DOCSLIB.ORG

Forwarding and Addressing in the Link Layer

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Forwarding and Addressing in the Link Layer Forwarding and Addressing in the Link Layer 3035/GZ01 Networked Systems Kyle Jamieson Lecture 4 Department of Computer Science University College London The link layer The link layer (L2) has the job of transferring a datagram point-to-point over a link Datagram link_send(packet, link-id) network_handle Wireless Node A Node B Node D Link layer Link layer Link layer Serial Link layer Node C Ethernet Unit of data is called a frame at the link layer Where is the link layer implemented? • In each and every host Host Applicaon • Network adapter Transport CPU Memory – Physical card Network – Chip in a device Link Network adapter – APaches to host’s Controller system bus Link • Implemented both in Physical PHY hardware and soRware – SoRware: device driver running on CPU – Hardware: FPGA, ASIC in network adapter Hardware or soware? Host • SoRware is more flexible, Applicaon unless you need: Transport CPU Memory Network 1. Time-criYcal funcYonality Link Network adapter – Backoff transmission Yming in Ethernet Controller Link Physical PHY 2. Highly parallel processing – Dot product computaons for CDMA, filtering for the PHY Today 1. Framing – Byte-oriented framing – Bit-oriented framing 2. Link layer addressing 3. Link layer switching and forwarding Framing: The problem Bit stream 1 0 0 0 1 0 0 1 1 Binary encoding Manchester encoding Time • We have seen how to encode bits on a link – Ethernet: Manchester encoding, synchronizaon on edges – Result in general: An infinite stream of bits • Problem: where does each frame begin and end? Byte-oriented framing • Treat each frame as a collecYon of bytes rather than bits • Byte-oriented framing link layer protocols: – PPP (point-to-point protocol), used to carry Internet Protocol (IP) packets over dialup lines, Virtual Private Networks – BISYNC (IBM, 60’s), Digital Data Communicaon Message Protocol (DDCMP), Digital Equipment Corporaon’s DECNET • BISYNC uses sennel characters to frame: • SYN: Beginning of frame • SOH: Start of header • STX: Start of text (packet data) • ETX: End of text • What if senYnel occurs in data? Character stuffing: insert escape character DLE before senYnel • What if escape character occurs in data? Escape the escape character PPP byte stuffing • Like BISYNC, PPP takes a senYnel-based approach • At the sender: – Stuff escape byte before each flag byte in payload – Stuff escape byte before each escape byte in payload • At the reCeiver: – Escape, flag byte à discard escape byte, keep flag byte, conYnue data recepYon – Single flag byte: interpret as the flag byte – Two escape bytes à discard one Byte-CounHng approaCh: DDCMP • Byte-coun/ng framing: Include number of bytes in header (Count field): • What if Count field is corrupted? – Will frame the wrong bytes – This is called a framing error – With high probability, CRC will detect the framing error and discard the frame • Do we sYll need to escape the SYNs? Bit-oriented framing • Main idea: View link as stream of bits instead of bytes • Example: High-Level Data Link Control (HDLC), used in Cisco routers and the V.42 standard for telephone modems • Choose some paern of bits as a senYnel e.g.: 1111111 Seven 1s • Bit stuffing algorithm: Modify the outgoing data stream as follows: • At sender: 111111 → 1111110 Six 1s Six 1s • At receiver: 1111110 → 111111 1111111 → (end of frame) Seven 1s • Size of frame depends on data it contains! • Not guaranteed free of framing errors Today 1. Framing 2. Link layer addressing 3. Link layer switching and forwarding 4. Virtualizing links Comparing addressing schemes • Network layer address (IP address) – FuncYon: move datagram to desYnaon network – 32-bit address, doPed quad notaon a.b.c.d where each component is an eight-bit unsigned integer – Hierarchical address space • Link layer address (MAC