DOCSLIB.ORG

OSI Model Overview Part 1 of 2

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
OSI Model Overview Part 1 of 2 OSI Model Overview Part 1 of 2 Table of Contents OSI and TCP/IP Models ................................................................................................................... 2 Why Use the OSI (or TCP/IP) Model? ............................................................................................. 4 OSI Layer Intro ................................................................................................................................ 6 OSI Layer 1 – Physical ...................................................................................................................... 7 OSI Layer 2 – Data-link .................................................................................................................... 9 OSI Layer 3 – Network .................................................................................................................. 14 Notices .......................................................................................................................................... 18 Page 1 of 18 OSI and TCP/IP Models OSI and TCP/IP Models 20 **020 Instructor: Let's get a little more abstract here. Let's talk about some models. The argument I get into with students every time is: "Well that protocol doesn't sit at that layer of the OSI model." "I know it doesn't; because OSI is a model." "Well SSL doesn't fit here." "I know it doesn't; because that's an implementation." And so I need you to step back just a little bit; just kind of let go here and say: This is theory. Now another way to deal with this theory in its implementation is to Page 2 of 18 actually kind of dig in to that protocol data unit and take a look at it. And how you do that-- I think-- the best way to do that is to go through a set of layers-- work through those layers with me here-- and then put it in action. If you're allowed to on your network, download the tool that will actually allow you to capture packets. I like Wireshark. It's a free, open source tool; and it's cross-platform capable. You have to be allowed to download it; and you also have to be able to well collect communications on your network to actually see it in action. If you can't do that and you can only download the tool, you can actually get pre-built packet captures that other people have collected and have put up on the internet. Well what is Wireshark? It is a way to look at all of the communications between hosts, with certain tools in place; and then you can inspect that individual protocol data unit and dig down inside of it and look at the actual protocols in use at what layers. So let's look at our models here. Page 3 of 18 Why Use the OSI (or TCP/IP) Model? Why Use the OSI (or TCP/IP) Model? Permit exchange of information among systems that are “open” or compliant with this standard • Reference framework to enable independent work • Definitions of security terminology • Standard descriptions of security services and mechanisms • Identify where services map to OSI model • Security management “Information may not be given to, accessed by, nor permitted to be inferred by, nor may any resource be used by those not appropriately authorized” - General Authorization Policy – ISO 7498-2 21 **021 So we've got these two different models. They allow us to abstract the communications that are going between two hosts, or maybe to many hosts, and allows us to create protocols that don't have to consider every single possibility of communication from me to you. Let's go back to mainframe days for a second. In mainframe days it was that node can talk to this node based on what rules I've laid out here. And this was a little bit of a brittle communication at that point. What we want is flexibility within our protocols. Page 4 of 18 So what we did is we said: Okay between me and you what we're going to do is we're going to abstract that communication in a bunch of different ways, in a layered fashion, that allows me to say: Well there's an improvement that I can make here without disturbing the unimproved stack on your side. So I can make improvements and optimizations for me; as long as I make sure that you understand and I follow the general rules or protocol; then you will be able to communicate with me on the other side. So a lesser client can communicate to a greater client, in a lot of cases. Now when we look at this information in the OSI and the TCP model, a lot of people get really hung up on the rules, really hung up on the terminology in here. And what I will say to you is just relax and let it wash over you a little bit. So this is a framework that is independent of the network; which is really, really nice. It allows us to define security terminology at different layers. So we can apply more rigor of security at different layers inside the OSI model when it suits the communication from me to say you; and we can add that security as we go along. Page 5 of 18 OSI Layer Intro OSI Layer Intro Defined by ISO 7498 • Also describes security mechanisms and where they fit in the model. Application Presentation Session Transport Network Data-link Physical 22 **022 So let's look at the model. Here's our model: Application, Presentation, Session, Transport, Network, Data-link and Physical layer. Sometimes these are mapped together. Page 6 of 18 OSI Layer 1 – Physical OSI Layer 1 – Physical Application • Transmits logical bits (1’s and Presentation 0’s) over a physical circuit • Electrical and physical Session