Protocol in General Outline. What is protocol. Why using protocol. What kind of Protocols are there.

Transcription

1 Protocol in General Information Network Center Beijing University of Posts and Telecommunications Sept Outline An overview on protocols Well-known protocol stacks Protocol mechanisms Protocol specification Protocol evaluation Standards What is protocol Why using protocol a set of rules to insure the information to be transferred between communication parties [a set of conventions governing the treatment and especially the formatting of data in an electronic communications system] defined by Webster. col&ct= It could be implemented by hardware or software Productivity: easy to implement by groups Lower cost: network resource sharing Compatibility: world-wide reachability Connectivity Strategic benefits... What kind of Protocols are there Asynchronous: Byte Xon/Xoff, KERMIT, Xmodem serious,... Synchronous: bit/binary SDLC, HDLC, BSC, X.25, ISDN, Layered Protocol OSI structure 1 ~ 7: phy ~ appl. TCP/IP Vendor specific / Standard: proprietary / de facto Computer network / Telecommunication Network

2 Major Standard Organizations and their contribution to communication system Major Protocol Stacks ISO ITU-T ( CCITT ) IEEE IETF IEE ANSI ETSI EIA DAVIC ATM Forum Frame Relay Forum TINAC MMCF NMF W3C Organization: Protocol ISO: OSI/rm IETF: TCP/IP IBM: SNA DEC: DECnet Novell: IPX/SPX Apple: Appletalk... IETF ( the Internet Engineering Task Force OSI 协议分层模型 Working groups classified into those dynamic changing areas Applications Area (APPS) General Area (GEN) Internet Area (INT) Operational Requirements Area (OPS) Real-time Applications and Infrastructure Area (RAIA) Routing Area (RTG) Security Area (SEC) Transport Area (TSV) System A Application Presentation Session Transport Network Data link Physical 网关 Gateway Router Bridge/Sw Hub 网关 Gateway Router Bridge/Sw Hub System B Application Presentation Session Transport Network Data link Physical 信息打包传送 : 从 A 到 B Functions of lower 3 layers in OSI 以太网 Hello, World. A= 数据 T 数据 I T 数据 I T 数据 令牌环网 B= 数据 T 数据 I T 数据 I T 数据 1.Physical Layer: responsible for the mechanical and electrical interface to the communications media. 2.Data Link Layer: responsible for the transmission, framing and error control over a single communications link. 3.Network Layer: responsible for the data transfer across the network, independent of both the media comprising the underlying subnetworks and topology of those sub-networks

3 Functions of upper layer 4 in OSI Telecommunications Network 4.Transport Layer: responsible for the reliability and multiplexing of data transfer across the network to the level provided by the application. 5.Session Layer: provides the management and data flow control services. 6.Presentation Layer: provide a common representation of application layer data. Basically responsible for adding structures to the units of data that are exchanged. 7.Application Layer: layer where the Goal of OSI is realized. Ultimately responsible for managing the communications between applications. Standard body --- ITU-T SS7 over IP signaling transport: RFC2719 (IETF) Examples SS7 V.xx X.xx I.xxx Q.xxxx SS7 Stack SS7 Protocols MTP-1: Message Transfer Part Level 1 MTP-2: Message Transfer Part Level 2 MTP-3: Message Transfer Part Level 3 SCCP: Signaling Connection Control Part ISUP: ISDN User Part TCAP: Transaction Capabilities Application Part MAP: Mobile Application Part DUP: Data User Part TCP/IP TCP/IP with OSI 3

4 Protocol for Computer Network Data Link Layer Protocols LAN Ethernet FDDI WAN Frame Relay ISDN ATM Asynchronous protocols XMODEM YMODEM ZMODEM BLAST Kermit Synchronous protocols BSC HDLC SDLC A HyperTerm protocol selection window Xmodem data block Xmodem data block How Xmodem works Confirmation Error free data exchange Negative Acknowledgement End of Transmission 4

