KARABEK `Transport Protocols and Client Server Applications', XTP Forum Research Affiliate

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xcap,协议

xcap,协议竭诚为您提供优质文档/双击可除xcap,协议篇一：Rest风格的xcap协议1、xcap协议的简介xcap（xmlconfigurationaccessprotocol，xml配置访问协议），也称xml配置接入协议。

它是ietF制定的一个协议，前面陆续发布了一系列草案，于20xx年5月正式成为RFc规范（RFc4825）。

该协议允许客户端读、写、修改存放在服务器中的xml 格式的应用配置数据。

xcap将xml文档中的节点映射到httpuRis中，使得这些组件能够直接通过http访问。

2、xcap协议的应用场合多个应用和服务之间共享好友列表（buddylists）多个应用和服务之间共享安全策略（authorizationpolicies）多个应用和服务之间共享呈现数据（presencelist）p>开放移动联盟（oma）定义的文档管理服务器（xdms）结构中，其中的xdm3和xdm4接口是xcap协议。

3、xcap的uRi的组成xcap的uRi映射分成两个部分：文档选择器（documentselector）与节点选择器(nodeselector)，文档选择器决定选择哪一个xml文档。

节点选择器决定选择文档中的哪一个节点和属性（是xpath的一个子集）。

在RFc的描述中，文档选择器与节点选择器之间以“~~”分隔，但是在一些文档中，xcap的uRi并不包含“~~”(也许是早期的文档，下面的例子当中uRi并不包含“~~”)。

文档选择器的结构：Rootservice/auid/users/usernameRootservice/auid/global/其中auid是唯一的程序id。

文档组织的层次结构如下：xcap的uRi的示例：4、Rest风格的xcap操作httpget获取一个xml文档节点举httpget获取一个xml文档节点属性举例创建一个xml文档节点举例替换一个xml文档节点举例篇二：lte架构及各个接口和协议类型一、Volte网络架构Volt网络架构有很多种，协议中介绍较为典型的如下ims架构&接口二、Volte接口三、Volte功能实体篇三：史上最强悍的Volte秘籍一Volte介绍1.1lte语音解决方案演进svlte(simultaneousVoiceandlte),即双待手机方式。

