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1、一些数据,从1978年到2007年，通信业年业务收入一直保持两位数增长并一直领先于GDP增幅。业务总量和业务收入年同比增长率均保持了两位数，年收入规模从7.3亿元扩张到7280亿元，年均增长率达到26.9%7887年，电信业务收入年平均增长率达到21.1%,7.3 亿-41.1亿8897年，电信业务收入年复合增长率达到42.2%,59.6亿 1421.3亿9807年，电信业务收入年平均增长率达到16.6%,1828.4亿 7280亿2007年，电信业务收入增长11.2%,GDP增速13.0%2008年，电信业务收入增长9.0%,GDP增速6.6%2009年上半年，电信业务收入增长2.3%，不到
2、GDP的1/3电信业的转型话务运营阶段转型阶段信息运营阶段,1,机会在哪里？,3G与宽带！2009年上半年，电信运营商资本开支投向主要是3G、传输网(光传输)、和宽带(FTTx)3G中国移动计划2009年底前3G覆盖238个城市，2011年覆盖所有地级市中国联通3G网络覆盖城市已由年初计划的284个扩大到年内的335个，2010年将近一步扩大覆盖面宽带业务具有高ARPU值，现金流稳定的特征宽带提速有线宽带和无线宽带的融合发展和无缝连接,2,Network layer in practice:IP and atm,The TCP/IP protocol suite,4,Transmission
3、Control Protocol/Internet ProtocolDeveloped by DARPA to connect universities and research labs,Telnet,FTP,email etc,TCP,UDP,IP,ICMP,IGMP,Device drivers,interface cards,TCP:Transmission Control ProtocolUDP:User Datagram ProtocolIP:Internet Protocol,The Internet Layered model,Internetworking with TCP/
4、IP,5,application,transport,IP,Data link and lower layer,application,transport,IP,Data link and lower layer,IP,Ethernet,Token ring,Token ring,Ethernet,Ethernet,IP protocol,IP protocol,TCP/UDP protocol,FTP,HTTP,SMTP,The TCP/IP suite,6,PING,telnet&rlogin,FTP,SMTP,X,Trace route,DNS,TFTP,BOOTP,SNMP,RPC,T
5、CP,UDP,ICMP,IP,IGMP,DATA LINK,ARP,RARP,Internet sub-layer,A sub-layer between the transport and network layers is required when various incompatible networks are joined togetherThis sub-layer is used at gateways between the different networksIn the internet this function is accomplished using the In
6、ternet Protocol(IP),7,IP,DLC LayerLink 1,DLC LayerLink 1,DLC LayerLink 1,On a gateway connecting different types of networks,IP is the protocol to realize inter-operability,IP addresses,32 bit address written as four decimal numbersOne per byte of address(202.120.39.134)IP Address classes,8,8,32,16,
7、32,16,32,Class A Address,Class B Address,Class C Address,16,32,Class D Address,(For multicast only),IPv4 address classes,9,Routing a packet in the network,10,1,2,1,2,3,1,3,2,1,2,3,4,1,2,3,1,2,3,4,IP router architecture,3 generations of IP routers,Bus based router,Bus based router with dist.routing,S
8、witch-based router with multi.Forwarding eng.,Host name,Each host has a unique nameDomain name system(DNS):a distributed database that provides a mapping between IP addresses and host namesE.g.,202.120.39.134 FRONT.SJTU.EDU.CN,13,Internet standards,Internet Engineering Task Force(IETF)Development on
9、 near term internet standardsOpen bodyMeets 3 times a yearRequest For Comments(RFCs)Official internet standardsAvailable from IETF web page:http:/www.ietf.org/,14,The Internet protocol(IP),Routing packets across the networkUnreliable serviceBest effort deliveryRecovery from lost packet must be done
10、at higher layersConnectionlessPackets are delivered independentlyCan arrive out of orderRe-ordering must be done at higher layersCurrent version V4,IPv4Future IPv6,15,IP header,16,Note that the minimum header size is 20 bytes,or 160 bits,IP header,17,Dynamic Host Configuration(DHCP),Automated method
11、 for assigning network numbersIP addresses,default routersComputer contact DHCP server at Boot-up timeServer assigns IP addressAllows sharing of address spaceMore efficient use of address spaceAdds scalabilityAddresses are“leased”for some timeNot permanently assigned,18,Address Resolution Protocol(A
12、RP),The role of the IP routing is to deliver the packet to its destination subnetTo the last hop routerAddressing inside a subnet,or a LAN,is based on local addresses,such as Ethernet addressesARP provides a mapping between IP addresses and LAN addressesRARP provides mapping from LAN addresses to IP
13、 addressesBoth accomplished by sending out a broadcast messageAn ARP cache is maintained at each node with recent mappings to avoid frequent address resolution(for better performance),19,ARP at source subnet,20,R1,(4)I am here at 00-01-21-32-32-32,(3)Hi all Where is my lovely router R1?,Computer S i
14、s configured to have a default router R1S wants to send a message to D,and D is outside of the same LANS sends an ARP request for Ethernet Address of R1R1 sends ARP responds to SS sends the message to R1 with Ethernet addressingR1 routes the packet to the next hop in the internet and the message wil
15、l be subsequently routed further toward D,ARP at destination subnet,21,R2,(3)Hi all I got a message for 202.120.39.134.Where is he?,(4)Hi R2 I am here at 00-01-01-11-AB-ED,An IP packet is delivered by the network from its source subnet to router R2.Router R2 realizes that the packet has reached its
16、destination subnet by comparing the destination address in the IP packet and its local interface configurations(subnet address and mask)Router R2 sends an ARP request on the interface to the subnetDestination node D responses to the requestPacket is delivered to D with Ethernet addressing,Routing in
