Domain 4 - Communication and Network Security Flashcards
<strong>OSI Model</strong>
International Organization for Standardization (ISO) developed the Open Systems Interconnection (OSI) Reference Model for protocols in the early 1980s.
Specifically, ISO 7498 defines the OSI Reference Model (more commonly called the OSI model).
Encapsulation
Encapsulation is the addition of a header, and possibly a footer, to the data received by each layer from the layer above before it’s handed off to the layer below.
Physical Layer
The Physical layer (layer 1) accepts the frame from the Data Link layer and converts the frame into bits for transmission over the physical connection medium.
The Physical layer is also responsible for receiving bits from the physical connection medium and converting them into a frame to be used by the Data Link layer.
Data Link Layer
The Data Link layer (layer 2) is responsible for formatting the packet from the Network layer into the proper format for transmission.
The proper format is determined by the hardware and the technology of the network.
SLIP, PPP, ARP, RARP, L2F, L2TP, PPTP, ISDN are examples
Network Layer
The Network layer (layer 3) is responsible for adding routing and addressing information to the data.
The Network layer accepts the segment from the Transport layer and adds information to it to create a packet.
The packet includes the source and destination IP
addresses.
Distance Vector Protocols
Distance vector routing protocols maintain a list of destination networks along with metrics of direction and distance as measured in hops.
RIP, IGRP,BGP
Link State Routing Protocols
Link state routing protocols maintain a topography map of all connected networks and use this map to determine the shortest path to the destination.
OSPF
Transport Layer
The Transport layer (layer 4) is responsible for managing the integrity of a connection and controlling the session. It accepts a PDU from the Session layer and converts it into a segment.
The Transport layer controls how devices on the network are addressed or referenced, establishes communication connections between nodes (also known as devices), and defines the rules of a session.
Session Layer
The Session layer (layer 5) is responsible for establishing, maintaining, and terminating communication sessions between two computers. It manages dialogue discipline or dialogue control (simplex, half-duplex, full-duplex), establishes checkpoints for grouping and recovery, and retransmits PDUs that have failed or been lost since the last verified
checkpoint.
NFS, SQL, RPC
Presentation Layer
The Presentation layer (layer 6) is responsible for transforming data received from the Application layer into a format that any system following the OSI model can understand.
It imposes common or standardized structure and formatting rules onto the data
Repsonsible for Encyprtion and Compression
Application Layer
The Application layer (layer 7) is responsible for interfacing user applications, network services, or the operating system with the protocol stack. It allows applications to communicate with the protocol stack.
The Application layer determines whether a remotecommunication partner is available and accessible. It also ensures that sufficient resources are available to support the requested communications.
EDI, NNTP, S-RPC, SET
Port Numbers
The IANA recommends that ports 49152 to 65535 be used as dynamic and/or private ports.
- Berkeley Software Distribution (BSD) uses ports 1024 through 4999.
- Many Linux kernels use 32768 to 61000.
- Microsoft, up to and including Windows Server 2003, uses the range 1025 to 5000.
- Windows 7, and Windows Server 2008 use the IANA range.
- FreeBSD, since version 4.6, has used the IANA suggested port range.
TCP 3-Way Handshake
- The client sends a SYN (synchronize) flagged packet to the server.
- The server responds with a SYN/ACK (synchronize and acknowledge) flagged packet back to the client.
- The client responds with an ACK (acknowledge) flagged packet back to the server.
UDP
Best Effort
header is 8 bytes long
4 sections (SP,DP,ML,CS)
IP Classes
Class A 1-126
Class B 128-191
Class C 192-223
Class D 224-239
Class E 240-255
ICMP
Internet Control Message Protocol (ICMP) is used to determine the health of a network or a specific link. ICMP is utilized by ping, traceroute, pathping, and other network management tools.
First, the IP header protocol field value for ICMP is 1 (0x01).
Ping of Death
Ping of death sends a malformed ping larger than 65,535 bytes (larger than the maximum IPv4 packet size) to a computer to attempt to crash it.
Smurf Attack
Smurf attacks generate enormous amounts of traffic on a target network by spoofing broadcast pings, and ping floods are a basic denial of service
(DoS) attack relying on consuming all of the bandwidth that a target has available.
IGMP
IGMP Internet Group Management Protocol (IGMP) allows systems to support multicasting. IGMP is used by IP hosts to register their dynamic multicast group membership.
It is also used by connected routers to discover these groups.
The IP header protocol field value for IGMP is 2 (0x02).
Telnet
Port 23
No transfer of files
Execuate commands
FTP
Port 20, 21
Anonymous or Specific Auth
TFTP
UDP port 69
No Auth
SMTP
Port 25
Email messages from client to server and other servers
POP3
Post Office Protocol 3
Port 110
Pull email down
IMAP
Internet Message Access Protocol
Port 143
Delete emails directly without downloading them to client