现代计算机网络讲义6(英语)+传输层ppt课件

我吓了一跳，蝎子是多么丑恶和恐怖的东西，为什么把它放在这样一个美丽的世界里呢？但是我也感到愉快，证实我的猜测没有错：表里边有一个活的生物Chapter 6The Transport Layern Heart of the whole protocol hierarchy.n Providing reliable,cost-effective data transport from the source to the destination2024/4/301Chapter 6The Transport Layer2我吓了一跳，蝎子是多么丑恶和恐怖的东西，为什么把它放在这样一个美丽的世界里呢？但是我也感到愉快，证实我的猜测没有错：表里边有一个活的生物6.1 The Transport ServiceServices Provided to the Upper LayersConnection-oriented and connectionlessSubnet vs HostTransport Service PrimitivesA standard set of primitives and work on a wide variety of networksBerkeley SocketsAn Example of Socket Programming:nAn Internet File Server2024/4/3026.1 The Transport ServiceServi我吓了一跳，蝎子是多么丑恶和恐怖的东西，为什么把它放在这样一个美丽的世界里呢？但是我也感到愉快，证实我的猜测没有错：表里边有一个活的生物6.1.1 Services Provided to the Upper Layersn The network,transport,and application layers.n The Transport address2024/4/3036.1.1 Services Provided to the我吓了一跳，蝎子是多么丑恶和恐怖的东西，为什么把它放在这样一个美丽的世界里呢？但是我也感到愉快，证实我的猜测没有错：表里边有一个活的生物6.1.2 Transport Service Primitives(1)The primitives for a simple transport service.2024/4/3046.1.2 Transport Service Primit我吓了一跳，蝎子是多么丑恶和恐怖的东西，为什么把它放在这样一个美丽的世界里呢？但是我也感到愉快，证实我的猜测没有错：表里边有一个活的生物6.1.2 Transport Service Primitives(2)nA state diagram for a simple connection management scheme.2024/4/3056.1.2 Transport Service Primit我吓了一跳，蝎子是多么丑恶和恐怖的东西，为什么把它放在这样一个美丽的世界里呢？但是我也感到愉快，证实我的猜测没有错：表里边有一个活的生物6.1.3 Berkeley SocketsThe socket primitives for TCP.2024/4/3066.1.3 Berkeley SocketsThe sock我吓了一跳，蝎子是多么丑恶和恐怖的东西，为什么把它放在这样一个美丽的世界里呢？但是我也感到愉快，证实我的猜测没有错：表里边有一个活的生物6.2 Elements of Transport ProtocolsnAddressingnConnection EstablishmentnConnection ReleasenFlow Control and BufferingnMultiplexingnCrash Recovery2024/4/3076.2 Elements of Transport Prot我吓了一跳，蝎子是多么丑恶和恐怖的东西，为什么把它放在这样一个美丽的世界里呢？但是我也感到愉快，证实我的猜测没有错：表里边有一个活的生物6.2.1 Addressing(1)nTSAPs,NSAPs and transport connectionsnA time-of-day server process listens at TSAP 1522 of host 2 to wait for an incoming call.nAn application process on host 1 issues a CONNECT request specifying TSAP 1208 as the source and TSAP 1522 as the destination.nThe time server process responds with the current time.nWell-known TSAP2024/4/3086.2.1 Addressing(1)TSAPs,NSA我吓了一跳，蝎子是多么丑恶和恐怖的东西，为什么把它放在这样一个美丽的世界里呢？但是我也感到愉快，证实我的猜测没有错：表里边有一个活的生物6.2.1 Addressing(2)nInitial connection protocolnprocess server nAs a proxy for less heavily used servers.nListen to a set of ports at the same timenThe requested server inherits the existing connection with the user2024/4/3096.2.1 Addressing(2)Initial co我吓了一跳，蝎子是多么丑恶和恐怖的东西，为什么把它放在这样一个美丽的世界里呢？但是我也感到愉快，证实我的猜测没有错：表里边有一个活的生物nName server or Directory server.nservices do exist independently of the process servernUser sets up a connection to the name server(a well-known TSAP).nSpecifying the service name,nName server sends back the TSAP address.nUser releases the connection with the name servernEstablishes a new one with the desired service.nA new service must register itself with the name server6.2.1 Addressing(3)2024/4/3010Name server or Directory serve我吓了一跳，蝎子是多么丑恶和恐怖的东西，为什么把它放在这样一个美丽的世界里呢？