specifications Transport • Devices – NICs, repeaters, Network concentrators Data-link Physical 23 **023 When we look at Layer 1, we are talking about electronic signals, shapes; and at this point the data is just 1s and 0s, electronic signals. It's on or it's off. Physical connector. What is the shape of the thing that you plug into the wall? Is it RJ45 or is it RJ11? Is it a BNC connector? The physical shape and characteristics of it are described at the Physical layer. One other Physical layer attribute that we might want to talk about is wiring schemes. So when we're talking about an eight cable- an eight connector Ethernet cable, is that Page 7 of 18 EIA/TIA specification? And I won't use the numbers here; but it could be we'll set it up one way or we'll set it up another way. By the way, in that communication between us, if we do it correctly and we wire all of our jacks the same, then we'll have communication. If we wire them to the other standard, we'll actually create what's called a crossover cable between two devices. So let's go back to our introduction to the course; and how could you be evil at this point? What could you do at the Physical layer? Well you could inject noise onto the channel if you wanted to. You could cut the cable. You could- you could listen in and capture that information. And so at the Physical layer we have to put in physical protection mechanisms. Page 8 of 18 OSI Layer 2 – Data-link OSI Layer 2 – Data-link Application • Physical addressing, error Presentation detection and reliable data transfer Session • LLC – link-layer control, Transport governs sequence numbers and acknowledgements Network • MAC – media-access control, Data-link governs data transfer and Physical collision handling • Devices – ATM, switches, bridges • Protocols: PPP, ARP 24 **024 As we go up a layer to the Data-link layer, now what we're doing is we're starting to abstract things. The Data-link layer-- remember, it knows nothing about the Physical layer except for I expect when this signal comes across that it is correct for what we're doing. Now this layer breaks into two sub- layers: the logical link control and the media-access control. When we talk about logical link control, this is sequence numbers and acknowledgements at a Layer 2 level. This is setting up so that we can transmit back and forth between Page 9 of 18 each other. Don't confuse that with the Network or the Transport layer. But we govern the sequence that we've received the bits and we can keep on signaling. More importantly at this layer is our address space; which is covered by the sub-layer media-access control. It governs the data transfers and the collision handling. How does it do that? Well when we talk about a MAC address, it is six pairs of hex that are uniquely tied to a particular node on that network. When we communicate to the rest of the nodes on that network in that what's called broadcast domain, what we will do is we will say; This is my MAC address; I'm looking for you. So I want to communicate directly for you- to you. On this broadcast domain that everybody else hears, you know that I'm only talking to you; and the rest of you should- don't pay any attention to this. That's what it boils down to. What happens if I don't know who you are; and I say: I'm looking for Steve? Everybody has to listen and say: Hum I'm not Steve. But Steve will raise his hand and go: Hi I'm Steve. Ah okay. Let's have a communication here. How do I communicate to everyone? When I broadcast to everyone looking for Steve, what I do is I Page 10 of 18 change the address of who I'm looking for to all f's in all of those hexadecimal representations. And thereby everybody on that piece of broadcast domain will pick up that signal; and they'll look at it and they'll say: This is destined for everybody? Well I'm everybody.
Load more

Recommended publications
  • Solutions to Chapter 2
    CS413 Computer Networks ASN 4 Solutions Solutions to Assignment #4 3. What difference does it make to the network layer if the underlying data link layer provides a connection-oriented service versus a connectionless service? [4 marks] Solution: If the data link layer provides a connection-oriented service to the network layer, then the network layer must precede all transfer of information with a connection setup procedure (2). If the connection-oriented service includes assurances that frames of information are transferred correctly and in sequence by the data link layer, the network layer can then assume that the packets it sends to its neighbor traverse an error-free pipe. On the other hand, if the data link layer is connectionless, then each frame is sent independently through the data link, probably in unconfirmed manner (without acknowledgments or retransmissions). In this case the network layer cannot make assumptions about the sequencing or correctness of the packets it exchanges with its neighbors (2). The Ethernet local area network provides an example of connectionless transfer of data link frames. The transfer of frames using "Type 2" service in Logical Link Control (discussed in Chapter 6) provides a connection-oriented data link control example. 4. Suppose transmission channels become virtually error-free. Is the data link layer still needed? [2 marks – 1 for the answer and 1 for explanation] Solution: The data link layer is still needed(1) for framing the data and for flow control over the transmission channel. In a multiple access medium such as a LAN, the data link layer is required to coordinate access to the shared medium among the multiple users (1).