address, Ethernet address): – FuncYon: move frame from one point to another point on the same network – 48-bit address (in most LANs) – Burned in NIC ROM, also someYmes soRware sePable – Usually a flat address space Link-layer addressing • Each adapter on LAN has unique link layer address, my_station_id! • Special broadcast address broadcast_id! Station Identifier (Ethernet 17 24 12 05 19 Address) • Each L3 protocol registers itself in net_handler array • L2 address-related funcYonality for inbound frames: • Test received_frame.destination against my_station_id or broadcast_id, drop if neither match • handler ß net_handler! !! !!!![received_frame.net_protocol]! • call handler(received_frame.payload)! Mapping network to link addresses • Goal: Translate from nework_send(data, length, IP, N) to link_send(data, length, IP, enet/18)! • Name-mapping table: example of soR state upper-layer network address link identifier G internet Ethernet/ L M N P Q K address station work work work work router 1 H station station server station station 2 enet/15 … 3 J M 4 enet/18 1 1 1 1 1 N 6 5 E P enet/14 17 15 18 14 22 19 Q enet/22 K enet/19 Ethernet F E enet/19 Ethernet station identifier Link layer addresses aren’t routable • Network layer routes from one network to another upper-layer network address link identifier G L M N P Q K work work work work router 1 H station station server station station 2 … 3 J 4 1 1 1 1 1 6 5 E 17 15 18 14 22 19 Ethernet F Ethernet station identifier (link layer address) The Address ResoluHon ProtoCol (ARP) L sending a datagram to N: L: network_send(data, length, IP, N)! L: link_send(“where is N?”, length, ARP, broadcast_id)! N: link_send(“N is at enet/18”, length, ARP, enet/17)! L: link_send(data, length, IP, enet/18)! upper-layer network address ARP table at L: link identifier G Internet enet/ L M N P Q K Address station TTL work work work work router 1 H station station server station station 2 … 3 J N 18 20 min 4 1 1 1 1 1 6 5 E 17 15 18 14 22 19 Ethernet F Ethernet station identifier ARP’s role in L3 roung • Walkthrough: send IP data from L to E via router K • Router K • Two ARP tables: one for each subnet • Two interfaces (interface ids 6, 4): one for each subnet, with two link-layer addresses (19, 27) L N K E work work router server station station 4 27 1 1 6 17 18 19 28 Ethernet Ethernet Example: roung between subnets L sending a datagram to E: L: network_send(data, length, IP, E)! L: link_send(data, length, IP, enet/28)! L: ARPs for K’s link layer address (enet/19) L: link_send(data, length, IP, enet/19)! K: ARPs for E’s link layer address (enet/28) on link/4 K: link_send(link/4, data, length, IP, enet/ 28)! L N K E work work router server station station 4 27 1 1 6 17 18 19 28 Ethernet Ethernet Hubs • Replicang device: bits coming in go out all ports – Operates at the physical layer (L1) • Doesn’t run CSMA/CD: immediately replicates bits • Collisions possible between all hosts • No frame buffering at the hub • Physical limitaons: can’t grow collision domain too big Hub Today 1. Framing 2. Link layer addressing 3. Link layer switChing and forwarding – Learning switches – Spanning Tree Protocol – Virtual LANs Ethernet nowadays: Switched • Hosts have dedicated, direct A connecYon to switch F B • Switches buffer frames 1 2 6 3 Switch S • Ethernet protocol used on each 5 4 incoming link, but no collisions – Each link in own collision domain C • Switching: Allows two E D conversaons A → A’ and B → B’ simultaneously, without collisions The switch table • How to tell which port to A forward packet? F B 21 22 26 1 2 • The switch table: 6 3 Switch S LAN addr Port Time-to-live 5 4 23 25 24 C • Switch table iniYally empty E D • How to build up switch table entries? Building the switch table: Self-learning • Switch table: entries of (LAN address, port id, Yme-to-live) • Learning algorithm: on receiving a packet from LAN address S to LAN address D: 1. Add S to switch table