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D-Link DES-3326S manual TCP Packet Header

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DES-3326S Layer 3 Fast Ethernet Switch User’s Guide

The header also contains a sequence number that is used to ensure the packets are received in the correct order. The packets are not numbered, but rather the octets the packets contain are. If there are 100 octets of data in each packet, the first packet is numbered 0, the second 100, the third 200, etc.

To insure that the data in a packet is received uncorrupted, TCP adds the binary value of all the octets in the packet and writes the sum in the checksum field. The receiving TCP recalculates the checksum and if the numbers are different, the packet is dropped.

Figure 5-10. TCP Packet Header

When packets have been successfully received, TCP sends an acknowledgement. This is simply a packet that has the acknowledgement number field filled in.

An acknowledgement number of 1000 indicates that all of the data up to octet 1000 has been received. If the transmitting TCP does not receive an acknowledgement in a reasonable amount of time, the data is resent.

98	Switch Management and Operating Concepts

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D-Link DES-3326S manual TCP Packet Header

Contents

DES-3326S Wichtige Sicherheitshinweise Page Warranties Exclusive HardwareSoftware Page Copyright Statement Link Offices for Registration and Warranty ServiceTrademarks Vcci Warning Bsmi Warning FCC WarningCE Mark Warning ViiiTable of Contents Snmp Using WEB-BASED Management Xii Layer 3 Switching IntroductionIntroduction Functions of a Layer 3 Switch Layer 2 Features FeaturesPerformance Features PortsDES-3326S Layer 3 Fast Ethernet Switch User’s Guide Layer 3 Switch Features Traffic Classification and Prioritization ManagementSupports Web-based management Switch Stacking Fast Ethernet TechnologyGigabit Ethernet Technology Unpacking and Setup UnpackingInstallation Desktop or Shelf InstallationRack Installation Installing rubber feet for desktop installationPower on 2B. Installing the switch on an equipment rackPower Failure Identifying External Components Front PanelRear panel view of the Switch Rear PanelSide Panels Optional Plug-in Modules100BASE-FX Fiber Module 2Km/15Km 1000BASE-T Module1000BASE-SX Fiber Module 62.5 ∝m1000BASE-LX Fiber Module BASE-LX two-port moduleGbic Two-Port Module Stacking Module with Gbic PortGbic Port Stacking Port11. Up to 6 Switches in a Switch Stack Switch LED Indicators Stacking Module LED Indicators13. Stacking Module LED Indicators Connecting Switch Switch to End NodeSwitch to Hub or Switch Switch connected to an End NodeSwitch Stack Connections Switch Stack connections between optional stacking Modules 10BASE-T Device100BASE-TX Device Switch Management Operating Concepts Local Console ManagementDiagnostic console port RS-232 DCE Managing Switch Stacks Determining the Switch Stack Order Switch Stack Order − First001122334450 2original MasterSwitch IP Address Console Boot ScreenSetting an IP Address TrapsSwitch Management and Operating Concepts Snmp Snmp performs the following functionsAuthentication TrapsDES-3326S Layer 3 Fast Ethernet Switch User’s Guide MIBs Link Change Event This trap is sentPacket Forwarding Filtering MAC Address Aging TimeSome filtering is done automatically by the switch Parameter Description Default Value Spanning TreeVariable Description Default Value Bridge Protocol Data Units Creating a Stable STP Topology STP Port States Port transitions from one state to another as followsSTP Port State Transitions Feature Default Value User-Changeable STA ParametersDES-3326S Layer 3 Fast Ethernet Switch User’s Guide Illustration of STP Before Applying the STA Rules After Applying the STA Rules Link Aggregation Link Aggregation Group Defaultvlan VLANsSome relevant terms Ieee 802.1Q VLANs802.1Q Vlan Packet Forwarding 802.1Q Vlan Tags Ieee 802.1Q Packet ForwardingIeee 802.1Q Tag Port Vlan ID Adding an Ieee 802.1Q TagSwitch Management and Operating Concepts Tagging and Untagging Ingress FilteringVLANs in Layer 2 Only Mode Definitions Layer 3-Based VLANsIP Addressing and Subnetting IP Addresses 255 Binary to Decimal Conversion Address Classes Subnet Masking Calculating the Number of Subnets and Nodes Classless InterDomain Routing Cidr Class a Subnet Masks Setting up IP Interfaces 10. Class B Subnet Masks12. Vlan Example Assigned Ports Internet Protocols Protocol Layering OSI Seven Layer Network