FortiOS 5.0和5.2 WAN 优化配置：客户端服务器架构说明书

WAN Optimization Configuration(FortiOS 5.0 and 5.2)Client/Server Architecture:Traffic across a WAN typically consists of clients on a client network communicating across a WAN with a remote server network. These communication sessions can be open text over the WAN or they can be encrypted by SSL VPN or IPsec VPNClient/Server architecture TopologyThis example configuration includes an Active-Passive WAN optimization with secure tunneling over IPSec VPN. The IPSec tunnel has already been configured and is functional. WAN optimization is added afterward.The Client-side FortiGate is 200D and Server-side FortiGate is 240DConfiguration steps:1) Configure the client-side FortiGate unit:Go to WAN Opt. & Cache > WAN Opt. Peers > PeersEnter a Local Host ID for the client-side FortiGate unit as Client-fgt·:Select Create New and add a Peer Host ID and the IP Address for the server-side FortiGateGo to WAN Opt & Cache > WAN Opt. Peers > Authentication GroupsSelect Create New to add the authentication group to be used for secure tunnelingGo to WAN Opt. & Cache > WAN Opt. Profiles > ProfilesSelect Create New to add a WAN Optimization profile that enables secure tunneling and includes the authentication groupSelect any protocol for optimizationSelect Transparent mode -- this will source your traffic as Client addressSelect Authentication group nameGo to Policy & Objects > Objects > AddressesSelect “Create New” to add a Firewall address for the client and server respectively. Go to Policy & Objects > Policy > IPv4Select “Create New” to add an active WAN optimization security policyThis policy is from Internal interface to IPSec tunnel interface with WAN optimization enabled with active state and required authentication profile which in this case is default.2) Configure Server-side FortiGate unit:Go to WAN Opt. & Cache > WAN Opt. Peers > PeersEnter a Local Host ID for the server-side FortiGate unit·Select Create New and add a Peer Host ID and the IP Address for the client-sideFortiGate:Go to Wan Opt. & Cache > WAN Opt. Peers > Authentication GroupsSelect Create new and add an authentication group to be used for secure tunneling:Go to Policy & Objects > Objects > AddressesSelect “Create New” to add a Firewall address for the client and server respectively.Create a passive WAN optimization policy that applies application controlThis policy is from IPSec interface to the Internal interface of the server-side FortiGate with WANoptimization enabled with passive state.From the CLI enter the following command to add a WAN optimization tunnel explicit proxy policy.configure firewall explicit-proxy-policyedit 1set proxy wanoptset dstintf port1set srcaddr allset dstaddr allset action acceptset schedule alwaysset service ALLendIMP------> Secure Tunneling:In Active-Passive WAN optimizationSelect “Enable Secure Tunnel” only in the active rule.In Peer-to-Peer WAN optimizationSelect “Enable Secure Tunnel” in the WAN optimization rule on both FortiGate units.Troubleshooting WAN optimization1) Browse from a PC on the client network browse to the IP address of a web server network http://192.168.100.111. You should be able to connect over the WAN optimization tunnel.2) Check WAN Opt. & Cache > Monitor it will show the protocol that has been optimized and the reduction rate in WAN bandwidth usage.If you cannot connect∙Try the following diagnose commands on FortiGate client or server∙Confirm the policy on client-side and server-side unit∙Check routing on the FortiGate units to make sure packets can be forwarded as required.e.g., You should be able to ping the internal network behind the client-side/server-sideFortiGate.Diagnostic ToolsA)CLI commands with sample output:FG240D-Server # diagnose wad tunnel listTunnel: id=2245 type=autovd=0 shared=no uses=1 state=2peer name=Client-fgt id=1776 ip=172.17.97.210SSL-secured-tunnel=no auth-grp=Auth-Secure-Tunnelbytes_in=0 bytes_out=0Tunnels total=1 manual=0 auto=1FG240D-Server # diagnose wad history list TCP 10stats history vd=0 proto=tcp period=last 10min--- LAN --- --- WAN ---bytes_in bytes_out bytes_in bytes_out ------------ ------------- ------------ -------------0 0 0 02951 5965 8385 57871924 3733 5173 39206414 11902 16710 12390…FG240D-Server # diagnose wad statssummarysessions total=1767 active=0 max=9cryptosoftwareenc total 58 active 0 max 1dec total 62 active 0 max 1…hardwareenc total 1089 active 0 max 1dec total 1108 active 0 max 1…Tunnelshttp tunnelbytes_in=46757 bytes_out=55162ftp tunnelbytes_in=0 bytes_out=0cifs tunnelbytes_in=116511 bytes_out=112450 mapi tunnelbytes_in=0 bytes_out=0tcp tunnelbytes_in=258547 bytes_out=187041 maintenancebytes_in=305405 bytes_out=141900 httpLAN:bytes_in=12662 bytes_out=178263 WAN:bytes_in=46757 bytes_out=55162 ftpLAN:bytes_in=0 bytes_out=0WAN:bytes_in=0 bytes_out=0cifsLAN:bytes_in=54055 bytes_out=60417 WAN:bytes_in=116511 bytes_out=112450 mapiLAN:bytes_in=0 bytes_out=0WAN:bytes_in=0 bytes_out=0tcpLAN:bytes_in=95389 bytes_out=182923 WAN:bytes_in=258547 bytes_out=187041FG240D-Server # diagnose wad session listSession: svr-side auto-detected 10.255.255.100:52468->192.168.100.111:80id=407974 vd=0 fw-policy=4state=3 app=http sub_type=0 dd_mode=3 dd_method=3SSL disabledWAN-side: to-clientTunnel Port:state=2 session_id=2101540166 remote_sid=244981077tunnel id=2252 SSL-secured=no peer=Client-fgt auth-grp=Auth-Secure-Tu nnelbuf_blocked=0 buf_block_threshold=2097152bytes_unconfirm_rcv=0 bytes_unconfirm_snd=0LAN-side: to-serverTCP Port:state=2 r_blocks=0 w_blocks=0 read_blocked=0bytes_in=0 bytes_out=0 shutdown=0x0Sessions total=1B)List of Relevant Diagnostics commandsdiagnose wad tunnel list --> will show you the established tunnelsget test wad 11 -- > Use this command on the FortiGate client to see the details about WANopt and statisticsdiag wacs stats >>>> Displays web cache statisticsdiag wacs recents >>>> Displays recent web cache database activityget test wad cifsget test wad 50 --> display Web Cache statsget test wad 53 --> to display firewall policiesdiagnose sys wccp listdiagnose debug application wad -1 -----> will show you the detailed informationdiagnose sys session filter dport 7810diagnose snipper packet any "port 7810" 4C)WAN MonitorThe reduction rate in traffic shaping ensures that WAN optimization for that particular protocol is optimized.。