5 Error correction Data Link Layer 1) data exchange with error correction ARP/RARP - Address Resolution Protocol/Reverse Address 2) data exchange with error correction 10 s t Network Layer Routing IP - Internet Protocol DHCP - Dynamic Host Configuration Protocol. ICMP / ICMPv6 - Internet Control Message Protocol. IGMP - Internet Group Management Protocol. MARS - Multicast Address Resolution Server. PIM - Protocol Independent Multicast-Sparse Mode (PIM-SM) RIP1/RIP2 - Routing Information Protocol. RIPng for IPv6. RSVP - Resource Reservation Protocol. VRRP - Virtual Router Redundancy Protocol RIP BGP-4 - Border Gateway Protocol. EGP - Exterior Gateway Protocol. HSRP - Cisco Hot Standby Router Protocol. IGRP - Interior Gateway Routing. NARP - NBMA Address Resolution Protocol NHRP - Next Hop Resolution Protocol. OSPF - Open Shortest Path First. Transport Layer Application Layer TCP - Transmission Control Protocol UDP - User Data Protocol Finger: User Information Protocol. Van Jacobson - compressed TCP. XOT - X.25 over TCP MPTCP - Multipath TCP SCPT XTP TELNET. COPS - Common Open Policy Service FTP - File Transfer Protocol. TFTP - Trivial File Transfer Protocol. HTTP - Hypertext Transfer Protocol. S-HTTP - Secure Hypertext Transfer Protocol. IMAP4 - Internet Message Access Protocol rev 4. IPDC - IP Device Control. ISAKMP - Internet Message Access Protocol version 4rev1. NTP - Network Time Protocol. POP3 - Post Office Protocol version 3. Radius. RLOGIN - Remote Login. RTSP - Real-time Streaming Protocol. SMTP - Simple Mail Transfer Protocol. SNMP - Simple Network Management Protocol. SOCKS TACACS+. WCCP - Web Cache Coordination Protocol 5

6 How Protocol Works Address Communication parties-address Language-code to be used Data structure/ PDU Interface definition Entities obey a set of rules ensure communication process success Routing Error control Congestion control Multiplexing/de-multiplexing Management others Each party involved in the communication process should be uniquely identified Each entity in the protocol stack has its unique address Each protocol has its unique way of addressing Each address type could be mapped with other types in some ways Communication Phase Communication Phase LINK INITIALIZATION INFORMATION TRANSFER Single direction or bi-direction FLOW CONTROL Stop-and-wait Sliding window ERROR DETECTION ARQ (Automatic repeat request) ERROR RECOVERY Retransmission Correct on service side LINK TERMINATION Benefits Error handling method Layered structure Benefits from layered structure: simplify the task to design implement maintain Redundant information required! parity ODD EVEN group,... Hamming code CRC Checksum... 6

7 Protocol specification API - Application Programming Interface Standards-description: Text / Flow chart Natural Language Pseudocode SDL Documentation and Implementation Example Function description interface form parameter description Return value Error code Other references program example Berkeley Sockets Connection-Oriented Socket Communication Primitive SOCKET BIND LISTEN ACCEPT CONNECT SEND RECEIVE CLOSE Meaning Create a new communication end point Attach a local address to a socket Announce willingness to accept connections; give queue size Block the caller until a connection attempt arrives Actively attempt to establish a connection Send some data over the connection Receive some data from the connection Release the connection Winsock Example WSARecv() Example WSARecv() Parameter Description Function description:receive data from a socket Header file :#include <winsock2.h> Interface form: int WSAAPI WSARecv ( SOCKET s, LPWSABUF lpbuffers, DWORD dwbuffercount, LPDWORD lpnumberofbytesrecvd, LPINT lpflags, LPWSAOVERLAPPED lpoverlapped, L P W S A O V E R L A P P E D _ C O M P L E T I O N _ R O U T I N E lpcompletionroutine ); s: 一个标识已连接套接口的描述字 lpbuffers: 一个指向 WSABUF 结构数组的指针 每一个 WSABUF 结构包含一个缓冲区的指针和缓冲区的长度 dwbuffercount:lpbuffers 数组中 WSABUF 结构的数目 lpnumberofbytesrecvd: 如果接收操作立即结束, 一个指向本调用所接收的字节数的指针 lpflags: 一个指向标志位的指针 lpoverlapped: 一个指向 WSAOVERLAPPED 结构的指针 ( 对于非重叠套接口则忽略 ) lpcompletionroutine: 一个指向接收操作结束后调用的例程的指针 ( 对于非重叠套接口则忽略 ) 7

