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TCP Protocol: The Overview – Part1


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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Private IP address ranges

IPv4 Private Address Ranges: IP addresses: — IP addresses: — IP addresses: –   Private IPv4 internet address ranges are defined in RFC1918 with the motivation to control growth of the internet routing tables and to preserve IPv4 addresses space to extend it’s life. The private ranges defined in this RFC are not routable over the internet and are intended for internal use only in private Internets/Intranets and that means these packets destined to these ranges will not be routable across the internet and should stay within the private network. …

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Jumbo Frames

In the past few days we have been doing some tests for Ethernet MTU “The never ending story” in our MPLS backbone.  Playing with MTU for long may have bad effects on your health on the long run but is still a must to have an operational network. We have tested a lot of things about packet fragmentation in the MPLS backbone, the appropriate MTU size when running ATOM and other MPLS services. We may share these tests when we write up a good documentation. One of the interesting topics I would like to share with you is Jumbo frames; …

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