讲Kerberos认证协议与X

– (4) TGS C : EKc,tgs[Kc,v || IDV || TS4 || Ticketv]
Tickettgs = Lifetime2]
EKtgs[Kc,tgs||
IDC||
ADC||
IDtgs
||
TS2
||
Ticketv = EKV[Kc,v||IDC||ADC|| IDv||TS4||Lifetime4]
IDtgs : TS2 : Lifetime2: Tickettgs:
确认这个ticket是为TGS制作的。告诉client该ticket签发的时间。告诉client该ticket的有效期； client用来访问TGS的ticket。
整理版ppt课件
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16. 基本原理(续)
(b) 票据许可服务交换
Ticketv = EKV[Kc,v||IDc||ADc||IDv||TS4||Lifetime4] Authenticatorc = EKc,v[IDc||ADc||TS5]
整理版ppt课件
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14. 公开公证或证书机构
• 可信的离线服务器 • server 有个公开的公钥 • server 对每个用户签名公钥证书 • 利用公钥加密
整理版ppt课件
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7. Kerberos系统满足的要求
• 安全。网络窃听者不能获得必要信息以假冒其它用户；Kerberos应足够强壮以至于潜在的敌
人无法找到它的弱点连接。
• 可靠。Kerberos应高度可靠，并且应借助于一个分布式服务器体系结构，使得一个系统能够
备份另一个系统。
• 透明。理想情况下，用户除了要求输入口令以外应感觉不到认证的发生。
TicketV = EKV[IDC||ADC||I整D理V版|p|pTt课S件2||Lifetime2]

Kerberos协议

（0）名词解析1、Authentication：身份鉴别2、TGT：票据(ticket-granting ticket)3、SSO：Single Sign On 单点4、KDC：密钥分发中心5、PKI：Public Key Infrastructure 即"公钥基础设施"6、Kerberors: Network Authentication Protocol7、DES：数据加密标准8、TGS：门票分配服务器（1）Kerberors协议Kerberors协议：Kerberors协议主要用于计算机网络的身份鉴别(Authentication),其特点是用户只需输入一次身份验证信息就可以凭借此验证获得的票据(ticket-granting ticket)访问多个服务，即SSO(Single Sign On)。

由于在每个Client和Service之间建立了共享密钥，使得该协议具有相当的安全性。

条件先来看看Kerberors协议的前提条件：如下图所示，Client与KDC，KDC与Service在协议工作前已经有了各自的共享密钥，并且由于协议中的消息无法穿透防火墙，这些条件就限制了Kerberors协议往往用于一个组织的内部，使其应用场景不同于X.509 PKI。

过程Kerberors协议分为两个部分：1 . Client向KDC发送自己的身份信息，KDC从Ticket Granting Service得到TGT(ticket-granting ticket)，并用协议开始前Client与KDC之间的密钥将TGT加密回复给Client。

此时只有真正的Client才能利用它与KDC之间的密钥将加密后的TGT解密，从而获得TGT。

（此过程避免了Client直接向KDC发送密码，以求通过验证的不安全方式）2. Client利用之前获得的TGT向KDC请求其他Service的Ticket，从而通过其他Service的身份鉴别。

xcp协议标准

xcp协议标准XCP（Universal Measurement and Calibration Protocol）是一种用于测量和校准汽车电子控制单元（ECU）的通信协议。