ModelProtocol Stack Layer Layer TCP/IP DES-3326S Layer 3 Fast Ethernet Switch User’s Guide Packet Headers TCP10. TCP Packet Header Switch Management and Operating Concepts Ethernet 10012. Ethernet Packet Header 101TCP and UDP Well-Known Ports 102UDP and Icmp 10313. Ethernet Packet Header 104Mapping Domain Names to Addresses Domain Name ResolutionDomain Name System 105Dhcp Servers 106IP Routing 107Packet Fragmentation and Reassembly 108ARP 109110 MulticastingMulticast Groups Address Assignment 111Internet Group Management Protocol Igmp 112Igmp Versions 1 11314. Igmp Type Codes 114Multicast Routing Algorithms 115116 FloodingMulticast Spanning Trees Reverse Path Broadcasting RPB 117Reverse Path Multicasting RPM 118119 Multicast Routing ProtocolsDistance Vector Multicast Routing Protocol Dvmrp Routing Information Protocol RIP Protocol-Independent Multicast Dense ModeRouting Protocols 120121 RIP Version 1 Message Format 12217. RIP v.1 Message Format 123RIP 1 Message 124RIP2 Message Format RIP 1 Route InterpretationRIP Version 2 Extensions 125Open Shortest Path First Ospf 126Link-State Algorithm 127Shortest Path Algorithm 128129 Ospf CostShortest Path Tree 19. Constructing a Shortest Path Tree 13020. Constructing a Shortest Path Tree 131Areas and Border Routers 132Link-State Packets 133134 Message Digest Authentication MD-5 Ospf AuthenticationSimple Password Authentication Backbone and AreaPartitioning the Backbone Virtual LinksAreas Not Physically Connected to Area 136Neighbors 137Building Adjacency AdjacenciesDesignated Router Election 138139 140 Adjacencies on Point-to-Point InterfacesOspf Packet Formats 141 Ospf Packet HeaderField Description 142 Hello Packet 143Hello Packet 144BDR 145Database Description Packet 14618. Database Description Packet 147Link-State Request Packet 148Link-State Update Packet 149Link-State Acknowledgment Packet 150Link-State Advertisement Formats 151Link State Advertisement Header 152Link-State Advertisement Header 153154 Router Links Advertisements 155Routers Links Advertisements 156FieldDescription 157158 159 Network Links Advertisements 160Network Link Advertisements 161Summary Link Advertisements 16231. Summary Link Advertisement 163Autonomous Systems External Link Advertisements 164AS External Link Advertisements 165166 Introduction 167168 Before You StartGeneral Deployment Strategy Vlan Layout 169Assigning IP Network Addresses and Subnet Masks to VLANs 170Management That opens, click on the Login to DES-3326S Manager buttonGetting Started Defining Static Routes172 Configuring the SwitchUser Accounts Management User Accounts Control Table 173Admin and User Privileges 174175 Configuration Mana Gement Admin UserSaving Changes Save Changes Screen 176Factory Reset 177Setting Up Web Management 178Ipaddress xxx.xxx.xxx.xxx/yyy.yyy.yyy.yyy 179Saving Configuration Changes 180Starting and Stopping the Web-based Manager 181Web-based Manager’s User Interface 182Areas of the User Interface 183Area Function 184Switch Information Setting Up The SwitchBasic Setup Click the Switch Information link in the Configuration menu10. Switch Information Basic Settings 186187 IP Address Configuring the Switch’s IP AddressTo set the switch’s IP address 11. Basic Switch Setup 188Broadcast request when it is powered New Switch IP Settings options areSwitch will send out a Bootp Up. The Bootp protocol allows IPManual 190Management Station IP Addresses Default GatewayVlan Name 191192 Snmp SettingsTo setup the switch for remote management Configuring Community Strings 193Setting Up Trap Receivers 194Stacking Information 19515. Switch Stack Display 19617. Stacking Information 197Show stacking mode/version 19819. Console CLI show stack Command 199200 201 Config stacking mode slaveConfig stacking mode master Configure Ports 20222. Port Configurations − Edit 203204 Locking a Port’s MAC Address LearningSpeed/Duplex Toggle the Speed/Duplex Auto field Serial Port Settings 205206 Baud RateData Bits 207 Stop BitsAuto-Logout To create a new 802.1Q Vlan Advanced SetupConfiguring VLANs 208To create a new 802.1Q VLAN, click the New button 20926 .1Q Static VLANs Entry Settings Edit 210Untagged PortTagged/Untagged Egress212 Ingress Filter 213To enable or disable GVRP, globally, on the switch 214Layer 3 IP Networking 215To setup IP Interfaces on the switch 216217 To setup an new IP interface, click the New buttonTo edit an existing IP interface, click on the Edit button 218 Interface NameIP Address Subnet Mask Setup the Routing Information Protocol RIPSwitch