IP(双语)期末复习.docx

Abbreviations:Acronyms: P743Chapter 1:1. Topologies, 2. Connection Strategies Circuit Switching, Packet SwitchingA. DatagramB. Virtual CircuitC. Source Routing3. Multiplexing4. TDM, FDM, Statistical TDM, WDM5. OSI modelthe Internet model6. Performance Metrics Bandwidth Latency = Propagation + Transmit + Queue Delay x Bandwidth Product7. 作业Chapter 2:1. Links Conducted media, Optical fiber, Wireless2. Encoding NRZ, Manchester, NRZI3. Reliable Transmission Stop-and-Wait Protocol, Go-Back-N Sliding Window Protocol4. MAC Protocol Channel Partitioning by time, frequency or code TDMA, FDMA, CDMA Taking Turns Random partitioning (dynamic), A. ALOHA: pure ALOHA, slotted ALOHAB. CSMA: non-persistent, p-persistent(0p1)c. CSMA/CD used in EthernetE. Binary Exponential Backoff strategya. At each retransmission, choose randomly from among a discrete set of values within exponentially increasing wait time (02r-1), r=min(n,10)b. Retransmit a finite n of times, 16 for example 5. Bus (Ethernet)6. Token ring difference between 802.5 &FDDI7. Wireless Networks Bluetooth-802.15.1, WiFi-802.11, WiMAX-802.16, 3G8.作业EthernetTransceiver Interface between the PC and the cable Detects idle backbone Listens for collisions Puts bits on cable from interface card Passes received bits to interface cardTransceiver cable (AUI cable) 5 twisted pair 2 pair for sending data and control 2 pair for receiving data and control 1 pair for powerNetwork Interface Card (NIC) Receives packets from PC software Formats frames Executes binary exponential backoff algorithm if required Detects incoming frames for itself Performs CRC error checking Has a hardware addressEthernet1. Frame FormatNOTE: This is DIX frame. The difference with 802.3 is the type field is changed as length field.1. Addresses unique, 48-bit unicast address assigned to each adapter broadcast: all 1s multicast: first bit is 1 Every Ethernet host has a unique address, burned into ROM by manufacturer Each manufacturer is given a unique prefix2. Bandwidth: 10Mbps, 100Mbps(Fast Ethernet), 1Gbps3. Length: 2500m (500m segments with 4 repeaters)Chap 3 Switching & Forwarding Circuit Switching Packet Switching Datagram (connectionless) Virtual Circuit (connection-oriented) Source Routing Bridge and LAN Switch Learning Bridge Spanning Tree AlgorithmDatagram Switching Each switch maintains a forwarding table. (switch 2 for example)DestinationPortABCDEFGH30332100Each switch maintains a VC tableSource Routing Assumed the source switch know the net topology well No upper bound of the header size Strip the first element rather than rotate the header. ORCreate a pointer to the current “next port”Chap 3 Switching & Forwarding Circuit Switching Packet Switching Datagram (connectionless) Virtual Circuit (connection-oriented) Source Routing Bridge and LAN Switch Learning Bridge Spanning Tree AlgorithmBridges and Extended LANs LANs have physical limitations (e.g., 2500m) Connect two or more LANs with a bridge accept and forward strategy level 2 connectionABridgeBCXYZPort 1Port 2 Switch & Bridge Learning Bridges Do not forward when unnecessary Maintain forwarding tableABridgeBCXYZPort 1Port 2 The table can be maintained by a human. But it a burden Learn table entries based on source address Table is an optimization; need not be complete A timeout is associated with each entry. Spanning Tree Algorithm Problem: loopsHOMEWORK Exercises 1，3，5，13，15，17 Required Reading Stallings chapter 3.1-3.2Chap 4 IP (include subnet & CIDR) ARP ICMP IPv6Chap 4 Connectionless (datagram-based) Best-effort delivery (unreliable service) packets are lost packets are delivered out of order duplicate copies of a packet are delivered packets can be delayed for a long time Datagram formatFragmentation & ReassemblyGlobal Addresses Properties globally unique hierarchical: network + hostSubnetting Add another level to address/routing hierarchy: subnet Subnet masks define variable partition of host part Subnets visible only within siteSubnet ExampleCIDR Use subnetting to share one address among multiple physical networks. CIDR collapses the multiple addresses onto one address Such as the class C network number from 192.4.16-192.4.31 has the same top 20 bits. IP forwarding revisited: The “longest match” princeple Such as the dest. IP =171.69.10.5 & 2 match network number (171.69 & 171.69.10)Chap 4 IP ARP ICMP IPv6 ARP table of IP to physical address bindings broadcast request if IP address not in table target machine responds with its physical address table entries are discarded if not refreshed (about 10 minutes) update table with source when you are the targetAddress TranslationChap 4 IP ARP ICMP IPv6Problems with IPv4 Address depletion 232=4.3 billion addresses Most organizations apply for class B network. Does not support host mobility Not secure enoughIPv6 Permit the old and new protocols to coexist for years What IPv6 has: IPv6 addresses are 16 bytes long, instead of 4 bytes in IPv4. Provides an effectively unlimited supply of Internet addresses IPv6 header contains only 7 fields (versus 13 in IPv4) Allows faster process of packets IPv6 has better support for options. IPv6 improves security (authentication and privacy). IPv6 pays more attention to type of service.IPv6 Addresses Notation 47CD:1234:4422:AC02:0022:1234:A456:0124 47CD:0000:0000:0000:0000:0000:A456:0124 47CD:A456:0124 :FFFF:128.96.33.81IPv6 Addresses (cont.) Three types of IPv6 address (Table 4.11) Unicast address Multicast address Others (Anycast address)IPv6 Packet HeadersIPv6 Extension Headers IPv6 implements several extension headers to allow more options. Destination options - provides information for the destination Fragmentation header - provides information in the event that packet fragments must be reassembled. Hop-by-hop header - provides information that each router must examine Routing header - provides additional routing information Security header - indicates the packets payload has been encrypted Authentication header - for IP authenticationCompatibility with IPv4IPv4 will be around for a long time. IPv6 allows IPv4 addresses. What happens when an IPv6 packet has to pass through a IPv4 router? TunnellingCompatibility with IPv4 (cont.)How to handle C having an IPv6 address?HOMEWORK Exercises 4，21，45，58 Review question1. What is the Time to Live field in an IP packet?2. How does IPv4 fragmentation differ from IPv6 fragmentation? Required Reading Stallings chapter 4.1, 4.3.1, 4.3.5Chap 5Simple Demultiplexer (UDP) Reliable Byte-Stream (TCP)Connection Establishment/TerminationSliding Window Revisited Flow ControlUDP Transport protocol above IP Adds multiplexing by ports simply passes IP through to the upper (application) layers No flow control, No congestion control, No connection Unreliable and unordered datagram service Gives apps the option to send packets unreliably Useful for multicast apps Minimal connection setup time : “connectionless” Low delay transmission for interactive text/audio/video Build own application-level protocol on top of UDP UDP Header: Only 8 bytes! (vs. IP 20 bytes header) Source port for UDP sending process Dest port for