它旨在提供一种标准化的方式，使不同供应商的工具能够与各种车辆的ECU进行通信和交互。

本文将详细介绍XCP协议的标准及其在汽车行业的应用。

一、XCP协议概述XCP协议是一种基于客户/服务器模型的通信协议，它定义了一套消息格式和通信机制，用于ECU的测量、校准和诊断。

XCP协议支持多种通信介质，如CAN、FlexRay和以太网等，使得工程师能够方便地与ECU进行通信，并进行实时数据的采集和ECU参数的调整。

二、XCP协议的消息格式1. 连接建立请求（CONNECT）CONNECT消息用于建立XCP主机与ECU之间的连接。

该消息包含XCP主机的身份标识和通信设置等信息。

2. 连接建立响应（CONNECT_RSP）CONNECT_RSP消息是ECU对CONNECT消息的响应，用于确认与XCP主机之间的连接是否建立成功。

该消息包含ECU的身份标识和通信参数等信息。

3. 读数据请求（GET_DAQ）GET_DAQ消息用于向ECU请求特定数据。

该消息包含所需数据的描述符，ECU将根据描述符提供相应的数据。

4. 读数据响应（GET_DAQ_RSP）GET_DAQ_RSP消息是ECU对GET_DAQ消息的响应，用于返回所请求数据的值。

5. 写数据请求（SET_DAQ）SET_DAQ消息用于向ECU发送需要修改的数据。

该消息包含数据的描述符和要修改的值。

6. 写数据响应（SET_DAQ_RSP）SET_DAQ_RSP消息是ECU对SET_DAQ消息的响应，用于确认数据的修改是否成功。

7. 发送事件请求（DAQ_EVENT_INFO）DAQ_EVENT_INFO消息用于向ECU发送特定事件的请求。

该消息包含事件的描述符，ECU将在满足事件触发条件时进行相应处理。

计算机网络原理习题讲解精编版

计算机网络原理习题讲解精编版MQS system office room 【MQS16H-TTMS2A-MQSS8Q8-MQSH16898】ChapterI1. Whatisthedifferencebetweenahostandanendsystem??2. Whatisaclientprogram?Whatisaserverprogram?Doesaserverprogramrequesta ndreceiveservicesfromaclientprogram?3. ,companyaccess,ormobileaccess.4. Dial-upmodems,HFC,,providearangeoftransmissionratesandcommentonwhetherthe transmissionrateissharedordedicated.5. .6. Whatadvantagedoesacircuit-switchednetworkhaveoverapacket-switchednetwork?WhatadvantagesdoesTDMhaveoverFDMinacircuit-switchednetwork?7. 2,000km 8102⨯prop d trans d trans d t =prop d trans d trans d prop d trans d trans d 8105.2⨯=s prop d trans d 6108⨯下列说法中,正确的是()。

A.在较小范围内布置的一定是局域网,币在较大范围内布置的一定是广域网B.城域网是连接广域网而覆盖园区的网络C.城域网是为淘汰局域网和广域网而提出的一种网络技术D.局域网是基于广播技术发展起来的网络,广域网是基于交换技术发展起来的向络解答:D 。

