unreachable
When a router can't send an IP datagram any further
Buffer Full
When a router's memory buffer for receiving incoming datagrams is full
Hops
Each IP datagram is allotted a certain number of routers, called hops, to pass through. If it reaches its limit of hops before arriving at its destination, the last router to receive that datagram deletes it. The executioner router then uses ICMP to send an obituary message, informing the sending machine of the demise of its datagram
Ping (Packet Internet Groper)
Used to check the physical and logical connectivity of machines on an internetwork
Traceroute
Used to discover the path a packet takes as it traverses an internetwork
Reverse Address Resolution Protocol (RARP)
discovers the identity of the IP address for diskless machines by sending out a packet that includes its MAC address
Address Resolution Protocol (ARP)
Used to find the hardware address from a known IP address
Proxy Address Resolution Protocol (Proxy ARP)
The technique in which one host, usually a router, answers ARP requests intended for another machine. By "faking" its identity, the router accepts responsibility for routing packets to the "real" destination. Proxy ARP can help machines on a subnet reach remote subnets without the need to configure routing or a default gateway.
IP Address
32-bit logical numeric identifier assigned to each machine on an IP network
Bit
one digit, 1 or 0
Byte
8 bits (with parity)
Octet
8 bits
Network Address/Number
numerical identifier for a remote network; uniquely identifies each network
Broadcast Address
address used by applications and hosts to send information to all nodes on a network
IP Address
may be depicted in dotted-decimal, hex, or binary
Node Address
uniquely identifies each machine on a network
What is the Class C address range in decimal and in binary?
192-223, 110xxxxx
What layer of the DoD model is equivalent to the Transport layer of the OSI model?
Host-to-Host
What is the valid range of a Class A network address?
1-126
What is the 127.0.0.1 address used for?
Loopback or diagnostics
How do you find the network address from a listed IP address?
Turn all host bits off
How do you find the broadcast address from a listed IP address?
Turn all host bits on
What is the Class A private IP address space?
10.0.0.0 through 10.255.255.255
What is the Class B private IP address space?
172.16.0.0 through 172.31.255.255
What is the Class C private IP address space?
192.168.0.0 through 192.168.255.255
What are all the available characters that you can use in hexadecimal addressing?
0-9 and A, B, C, D, E, and F
What is the decimal and hexadecimal equivalent of the binary number 10011101?
157 & 0x9D
Which of the following allows a router to respond to an ARP request that is intended for a remote host?
Proxy ARP
You want to implement a mechanism that automates the IP configuration, including IP address, subnet mask, default gateway, and DNS information. Which protocol will you use to accomplish this?
DHCP
What protocol is used to find the hardware address of a local device?
ARP
Which of the following are layers in the TCP/IP model?
Application, Transport, Internet
Which class of IP address provides a maximum of only 254 host addresses per network ID?
Class C
Which of the following describe the DHCP Discover message?
It uses FF:FF:FF:FF:FF:FF as a layer 2 broadcast; It uses UDP as the Transport layer protocol
Which layer 4 protocol is used for a Telnet connection?
TCP
Which statements are true regarding ICMP packets?
They can provide hosts with information about network problems; They are encapsulated within IP datagrams
Which of the following services use TCP?
SMTP, FTP, HTTP
Which of the following services use UDP?
DHCP, SNMP, TFTP
Which of the following are TCP/IP protocols used at the Application layer of the OSI model?
Telnet, FTP, TFTP
If you use either Telnet or FTP, which is the highest layer you are using to transmit data?
Application
The DoD model (also called the TCP/IP stack) has four layers. Which layer of the DoD model is equivalent to the Network layer of the OSI model?
Internet
Which of the following is a private IP address?
172.20.14.36
What layer in the TCP/IP stack is equivalent to the Transport layer of the OSI model?
Host-to-Host
Which statements are not true regarding ICMP packets?
UDP will send an ICMP Information request message to the source host; ICMP guarantees datagram delivery; ICMP is encapsulated within UDP datagrams
What is the address range of a Class B network address in binary?
10xxxxxx
Which of the following protocols use both TCP and UDP?
DNS
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