Active Yes32. RIP Status 220221 TX Mode DisabledRX Mode MD5 Key Table Configuration 222223 Key IDKey Setup Ospf 224State Ospf Area SettingCurrent Route ID AS Border Router 225Area ID Default Cost Stub ImportStub Default Cost Type227 Ospf Interface ConfigurationRemove 228 Router PriorityHello Interval 229 Auth TypeSimple Auth Key Ospf Interface Configuration − MonitorKey Configuration MetricVirtual Interface Configuration 231232 Neighbor RouterStatus Area Aggregation Configuration 233Route Redistribution Settings 234Protocol Source ProtocolDestination Metric Type236 IP Multicasting 237State Disabled Igmp Snooping SettingsTo configure Igmp Snooping 238Max Response Igmp Interface ConfigurationQuery Robustness Var46. Igmp Interface Setup 240241 VersionQuery Interval Time Dvmrp Interface ConfigurationMax Response Robustness49. Dvmrp Interface Configuration − Edit 243Probe Interval InterfaceName System 244State Disabled PIM-DM SettingsNeighbor Timeout Interval Metric50. PIM-DM Interface Configuration 24651. PIM-DM Interface Configuration − Edit 247Interval Static Router Port SettingsJoin/Prune 248To setup a static router port 24953. Static Router Port Settings − Add 250251 To configure a port for port mirroringPort Mirroring 252 Source PortDirection Ingress 253 To configure a forwarding priority for a given MAC addressPriority 56. MAC Address Priority − Add 254Source/Destinatio MAC AddressUser Priority 255IP Address Filtering 2560.0 257258 Forwarding 259Unicast MAC Address Forwarding 26063. Unicast MAC Address Settings − Add 261262 Multicast MAC Address ForwardingUnit 65. Multicast MAC Address Settings 263None 264IP Forwarding 265266 To add a new static/default route, click the New buttonGateway IP 267 Static ARPTo add a new static ARP entry, click the New button STP Switch Settings 26872. STP Switch Settings 269270 STP Port Settings 27173. STP Port Settings 272273 CostPriority 274 74. Link Aggregation 275Following fields can be set 276Tftp Utilities Update Firmware from ServerUtilities Port Member77. Download Firmware from Server 278Use Configuration File on Server 279280 Save Settings To ServerSave History Log to Server Utilities BOOTP/DHCP Relay 281Relay Time Threshold Bootp Hops Count LimitRelay Status 282To add a new entry, click the New button 283284 To configure DNS Relay, click on the DNS Relay linkDNS Relay 285 0.0 To add a new entry to the table, click on the New buttonAddress The IP address of the domain name Above287 Network MonitoringPort Utilization 87. Port Utilization window 288289 Port Error StatisticsUpdate 88. Port Error Packet Statistics window 290RX Frames Update IntervalCRC Error UndersizeExcessive Deferral Drop PacketsTX Frames Late CollisionPort Packet Analysis 293Unicast RX FramesFrames/sec Frames/sec Multicast RXTotal/sec TX Frames MAC Address TableTotal/sec TX Bytes Total/secIP Address Table 296297 91. IP Address Table 298Routing Table Netmask 300301 To view the switch’s ARP table, click on the ARP Table linkARP Table 93. ARP Table 302303 Ospf Link State Database TableArea ID Displays the Ospf Area ID Sequence 304305 Ospf Neighbor TablePriorityrouter Ospf Virtual Neighbor Table Dvmrp Neighbor Address Table 307Name Gvrp StatusLearned Expire309 Router PortsIgmp Snooping Status 100. Igmp Snooping Table 310IP Multicast Forwarding Table 311312 Igmp Group TableProtocol Routing protocol in use 313 Dvmrp Routing TableQuerier IP Click the Switch History link on the Applications menu Switch HistoryTo view the switch history log 314104. Switch History 315Technical Specifications 316Physical and Environmental 317318 EMIUnderstanding Troubleshooting Spanning Tree Protocol 319Blocking State Port in the blocking state does the following321 Listening State Port in the listening state does the following323 Learning State Port in the learning state does the following325 Forwarding State Port in the forwarding state does the following327 Disabled State Disabled port does the following329 Troubleshooting STP Spanning Tree Protocol FailureFull/Half Duplex Mismatch 331Unidirectional Link 333 Resource Errors Packet CorruptionAvoiding Trouble Know where the root is locatedIdentifying a Data Loop Know which links are redundantMinimize the number of ports in the blocking state 337 Understanding and Troubleshooting the Spanning Tree Protocol Impact of Layer 3 Switching 339Understanding and Troubleshooting the Spanning Tree Protocol 341 Brief Review Bitwise Logical Operations Not Index Spanning Tree Protocol Vlan Offices Registration Card