但是我也感到愉快，证实我的猜测没有错：表里边有一个活的生物6.2.2 Connection Establishment(1)nCONNECTION REQUEST and CONNECTION ACCEPTED.nProblem:network can lose,store,and duplicate packets.nEstablishing connections in a reliable waynThrow-away transport addresses nMakes the process server model impossible nGive each connection a connection identifierni.e.a sequence numbernMaintain a certain amount of history information,crash?nEnsure that no packet lives longer than some known time 2024/4/30116.2.2 Connection Establishment我吓了一跳，蝎子是多么丑恶和恐怖的东西，为什么把它放在这样一个美丽的世界里呢？但是我也感到愉快，证实我的猜测没有错：表里边有一个活的生物nT is some small multiple of the true maximum packet lifetime nEach host with a time-of-day clock.nThe clocks at different hosts need not be synchronized.nThe clock continue running even if the host goes down.nA binary counter increments at uniform intervals.nThe number of bits in the counter must equal or exceed the number of bits in the sequence numbers.6.2.2 Connection Establishment(2)2024/4/3012T is some small multiple of th我吓了一跳，蝎子是多么丑恶和恐怖的东西，为什么把它放在这样一个美丽的世界里呢？但是我也感到愉快，证实我的猜测没有错：表里边有一个活的生物6.2.2 Connection Establishment(3)nEnsure that two identically numbered TPDUs are never outstanding at the same time.nWhen a connection is set up,the low-order k bits of the clock are used as the initial sequence number(also k bits,for data).nEach connection starts numbering its TPDUs with a different initial sequence number.nThe sequence space should be so large that by the time sequence numbers wrap around,old TPDUs with the same sequence number are gone.nOnce connection established on the initial sequence number,any sliding window protocol can be used for data flow control.2024/4/30136.2.2 Connection Establishment我吓了一跳，蝎子是多么丑恶和恐怖的东西，为什么把它放在这样一个美丽的世界里呢？但是我也感到愉快，证实我的猜测没有错：表里边有一个活的生物6.2.2 Connection Establishment(4)nForbidden regionna host crashes nTPDUs may not enter the forbidden region.nThe resynchronization problem.nthe delayed duplicate problem for data TPDUs solved2024/4/30146.2.2 Connection Establishment我吓了一跳，蝎子是多么丑恶和恐怖的东西，为什么把它放在这样一个美丽的世界里呢？但是我也感到愉快，证实我的猜测没有错：表里边有一个活的生物6.2.2 Connection Establishment(5)nEstablishing a connection using a three-way handshake.(CR-CONNECTION REQUEST)nControl TPDUs may also be delayednNormal operationnOld CONNECTION REQUEST appearing out of nowhere.nDuplicate CONNECTION REQUEST and duplicate ACK.2024/4/30156.2.2 Connection Establishment我吓了一跳，蝎子是多么丑恶和恐怖的东西，为什么把它放在这样一个美丽的世界里呢？但是我也感到愉快，证实我的猜测没有错：表里边有一个活的生物6.2.3 Connection Release(1).nReleasing a connection is easier than establishing one,but.nAsymmetric releasenAbrupt disconnection with loss of data2024/4/30166.2.3 Connection Release(1).Re我吓了一跳，蝎子是多么丑恶和恐怖的东西，为什么把它放在这样一个美丽的世界里呢？