17、 the multi-AS Internet,The Internet is divided into sub-networks,each under the control of a single authority known as an Autonomous Systems(AS)Routing algorithms are divided into two categoriesInterior protocols(within an AS)Exterior protocols(between ASs)Interior protocols use shortest path algori
18、thmsDistance vector proto.Based on Bellman-FordLink state proto.Based on Dijkstras algorithmExterior protocols route packets across ASsIssue:no single cost metric,policy routing,etcHierarchical routing based on“peering”agreementsExample:Exterior Gateway Protocol(EGP)and Border Gateway Protocols(BGP)
19、,22,Border Gateway Protocol(BGP),Routing between Autonomous systemsFind a path(no optimality)to destination(AS)Path must satisfy policy criteria,23,AS corporation,AS Large service provider,AS Large service provider,AS Small ISP,AS corporation,AS corporation,AS Small ISP,AS Small ISP,Transit AS,Multi
20、-homed AS(No transit traffic),Stub AS,BGP overview,BGP speaker one per ASEstablishes(TCP)sessions with other“speakers”to exchange reachability informationBorder“gateways”routers that interface between ASsBGP advertises complete paths to destination ASAvoid loop problemsEnable policy decisions(e.g.av
21、oid certain ASs)AS numbers centrally assigned 16 bit numbers for transit ASs,24,128.64.3128.61.2,192.12.2,Path to 128.64.2:(AS-144,AS-367),AS-12,AS-144,AS-367,AS-298,Relationship between ASs,ISP“tiers”Tier-1 ISPs provide global reachabilityTier-2 ISPs regional/countryTier-3 ISPs localProvider-custom
22、er relationship(transit)Smaller ASs purchase internet access from larger onesPeeringISPs of similar size are“peers”and forward each others traffic at no chargePaid peering:a small ISP may purchase the right to peer with a larger providerPolicy issueWhich route would an ISP advertise?,25,Tier-1 ISP,T
23、ier-2 ISP,Tier-1 ISP,Tier-2 ISP,Tier-3 ISP,IPv6,Effort started in 1991 as IPngMotivationNeed to increase IP address spaceSupport for real-time applications QoSSecurity,mobility and auto-configurationMajor changesIncreased address space(128bit)Support for QoS via Flow Label fieldSimplified headerSecu
24、rityTransition to IPv6Cannot be done at once;must support co-existanceDual-stack:routers run both IPv4 and IPv6Tunneling:IPv6 packets carried in payload of IPv4 packets,or vice versa,26,QoS in the Internet,Quality of Service parametersDropped packetsDelayJitterOut-of-order deliveryErrorApplications
25、that require QoSMultimedia streaming IPTVIP telephony,or VoIPVideo conferencingOnline gameRemote control,27,QoS mechanisms,IntServ:integrated servicesbest-effort service,real-time service,and controlled link sharingResource reserved prior to data transferResource released after transfer completes,28
26、,request,grant,QoS mechanisms(cont.),DiffServ:differentiated servicesTagging on ingress edge nodeUn-tagging on egress edge nodeRouted/processed in network according to the tag/labelRealizes service differentiation through per-hop behavior(PHB),29,DiffServ and MPLS,30,MPLS:Multi-Protocol Label Switch
27、ing,ATM-Asynchronous Transfer Mode,1980s effort by the phone companies to develop an integrated network standard(B-ISDN)that can support voice,data,video,etc.ATM uses small(53 Bytes)fixed size packets called“cells”Why cells?Cell switching has properties of both packet and circuit switching Easier to
28、 implement high speed switches Why 53 bytes?Small cells are good for voice traffic(limit sampling delays)For 64Kbps voice it takes 6 ms to fill a cell with data ATM networks are connection oriented Virtual circuits,31,ATM Reference Architecture,Upper layers Applications TCP/IP ATM adaptation layer S
29、imilar to transport layer Provides interface between upper layers and ATM Break messages into cells and reassemble ATM layer Cell switching Congestion control Physical layer ATM designed for SONET Synchronous optical network TDMA transmission scheme with 125 s frames,32,ATM Cell format,33,VPI/VCI,34
30、,ATM cell switches,35,ATM summary,ATM is mostly used as a“core”network technology ATM Advantages Ability to provide QoS Ability to do traffic management Fast cell switching using relatively short VC numbers ATM disadvantages It not IP-most everything was design for TCP/IP Its not naturally an end-to
31、-end protocol Does not work well in heterogeneous environment Was not design to inter-operate with other protocols Not a good match for certain physical media(e.g.,wireless)Many of the benefits of ATM can be“borrowed”by IPCell switching core routers Label switching mechanisms,36,Project#1,Try to identify at least 3 applications that use plaint text password/identification methodUse Wireshark to capture the plaint text passwordWrite a report to describe the problemDue date:Oct.28,37,