with incident port id 2. If D is broadcast_id: forward out all ports 3. If D is in switch table, lookup entry and forward to resulYng port id. Otherwise, forward out all ports • Periodically flush link table entries based on Yme-to-live Building up the switch table: example 1. Aà S: [A (enet/21) à D (enet/24)] A S à (all ports) F 2. B à S: [B (enet/22) à C (enet/23)] B 21 22 26 S à (all ports) 1 2 à à 6 3 3. D S: [D (enet/24) B (enet/22)] Switch S S à port 2 only 5 4 23 25 24 Switch table: C LAN addr Port TTL E D enet/21 1 20 min enet/22 2 20 min enet/24 4 20 min Aside: What is a hub? Hub Switch • Differences – Physical layer (L1) device – Link-layer (L2) device – Replicang device: bits in one – SelecYvely forward frame to port go out all ports one or more outgoing links – No medium access control – CSMA/CD MAC – No frame buffering – Buffers frames • CommonaliYes – Hosts are unaware of – Hosts are unaware of presence of hubs presence of switches – No configuraon needed – No configuraon needed InterConneCHng LANs Link layer addresses S 1 4 2 3 S1 11 1 1 S3 2 S 1 21 2 A 3 4 2 12 3 4 13 D 22 23 B C E F • Switches can connect LANs as well as hosts • SomeYmes called bridges in this context • The enYrety is called an extended LAN InterConneCHng LANs: example Suppose C sends frame to F, F responds to C Link layer addresses S 1 4 2 3 S1 11 1 1 S3 2 S 1 21 2 A 3 4 2 12 3 4 13 D 22 23 B C E F Address Port 13 4 InterConneCHng LANs: example Suppose C sends frame to F, F responds to C S 1 4 2 3 S1 11 1 1 S3 2 S 1 21 2 A 3 4 2 12 3 4 13 D 22 23 B C E F Address Port 13 4 Address Port 13 1 InterConneCHng LANs: example Suppose C sends frame to F, F responds to C S 1 4 2 3 S1 11 1 1 S3 2 S 1 21 2 A 3 4 2 12 3 4 13 D 22 23 B C E F Address Port 13 1 Address Port 13 4 Address Port 13 1 Address Port 13 1 InterConneCHng LANs: example Suppose C sends frame to F, F
Load more

Recommended publications
  • Ipv6 … a Simplified Explanation
    IPv6 … A Simplified Explanation Presented by Bryan Crisler Senior Network Engineer Time Warner Cable Housekeeping • Take this time to locate: – Emergency Exits – Bathrooms – Breakroom/Water Fountain – Note taking utensils • Put your Phones on Vibrate – If you need to take a call, feel free to step out of the room. About your Speaker • Bryan Crisler – Started in Cable @ Charter Communications, Riverside, CA in June 2005 – Currently a Senior Network Engineer at Time Warner Cable About your Speaker • Held following positions: – Broadband Technician I-IV (Charter) – Network Operations Specialist (Charter) – Network Technician (Charter) – Network Engineer (Charter & TWC) – SR Network Engineer (TWC) About your Speaker • Email: [email protected] • LinkedIn: linkedin.com/in/bcrisler Today’s Lesson Plan • Session 1: So What About IPv6? • Session 2: Every Day IPv6 and You So What About IPv6? Session 1 Basic History of IP • IP – Internet Protocol • Defined in RFC 791, dated 1981, written by Information Sciences Institute @ USC • Written for DARPA (Defense Advanced Research Projects Agency) Basic History of IP • “… Internet Protocol is designed for use in interconnected systems of packet-switched computer communication networks…provides for transmitting blocks of data called datagrams from sources to destinations… identified by fixed length addresses.” (RFC 791, section 1.1) Versions of IP • IPv0 – 3: Experimental Only • IPv4: Defined in 1981 by RFC 760 & 791. First version to implemented publically. Still in use today. • IPv5: Also experimental, called Internet Stream Protocol. • IPv6: Also called IP Next Generation (IPng), Defined in 1998 by RFC 2460-2467 IP Addressing • Layer 3 (Network) form of Addressing • Two different forms of IP Address: – IPv4 • Uses Dotted Decimal (192.168.0.1) • Has 4,294,967,296 total address (public & private) • 32 bit address – IPv6 • Uses Hexadecimal Notation (FE80::1) • Has 3.4×1038 total address (public & private) • 128 bit address IP Addressing – cont.
