Chapter 4 - Network Protocols and routing Flashcards
TCP/IP is a suite of protocols, or standards, that includes:
TCP, IP (IPv4 and IPv6), UDP, ARP, and many others
Message headers used at the Transport layer
Each layer adds its own data and addresses its transmission to the corresponding layer in the destination device
Layers 7, 6 and 5 → Data and instructions, known as the payload, are generated by an application running on the source host
Layer 4 → A Transport layer protocol, usually either TCP or UDP, adds a header to the payload. This header includes a port number to identify the receiving application on the destination host. The entire message then becomes a segment (when using TCP) or datagram (when using UDP)
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 packet is passed to the Data Link layer on the NIC, which encapsulates this data with its own header and trailer, creating a frame. This layer’s frame includes a physical address used to find a node on the local network.
Layer 1 → The Physical layer on the NIC receives the frame and places the actual transmission on the network.
OSI: aplique presente na seção para transportar o network para o datalink physical
7 Application 6 Presentation 5 Session 4 Transport 3 Network 2 Datalink 1 Physical
Connectivity devices are known by the highest OSI layer they read and process
For an example, if a switch reads and processes the Data Link layer header but passes the message along without reading higher-layer headers, it is known as a Layer 2 switch.
On the other hand, a router that reads and processes the Network layer header and leaves alone the Transport layer header is known as a Layer 3 device.
TCP (Transmission Control Protocol)
(1) connection-oriented
(2) sequencing and checksums
(3) flow control
TCP manages all these elements - the three-way handshake, checksums, sequencing, and flow control - by posting data to fields in the TCP header at the beginning of a TCP segment.
(1) before TCP transmits data, it ensures that a connection or session is established.
The TCP uses a three-step process called a three-way handshake to establish a TCP connection.
(2) TCP sends a character string called a checksum; TCP on the destination host then generates a similar string. If the two checksums fail to match, the destination host asks the source to retransmit the data.
In addition, because messages don’t always arrive in the same order they were created, TCP attaches a chronological sequence number to each segment so the destination host can, if necessary, reorder segments as they arrive.
(3) Flow control is the process of gauging the appropriate rate of transmission based on how quickly the recipient can accept data.
The 10 header’s fields in a TCP Segment
Headers are constructed in groups of 32 bits called words.
Each word consists of 4 bytes, called blocks, of 8 bits each.
Remember, the data field in the bottom row is not part of the TCP header.
UDP (User Datagram Protocol) is an unrealible, connectionless protocol
The term unreliable does not mean that UDP can’t be used reliably.
Instead, it means that UDP does not guarantee delivery of data, and no connection is established by UDP before data is transmitted.
UDP provides no handshake to establish a connection, acknowledgment of transmission received, error checking, sequencing, or flow controls and is, therefore, more efficient and faster than TCP.
UDP is useful when a great volume of data must be transferred quickly, such as live audio or video transmissions over the Internet.
UDP header contains only four fields:
(1) Source port
(2) Destination port
(3) Length, and
(4) Checksum
IP (Internet Protocol) → It specifies where data should be delivered, identifying the data’s source and destination IP address.
IP is the protocol that enables TCP/IP to internetwork - that is, to transverse more than one LAN segment and more than one type of network through a router.
IP is a connectionless protocol, meaning IP does not establish a session to send its packets.
Each IP packet travels separately from all other packets in its series, where some messages might take a different route than others, even though they’re going to the same place.
Once IP delivers the message to the correct host, it depends on TCP to ensure the messages are put back in the right order, if that’s necessary.
It also relies on either TCP or UDP to ensure each message reaches the correct application on the receiving host.
ICMP (Internet Control Message Protocol) → Whereas IP helps direct data to its correct destination, ICMP is 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 expired (that is, when data has traveled its allotted number of hops).
ICMP announces these transmission failures to the sender, but does not correct errors it detects - those functions are left to higher-layer protocols, such as TCP.
However, ICMP’s announcements provide critical information for troubleshooting network problems.
ICMP messages are generated automatically by network devices, such as routers, and by utilities, such as ping.
Because it operates at Layer 3 alongside IP, ICMP messages contain both an IP header and an ICMP header.
IPv6 relies on ICMPv6 (Internet Control Message Protocol for use with IPv6) to perform the functions that ICMPv4 and ARP peform in IPv4 networks. This includes detecting and reporting data transmition erros, discovering other nodes on a network, and managing multicasting.
ARP (Address Resolution Protocol) on IPv4 Networks
ARP works in conjunction with IPv4 to discover the MAC address of a node on the local network and to maintain a database that maps local IP addresses to MAC addresses.
ARP is a layer 2 protocol…… to be continued
