TCP/IP Core Protocols
Open, does not need a license to use it and routable. determine the best path for directing data over a network. also adds a header to data inherited from the layer before it
Layer 4�The Transport layer protocol
TCP or UDP, adds a header to the payload. header includes a port number to identify the receiving application on the destination host. becomes a segment or datagram, depending on the protocol
Layer 3�The Network layer
Adds its own header to the passed-down segment or datagram. This header identifies the IP address of the destination host and the message is called a packet.
Layer 2�The Data Link layer
on the NIC, encapsulates this data with its own header and trailer, creating a frame. This layer's frame includes physical addresses used to find nodes on the local network.
Layer 1�The Physical layer
the NIC receives the frame and places the actual transmission on the network. The receiving host de-encapsulates the message at each layer in reverse order and then presents the payload to the receiving application.
Connectivity devices
Allow two or more networks or multiple parts of one network to connect and exchange data.
TCP (Transmission Control Protocol)
Operates in the Transport layer of the OSI model and provides reliable data delivery services.
Connection-oriented protocol
Before TCP transmits data, it ensures that a connection or session is established
Threeway handshake
Performed before TCP transmits the actual data.
Checksum
TCP sends a character string, on the destination host then generates a similar string. If the fail to match, the destination host asks the source to re-transmit the data.
Sequence number
Messages don't always arrive in the same order they were created, TCP attaches a chronological order to each segment so the destination host can, if necessary, reorder segments as they arrive.
Flow control
The process of gauging the appropriate rate of transmission based on how quickly the recipient can accept data.
Source port (16 bits)
Indicates the port number at the source node.
Destination port (16 bits)
Indicates the port number at the destination node.
Acknowledgment number ( 32 bits)
Confirms receipt of the data via a return message to the sender.
TCP header length (4 bits)
Can be a minimum of 20 bytes to a maximum of 60 bytes in 20-byte increments. Called the Data
offset field, because it's the offset from the beginning of the segment until the start of the data carried by the segment.
Reserved (6 bits)
Indicates a field reserved for later use.
Flags (6 bits)
Identifies a collection of six 1-bit fields or flags that signal special conditions about other fields in the header. (URG, ACK, PSH, RST, SYN, FIN)
URG � The Urgent pointer
If set to 1, field later in the segment contains information for the receiver. (If set to 0, the receiver will ignore the field.)
ACK� The Acknowledgment
If set to 1, field earlier in the segment contains information for the receiver. (If set to 0, the receiver will ignore the field.)
PSH �
If set to 1, It indicates that data should be sent to an application without buffering.
RST� Requesting
If set to 1, The sender is requesting that the connection be reset.
SYN�synchronization
If set to 1, the sender is requesting, of the sequence numbers between the two nodes. This code indicates that no payload is included in the segment, and the acknowledgment number should be increased by 1 in response.
FIN�
If set to 1, the segment is the last in a sequence and the connection should be closed.
Request for a connection
Computer A issues a message to computer B with its SYN bit set, indicating the desire to communicate and synchronize sequence numbers.
Response to the request
After computer B receives this message, it responds
with a segment whose ACK and SYN flags are both set
Connection established
Computer A issues a segment whose sequence number is 937013559 (because this is what computer B indicated it expects to receive).
UDP (User Datagram Protocol)
provides no error checking or sequencing, a great volume of data must be transferred quickly, such as live audio or video transmissions over the Internet. more efficient for carrying messages that fit within one data packet. optional in IPv4, but required
IP (Internet Protocol)
Belongs to the Network layer of the OSI model. specifies how and where data should be delivered, including the data's source and destination addresses. enables TCP/IP to Internetwork.
Internetwork
IP is the protocol that enables TCP/IP, that is, to traverse more than one LAN segment and more than one type of network through a router.
Internet header length (4 bits)
Indicates the length of the TCP header in bytes. The header can be a minimum of 20 bytes to a maximum of 60 bytes,
Differentiated services (DiffServ)
Informs routers the level of precedence they should apply when processing the incoming packet. Differentiated services allows up to 64 values and a wide range of priority handling options
Total length
Identifies the total length of the IP packet, including the header and data, in bytes. An IP packet, including its header and data, cannot exceed 65,535 bytes.
Time to Live (8 bits)
Indicates the maximum duration that the packet can remain on the network before it is discarded. the maximum number of router
hops it has remaining.
Header checksum (16 bits)
Allows the receiving host to calculate whether the IP header has been corrupted during transmission. If the checksum message does not match packet is presumed to be corrupt and is discarded.
ICMP (Internet Control Message Protocol)
a Network layer core protocol that reports on the success or failure of data delivery. It can indicate when part of a network is congested, when data fails to reach its destination, and when data has been discarded because the allotted Time to Live has ex
IGMP (Internet Group Management Protocol)
at the Network layer of the OSI model to manage multicasting. does not necessarily issue transmissions to every node on a segment. used for teleconferencing or videoconferencing over the Internet.
ARP (Address Resolution Protocol)
a Layer 2 protocol that
uses IP in Layer 3, and operates only within its local network bound by routers. to discover the MAC (physical) address of a host or node on the local network.