但是我也感到愉快，证实我的猜测没有错：表里边有一个活的生物6.2.3 Connection Release(2)nSymmetric releasenTreats the connection as two unidirectional connectionsnRequires each one to be released separatelynThe two-army problem.nno protocol exists that works 2024/4/30176.2.3 Connection Release(2)Sy我吓了一跳，蝎子是多么丑恶和恐怖的东西，为什么把它放在这样一个美丽的世界里呢？但是我也感到愉快，证实我的猜测没有错：表里边有一个活的生物6.2.3 Connection Release(3)nReleasing a connection using a three-way handshake n(a)Normal case of a three-way handshake.n(b)final ACK lost.2024/4/30186.2.3 Connection Release(3)Re我吓了一跳，蝎子是多么丑恶和恐怖的东西，为什么把它放在这样一个美丽的世界里呢？但是我也感到愉快，证实我的猜测没有错：表里边有一个活的生物6.2.3 Connection Release(4)(c)Response lost.(d)Response lost and subsequent DRs lost.6-14,c,d2024/4/30196.2.3 Connection Release(4)(c我吓了一跳，蝎子是多么丑恶和恐怖的东西，为什么把它放在这样一个美丽的世界里呢？但是我也感到愉快，证实我的猜测没有错：表里边有一个活的生物6.2.4 Flow control and buffering(1)nDifference between Link layer and Transfer LayernA router usually has few lines,a host may have numerous connections and needs more buffer.nBuffer size,wide variation in TPDU size nDynamically adjust their buffer allocations 2024/4/30206.2.4 Flow control and bufferi我吓了一跳，蝎子是多么丑恶和恐怖的东西，为什么把它放在这样一个美丽的世界里呢？但是我也感到愉快，证实我的猜测没有错：表里边有一个活的生物6.2.5 Flow Control and Buffering(2)nDynamic buffer allocation.2024/4/30216.2.5 Flow Control and Bufferi我吓了一跳，蝎子是多么丑恶和恐怖的东西，为什么把它放在这样一个美丽的世界里呢？但是我也感到愉快，证实我的猜测没有错：表里边有一个活的生物6.2.5 Multiplexingn(a)Upward multiplexing.nIf only one network address is available on a host n(b)Downward multiplexing.nneeds more bandwidth 2024/4/30226.2.5 Multiplexing(a)Upward m我吓了一跳，蝎子是多么丑恶和恐怖的东西，为什么把它放在这样一个美丽的世界里呢？但是我也感到愉快，证实我的猜测没有错：表里边有一个活的生物6.2.6 Crash Recovery(1)nWhen network or router crashes,recovery is straightforward nDatagram servicesnConnection oriented services:building a new connection and retransfer from not received TPDUnHost Crashes nA trouble 2024/4/30236.2.6 Crash Recovery(1)When n我吓了一跳，蝎子是多么丑恶和恐怖的东西，为什么把它放在这样一个美丽的世界里呢？但是我也感到愉快，证实我的猜测没有错：表里边有一个活的生物6.2.6 Crash Recovery(2)nA examplenClient is sending a file to server using a stop-and-wait protocolnThe server passes the incoming TPDUs to the transport user,one by one.nServer crashes and reboots,reinitializes its tables,so no longer knows precisely where it was.nServer sends a broadcast TPDU to all other hosts,requests its clients inform the status of all open connections.2024/4/30246.2.6 Crash Recovery(2)A exa我吓了一跳，蝎子是多么丑恶和恐怖的东西，为什么把它放在这样一个美丽的世界里呢？但是我也感到愉快，证实我的猜测没有错：表里边有一个活的生物6.2.6 Crash Recovery(3)nClient can be in one of two states:nOne TPDU outstanding,S1nOr no TPDU outstanding,S0nWhether to retransmit the most recent TPDU?nEvents are possible at the server:nSending an acknowledgement(A),nWriting to the output process(W),nCrashing(C).2024/4/30256.2.6 Crash Recovery(3)Clien我吓了一跳，蝎子是多么丑恶和恐怖的东西，为什么把它放在这样一个美丽的世界里呢？但是我也感到愉快，证实我的猜测没有错：表里边有一个活的生物6.2.6 Crash Recovery(4)nDifferent combinations of client and server strategy.nThere are always situations where the protocol fails to recover properly.nRecovery from layer N crash can only be done by layer N+1 2024/4/30266.2.6 Crash Recovery(4)Differ我吓了一跳，蝎子是多么丑恶和恐怖的东西，为什么把它放在这样一个美丽的世界里呢？