Network+ Chapter 1: Network Models
Type field
indicates what's encapsulated in the frame
HUB frame delivery
make an exact copy of a received frame, and would send a copy to every connected port expect the sender. Only the addressed NIC would process the frame, with all the other NICs dropping the non-addressed frame.
TCP/IP Model (4 Layers)
4. Application 3. Transport 2. Internet 1. Link/Network Interface
Protocol Suite
TCP/IP is really several network protocols designed to work together. IP makes sure that a piece of data gets to where it needs to go on a network. It does this by giving each device on the network a unique numeric identifier called an IP address
Extended Unique Identifier
The IEEE forms MAC addresses from a numbering name space originally called MAC-48, which simply means that the MAC address will be 48 bits, with the first 24 bits defining the OUI, just as described here. The current term for this numbering name space is EUI-48.
Broadcast address
The MAC address of FF-FF-FF-FF-FF-FF is the Layer 2 broadcast address—if a NIC sends a frame using the broadcast address, every single NIC on the network will process that frame.
Link Layer (Layer 1 TCP/IP)
The TCP/IP model lumps together the OSI model's Layer 1 and Layer 2 into a single layer
UDP Datagram
UDP also gets data from the Application layer and adds port and length numbers plus a checksum to create a container called a ___ _________
UTP
Unshielded Twisted Pair: contains pairs of wires that can transmit and receive data.
The connectionless protocol
User Datagram Protocol (UDP)
Segmentation
When a serving computer receives a request for some data, it must be able to chop the requested data into chunks that will fit into a packet (and eventually into the NIC's frame), organize the packets for the benefit of the receiving system, and hand them to the NIC for sending
Internet Layer/ "IP Packet Layer" (Layer 2 TPC/IP)
Any device or protocol that deals with pure IP packets—getting an IP packet to its destination—sits in the __________ layer. IP Packets are created at this layer
Layer 3
At the network layer, containers called packets get created and addressed so they can go from one network to another. IP is the primary logical addressing protocol for TCP/IP, and it makes sure that a piece of data gets to where it needs to go on the network
Generic Frame
Begins with MAC address of the NIC to which data is being sent, followed by NIC of the MAC sending the information. Next comes the Type field, which indicates what's encapsulated in the frame. Then comes the data field that contains the encapsulated information, followed by a special bit of checking information called Frame check sequence (FCS).
Broadcast Message
If an NIC doesn't know the MAC address of the destination MAC address, the NIC sends a _______ message onto the network to ask for it
Internet Message Access Protocol (IMAP)
Internet protocol used for sending email messages
IP address is also known as...
Logical Address
2 Unique System Identifiers in a TCP/IP network
MAC address and IP address. MAC address is burned into the NIC, while the IP address is stored in the system's software
Hexadecimal Numbering System
MAC addresses are broken up using hex translation
MAC Address
Media Access Control Address is a unique 48-bit value that is managed by the Institute of Electrical and Electronics Engineers (IEEE)
NIC Concerns
NICs don't care what's inside the frame, they simply take whatever data is passed to it (via its device driver) and addresses it for the correct system. Essentially, the contents of the canisters(frames) from the mailroom in ELF are of no concern to the NIC, they care about the destination
NIC
Network Interface cards serve as the interface between the PC and the network. These cards give each system a unique identifier called a MAC address. Most modern PCs have NICs built into the motherboard. Network Cards operate on both the Data link layer and the physical layer (Layer 1 and 2)
MAC address are also known as...
Physical addresses
OSI Model (In Order)
Physical, Data Link, Network, Transport, Session, Presentation, Application
Layer 5
Session Layer: - creates the session between clients. establishes session - uses a session ID to keep the data stream separate
Layer 2
The data link layer is considered to be Layer _. Any device that deals with a MAC address is part of the Data Link Layer. Switches handle traffic using MAC addresses, so they are included in this layer
Organizationally Unique Identifier (OUI)
The first six digits of a MAC address (ex 00-40-05-60-7D-49) represent the number of the NIC manufacturer
Device ID
The last six digits, in this example 60-7D-49, are the manufacturer's unique serial number for that NIC; this portion of the MAC is often referred to as the ______ __. (To see this, type ipconfig /all in windows command prompt. This will display the MAC address, but is referred to as the Physical Address)
Layer 1
The physical layer defines the method of moving data between computers, through cabling and a central box. Anything moving data from one system to another, copper wires, fiber and radio waves is part of the physical layer
Packet
The protocol data unit for the Network Layer (Layer 3)
de-encapsulation
The receiving computer reverses the process of encapsulation, stripping all the extra header information out as the data goes up the stack
Protocol Data Unit (PDU)
The unit of data specified by a protocol at each layer of the OSI seven-layer model is called a ______________ ______ ______
Layer 4
Transport Layer; Because most chunks of data are much larger than a single packet, they must be chopped up before they can be sent across a network. The Transport layer also initializes requests for packets that weren't received in good order
Network Protocol
To move past the physical MAC addresses and start using logical addressing requires some special software called a _____________ __________. These exist in every operating system. They not only have to create unique identifiers for each system, but also must create a set of communication rules for issues like how to handle data chopped up into multiple packets and how to ensure those packets get from one subnet to another.
The connection-oriented protocol
Transmission Control Protocol (TCP)
TCP/IP
Transmission Control Protocol/ Internet Protocol
oscilloscope
a powerful tool that enables you to see electrical pulses
Transport Layer (Layer 3 TCP/IP)
combines features of the OSI Transport and Session layers with a dash of Application layer just for flavor. While the TCP/IP model is certainly involved with the segmentation and reassembly of data, it also defines other functions, such as connection-oriented and connectionless communication.
