examines a message’s destination IP address and routes the message onto the proper network or subnetwork as the next link in the chain of the communication.

Router

connects local area networks of different types together.

Gateway

is responsible for placing TCP/IP packets on the network medium and receiving TCP/IP packets off the network medium.

Network Interface Layer

is responsible for addressing, packaging, and routing functions.

Internet Layer

is responsible for IP addressing, routing, and the fragmentation and reassembly of packets.

Internet Protocol

is responsible for the resolution of the Internet layer address to the Network Interface layer such as a hardware address.

Address Resolution Protocol

is responsible for providing diagnostic functions and reporting errors due to the unsuccessful delivery of IP packets.

Internet Control Message Protocol

is responsible for the management of IP multicast groups.

Internet Group Management Protocol

is responsible for providing the Application layer with session and datagram communication services.

Transport Layer

is responsible for establishment of a ____ connection, the sequencing and acknowledging of packets sent, and the recovery of packets lost during transmission.

Transmission Control Protocol

is used when the amount of data to be transferred is small, when the overhead of establishing a TCP connection is not desired, or when the applications or upper layer protocols provide reliable delivery.

User Datagram Protocol

allows applications to access the services of the other layers and defines the protocols that applications use to exchange data.

Application layer

is used to transfer files that make up the Web pages of the World Wide Web.

Hypertext Transfer Protocol

is used for interactive file transfer.

File Transfer Protocol

is used for the transfer of mail messages and attachments.

Simple Mail Transfer Protocol

It is a terminal emulation protocol used for logging on remotely to network hosts

Telnet

is used to resolve a host name to an IP address.

Domain Name System

is used by routers to exchange routing information on an IP internetwork.

Routing Information Protocol

is used to collect and exchange network management information between a network management console and network devices.

Simple Network Management Protocol

Networking Commands: sends a special network packet called an ICMP ECHO_REQUEST to network hosts

ping

Networking Commands: prints the route packets trace to a network host

traveroute/tracepath

Networking Commands: shows/manipulates routing, devices, policy routing, and tunnels

Networking Commands: prints network connections, routing tables, interface statistics, masquerade connections, and multicast memberships

netstat

Networking Commands: Internet file transfer program

ftp

Networking Commands: Non-interactive network downloader

wget

Networking Commands: OpenSSH SSH client (remote login program) • Sample usage of ping:

ssh

Process States: Running

Process States: Sleeping

Process States: Uninterruptible sleep Process is waiting for I/O such as a disk drive.

Process States: Traced or stopped

Process States: A defunct or “zombie” process This is a child process that has been terminated, but has not been cleaned up by its paren

Characters used with process states: A high priority process

Characters used with process states: A low priority process

Characters used with process states: Has pages locked into memory This is for real-time and custom I/O.

Characters used with process states: A session leader

Characters used with process states: Multi-threaded

Characters used with process states: In the foreground process group

The ps Command with the aux option: User ID This is the owner of the process.

USER

The ps Command with the aux option: CPU usage in percent

%CPU

The ps Command with the aux option: Memory usage in percent

%MEM

The ps Command with the aux option: Virtual Memory Size

VSZ

The ps Command with the aux option: Resident Set Size This is the amount of physical memory (in kilobytes) the process is using.

RSS

The ps Command with the aux option: This is the time when the process has started. For values over 24 hours, a date is used.

START