通常而言,局域网的覆盖范围较小,而广域网的覆盖范围较大,但这并不绝对。

有时候在一个不大的范围内采用广域网,这取决于应用的需要和是否采用单一网络等多种因素。

Documentation for Satellite Transport Protocol (STP

Documentation for Satellite Transport ProtocolTom HendersonAugust20001IntroductionThis document describes the Satellite Transport Protocol(STP),an experimental transport protocol for use over IP-compatible networks that was developed under the University of California,Berkeley’s BARW AN research project.STP was originally developed for the BSDi Unix operating system and was subsequently ported to FreeBSD Unix,and is freely available at ftp:///pub/stp/.STP was speciﬁcally designed to overcome the following three problems encountered with TCP over satellite links(partic-ularly satellite links that are asymmetric in bandwidth).These problems persist even in state-of-the-art TCP implementations that have satellite-friendly options such as“SACK”and“window-scale”:Reverse channel usage For unidirectional data transfers,STP uses less of the reverse channel bandwidth than does TCP, commonly achieving an average reduction of20%for object-laden Web pages(such as ),and a reduction of up to an order of magnitude for large images andﬁle transfers.Performance with high BERs By using selective negative acknowledgments and a robust data acknowledgment system, STP operates efﬁciently under BERs that can range as low as.Sensitivity to RTT variations STP is relatively immune to problems related to highly-varying round trip times(such as burstiness due to ACK clumping in TCP).In a satellite environment with multiple access delays,the round trip time can be highly variable.STP provides TCP-like reliable byte-streaming data service.An example application that could beneﬁt from using STP is a protocol conversion gateway in a satellite system.Such an application,as well as some further background and performance results,are described in:[HK97]T.Henderson and R.Katz,Satellite Transport Protocol(STP):An SSCOP-based Transport Protocol for Datagram Satellite Networks,2nd International Workshop on Satellite-based Information Services(WOSBIS‘97),Budapest,Hungary, Oct.1,1997.[HK99]T.Henderson and R.Katz,Transport Protocols for Internet-Compatible Satellite Networks,IEEE Journal on Se-lected Areas in Communications,V ol.17,No.2,pp.345-359,February1999.2OperationSTP has four basic packet types for data transfer(we ignore,for now,the additional packet types needed for connection setup and release).The Sequenced Data(SD)packet is simply a variable length segment of user data,together with a24bit sequence number and a checksum.SD packets which have not yet been acknowledged are stored in a buffer,along with a timestamp indicating the last time that they were sent to the receiver.No control data is included in the SD packets;instead,the transmitter and receiver exchange POLL and STAT(us)messages.Periodically,the transmitter sends a POLL packet to the receiver.This POLL packet contains a timestamp and the sequence number of the next in-sequence SD packet to be sent.The receiver responds to the POLL by issuing a STAT message which echoes the timestamp,includes the highest in-sequence packet to have been successfully received,and contains a list of all gaps in the sequence number space.The STAT message is similar in concept to a TCP selective acknowledgment,except that the STAT message reports the entire state of the receiver buffer(rather than the three most recent gaps in a SACK).Since each STAT message is a complete report of the state of the receiver,STP is robust to the loss of POLLs or STATs.The fourth basic packet type is called a USTAT(unsolicited STAT)TATs are data-driven explicit negative ac-knowledgments,and are used by the receiver to immediately report gaps in the received sequence of packets without waiting for a POLL message to arrive.This allows the POLL and STAT exchange to be run at a low frequency(typically two or three per RTT when the RTT is large).In a network in which sequence integrity is guaranteed or highly likely,a USTAT can be sent upon any reception of a packet numbered beyond the next expected.If resequencing by the network is possible,USTATs can be delayed until there is a high probability that the missing packet was not reordered by the network.However,if the1USTAT is sent too early there is only the small penalty of a redundant TATs are the primary form of negative acknoFigure1:Example of STP bulk data transfer.The basic operation of STP can best be illustrated by an example.For simplicity,Figure1only illustrates one direction of data transfer,assumes that sequence integrity of transmissions is preserved,and does not contain packets involved with beginning and closing a connection.In the example,the transmitter sends a series of consecutively numbered packets.After packet(SD)#4is sent,a POLL packet is sent(due to either the expiration of a POLL timer or a threshold on the number of new packets sent).The POLL tells the receiver that the next message to be sent is#5,so the receiver knows that it should have received packets0through4.In this case,since they have all been received,the receiver returns a STAT packet acknowledging all data up to and including packet#4.After sending the POLL,the transmitter continues with packets5through9.However, packet#7is lost.The receiver detects this loss upon receipt of packet#8and immediately requests retransmission of#7with a USTAT packet.Before this USTAT is received at the transmitter,the transmitter agains sends a POLL packet.Upon reception of the USTAT,the transmitter immediately resends#7,continues on with new data transmission,and then receives a STAT packet again reporting#7as missing.However,the timestamp in the STAT packet allows the transmitter to determine that the retransmission has not yet had an opportunity to reach the receiver,thereby avoiding an unnecessary retransmission.If#7had again been lost,the next STAT message would have stimulated a second retransmission.Figure2illustrates a hypothetical data transaction in which the