    [Show full text]
  • Impact Analysis of System and Network Attacks
    View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by DigitalCommons@USU Utah State University DigitalCommons@USU All Graduate Theses and Dissertations Graduate Studies 12-2008 Impact Analysis of System and Network Attacks Anupama Biswas Utah State University Follow this and additional works at: https://digitalcommons.usu.edu/etd Part of the Computer Sciences Commons Recommended Citation Biswas, Anupama, "Impact Analysis of System and Network Attacks" (2008). All Graduate Theses and Dissertations. 199. https://digitalcommons.usu.edu/etd/199 This Thesis is brought to you for free and open access by the Graduate Studies at DigitalCommons@USU. It has been accepted for inclusion in All Graduate Theses and Dissertations by an authorized administrator of DigitalCommons@USU. For more information, please contact [email protected]. i IMPACT ANALYSIS OF SYSTEM AND NETWORK ATTACKS by Anupama Biswas A thesis submitted in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE in Computer Science Approved: _______________________ _______________________ Dr. Robert F. Erbacher Dr. Chad Mano Major Professor Committee Member _______________________ _______________________ Dr. Stephen W. Clyde Dr. Byron R. Burnham Committee Member Dean of Graduate Studies UTAH STATE UNIVERSITY Logan, Utah 2008 ii Copyright © Anupama Biswas 2008 All Rights Reserved iii ABSTRACT Impact Analysis of System and Network Attacks by Anupama Biswas, Master of Science Utah State University, 2008 Major Professor: Dr. Robert F. Erbacher Department: Computer Science Systems and networks have been under attack from the time the Internet first came into existence. There is always some uncertainty associated with the impact of the new attacks.
    [Show full text]
  • Network Design Reference for Avaya Virtual Services Platform 4000 Series
    Network Design Reference for Avaya Virtual Services Platform 4000 Series Release 4.1 NN46251-200 Issue 05.01 January 2015 © 2015 Avaya Inc. applicable number of licenses and units of capacity for which the license is granted will be one (1), unless a different number of All Rights Reserved. licenses or units of capacity is specified in the documentation or other Notice materials available to You. “Software” means computer programs in object code, provided by Avaya or an Avaya Channel Partner, While reasonable efforts have been made to ensure that the whether as stand-alone products, pre-installed on hardware products, information in this document is complete and accurate at the time of and any upgrades, updates, patches, bug fixes, or modified versions printing, Avaya assumes no liability for any errors. Avaya reserves thereto. “Designated Processor” means a single stand-alone the right to make changes and corrections to the information in this computing device. “Server” means a Designated Processor that document without the obligation to notify any person or organization hosts a software application to be accessed by multiple users. of such changes. “Instance” means a single copy of the Software executing at a Documentation disclaimer particular time: (i) on one physical machine; or (ii) on one deployed software virtual machine (“VM”) or similar deployment. “Documentation” means information published by Avaya in varying mediums which may include product information, operating Licence types instructions and performance specifications that Avaya may generally Designated System(s) License (DS). End User may install and use make available to users of its products and Hosted Services.
    [Show full text]
  • Networking Packet Broadcast Storms
    Lesson Learned Networking Packet Broadcast Storms Primary Interest Groups Balancing Authorities (BAs) Generator Operators (GOPs) Reliability Coordinators (RCs) Transmission Operators (TOPs) Transmission Owners (TOs) that own and operate an Energy Management System (EMS) Problem Statement When a second network cable was connected from a voice over internet protocol (VOIP) phone to a network switch lacking proper settings, a packet broadcast storm prevented network communications from functioning, and supervisory control and data acquisition (SCADA) was lost for several hours. Broadcast storm events have also arisen from substation local area network (LAN) issues. Details A conference room was set up for a training class that needed to accommodate multiple PCs. The bridge protocol data unit (BPDU) packet propagation prevention setting was disabled on a port in the conference room in order to place a network switch off of that port. Upon completion of the training, the network switch was removed; however, the BPDU packet propagation setting was inadvertently not restored. As part of a telephone upgrade project, the traditional phone in this conference room was recently replaced by a VOIP phone. Later, an additional network cable was connected to the output port of this VOIP phone into a secondary network jack within the conference room. When the second network cable was connected from a VOIP phone to a network switch lacking proper settings, a switching loop resulted. Spanning tree protocol is normally used to prevent switching loops from propagating broadcast packets continuously until the network capacity is overwhelmed. A broadcast packet storm from the switching loop prevented network communications from functioning and SCADA was lost for several hours.