    [Show full text]
  • ISSN: 2320-5407 Int. J. Adv. Res. 5(4), 422-426 RESEARCH ARTICLE
    ISSN: 2320-5407 Int. J. Adv. Res. 5(4), 422-426 Journal Homepage: - www.journalijar.com Article DOI: 10.21474/IJAR01/3826 DOI URL: http://dx.doi.org/10.21474/IJAR01/3826 RESEARCH ARTICLE CHALLENGING ISSUES IN OSI AND TCP/IP MODEL. Dr. J. VijiPriya, Samina and Zahida. College of Computer Science and Engineering, University of Hail, Saudi Arabia. …………………………………………………………………………………………………….... Manuscript Info Abstract ……………………. ……………………………………………………………… Manuscript History A computer network is a connection of network devices to data communication. Multiple networks are connected together to form an Received: 06 February 2017 internetwork. The challenges of Internetworking is interoperating Final Accepted: 05 March 2017 between products from different manufacturers requires consistent Published: April 2017 standards. Network reference models were developed to address these challenges. Two useful reference models are Open System Key words:- Interconnection (OSI) and Transmission Control Protocol and Internet OSI, TCP/IP, Data Communication, Protocol (TCP/IP) serve as protocol architecture details the Protocols, Layers, and Encapsulation communication between applications on network devices. This paper depicts the OSI and TCP/IP models, their issues and comparison of them. Copy Right, IJAR, 2017,. All rights reserved. …………………………………………………………………………………………………….... Introduction:- Network reference models are called protocol architecture in which task of communication can be broken into sub tasks. These tasks are organized into layers representing network services and functions. The layered protocols are rules that govern end-to-end communication between devices. Protocols on each layer will interact with protocols on the above and below layers of it that form a protocol suite or stack. The most established TCP/IP suite was developed by Department of Defence's Project Research Agency DARPA based on OSI suite to the foundation of Internet architecture.
    [Show full text]
  • Logical Link Control and Channel Scheduling for Multichannel Underwater Sensor Networks
    ICST Transactions on Mobile Communications and Applications Research Article Logical Link Control and Channel Scheduling for Multichannel Underwater Sensor Networks Jun Li ∗, Mylene` Toulgoat, Yifeng Zhou, and Louise Lamont Communications Research Centre Canada, 3701 Carling Avenue, Ottawa, ON. K2H 8S2 Canada Abstract With recent developments in terrestrial wireless networks and advances in acoustic communications, multichannel technologies have been proposed to be used in underwater networks to increase data transmission rate over bandwidth-limited underwater channels. Due to high bit error rates in underwater networks, an efficient error control technique is critical in the logical link control (LLC) sublayer to establish reliable data communications over intrinsically unreliable underwater channels. In this paper, we propose a novel protocol stack architecture featuring cross-layer design of LLC sublayer and more efficient packet- to-channel scheduling for multichannel underwater sensor networks. In the proposed stack architecture, a selective-repeat automatic repeat request (SR-ARQ) based error control protocol is combined with a dynamic channel scheduling policy at the LLC sublayer. The dynamic channel scheduling policy uses the channel state information provided via cross-layer design. It is demonstrated that the proposed protocol stack architecture leads to more efficient transmission of multiple packets over parallel channels. Simulation studies are conducted to evaluate the packet delay performance of the proposed cross-layer protocol stack architecture with two different scheduling policies: the proposed dynamic channel scheduling and a static channel scheduling. Simulation results show that the dynamic channel scheduling used in the cross-layer protocol stack outperforms the static channel scheduling. It is observed that, when the dynamic channel scheduling is used, the number of parallel channels has only an insignificant impact on the average packet delay.