client(the initiator of the connection)writes400bytes of data to a server and receives an8000byte response.The example illustrates typical system calls that would be used by the application.The connection uses TCP-like window control,so that the congestion window builds by one packet for each packet acknowledged.The server is listening on a particular port,and the client connects to that port by issuing a connect()system call,which causes STP to send a BGN packet.This exchange of BGN and BGNAK coordinates the sequence numbers to be used by both sides and establishes the window sizes in each direction.The client then writes400bytes to the socket,which stimulates an SD to be sent to the other side.In this case,the client is conﬁgured to POLL with theﬁrst burst of data,so the actual packet sent is a concatenation of an SD with a POLL(see Appendix A about concatenation of packet types).The server responds to the POLL by issuing a STAT,reporting the next sequence number(#2)that the server expects to receive.The server then writes8000bytes of data to the socket,and it requires six packets to complete the transfer.Upon successful completion of the data transfer,both sides exchange END messages to close down their respective halves of the connection.3UseAn application that normally uses TCP can be easily converted to one that uses STP by changing the protocol number used to invoke the TCP socket.For example,the following example line of C code opens a socket and returns aﬁle descriptor pointer which is assigned to sockfd:sockfd=socket(PF_INET,SOCK_STREAM,IPPROTO_TCP);socket()listen()accept()write(400)read()write(5000)write(3000)close()read()close()Figure 2:Example of a STP transaction.STP can instead be invoked by deﬁning a constant IPPROTO_STP ,with the value equal to the STP protocol number,and by replacing the use of IPPROTO_TCP above.All subsequent operations on the descriptor sockfd will then use an instance of the STP protocol.We have selected protocol number 11(allocated to the now-defunct Network V oice Protocol)as the STP protocol number,although it would be ﬁne to allocate a number from the free space.3.1Socket buffer sizesIn order to sustain high throughput over satellite channels,the socket buffers must be set to a value larger than the kernel defaults.In BSD systems,the SO_SNDBUF and SO_RCVBUF socket options typically default to 64KB.The setsockopt()system call can raise this limit on a per-socket basis;the maximum socket buffer size is implementation dependent.3.2Conﬁguration optionsThere are a number of conﬁguration options that affect the performance and operation of the protocol.All conﬁguration options are listed in the ﬁle stp.h ,but we summarize here a few of the main options and their implications.If any of these options are desired to be accessible and changeable without recompiling the kernel,they can be added as ioctls .3.2.1Flow controlWINDOW_CONTROL Set to 1if TCP-like window control is to be used.Mutually exclusive with RATE–SDP_THRESHOLD When opening up the window,this constant tells the transmitter to POLL at the end of each burst of data.–IDLE_RESTART Number of seconds of idle time after which the sender should reset the congestion window to its initial value.RATE_CONTROL Set to1if an explicit sending RATE is to be used.Mutually exclusive with WINDOW1Yahoo,AOL,Microsoft,Excite,Altavista,CNN,Xoom,,Lycos,and Amazon.servers OtherclientsFigure3:Illustration of the environment used for performance experiments.5SummaryThe Satellite Transport Protocol is speciﬁcally designed to outperform TCP in environments characterized by either high bandwidth-delay products,high bit error rates,or bandwidth asymmetry(or a combination of the above).The main differ-ence between STP and TCP is how the two protocols acknowledge data–STP attempts to acknowledge data as infrequently as possible while still offering rapid recovery from losses in the data transfer.The tradeoff between the two(rapid recovery from errors and reverse channel efﬁciency)can be tuned by optimizing the frequency and conditions under which the data transmitter sends POLL packets to the receiver.5.1Lessons learnedBased on experience with this protocol,the following recommendations are offered on using STP:1.If the objective is to only perform a protocol conversion between TCP and STP,operating in split mode(i.e.,not go-ing through any application),it would be better to modify this implementation to perform the split entirely in-kernel.Essentially what must be done is to allow a TCP and a STP connection to share a single send/receive buffer and co-ordinate access between the two.For example,in passing a packet from a TCP connection to a STP connection,passa pointer to the received packet.STP can then overwrite the header information and now“owns”the packet,but nomemory-to-memory copies are needed.2.There does not appear to be much of an advantage over TCP when using STP to tie Web caches together,because thenature of data transfer between proxies for most object-laden Web pages is that packets between the caches dribble through at the rate at which they are received from the Internet,and more frequent ACKing(POLLing)is therefore required to sustain the connection.In such a case,it would be worthwhile to consider a different type of application that gathered up whole pages,perhaps compressed them,and sent the whole page as a unit to the cache;i.e.,turn the data into more of a bulk transfer,which is what STP excels at.In the extreme,if the channel were not very lossy it may be worthwhile to consider running an application-level protocol sending such complete pages over UDP,thereby avoiding the socket buffer kernel resources that reliable streaming protocols like TCP and STP require.A Appendix:Additional implementation informationThis appendix provides additional information,although the code is the best source.Figure4illustrates the STP states and the main state transitions between them.Not all possible state transitions are shown,only