    [Show full text]
  • Br-Asi01 Br-Asx01
    BR-ASI01 BR-ASX01 Data Comm for Business, Inc. 807 Pioneer Street Champaign, IL 61820 217-352-3207 Rev. Date: October 17, 1996 This manual applies to both the “I” and “X” router models. The “I” model (BR-ASI01) is single protocol TCP/IP only. The “X” model (BR-ASX01) is a multi-protocol router that routes TCP/IP, IPX, DECnet, and Appletalk. When using this manual with “I” model router, ignore the manual sections pertaining to protocols other than TCP/IP. CHAPTER 1 - INTRODUCTION 7 ABOUT THE BR ROUTER 7 Getting Started 7 Hardware Installation 7 RouterView Software Installation 8 Command Line Preparation 8 Quickstart Configuration 8 Appendices and Index 8 CHAPTER 2 - GETTING STARTED 9 A FEW NOTES 9 Please Read The Manuals 9 Warranty and Service 9 Getting Help With the BR Router 9 WHAT YOU WILL NEED TO GET STARTED 9 Supplied with the BR Router 9 Needed For Installation 10 Ethernet Connection Requirements 10 Thick Ethernet 10 Thin Ethernet 10 10Base-T Twisted-Pair Ethernet 10 Telco Line Connection Requirements 11 RS-232 Port 11 CHAPTER 3 - HARDWARE INSTALLATION 13 Mounting the Router 13 Connecting the Router to the Ethernet 14 Connecting to Thick Ethernet 14 Connecting to Thin Ethernet 14 Connecting to Twisted-Pair Ethernet 14 Connecting a Line Device to the BR Router 14 Connecting Devices to the RS-232C Port 15 Connecting an Out-of-Band Management Console 15 Powering Up the Router 15 CHAPTER 4 - ROUTERVIEW SOFTWARE INSTALLATION 17 RouterView for Windows 17 System Requirements 17 Installing and Running RouterView for Windows 17 RouterView
    [Show full text]
  • Discussion Chapter#9 Services of Data-Link
    The Islamic University of Gaza ECOM 4314: Data Communication Faculty of Engineering Instructor: Dr. Aiman Abu Samra Department of Computer Engineering T.A.: Eng. Alaa O. Shama Discussion Chapter#9 The data-link layer of a node (host or router) is responsible for delivering a datagram to the next node in the path. The data-link layer is located between the physical and the network layers. The datalink layer provides services to the network layer; it receives services from the physical layer. data-link layer of the source host needs only to encapsulate the datagram received from the network in a frame, the data-link layer of the destination host needs to decapsulate the datagram from the frame, but each intermediate node needs to both encapsulate and decapsulate, because each link may be using a different protocol with a different frame format. Even if one link and the next are using the same protocol, encapsulation and decapsulation are needed because the link-layer addresses are normally different. Services of Data-Link: 1. Framing The data-link layer at each node needs to encapsulate the datagram (packet received from the network layer) in a frame before sending it to the next node. The node also needs to decapsulate the datagram from the frame received on the logical channel. 2. Flow control If the rate of produced frames is higher than the rate of consumed frames, frames at the receiving end need to be buffered while waiting to be consumed (processed). Definitely, we cannot have an unlimited buffer size at the receiving side.
    [Show full text]
  • Understanding Linux Internetworking
    White Paper by David Davis, ActualTech Media Understanding Linux Internetworking In this Paper Introduction Layer 2 vs. Layer 3 Internetworking................ 2 The Internet: the largest internetwork ever created. In fact, the Layer 2 Internetworking on term Internet (with a capital I) is just a shortened version of the Linux Systems ............................................... 3 term internetwork, which means multiple networks connected Bridging ......................................................... 3 together. Most companies create some form of internetwork when they connect their local-area network (LAN) to a wide area Spanning Tree ............................................... 4 network (WAN). For IP packets to be delivered from one Layer 3 Internetworking View on network to another network, IP routing is used — typically in Linux Systems ............................................... 5 conjunction with dynamic routing protocols such as OSPF or BGP. You c an e as i l y use Linux as an internetworking device and Neighbor Table .............................................. 5 connect hosts together on local networks and connect local IP Routing ..................................................... 6 networks together and to the Internet. Virtual LANs (VLANs) ..................................... 7 Here’s what you’ll learn in this paper: Overlay Networks with VXLAN ....................... 9 • The differences between layer 2 and layer 3 internetworking In Summary ................................................. 10 • How to configure IP routing and bridging in Linux Appendix A: The Basics of TCP/IP Addresses ....................................... 11 • How to configure advanced Linux internetworking, such as VLANs, VXLAN, and network packet filtering Appendix B: The OSI Model......................... 12 To create an internetwork, you need to understand layer 2 and layer 3 internetworking, MAC addresses, bridging, routing, ACLs, VLANs, and VXLAN. We’ve got a lot to cover, so let’s get started! Understanding Linux Internetworking 1 Layer 2 vs.