    [Show full text]
  • Physical Layer Overview
    ELEC3030 (EL336) Computer Networks S Chen Physical Layer Overview • Physical layer forms the basis of all networks, and we will first revisit some of fundamental limits imposed on communication media by nature Recall a medium or physical channel has finite Spectrum bandwidth and is noisy, and this imposes a limit Channel bandwidth: on information rate over the channel → This H Hz is a fundamental consideration when designing f network speed or data rate 0 H Type of medium determines network technology → compare wireless network with optic network • Transmission media can be guided or unguided, and we will have a brief review of a variety of transmission media • Communication networks can be classified as switched and broadcast networks, and we will discuss a few examples • The term “physical layer protocol” as such is not used, but we will attempt to draw some common design considerations and exams a few “physical layer standards” 13 ELEC3030 (EL336) Computer Networks S Chen Rate Limit • A medium or channel is defined by its bandwidth H (Hz) and noise level which is specified by the signal-to-noise ratio S/N (dB) • Capability of a medium is determined by a physical quantity called channel capacity, defined as C = H log2(1 + S/N) bps • Network speed is usually given as data or information rate in bps, and every one wants a higher speed network: for example, with a 10 Mbps network, you may ask yourself why not 10 Gbps? • Given data rate fd (bps), the actual transmission or baud rate fb (Hz) over the medium is often different to fd • This is for
    [Show full text]
  • Telematics Chapter 3: Physical Layer
    Telematics User Server watching with video Chapter 3: Physical Layer video clip clips Application Layer Application Layer Presentation Layer Presentation Layer Session Layer Session Layer Transport Layer Transport Layer Network Layer Network Layer Network Layer Data Link Layer Data Link Layer Data Link Layer Physical Layer Physical Layer Physical Layer Univ.-Prof. Dr.-Ing. Jochen H. Schiller Computer Systems and Telematics (CST) Institute of Computer Science Freie Universität Berlin http://cst.mi.fu-berlin.de Contents ● Design Issues ● Theoretical Basis for Data Communication ● Analog Data and Digital Signals ● Data Encoding ● Transmission Media ● Guided Transmission Media ● Wireless Transmission (see Mobile Communications) ● The Last Mile Problem ● Multiplexing ● Integrated Services Digital Network (ISDN) ● Digital Subscriber Line (DSL) ● Mobile Telephone System Univ.-Prof. Dr.-Ing. Jochen H. Schiller ▪ cst.mi.fu-berlin.de ▪ Telematics ▪ Chapter 3: Physical Layer 3.2 Design Issues Univ.-Prof. Dr.-Ing. Jochen H. Schiller ▪ cst.mi.fu-berlin.de ▪ Telematics ▪ Chapter 3: Physical Layer 3.3 Design Issues ● Connection parameters ● mechanical OSI Reference Model ● electric and electronic Application Layer ● functional and procedural Presentation Layer ● More detailed ● Physical transmission medium (copper cable, Session Layer optical fiber, radio, ...) ● Pin usage in network connectors Transport Layer ● Representation of raw bits (code, voltage,…) Network Layer ● Data rate ● Control of bit flow: Data Link Layer ● serial or parallel transmission of bits Physical Layer ● synchronous or asynchronous transmission ● simplex, half-duplex, or full-duplex transmission mode Univ.-Prof. Dr.-Ing. Jochen H. Schiller ▪ cst.mi.fu-berlin.de ▪ Telematics ▪ Chapter 3: Physical Layer 3.4 Design Issues Transmitter Receiver Source Transmission System Destination NIC NIC Input Abcdef djasdja dak jd ashda kshd akjsd asdkjhasjd as kdjh askjda Univ.-Prof.