8 Example WSARecv() Return Value Example WSARecv() Error code 若无错误发生且接收操作立即完成, 则 WSARecv() 函数返回所接收的字节数 如果连接结束, 则返回 0 请注意在这种情况下完成指示 ( 启动指定的完成例程或设置一个事件对象 ) 将早已发生 否则的话, 将返回 SOCKET_ERROR 错误, 应用程序可通过 WSAGetLastError() 来获取相应的错误代码 错误代码 WSA_IO_PENDING 表示重叠操作成功启动, 过后将有完成指示 任何其他的错误表示重叠操作未能成功地启动, 以后也不会有完成指示 如果设置了 MSG_INTERRUPT 标志, 则返回值的含义变化 零表示成功, 具体含义同上 否则的话, 返回值直接包含如下所示的错误代码 由于中断环境中无法调用 WSAGetLastError(), 故是必需的 请注意仅适用于 Win16 环境, 仅适用于 PROTOCOL_INFO 结构中设置了 XP1_INTERRUPT 位的协议 WSANOTINITIALISED 在调用本 API 之前应成功调用 WSAStartup() WSAENETDOWN 网络子系统失效 WSAENOTCONN 套接口未连接 WSAEINTR 通过 WSACancelBlockingCall() 函数取消 ( 阻塞 ) 调用 WSAEINPROGRESS 一个阻塞的 WinSock 调用正在进行中, 或者服务提供者仍在处理一个回调函数 WSAENETRESET 由于远端的复位造成连接的中止 WSAENOTSOCK 描述字不是一个套接口 WSAEOPNOTSUPP 设置了 MSG_OOB, 但是该套接口不是诸如 SOCK_STREAM 流类型的, 与套接口相关的通讯域不支持带外数据, 或者套接口是单向的, 只支持发送操作 WSAESHUTDOWN 套接口已经关闭 ; 一个套接口以 SD_RECEIVE 或 SD_BOTH 的 how 参数 shutdown() 后, 无法进行 WSARecv() 调用 WSAEWOULDBLOCK 重叠套接口 : 太多重叠的输入 / 输出请求 非重叠套接口 : 套接口被标志为非阻塞, 但是操作不能立即完成 WSAEINVAL 套接口未用 bind() 捆绑, 或者套接口未用重叠标志创建 WSAECONNABORTED 由于超时或其他错误导致虚电路中止 WSAECONNRESET 虚电路被远端复位 WSAEDISCON 远端优雅的结束了连接 WSA_IO_PENDING 成功启动一个重叠操作, 过后将有完成指示 Example WSARecv() Other references Well-known Ports (0~1024) WSACloseEvent(), WSACreateEvent(), WSAGetOverlappedResult(), WSASocket(), WSAWaitForMultipleEvents() Port 7: Echo Echo Request Port 21: FTP File transfer Port 23: Telnet Remote login Port 25: SMTP Port 69: TFTP Trivial File Transfer Protocol Port 80: HTTP World Wide Web Port 110: POP-3 Remote access Protocol Evaluation A protocol tester framework Standardization Robustness Efficiency Performance Availability Cost for implementation Interface / API Test channel Main test port 8

9 Test environment Protocol testing and evaluation tools General purpose Specific protocol tester and analyzer Appearance: dedicated hardware + software Protocol analyzer Probe PC + software Protocol analyzer Sniffer Ethereal General purpose Specific protocol tester and analyzer Versatile to development environment Need professional skill to operate Relatively higher cost Example: LAN protocol analyzer Telecommunication network protocol tester and analyzer Dedicated purpose Ease to operate Low cost Example: RS-232 tester ISDN tester and analyzer GSM tester WinSock Peek Appearance RS232 tester Dedicated hardware + software Protocol analyzer Vendors: HP(Agilent), WWG, NAI, RAD, shomiti,,... Probe IP Network equipment vendor specific: Nortel, 3Com,... 9

10 PC based protocol analyzer Protocol Analysis and inspection Network protocol analyzer High-performance monitoring Troubleshooting Simulation in internetworking environments System development Protocol analyzer Xray EtherBoy EtherPeek Sniffer DPI (Deep packet inspection) Protocol call monitor Application Transport Winsock IP Data Link Physics TTCN-3 Language TTCN-3 example TTCN (Tree and Tabular Combined Notation) TTCN-3 (Testing and Test Control Notation): A flexible and powerful language applicable to the specification of all types of reactive system tests over a variety of communication interfaces. Typical areas of application protocol testing (including mobile and Internet protocols) service testing (including supplementary services) module testing testing of CORBA based platforms, API testing etc. TTCN-3 is applicable to conformance, interoperability, robustness, regression, system and integration testing. Test User 10

11 Other issues Summary Protocol engineering: design/specification/description/formalization/ evaluation/simulation/modeling/implementatio n/security/... Protocol test: conformance/interoperability/performance/an alyze/verification/ Overview on protocols Reference models (OSI, TCP/IP) Well-known protocols Protocol mechanisms Protocol specification Protocol evaluation Standardization Questions and exercises References If you design a protocol, what steps should you proceed? How to balance the functionality and layered structure when design a protocol? How to involved in the protocol standardization processes? The importance to using a standard protocol? (socket programming) 11