Chapter 4
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A communication protocol is a system of rules that allows two or more entities of a to transmit via any kind of variation of a . The protocol defines the rules, , semantics and of and possible . Protocols may be implemented by , , or a combination of both.
A Request for Comments (RFC) is a publication from the (ISOC) and its associated bodies, most prominently the (IETF), the principal technical development and standards-setting bodies for the .
An RFC is authored by individuals or groups of engineers and in the form of a describing methods, behaviors, research, or innovations applicable to the working of the Internet and Internet-connected systems. It is submitted either for or to convey new concepts, information, or occasionally engineering humor. The IETF adopts some of the proposals published as RFCs as . However, many RFCs are informational or experimental in nature and are not standards.
A default gateway is the in a using the that serves as the forwarding host () to other networks when no other route specification matches the destination of a packet.
IEEE is the world’s largest technical professional organization dedicated to advancing technology for the benefit of humanity.
The Internet Architecture Board (IAB) is "a committee of the (IETF) and an advisory body of the (ISOC). Its responsibilities include architectural oversight of IETF activities, Internet Standards Process oversight and appeal, and the appointment of the (RFC) Editor. The IAB is also responsible for the management of the IETF protocol parameter registries.
IAB subsidiary groups : IETF (short-term result in RFC ) and IRTF ( long-term)
Standards that we used to see :
RS23-C : EIA
OSI : defined by ISO ( International Organization for Standardization )
TCP/IP : IAB ( TCP/IP defined in RFC )
T1 : AT&T
Header is used to describe meta data, the header is divided into several fields that will describe the characteristics of the data. In the data link layer, apart from having a header, it also has a tailer which functions to checksum crc to see if there are any wrong bits.
Encapsulation: the process of adding a header in each layer drop
In Physical Layer all data become bits stream.
The network is unreliable and it is desirable to divide the information into smaller segments to maximize the probability that each one of them can be delivered correctly to the destination
In MSS ( Message Segment Size ) maximum size is 1460
Message in Application Layer
Segment in Transport Layer
Network Layer
Routing
layer 2 . one hop
layer 3 . end to end
Addressing IPv4 :
Physical address ( MAC Address ) : like your ID Number
Logical Address ( IP Address )
Port Number : to identify which website as the destination
Virtual Host
Routing Information Protocol (RIP) is a distance-vector routing protocol. Routers running the distance-vector protocol send all or a portion of their routing tables in routing-update messages to their neighbors.
You can use RIP to configure the hosts as part of a RIP network. This type of routing requires little maintenance and also automatically reconfigures routing tables when your network changes or network communication stops. RIPv2 was added to the IBM product so you can send and receive RIP packets to update routes throughout your network.
LAYER 4
transport layer
end to end Quality service
TCP ~ reliable
UDP ~ fast
LAYER 5
session layer is like a host that regulates the running of the ongoing process The session layer is used to remember where the last process that occurred before the interrupt occurred so after completing the interrupt the process does not have to be repeated from the beginning and will also continue from where the process was stopped because of the interrupt
LAYER 6
presentation layer
Encoding Decoding
Compression Decompression
Encryption Decryption
LAYER 7
application layer
it is an action which pages destination ( get , put , post , delete , etc )
http number , protocol
layer 1 repeater have to use the same network
layer 2 switch or bridge can used different network like for example ethernet wireless and wired.
Ethernet have 2 standards : Ethernet 2.0 and IEEE 802.3
In data communications networks, packet segmentation is the process of dividing a data into smaller units for transmission over the network. Packet segmentation happens at layer four of the ; the . Segmentation may be required when:
The data packet is larger than the supported by the network
Internet Protocol version 4 (IPv4) is the fourth version of the (IP). It is one of the core protocols of standards-based methods in the and other networks. IPv4 was the first version deployed for production on in 1982 and on the in January 1983. It is still used to route most Internet traffic today, despite the ongoing deployment of a successor protocol, .
IPv4 uses a 32- address space which provides 4,294,967,296 (232) unique addresses, but large blocks are reserved for special networking methods.
Open Shortest Path First (OSPF) is a for (IP) networks. It uses a (LSR) algorithm and falls into the group of (IGPs), operating within a single (AS). It is defined as OSPF Version 2 in RFC 2328 (1998) for .The updates for are specified as OSPF Version 3 in RFC 5340 (2008).OSPF supports the (CIDR) addressing model.
OSPF is a widely used IGP in large . , another LSR-based protocol, is more common in large networks.
A routing protocol specifies how communicate with each other to distribute information that enables them to select routes between on a . Routers perform the traffic directing functions on the Internet; are forwarded through the networks of the internet from router to router until they reach their destination computer. algorithms determine the specific choice of route. Each router has a prior knowledge only of networks attached to it directly. A routing protocol shares this information first among immediate neighbors, and then throughout the network. This way, routers gain knowledge of the . The ability of routing protocols to dynamically adjust to changing conditions such as disabled connections and components and route data around obstructions is what gives the Internet its and .
Dynamic routing, also called adaptive routing, is a process where a router can forward data via a different route or given destination based on the current conditions of the communication circuits within a system. The term is most commonly associated with to describe the capability of a network to 'route around' damage, such as loss of a node or a connection between nodes, so long as other path choices are available. Dynamic routing allows as many routes as possible to remain valid in response to the change. ( need to exchange routing information )
Static routing is a form of that occurs when a router uses a manually-configured routing entry, rather than information from dynamic routing traffic. In many cases, static routes are manually configured by a by adding in entries into a , though this may not always be the case. Unlike , static routes are fixed and do not change if the network is changed or reconfigured. Static routing and are not mutually exclusive. Both dynamic routing and static routing are usually used on a router to maximize routing efficiency and to provide backups in the event that dynamic routing information fails to be exchanged. Static routing can also be used in , or to provide a .