但是我也感到愉快，证实我的猜测没有错：表里边有一个活的生物6.3 A Simple Transport ProtocolThe Example Service PrimitivesThe Example Transport EntityThe Example as a Finite State Machine2024/4/30276.3 A Simple Transport Protoco我吓了一跳，蝎子是多么丑恶和恐怖的东西，为什么把它放在这样一个美丽的世界里呢？但是我也感到愉快，证实我的猜测没有错：表里边有一个活的生物6.3.1 The Example Service PrimitivesnCONNECTnDuring the call,the caller is blocked nIf the connection succeeds,the caller is unblocked and can start transmitting data.nOr rejected and the caller is unblocked and given an error return nLISTENnTo accept incoming calls nThe process then blocks until some remote process attempts to establish a connection to its TSAP.nDISCONNECTnWhen both sides have disconnected,the connection is released.A symmetric disconnection model.2024/4/30286.3.1 The Example Service Prim我吓了一跳，蝎子是多么丑恶和恐怖的东西，为什么把它放在这样一个美丽的世界里呢？但是我也感到愉快，证实我的猜测没有错：表里边有一个活的生物6.3.1 The example service primitives(2)nSENDnAn active call,transmits datanRECEIVEnA passive call,blocks until a TPDU arrives.nEach primitive corresponds to a library procedure that executes the primitive.nThe parameters library procedures:nconnum=LISTEN(local)nconnum=CONNECT(local,remote)nstatus=SEND(connum,buffer,bytes)nstatus=RECEIVE(connum,buffer,bytes)nstatus=DISCONNECT(connum)2024/4/30296.3.1 The example service prim我吓了一跳，蝎子是多么丑恶和恐怖的东西，为什么把它放在这样一个美丽的世界里呢？但是我也感到愉快，证实我的猜测没有错：表里边有一个活的生物6.3.2 The Example Transport Entity(1)nUsing a connection-oriented,reliable network service nProcedures to_net and from_net,parametersnConnection identifier,which maps onto network virtual circuitsnQ bits,indicate control message,only one(CREDIT)in example nM bits,more data in the next packetnPacket typenA pointer to the data itselfnAn integer giving the number of bytes of data.2024/4/30306.3.2 The Example Transport En我吓了一跳，蝎子是多么丑恶和恐怖的东西，为什么把它放在这样一个美丽的世界里呢？但是我也感到愉快，证实我的猜测没有错：表里边有一个活的生物6.3.2 The Example Transport Entity(2).nThe network layer packets type used in example 2024/4/30316.3.2 The Example Transport En我吓了一跳，蝎子是多么丑恶和恐怖的东西，为什么把它放在这样一个美丽的世界里呢？但是我也感到愉快，证实我的猜测没有错：表里边有一个活的生物6.3.2 The Example Transport Entity(3)nEach connection is in one of seven statesnIdle Connection not established yet.nWaiting CONNECT has been executed,CALL REQUEST sent.nQueued A CALL REQUEST has arrived;no LISTEN yet.nEstablished The connection has been established.nSending The user is waiting for permission to send a packet.nReceiving A RECEIVE has been done.nDisconnecting a DISCONNECT has been done locally.2024/4/30326.3.2 The Example Transport En我吓了一跳，蝎子是多么丑恶和恐怖的东西，为什么把它放在这样一个美丽的世界里呢？