Data field
contains the encapsulated information in the frame
IP uses a ___________ _____________ notation
dotted decimal (ex: 192.168.4.232)
Switch frame delivery
sends the frame only to the interface associated with the destination MAC address
Segments ( also known as Datagrams)
the transport protocol breaks up the data into chunks called ____________. Embedded into the data of each packet containing a ____________ is a sequencing number. By reading the sequencing numbers, the receiving system knows both the total number of ____________ and how to put them back together.
The Two Aspects of NIC
1. Logical Link Control (LLC): talks to the system's operating system (via device drivers) The LLC handles multiple network protocols and provides flow control 2. Media Access Control (MAC: creates and addresses the frame. It adds the NIC's own MAC address and attaches MAC addresses to the frames
3 Sections of a Frame
1. The Header (MAC addresses and type) starts 2. Followed by the payload (whatever is encapsulated in the frame) 3. Finally followed by the trailer (Frame Check Sequence)
Packet (structure)
A frame of some type enables the data to move from one device to another. Inside that frame are both an IP-specific container that enables routers to determine where to send data—regardless of the physical connection type—and the data itself. In TCP/IP, that inner container is the __________
Frame
All networks transmit data by breaking whatever is moving across the Physical layer (files, print jobs, Web pages, and so forth) into discrete chunks called. A _____ is basically a container for a chunk of data moving across a network. A _____ encapsulates information and data for easier transmission. (Imagine Buddy the Elf shooting messages up the tubes in the mail room)
Layer 7
Application Layer: The last and most visible part of any network is the software applications that use it. Application layer doesn't refer to the applications themselves. It refers to the code built into all operating systems that enables network-aware applications. All operating systems have Application Programming Interfaces (APIs) that programmers can use to make their programs network-aware
Only OSI Layer with sublayers
Data Link Layer (Layer 2)
Encapsulation
Encompasses the entire process of preparing data to go onto a network (The entire OSI model). This includes all the steps from the application to the Application, Presentation, Session, Transport, Network, and Data Link layers. Each layer adds more information so that the data gets to the correct recipient and the recipient knows what to do with the data.
Basic send/receive process
First, the sending system's operating system hands some data to its NIC. The NIC builds a frame to transport that data to the receiving NIC. After the NIC creates the frame, it adds the Frame Check Sequence, and then dumps it and the data into the frame. Next, the NIC puts both the destination MAC address and its own MAC address onto the frame. It then sends the frame through the cable to the network. The frame propagates down the wire into the central box. The switch sends unicast frames to the destination address and sends broadcast frames to every system on the network. The NIC receives the frame, then the NIC strips off all the framing information and sends the data to the software—the operating system—for processing. The receiving NIC doesn't care what the software does with the data; its job stops the moment it passes on the data to the software.
Frame size limits
Frames used in most wired networks hold up to 1500 bytes of data each. When a large file needs to be sent, the system's software chops up the data into frame-sized chunks, and then hands it off to the NIC for shipment. When the receiving system begins to accept frames, the system's software recombines the data chunks as they come in.
Frame Check Sequence Verification process
How can 4 bytes tell you if all 1500 bytes in the data are correct? That's the magic of the math of the cyclical redundancy check. The NIC sending the frame does a little math to make the CRC. Using binary arithmetic, it works a division problem on the data using a divisor called a key. The result of this division is the CRC. When the frame gets to the receiving NIC, it divides the data by the same key. If the receiving NIC's answer is the same as the CRC, it knows the data is good; if it's not good, the frame is dropped.
Packet within a frame
IP packets don't leave their PC home without any clothes on! Each IP packet is handed to the NIC, which then encloses the IP packet in a regular frame. visualize the packet as an envelope, with the envelope being put in the tube from the mailroom in the Elf.
Logical Addressing Method
Large networks need a ___________ ___________ method, like a postal code or telephone numbering scheme, that ignores the hardware and enables you to break up the entire large network into smaller networks called subnets
Please Do Not Throw Sausage Pizza Away
Physical, Data Link, Network, Transport, Session, Presentation, Application (Acronym)
Layer 6
Presentation Layer: translates data from lower layers into a format usable by the Application layer, and vice versa.
Reassembly
Recognize a series of incoming packets as one data transmission, reassemble the packets correctly based on information included in the packets by the sending system, and verify that all the packets for that piece of data arrived in good shape.
TCP Segment
To see the Transport layer in action, strip away the IP addresses from an IP packet. What's left is a chunk of data in yet another container called a ___ ________. These segments have many other fields that ensure the data gets to its destination in good order. These fields have names such as Destination port, Source port, Checksum, Flags, and Acknowledgement.
Sending an IP Packet in a Frame
When you send data from one computer to another on a TCP/IP network such as the Internet, that data can go through many routers before it reaches its destination. Each router strips off the incoming frame, determines where to send the data according to the IP address in the packet, creates a new frame, and then sends the packet within a frame on its merry way. The new frame type will be the appropriate technology for whatever connection technology connects to the next router. That could be a cable or DSL network connection
The Application Layer (Layer 4 TCP/IP)
combines features of the top three layers of the OSI model. Every application, especially connection-oriented applications, must know how to initiate, control, and disconnect from a remote system. No single method exists for doing this. Each TCP/IP application uses its own method.
Router
connects each of the subnets. They use the IP address (not the MAC), to forward data. This enables networks to connect across data lines that don't use ethernet, like the telephone network. Each network types uses a unique frame
Frame Check Sequence.
uses a type of binary math called cyclic redundancy check (CRC) that the receiving NIC uses to verify that the data arrived intact