the main ones that indicate in general how a state is reached.Typical stimuli and responses that occur between state changes are illustrated.In addition,one of four main timers may be running in a state(BEGIN,END,KEEPALIVE(KA),or POLL).In italics next to the state bubble is the timer(if any)that is running in that state.Figure4:Illustration of the major state transitions in STP.Sequenced Data (SD) 15 16310source portdest. port typechecksum instancesequence number Unsolicited STAT (USTAT)list element 1list element 2source port dest. port type checksum instance sequence number 15 16310STAT list element 1list element 2list element n windowtimestamp 15 16310source port dest. port typechecksum instance sequence number END, ENDAKsource port dest. port type checksuminstance sequence number 15 16310timestamp POLLsource portdest. port type checksum instance sequence number15 16310window timestamp BGN, BGNAK Figure 5:Illustration of the key packet types in STP.Figure 5illustrates the key packet types used by STP.The ﬁelds are byte-aligned and the data portion of packets is 32-bit aligned.Above,we discussed the use of the SD,POLL,STAT,and USTAT packets.The BGN and BGNAK are used to open a connection,and the END and ENDAK are used to close a connection.Each packet contains a 12-byte common header that includes the source and destination port numbers (as in TCP),a type ﬁeld,a 24-bit sequence number,a 16-bit checksum,and an instance number (to distinguish between different connections that may happen to use the same port numbers).Certain packets are permitted to be concatenated for the purpose of conserving the number of packets transmitted;for example,an SD and a POLL packet may be concatenated,in which case the type ﬁeld is the logical “OR”of the SD and POLL values,and the POLL timestamp precedes the data.B Appendix:Relation of STP to other protocolsSTP is derived from the ATM-based link layer protocol known as SSCOP(Service Speciﬁc Connection Oriented Protocol) [ITU94].SSCOP was intended to become the end-to-end native transport protocol for ATM,but ATM has never been deployed end-to-end.SSCOP is currently used as the signaling link layer protocol in the Signaling AAL(SAAL),and as a link layer protocol for wideband CDMA networks.SSCOP itself is derived from two convergent research efforts in the late1980s:light-weight transport protocol research at AT&T Bell Laboratories by Sabnani,Netravali,and Roome(the so-called SNR transport protocol[Net90]),and satellite protocol research at COMSAT Laboratories[Mil86].Many of the features in satellite-optimized TCP can be found in STP.For example,the concept of selective negative ac-knowledgments are implemented in SCPS-TP(TCP for space communications)[Tra97].”Rate-pacing”TCP implementations and reductions in the amount of ACK trafﬁc were investigated by[Bal97].The expansion of TCP protocol syntax to handle large delay-bandwidth product links was standardized in Internet RFC1323[Jac92].The fast retransmit mechanism in TCP [Ste97]makes allﬁrst order loss recovery data-driven(although repeat losses in TCP are always handled by a timeout).The main difference between TCP and these satellite-optimized TCPs is that STP implements the desirable features as default pro-tocol behavior.In fact,such TCP extensions can be viewed as TCP evolving towards the basic STP design philosophy.As a result,the performance of suitably modiﬁed TCPs can approach that of STP over satellite channels.There have been many other transport protocols invented over the years.Rather than exhaustively comparing STP with all of them,I will brieﬂy discuss STP’s relation to two protocols explicitly designed for the satellite or related environments: the Network Block Transfer(NETBLT)protocol[Cla87]and the Xpress Transport Protocol(XTP)[Wea94].NETBLT is designed for largeﬁle transfers in which the application submits data to the network in large,ﬁxed block sizes called”buffers.”While NETBLT uses selective acknowledgments and supports rate controls in addition to window control,STP provides a byte streaming data service(which is more closely aligned with applications),has a looser coupling between protocol logic and timers(reducing reliance on accurate values of the RTT),offers reduced latency in protocol handshaking(making it suitable for small transfers),and incorporates dynamic congestion control.As for XTP,many of the design principles of STP are also reﬂected in XTP(such as transmitter driven acknowlegments,USTATs and”fastnaks,”selective acknowledgments).The main differences are that XTP has a much richer API(including multicast support)and exposes much more protocol policy to the applications,whereas STP was designed to meet the standard sockets API for unicast trafﬁc and is more optimized for bit-efﬁciency(such as smaller protocol headers).References:[Bal97]H.Balakrishnan,V.Padmanabhan,and R.Katz,”The Effects of Asymmetry on TCP Performance,”Proceedings of Third ACM/IEEE MobiCom Conference,pp.77-89,Sept.1997.[Cla87]D.Clark,mbert,and L.Zhang,”NETBLT:A Bulk Data Transfer Protocol,”Internet RFC998,1987.[ITU94]”B-ISDN Signaling ATM Adaptation Layer–Service Speciﬁc Connection Oriented Protocol,”ITU-T Recommen-dation Q.2110,1994.[Jac92]Jacobson,V.,R.Braden,and D.Borman,”TCP Extensions for High Performance,”Internet RFC1323,1992.[Mil86]ls,D.Chitre,H.Chong,and A.Agarwal,”A Joint COMSAT/NBS Experiment on Transport Protocol,”Proceedings of7th International Conference on Digital Satellite Communications(ICDSC),May1986.[Net90]ravali,W.Roome,and K.Sabnani,”Design and Implementation of a High-Speed Transport Protocol,”IEEE Transactions on Communications,vol.38,no.11,pp.2025-38,Nov.1990.[Ste97]Stevens,W.R.,”TCP Slow Start,Congestion Avoidance,Fast Retransmit,and Fast Recovery Algorithms,”Internet RFC2001,1997.[Tra97]E.Travis,W.Durst,and ler,”TCP Extensions for Space Communications,”Wireless Networks,vol.3,no. 5,pp.389-403,1997.[Wea94]A.Weaver,”Xpress Transport Protocol,Version4.0,”/netlab/xtp tutorial.ps, 1994.。

