Ports and Protocols Introduction

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Time
7 hours 50 minutes
Difficulty
Beginner
CEU/CPE
8
Video Transcription
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>> Our next section is on protocols and port numbers,
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and this is a big portion of the exam.
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You've just spent some time going through
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the OSI model and the TCP/IP model.
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We've talked about the fact that TCP/IP is really
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a protocol suite with lots of
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different protocols that make up the suite.
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Each one of those protocols has
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a port number assigned to them.
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A port number is a software Identifier slot.
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When the traffic gets to your system,
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your system knows which application or
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service is needed in order to process the traffic.
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With your port numbers,
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there's an endpoint for communication.
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They're not a physical port
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>> that you plug something into,
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>> but they are conceptual entryway into the system.
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When one system is going to connect to
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another system via the network,
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they have a conceptual port number.
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Now, with your port numbers,
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there are what are referred to as well-known ports,
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which is mostly what we're going to work with.
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The idea is that all of
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these protocols that we're
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>> going to talk about in class,
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>> these application layer protocols
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and application layer services,
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all have ports that are assigned
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to them so that, by default,
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web traffic is port 80,
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DNS traffic is port 53, and so on.
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With these well-known port numbers,
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you have to remember from 0-1,023 of the port numbers.
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I just wanted to see who was listening there.
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You don't have to memorize 1,023 port numbers,
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but there are about 20 that you
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just need to know really well.
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There'll be a lot of port questions
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on the exam and hopefully,
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some of you guys will stick around for
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the security ports exam as well.
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You have to know your port numbers on that exam too,
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so you might as well memorize with a smile
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because these will come up multiple times.
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For your registered port numbers,
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vendors will register a certain sort of
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proprietary services or software with IANA,
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which is the organization that manages port numbers.
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These are the ones that are reserved because
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they're used specifically by vendors.
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There are dynamic ports from
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49,152 all the way up to 65,535.
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These are referred to as ephemeral ports.
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These are temporary ports that
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aren't assigned to anything particular,
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but that can be used in order
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to indicate some connection.
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It's often used as a source port number.
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When computer A connects to computer B,
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the destination IP address is
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going to be computer B's IP address,
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and whatever service, for example,
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web server computer B port 80.
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What's also on the data packet is
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the source address and a source port.
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A source port is an arbitrary number,
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usually over 49,152.
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Ultimately, that's a way of
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identifying when traffic comes back into the network.
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It's often used with network address translation,
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so when we talk about ports to memorize,
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I want you to focus on the well-known ports.
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I'll give you a list of following this section.
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For registered ports, know what the range is
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and other for the vendors and proprietary things.
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For a dynamic ports,
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again, we are not worried too much about specifics,
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for your own knowledge,
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know that source ports are pulled from that range.
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