但是我也感到愉快，证实我的猜测没有错：表里边有一个活的生物6.3.2 The Example Transport Entity(4)nTransitions occurs when the following events occur na primitive is executedna packet arrivesnthe timer expires.nA flow control mechanism different from the sliding window.nWhen RECEIVE is called,a special credit message is sent to the sending machinenWhen SEND is called,the transport entity checks to see if a credit has arrived on the specified connection.nIf so,the message is sent and the credit decremented;nif not,the transport entity puts itself to sleep until a credit arrives 2024/4/30336.3.2 The Example Transport En我吓了一跳，蝎子是多么丑恶和恐怖的东西，为什么把它放在这样一个美丽的世界里呢？但是我也感到愉快，证实我的猜测没有错：表里边有一个活的生物nThe example protocol in graphical form.2024/4/3034The example protocol in graphi我吓了一跳，蝎子是多么丑恶和恐怖的东西，为什么把它放在这样一个美丽的世界里呢？但是我也感到愉快，证实我的猜测没有错：表里边有一个活的生物2024/4/30352023/7/3135我吓了一跳，蝎子是多么丑恶和恐怖的东西，为什么把它放在这样一个美丽的世界里呢？但是我也感到愉快，证实我的猜测没有错：表里边有一个活的生物2024/4/30362023/7/3136我吓了一跳，蝎子是多么丑恶和恐怖的东西，为什么把它放在这样一个美丽的世界里呢？但是我也感到愉快，证实我的猜测没有错：表里边有一个活的生物2024/4/30372023/7/3137我吓了一跳，蝎子是多么丑恶和恐怖的东西，为什么把它放在这样一个美丽的世界里呢？但是我也感到愉快，证实我的猜测没有错：表里边有一个活的生物2024/4/30382023/7/3138我吓了一跳，蝎子是多么丑恶和恐怖的东西，为什么把它放在这样一个美丽的世界里呢？但是我也感到愉快，证实我的猜测没有错：表里边有一个活的生物2024/4/30392023/7/3139我吓了一跳，蝎子是多么丑恶和恐怖的东西，为什么把它放在这样一个美丽的世界里呢？但是我也感到愉快，证实我的猜测没有错：表里边有一个活的生物2024/4/30402023/7/3140我吓了一跳，蝎子是多么丑恶和恐怖的东西，为什么把它放在这样一个美丽的世界里呢？但是我也感到愉快，证实我的猜测没有错：表里边有一个活的生物2024/4/30412023/7/3141我吓了一跳，蝎子是多么丑恶和恐怖的东西，为什么把它放在这样一个美丽的世界里呢？但是我也感到愉快，证实我的猜测没有错：表里边有一个活的生物2024/4/30422023/7/3142我吓了一跳，蝎子是多么丑恶和恐怖的东西，为什么把它放在这样一个美丽的世界里呢？但是我也感到愉快，证实我的猜测没有错：表里边有一个活的生物6.3.3 The Example as a Finite State Machine(1)nThe example protocol as a finite state machinenEach entry has an predicate,an action,and the new state.nBlank entries correspond to impossible or invalid eventsnThe advantage of representing the protocol as a matrix nIt is easier to systematically check each combination of state and event to see if an action is required.ngives a much more regular and systematic design nprotocol description 2024/4/30436.3.3 The Example as a Finite 我吓了一跳，蝎子是多么丑恶和恐怖的东西，为什么把它放在这样一个美丽的世界里呢？但是我也感到愉快，证实我的猜测没有错：表里边有一个活的生物6.3.3 The Example as a Finite State Machine(2)2024/4/30446.3.3 The Example as a Finite 我吓了一跳，蝎子是多么丑恶和恐怖的东西，为什么把它放在这样一个美丽的世界里呢？但是我也感到愉快，证实我的猜测没有错：表里边有一个活的生物nCongestion:too many packets into the network too quickly in transport layernCongestion control mechanismsnDesirable bandwidth allocationnRegulating the sending rate6.4 Congestion ControlCongestion:too many packets i45我吓了一跳，蝎子是多么丑恶和恐怖的东西，为什么把它放在这样一个美丽的世界里呢？但是我也感到愉快，证实我的猜测没有错：表里边有一个活的生物6.4.1 Desirable Bandwidth Allocation(1)(a)Goodput and(b)delay as a function of offered loadnEfficiency allocation:to use all of the available network capacitynPower=load(goodput)/delay6.4.1 Desirable Bandwidth Allo46我吓了一跳，蝎子是多么丑恶和恐怖的东西，为什么把它放在这样一个美丽的世界里呢？但是我也感到愉快，证实我的猜测没有错：表里边有一个活的生物nFairness:how to divide bandwidth between sendersnMax-min Fairness allocationnIf the bandwidth given to one flow cannot be increased without decreasing the bandwidth given to another flow6.4.1 Desirable Bandwidth Allocation(2)Max-min bandwidth allocation for four flowsFairness:how to divide bandwi47我吓了一跳，蝎子是多么丑恶和恐怖的东西，为什么把它放在这样一个美丽的世界里呢？