kafka的安全协议和认证

kafka的安全协议和认证Apache Kafka作为分布式流处理平台，提供了多种安全协议和认证机制以确保其在生产环境中的安全性。

以下是一些关键的安全措施：1. SSL/TLS协议：-用于网络层的加密通信，可以防止数据在传输过程中被窃取或篡改。

-在Kafka集群中启用SSL（Secure Sockets Layer）或TLS（Transport Layer Security）后，生产者、消费者以及Broker之间的所有网络流量都会被加密。

2. SASL (Simple Authentication and Security Layer) 认证：- SASL提供了一系列的身份验证机制，Kafka支持几种SASL认证机制，包括：- SASL/PLAIN：基于明文的简单认证机制，用户名和密码通过网络以明文形式发送，但在使用SSL/TLS的情况下可以保证安全。

-SASL/SCRAM-SHA-256 / SCRAM-SHA-512：更安全的认证方式，采用了Salted Challenge Response Authentication Mechanism (SCRAM)，对密码进行哈希处理，并且在认证过程中添加了随机挑战响应机制，即使密码泄露，也无法直接用作认证。

- SASL/GSSAPI (Kerberos)：适用于大型企业环境，采用Kerberos身份验证系统进行身份认证。

3. OAuthBearer Token机制：-自Kafka 0.10.2版本开始引入的支持OAuthBearer token的SASL 机制，允许使用现有的OAuth服务来授权访问Kafka集群。

4. IP白名单与ACL（Access Control List）：- Kafka也支持配置IP白名单，只允许特定IP地址范围内的客户端连接到Broker。

- ACL则用于精细控制不同用户或用户组对于Kafka Topic的操作权限，如读、写、创建、删除等操作。

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Transport Protocols and Client Server Applications P. Davids, R. Karabek 1.Motivation Common protocol performance evaluation and measurement focus primarily onthroughput. Apart from the fact that the maximum throughput of a protocol isnot only influenced by the employed transport mechanisms but also by the qual-ity of the protocol implementation and the performance of the machine, there isan other performance measure which is equally important: Transaction-rates inClient-Server application environments.

Transaction-oriented applications are of increasing importance with the growingdemand for data-bank applications and information services like for instance theworld wide web. Characteristic for such scenarios is the high number of transac-tions, that is request-response associations (i.e. data-bank queries), per time unit.Such transactions are usually extremely short-lived associations which are estab-lished at request time and are torn down after the reception of the response.

One obvious solution for such applications is the use of connectionless protocolssuch as UDP, because there is no explicit connection establishment and termina-tion. Unfortunately the use of connectionless protocols leads to additional over-head for applications, because error-detection and -recovery, (detection ofduplicate packets, retransmission of lost packets etc.) has to be carried out by theapplication. Especially the necessary timer management cannot be implementedefficiently in the application.

Therefore the predominantly employed transport protocol for transaction orient-ed applications is the connection oriented TCP protocol, even though this limitsthe performance of the application because of the additional overhead producedby the connection management (connection establishment and -teardown) andthe associated handshaking mechanism.

There are more advanced protocols which handle connection management (anderror recovery and detection mechanisms) more efficiently. Such a protocol is theXTP (eXpress transfer protocol) protocol, which was initially intended as an in-tegrated network and transport protocol. All network-layer functionality of XTPhas been dropped with the latest revision of XTP (which is currently being stan-dardized) so that in the future XTP will be a true transport protocol.

XTP features advanced connection management mechanisms such as fast con-nection establishment and teardown as well as optimized error mechanismswhich makes it especially suitable for transaction based applications.

2.Measurement Results To measure the protocol performance in environments with high transactionrates a 'transaction-generator' consisting of a simple server and a client applica-tion was employed. The server accepts incoming connections, receives a 100 bytemessage, 'echoes' it back to the client and terminates the connection. The Clientapplications opens a connection to the server, sends a message, waits for the re-ception of the response and closes the connection. This procedure is repeated inthe client and the server application for selectable number of times. The duration of these iterations and especially the mean transaction duration are measuredand gives an indication of the performance of the protocols in high transactionrate scenarios.

The measurements were carried out on two SUN IPX stations under SunOS 4.1.3connected by via Ethernet. Further measurements were carried out where thetwo stations were connected via a dedicated intermediate system [1], [3] whichintroduced variable delays, packet losses and/or packet duplications. As proto-cols the KRM (Kernel Reference Model) XTP3.6 and the standard TCP/IP imple-mentation of SunOS 4.1.3 were used.

For a small number of iterations the measurements showed similar transactiondurations for XTP and TCP (around 9 ms). The fact that the fast connection man-agement features of XTP did not lead to a better overall performance may be dueto the fact, that performance gains were cancelled out by the implementation de-ficiencies of the reference implementation.

The measurements showed radically different results when the number of itera-tions where increased. With XTP the transaction duration remained constant ataround 9.2 ms per transaction while it increased nearly linear to a mean durationof 28 ms with TCP. The duration for individual transactions at 10,000 iterationsis shown in figure 1.

Fig. 1: Transaction durations of XTP and TCPThere resulting maximum transaction rates (maximum number of transactionsper second) are shown in the following table: