Virtual Circuit

Each packet is sent based on the package label. To follow the design idea of

online-oriented link usage, we assume the package has a label

when it reaches the router .In this case, the sent decision is based on the value of the label, or virtual circuit identifier as it is sometimes called.

To create an oriented connection service, a three-phase process is used:

data transfer construction, and disconnection. To create a service with oriented connection, a three-way process is used phase: data transfer construction, and disconnection. At the construction stage, the source addresses and destination of the sender’s sender used to make recordings in the router table for CO service.In the disconnection phase, the source and destination inform the router about it delete address entries. Data transfer occurs between these two phases. In the construction phase, a router creates a record for one virtual circuit. For example, assume that source A needs to create a virtual circuit with destination B.It is necessary to exchange two auxiliary packages between senders and recipients: demand package and recognition package . Demand Package the request package is sent from the source to the destination ,it auxiliary package carries source and destination addresses.

 He still do not know the exit label, which will be found during the step of

recognition. The router then transmits the packet from port 3 to router R3.

Router R3 takes the setup request package Events happen the same way

as in the R1 router, the three table columns are completed in this

case gateway entry (entry label (and exit gateway (Router R4 takes the setup request packet Again, the three columns completed: input port (input label (22)), and output port (35).

Destination B takes the configuration package and if it is e

ready to receive the package from A, he assigns them a label

input packets coming from A, in this case 77.This label allows the destination to know that packets come from A, and not from other sources. The package also bears the label of 77, chosen by the destination as input label for package by A. Router R4 uses this label to complete column filling, specifically the output label column.Note that 77 is the input label for destination B, but the output label for router R4.The R4 router sends an acknowledgment to the R3 router that contains its input label in the table, selected in the setup phase Router R3 uses this as a label exit to the table3.

The R3 router sends a recognition to the R1 router that contains its input label

in the table, selected in the setup phase Router R1 uses this

as the output label on the table 4.

Finally the R1 router sends a recognition to source A that contains the label

its input to the table, selected at the setup stage. Source uses this as the output label for the data packet that will sent to destination B. The second stage is called the data transfer phase.Once all routers have created their own routing tables for a circuit special virtual then network layer packets belonging to a message can be sent one after the other. It shows the process of a single package, but the process is same for 1, 2, or 100 packs.

The source computer uses the label 14 which has received it from the R1 router in phase setup.

The Router R1 transmits the packet to the R3 router, but changes the label to 66.The R3 router transmits the packet to the R4 router, but changes the label to 22. Finally, the R4 router sends the packet to its final tag destination

77.All message packages follow the same tag line for it reach their destination. In the disconnection phase after sending all packets to B, A sends a packet

t special called a disconnection package.Destination B responds with a confirmation package.All routers delete the relevant records from their tables.

For this we will discuss the services provided by layer network in unrelated service as prevalent today on the Internet.To better understand the issues to be discussed, let’s give one example.

 We assume that Iliri, who is working on a publishing, publishing company, “Wonderful Publications”,

-needs to send a message to Fatjon, the manager of

flower shop, “Only Flowers”,

-to inform him that the advertising brochure

for the store is printed and is ready to be transported.

•Illyrian sends him a message using e-mail.

•Let us follow the imaginary path that Ilir’s message takes for him

reached Fatjon.

The company “Wonderful Publications” uses a LAN, which is i

connected via a WAN cable to a regional ISP called

BESTNET;The company “Only Flowers” also uses a LAN, which is e

connected via a DSL WAN to another regional ISP

called ServeNet.

Both regional ISPs are connected via SONET WANs

high speed on a national ISP.

-The message that Iliri sends to Fatjon may have been divided into many

packets in the network layer.

-As we will see soon, packages may or may not follow it

same route.

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Next Post

Virtual Circuit-II

Mon Apr 27 , 2020
For the sake of discussion, we follow the path of one single packages from Ilir’s computer for tek Fatjon’s computer. We will also assume that the package before it reaches at its destination, pass through routers R1 R3, R5, R6, and R8. Two computers include five layers of TCP / […]

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