    [Show full text]
  • Application Protocol Data Unit Meaning
    Application Protocol Data Unit Meaning Oracular and self Walter ponces her prunelle amity enshrined and clubbings jauntily. Uniformed and flattering Wait often uniting some instinct up-country or allows injuriously. Pixilated and trichitic Stanleigh always strum hurtlessly and unstepping his extensity. NXP SE05x T1 Over I2C Specification NXP Semiconductors. The session layer provides the mechanism for opening closing and managing a session between end-user application processes ie a semi-permanent dialogue. Uses MAC addresses to connect devices and define permissions to leather and commit data 1. What are Layer 7 in networking? What eating the application protocols? Application Level Protocols Department of Computer Science. The present invention pertains to the convert of Protocol Data Unit PDU session. Network protocols often stay to transport large chunks of physician which are layer in. The term packet denotes an information unit whose box and tranquil is remote network-layer entity. What is application level security? What does APDU stand or Hop sound to rot the meaning of APDU The Acronym AbbreviationSlang APDU means application-layer protocol data system by. In the context of smart cards an application protocol data unit APDU is the communication unit or a bin card reader and a smart all The structure of the APDU is defined by ISOIEC 716-4 Organization. Application level security is also known target end-to-end security or message level security. PDU Protocol Data Unit Definition TechTerms. TCPIP vs OSI What's the Difference Between his Two Models. The OSI Model Cengage. As an APDU Application Protocol Data Unit which omit the communication unit advance a.
    [Show full text]
  • RT-ROS: a Real-Time ROS Architecture on Multi-Core Processors
    Future Generation Computer Systems 56 (2016) 171–178 Contents lists available at ScienceDirect Future Generation Computer Systems journal homepage: www.elsevier.com/locate/fgcs RT-ROS: A real-time ROS architecture on multi-core processors Hongxing Wei a,1, Zhenzhou Shao b, Zhen Huang a, Renhai Chen d, Yong Guan b, Jindong Tan c,1, Zili Shao d,∗,1 a School of Mechanical Engineering and Automation, Beihang University, Beijing, 100191, PR China b College of Information Engineering, Capital Normal University, Beijing, 100048, PR China c Department of Mechanical, Aerospace, and Biomedical Engineering, The University of Tennessee, Knoxville, TN, 37996-2110, USA d Department of Computing, The Hong Kong Polytechnic University, Hong Kong, China article info a b s t r a c t Article history: ROS, an open-source robot operating system, is widely used and rapidly developed in the robotics Received 6 February 2015 community. However, running on Linux, ROS does not provide real-time guarantees, while real-time tasks Received in revised form are required in many robot applications such as robot motion control. This paper for the first time presents 20 April 2015 a real-time ROS architecture called RT-RTOS on multi-core processors. RT-ROS provides an integrated Accepted 12 May 2015 real-time/non-real-time task execution environment so real-time and non-real-time ROS nodes can be Available online 9 June 2015 separately run on a real-time OS and Linux, respectively, with different processor cores. In such a way, real-time tasks can be supported by real-time ROS nodes on a real-time OS, while non-real-time ROS nodes Keywords: Real-time operating systems on Linux can provide other functions of ROS.