    [Show full text]
  • Web Management Guide
    Web Management Guide Digital Data Communications GmbH. http://www.level1.com Web Management Guide GTP-2871 28-Port L3 Lite Managed Gigabit PoE Switch GTP-5271 52-Port L3 Lite Managed Gigabit PoE Switch How to Use This Guide This guide includes detailed information on the switch software, including how to operate and use the management functions of the switch. To deploy this switch effectively and ensure trouble-free operation, you should first read the relevant sections in this guide so that you are familiar with all of its software features. Who Should Read This guide is for network administrators who are responsible for operating and this Guide? maintaining network equipment. The guide assumes a basic working knowledge of LANs (Local Area Networks), the Internet Protocol (IP), and Simple Network Management Protocol (SNMP). How this Guide This guide provides detailed information about the switch’s key features. It also is Organized describes the switch’s web browser interface. For information on the command line interface refer to the CLI Reference Guide. The guide includes these sections: u Section I “Web Configuration” — Includes all management options available through the web browser interface. Related This guide focuses on switch software configuration through the web browser. Documentation For information on how to manage the switch through the command line interface, see the following guide: CLI Reference Guide Note: For a description of how to initialize the switch for management access via the CLI, web interface or SNMP, refer to “Initial Switch Configuration” in the CLI Reference Guide. Conventions The following conventions are used throughout this guide to show information: Note: Emphasizes important information or calls your attention to related features or instructions.
    [Show full text]
  • (Rapid) Spanning Tree Protocol
    STP – Spanning Tree Protocol indigoo.com STP & RSTP (RAPID) SPANNING TREE PROTOCOL DESCRIPTION OF STP AND RSTP, PROTOCOLS FOR LOOP FREE LAN TOPOLOGIES Peter R. Egli INDIGOO.COM1/57 © Peter R. Egli 2015 Rev. 1.60 STP – Spanning Tree Protocol indigoo.com Contents 1. Goal of STP: Loop-free topology for Ethernet networks 2. STP standards overview 3. IEEE 802.1D STP protocol 4. IEEE 802.1w RSTP Rapid STP 5. IEEE 802.1Q CST Common Spanning Tree 6. Cisco PVST+ and PVRST+ 7. IEEE 802.1s MST Multiple Spanning Tree Protocol 8. STP Pros and Cons 2/57 © Peter R. Egli 2015 Rev. 1.60 STP – Spanning Tree Protocol indigoo.com 1. Goal of STP: Loop-free topology for Ethernet networks Ethernet bridges (or switches) must forward unknown unicast and broadcast Ethernet frames to all physical ports. Therefore Ethernet networks require a loop-free topology, otherwise more and more broadcast and unknown unicast frames would swamp the network (creation of frame duplicates resulting in a broadcast storm). Unknown unicast frame: Frame with a target Ethernet address that is not yet known by the receiving bridge. Broadcast frame: Ethernet frame with a broadcast target Ethernet address, e.g. for protocols such as ARP or BOOTP / DHCP. Broadcast Ethernet frames and unknown unicast frames circle forever in an Ethernet network with loops. 3/57 © Peter R. Egli 2015 Rev. 1.60 STP – Spanning Tree Protocol indigoo.com 2. STP standards overview: A number of different STP ‘standards’ and protocols evolved over time. Standard Description Abbreviation Spanning Tree Protocol • Loop prevention. IEEE 802.1D • Automatic reconfiguration of tree in case of topology changes (e.g.