但是我也感到愉快，证实我的猜测没有错：表里边有一个活的生物6.4.1 Desirable Bandwidth Allocation(3)Changing bandwidth allocation over timenConvergencenTo converge quickly to the ideal operating point6.4.1 Desirable Bandwidth Allo48我吓了一跳，蝎子是多么丑恶和恐怖的东西，为什么把它放在这样一个美丽的世界里呢？但是我也感到愉快，证实我的猜测没有错：表里边有一个活的生物6.4.2 Regulating the Sending Rate(1)nThe sending rate is limited by receiver and network6.4.2 Regulating the Sending R49我吓了一跳，蝎子是多么丑恶和恐怖的东西，为什么把它放在这样一个美丽的世界里呢？但是我也感到愉快，证实我的猜测没有错：表里边有一个活的生物6.4.2 Regulating the Sending Rate(2)nThe form of the feedback returned by the networknExplicit or implicitnPrecise or imprecisenSome congestion control protocols6.4.2 Regulating the Sending R50我吓了一跳，蝎子是多么丑恶和恐怖的东西，为什么把它放在这样一个美丽的世界里呢？但是我也感到愉快，证实我的猜测没有错：表里边有一个活的生物nAdditive Increase Multiplicative Decrease(AIMD)control law.User 1s allocationUser 2s allocation6.4.2 Regulating the Sending Rate(3)Additive Increase Multiplicati51我吓了一跳，蝎子是多么丑恶和恐怖的东西，为什么把它放在这样一个美丽的世界里呢？但是我也感到愉快，证实我的猜测没有错：表里边有一个活的生物6.4.3 TCP Congestion Control(1)nCongestion Window in TCP TahoenSlow start followed by additive increase2024/4/30526.4.3 TCP Congestion Control(1我吓了一跳，蝎子是多么丑恶和恐怖的东西，为什么把它放在这样一个美丽的世界里呢？但是我也感到愉快，证实我的猜测没有错：表里边有一个活的生物6.4.3 TCP Congestion Control(2)nFast recovery and the sawtooth pattern of TCP Reno.6.4.3 TCP Congestion Control(53我吓了一跳，蝎子是多么丑恶和恐怖的东西，为什么把它放在这样一个美丽的世界里呢？但是我也感到愉快，证实我的猜测没有错：表里边有一个活的生物6.4.4 Wireless NetworksnPacket loss,a congestion signal or transmission errors?nSome wireless links have a long round-trip times,such as satellites.nWireless links have variable capacity.2024/4/30546.4.4 Wireless NetworksPacket 我吓了一跳，蝎子是多么丑恶和恐怖的东西，为什么把它放在这样一个美丽的世界里呢？但是我也感到愉快，证实我的猜测没有错：表里边有一个活的生物6.5 The Internet Transport Protocols:TCP*Introduction to TCPThe TCP Service ModelThe TCP ProtocolThe TCP Segment HeaderTCP Connection EstablishmentTCP Connection ReleaseTCP Connection Management ModelingTCP Transmission PolicyTCP Congestion ControlTCP Timer ManagementWireless TCP and UDPTransactional TCP2024/4/30556.5 The Internet Transport Pro我吓了一跳，蝎子是多么丑恶和恐怖的东西，为什么把它放在这样一个美丽的世界里呢？但是我也感到愉快，证实我的猜测没有错：表里边有一个活的生物6.6 Performance IssuesPerformance Problems in Computer NetworksNetwork Performance MeasurementSystem Design for Better PerformanceFast TPDU ProcessingProtocols for future high-performance networks2024/4/30566.6 Performance IssuesPerforma我吓了一跳，蝎子是多么丑恶和恐怖的东西，为什么把它放在这样一个美丽的世界里呢？但是我也感到愉快，证实我的猜测没有错：表里边有一个活的生物nCongestion,caused by resource overloadsnStructural resource imbalancenSynchronous overloads nPoor system tuningnIncorrect timeouts settingnBandwidth-delay productnThe window must be at least as large as the bandwidth-delay productnTime-critical applications 6.6.1 Performance Problems in Computer Networks(1)2024/4/3057Congestion,caused by resource我吓了一跳，蝎子是多么丑恶和恐怖的东西，为什么把它放在这样一个美丽的世界里呢？