    [Show full text]
  • Data Link Layer
    Data link layer Goals: ❒ Principles behind data link layer services ❍ Error detection, correction ❍ Sharing a broadcast channel: Multiple access ❍ Link layer addressing ❍ Reliable data transfer, flow control: Done! ❒ Example link layer technology: Ethernet Link layer services Framing and link access ❍ Encapsulate datagram: Frame adds header, trailer ❍ Channel access – if shared medium ❍ Frame headers use ‘physical addresses’ = “MAC” to identify source and destination • Different from IP address! Reliable delivery (between adjacent nodes) ❍ Seldom used on low bit error links (fiber optic, co-axial cable and some twisted pairs) ❍ Sometimes used on high error rate links (e.g., wireless links) Link layer services (2.) Flow Control ❍ Pacing between sending and receiving nodes Error Detection ❍ Errors are caused by signal attenuation and noise. ❍ Receiver detects presence of errors signals sender for retrans. or drops frame Error Correction ❍ Receiver identifies and corrects bit error(s) without resorting to retransmission Half-duplex and full-duplex ❍ With half duplex, nodes at both ends of link can transmit, but not at same time Multiple access links / protocols Two types of “links”: ❒ Point-to-point ❍ PPP for dial-up access ❍ Point-to-point link between Ethernet switch and host ❒ Broadcast (shared wire or medium) ❍ Traditional Ethernet ❍ Upstream HFC ❍ 802.11 wireless LAN MAC protocols: Three broad classes ❒ Channel Partitioning ❍ Divide channel into smaller “pieces” (time slots, frequency) ❍ Allocate piece to node for exclusive use ❒ Random
    [Show full text]
  • OSI Model and Network Protocols
    CHAPTER4 FOUR OSI Model and Network Protocols Objectives 1.1 Explain the function of common networking protocols . TCP . FTP . UDP . TCP/IP suite . DHCP . TFTP . DNS . HTTP(S) . ARP . SIP (VoIP) . RTP (VoIP) . SSH . POP3 . NTP . IMAP4 . Telnet . SMTP . SNMP2/3 . ICMP . IGMP . TLS 134 Chapter 4: OSI Model and Network Protocols 4.1 Explain the function of each layer of the OSI model . Layer 1 – physical . Layer 2 – data link . Layer 3 – network . Layer 4 – transport . Layer 5 – session . Layer 6 – presentation . Layer 7 – application What You Need To Know . Identify the seven layers of the OSI model. Identify the function of each layer of the OSI model. Identify the layer at which networking devices function. Identify the function of various networking protocols. Introduction One of the most important networking concepts to understand is the Open Systems Interconnect (OSI) reference model. This conceptual model, created by the International Organization for Standardization (ISO) in 1978 and revised in 1984, describes a network architecture that allows data to be passed between computer systems. This chapter looks at the OSI model and describes how it relates to real-world networking. It also examines how common network devices relate to the OSI model. Even though the OSI model is conceptual, an appreciation of its purpose and function can help you better understand how protocol suites and network architectures work in practical applications. The OSI Seven-Layer Model As shown in Figure 4.1, the OSI reference model is built, bottom to top, in the following order: physical, data link, network, transport, session, presentation, and application.
    [Show full text]
  • Medium Access Control Layer
    Telematics Chapter 5: Medium Access Control Sublayer User Server watching with video Beispielbildvideo clip clips Application Layer Application Layer Presentation Layer Presentation Layer Session Layer Session Layer Transport Layer Transport Layer Network Layer Network Layer Network Layer Univ.-Prof. Dr.-Ing. Jochen H. Schiller Data Link Layer Data Link Layer Data Link Layer Computer Systems and Telematics (CST) Physical Layer Physical Layer Physical Layer Institute of Computer Science Freie Universität Berlin http://cst.mi.fu-berlin.de Contents ● Design Issues ● Metropolitan Area Networks ● Network Topologies (MAN) ● The Channel Allocation Problem ● Wide Area Networks (WAN) ● Multiple Access Protocols ● Frame Relay (historical) ● Ethernet ● ATM ● IEEE 802.2 – Logical Link Control ● SDH ● Token Bus (historical) ● Network Infrastructure ● Token Ring (historical) ● Virtual LANs ● Fiber Distributed Data Interface ● Structured Cabling Univ.-Prof. Dr.-Ing. Jochen H. Schiller ▪ cst.mi.fu-berlin.de ▪ Telematics ▪ Chapter 5: Medium Access Control Sublayer 5.2 Design Issues Univ.-Prof. Dr.-Ing. Jochen H. Schiller ▪ cst.mi.fu-berlin.de ▪ Telematics ▪ Chapter 5: Medium Access Control Sublayer 5.3 Design Issues ● Two kinds of connections in networks ● Point-to-point connections OSI Reference Model ● Broadcast (Multi-access channel, Application Layer Random access channel) Presentation Layer ● In a network with broadcast Session Layer connections ● Who gets the channel? Transport Layer Network Layer ● Protocols used to determine who gets next access to the channel Data Link Layer ● Medium Access Control (MAC) sublayer Physical Layer Univ.-Prof. Dr.-Ing. Jochen H. Schiller ▪ cst.mi.fu-berlin.de ▪ Telematics ▪ Chapter 5: Medium Access Control Sublayer 5.4 Network Types for the Local Range ● LLC layer: uniform interface and same frame format to upper layers ● MAC layer: defines medium access ..
