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TCP Protocol: TCP 3-way handshaking #2

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In the last post, we have explained the TCP 3-way handshaking from an abstract point of view, and knew that one of the main functions of this handshaking is to exchange and synchronize some parameters for the TCP connection endpoints to facilitate its job. We also knew that two of the main parameters that the end-points exchange in the TCP 3-way handshaking are the SEQUENCE and ACK numbers. Today, we will continue the 3-way handshaking process in more details. Above is a TCP capture file which I downloaded from “Wireshark” wiki page that shows 3 packets in sequence between two end-hosts. From …

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TCP Protocol: Three-way Handshake

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We all know by now that the basic function of the TCP protocol is to send a stream of bytes that has no shape or fixed size over a network reliably to a receiver. We all also know that reliable delivery involves building a connection between two end-hosts, and this will be the first step that the TCP stack do to exchange data. Above figure, has a host on a side and a server on the other. Host needs to get/download a file from the server via FTP protocol which is dependent on TCP. The Host will start off by allocating …

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TCP Protocol: The Overview – Part1

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One of the most important layers we – as network engineers – hate and avoid in the OSI reference model is the transport layer with its popular and dominant protocol; TCP. Most of network engineers abandoned diving into TCP protocol because they consider it a host-to-host communication protocol that usually works without a problem. End systems either Windows or Linux gets installed with their own version of TCP stack with some pre-configured values that usually don’t break, so why would we bother ourselves learning about one of the most important protocol in the TCP/IP stack! The irony here is that, System Engineers, Application …

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Understand MTU and MRU – The Full Story

MTU or Maximum transmission unit is a topic that pops up every once in a while in different discussions. Although it’s a simple concept, it causes a lot of confusion specially for those who are new to the field. MTU typically becomes an issue of concern during network changes, like adding new vendors equipment or upgrading to a new software. One reason for that is the difference in  implementations used by different vendors or even between different OS versions or equipment  from the same vendor. Here is an example for such confusion  MTU and ping size confusion. On the other …

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PPPoE MTU Explained

PPPoE MTU is a buzz word that many people ask about even if they don’t have anything to do with network engineering. Just being a broadband subscriber with a PPPoE circuit is enough to get introduced to the concept. In this post I will be explaining how PPPoE MTU is calculated and what is the default value. Therefore I would expect the reader to be familiar with what MTU is and with What PPPoE is. PPPoE MTU: PPPoE MTU defines the maximum number of bytes that a PPPoE payload can have. This typically starts from IP layer in most cases. …

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What is MTU?

MTU stands for Maximum transmission unit, which is the maximum packet length that can be sent on an egress interface toward a destination. MTU is an attribute of the egress interface and is typcially considered over a full path from the source to destination. MTU size differes from one media to another and is often a source of issues when configured incorrectly in the network. The following posts will give deep understanding for What is MTU and how you can manipulate it and set it to the correct value. Understanding MTU and MRU .. The full story The post starts …

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