但是我也感到愉快，证实我的猜测没有错：表里边有一个活的生物6.6.1 Performance Problems in Computer Networks(2)The bandwidth-delay product The state of transmitting(a)At t=0(b)After 500 sec(c)After 20 msec(d)after 40 msec.2024/4/30586.6.1 Performance Problems in 我吓了一跳，蝎子是多么丑恶和恐怖的东西，为什么把它放在这样一个美丽的世界里呢？但是我也感到愉快，证实我的猜测没有错：表里边有一个活的生物6.6.2 Network Performance Measurement(1)nThe basic loop for improving network performance.nMeasure relevant network parameters.nhow long a activity takesnhow often some event has happened nthe amount of somethingnTry to understand what is going on.nChange one parameter.2024/4/30596.6.2 Network Performance Meas我吓了一跳，蝎子是多么丑恶和恐怖的东西，为什么把它放在这样一个美丽的世界里呢？但是我也感到愉快，证实我的猜测没有错：表里边有一个活的生物nWhen measuring network performance,pay attention to:nSample size is large enoughnSamples are representativenBe careful when using a coarse-grained clocknNothing unexpected is going on during your testsnCaching can wreak havoc with measurementsnUnderstand what you are measuringnBe careful about extrapolating the results6.6.2 Network Performance Measurement(2)2024/4/3060When measuring network perform我吓了一跳，蝎子是多么丑恶和恐怖的东西，为什么把它放在这样一个美丽的世界里呢？但是我也感到愉快，证实我的猜测没有错：表里边有一个活的生物6.6.3 System Design for Better PerformancenRules:nCPU speed is more important than network speed.nReduce packet count to reduce software overhead.nMinimize context switches.nMinimize copying.nBuy more bandwidth but not lower delay.nAvoiding congestion is better than recovering from it.nAvoid timeouts.2024/4/30616.6.3 System Design for Better我吓了一跳，蝎子是多么丑恶和恐怖的东西，为什么把它放在这样一个美丽的世界里呢？但是我也感到愉快，证实我的猜测没有错：表里边有一个活的生物6.6.4 Fast TPDU Processing(1)*The fast path from sender to receiver is shown with a heavy line.The processing steps on this path are shaded.2024/4/30626.6.4 Fast TPDU Processing(1)我吓了一跳，蝎子是多么丑恶和恐怖的东西，为什么把它放在这样一个美丽的世界里呢？但是我也感到愉快，证实我的猜测没有错：表里边有一个活的生物6.6.4 Fast TPDU Processing(2)*(a)TCP header.(b)IP header.In both cases,the shaded fields are taken from the prototype without change.2024/4/30636.6.4 Fast TPDU Processing(2)我吓了一跳，蝎子是多么丑恶和恐怖的东西，为什么把它放在这样一个美丽的世界里呢？但是我也感到愉快，证实我的猜测没有错：表里边有一个活的生物6.6.4 Fast TPDU Processing(3)A timing wheel.2024/4/30646.6.4 Fast TPDU Processing(3)我吓了一跳，蝎子是多么丑恶和恐怖的东西，为什么把它放在这样一个美丽的世界里呢？但是我也感到愉快，证实我的猜测没有错：表里边有一个活的生物6.6.5 Protocols for Gigabit Networks(1)nUsing 32-bit sequence numbers will fail.nCommunication speeds have improved much faster than computing speeds.nGo back n protocol performs poorlynDelay limited rather than bandwidth limited in that long gigabit lines2024/4/30656.6.5 Protocols for Gigabit Ne我吓了一跳，蝎子是多么丑恶和恐怖的东西，为什么把它放在这样一个美丽的世界里呢？但是我也感到愉快，证实我的猜测没有错：表里边有一个活的生物6.6.5 Protocols for Gigabit Networks(2)Time to transfer and acknowledge a 1-megabit file over a 4000-km line.2024/4/30666.6.5 Protocols for Gigabit Ne我吓了一跳，蝎子是多么丑恶和恐怖的东西，为什么把它放在这样一个美丽的世界里呢？但是我也感到愉快，证实我的猜测没有错：表里边有一个活的生物nSome ways to deal with the problemsnDesign for speed,not for bandwidth optimization nTo build fast network interfaces