    [Show full text]
  • Fedramp Master Acronym and Glossary Document
    FedRAMP Master Acronym and Glossary Version 1.6 07/23/2020 i​[email protected] fedramp.gov Master Acronyms and Glossary DOCUMENT REVISION HISTORY Date Version Page(s) Description Author 09/10/2015 1.0 All Initial issue FedRAMP PMO 04/06/2016 1.1 All Addressed minor corrections FedRAMP PMO throughout document 08/30/2016 1.2 All Added Glossary and additional FedRAMP PMO acronyms from all FedRAMP templates and documents 04/06/2017 1.2 Cover Updated FedRAMP logo FedRAMP PMO 11/10/2017 1.3 All Addressed minor corrections FedRAMP PMO throughout document 11/20/2017 1.4 All Updated to latest FedRAMP FedRAMP PMO template format 07/01/2019 1.5 All Updated Glossary and Acronyms FedRAMP PMO list to reflect current FedRAMP template and document terminology 07/01/2020 1.6 All Updated to align with terminology FedRAMP PMO found in current FedRAMP templates and documents fedramp.gov page 1 Master Acronyms and Glossary TABLE OF CONTENTS About This Document 1 Who Should Use This Document 1 How To Contact Us 1 Acronyms 1 Glossary 15 fedramp.gov page 2 Master Acronyms and Glossary About This Document This document provides a list of acronyms used in FedRAMP documents and templates, as well as a glossary. There is nothing to fill out in this document. Who Should Use This Document This document is intended to be used by individuals who use FedRAMP documents and templates. How To Contact Us Questions about FedRAMP, or this document, should be directed to ​[email protected]​. For more information about FedRAMP, visit the website at ​https://www.fedramp.gov​.
    [Show full text]
  • The OSI Model: Understanding the Seven Layers of Computer Networks
    Expert Reference Series of White Papers The OSI Model: Understanding the Seven Layers of Computer Networks 1-800-COURSES www.globalknowledge.com The OSI Model: Understanding the Seven Layers of Computer Networks Paul Simoneau, Global Knowledge Course Director, Network+, CCNA, CTP Introduction The Open Systems Interconnection (OSI) model is a reference tool for understanding data communications between any two networked systems. It divides the communications processes into seven layers. Each layer both performs specific functions to support the layers above it and offers services to the layers below it. The three lowest layers focus on passing traffic through the network to an end system. The top four layers come into play in the end system to complete the process. This white paper will provide you with an understanding of each of the seven layers, including their functions and their relationships to each other. This will provide you with an overview of the network process, which can then act as a framework for understanding the details of computer networking. Since the discussion of networking often includes talk of “extra layers”, this paper will address these unofficial layers as well. Finally, this paper will draw comparisons between the theoretical OSI model and the functional TCP/IP model. Although TCP/IP has been used for network communications before the adoption of the OSI model, it supports the same functions and features in a differently layered arrangement. An Overview of the OSI Model Copyright ©2006 Global Knowledge Training LLC. All rights reserved. Page 2 A networking model offers a generic means to separate computer networking functions into multiple layers.
    [Show full text]