    [Show full text]
  • Network Storm Testing
    NETWORK STORM TESTING VERIFYING THE ROBUSTNESS OF CONTROL SYSTEM COMMUNICATIONS In this white paper, we discuss a stress situation that can impact communication and redundancy of networked control systems. How can this situation arise, and why should we test for it? Furthermore, we look into what we recommend, how control systems should be tested to avoid that their communication is impacted by network overload. 1/7 INTRODUCTION Let us start with a citation from a senior engineer with A normal Ethernet switch forwards broadcast and the major E&P company of Norway: multicast traffic on all its ports. Other (up- or down- link) switches receiving these broadcast or multicast “Be a demanding customer, prior to FAT, messages, will again forward them to all their ports and apply traffic generator packets on network so on. In an Ethernet network, any looped packet might remain on the network forever. A network storm, i.e. a segments to full bandwidth. Peer to Peer, network stress situation can arise in various ways and multicast and broadcast packets. Graceful can cause a Denial of Service (DoS) in the worst case. reconnect after storm or need for restart?” Probably, the most common reason for a network – Sr. IT Security Engineer, Statoil ASA storm is cabling problems, in particular if a cable loop But what is an unexpected network overload, or net- is present. Other factors contributing to a network work storm situation actually? A network storm can be stress situation are: compared to a room full of people talking loudly and making a conversation between 2 individuals impos- Poor network management and monitoring; sible.
    [Show full text]
  • Pakedge SK-8-EP User Guide
    SX-8-EP Enterprise-AV, Smart Managed Switches User Guide This device complies with Part 15 of the FCC Rules. Operation is subject to the following two conditions: 1. This device may not cause harmful interference. 2. This device must accept any interference received, including interference that may cause undesired operation. NOTE: This equipment has been tested and found to comply with the limits for a Class B digital device, pursuant to Part 15 of the FCC Rules. These limits are designed to provide reasonable protection against harmful interference in a residential installation. This equipment generates, uses and can radiate radio frequency energy and, if not installed and used in accordance with the instructions, may cause harmful interference to radio communications. However, there is no guarantee that interference will not occur in a particular installation. If this equipment does cause harmful interference to radio or television reception, which can be determined by turning the equipment off and on, the user is encouraged to try to correct the interference by one of the following measures: Reorient or relocate the receiving antenna. Increase the separation between the equipment and receiver. Connect the equipment into an outlet on a circuit different from that to which the receiver is connected. Consult the dealer or an experienced radio/TV technician for help. WARNING: Any changes or modifications not expressly approved by the party responsible for compliance could void the user's authority to operate this equipment. WARNING: TO PREVENT FIRE OR SHOCK HAZARD, DO NOT EXPOSE THIS PRODUCT TO RAIN OR MOISTURE. THE UNIT MUST NOT BE EXPOSED TO DRIPPING OR SPLASHING WATER.
    [Show full text]
  • Location-Based Deferred Broadcast for Ad-Hoc Named Data Networking
    future internet Article Location-Based Deferred Broadcast for Ad-Hoc Named Data Networking Meng Kuai *,† ID and Xiaoyan Hong * Department of Computer Science, The University of Alabama, Tuscaloosa, AL 35487, USA * Correspondence: [email protected] (M.K.); [email protected] (X.H.); Tel.: +1-205-454-6260 (M.K.); +1-205-348-4042 (X.H.) † Kuai is currently with GetHired, Inc. 540 University Ave, Palo Alto, CA 94301, USA. Received: 1 May 2019; Accepted: 14 June 2019; Published: 24 June 2019 Abstract: The emerging connected and autonomous vehicles (CAVs) challenge ad hoc wireless multi-hop communications by mobility, large-scale, new data acquisition and computing patterns. The Named Data Networking (NDN) is suitable for such vehicle ad hoc networks due to its information centric networking approach. However, flooding interest packets in ad-hoc NDN can lead to broadcast storm issue. Existing solutions will either increase the number of redundant interest packets or need a global knowledge about data producers. In this paper, a Location-Based Deferred Broadcast (LBDB) scheme is introduced to improve the efficiency and performance of interest broadcast in ad-hoc NDN. The scheme takes advantage of location information to set up timers when rebroadcasting an interest. The LBDB is implemented in V-NDN network architecture using ndnSIM simulator. Comparisons with several existing protocols are conducted in simulation. The results show that LBDB improves the overhead, the average number of hops and delay while maintaining an average satisfaction ratio when compared with several other broadcast schemes. The improvement can help offer timely data acquisition for quick responses in emergent CAV application situations.
    [Show full text]