hdlc

.25, PPP, HDLC, and other Wan protocols, provide transmission rates up to T1/E1, and provide network address translation (NAT) functions. Supports PAD (X.3, X.28, and X.29) protocols and provides password protection.Based on this network application scenario, you can select the 3Com OfficeConnect NETBuilder router, which is one of the most widely used models. OfficeConnect NETBuilder has a 10 BASE-T lanport (LAN port) and two WAN ports (WAN port ). Ea

support PPPOE. However, in 2.4.18, You need to enable the immature code of the kernel. The Kernel configuration is as follows: Code maturity level options --> [*] Prompt for development and/or incomplete code/drivers Networking options --> [*] Packet socket [*] Packet socket: mmapped io Network device support --> [*] Ppp (point-to-point protocol) support [*] Ppp multilink support (experimental) [*] Ppp filtering [*] Ppp support for async serial ports [*] Ppp support for sync tty ports [*] Ppp d

g (x) is the verification code FCS (frame check series ).Any code composed of binary strings can correspond to a polynomial with a coefficient of only '0' and a value of '1. For example, code 1010111 corresponds to a polynomial of X6 + X4 + X2 + x + 1, while a polynomial of code 101111 corresponds to X5 + X3 + X2 + x + 1.CRC verification is divided into many different standards based on the generated polynomials used. Common include:Example of name generation Polynomial CRC-4 X4 + x + 1 3 ITU g

rate is 115200bps. In synchronous mode, X.25, frame relay, PPP, HDLc, slip, lapb, and other link layer protocols support IP and IPX, while the highest transmission rate is only 64000bps. V.24 The cable interface is divided into the DCE and DTE sides, corresponding to the data circuit device (network side) and data terminal device (user side), corresponding to the DCE side is the socket (25 holes ), the DTE side is a plug (50-pin ). vrouters belong to

. Glossary (2 points for each question, 10 points in total)1. transparent transmission 2. half-duplex communication 3. Data Communication 4. QoS 5 and IPv4 address 4. Calculation questions (6 points for each question, 30 points in total)1. Briefly describe the main features and working principles of the 56k modem.2. Briefly describe the main content of network management.3. Briefly describe the principles and functions of VLANs.4. Illustrate the working principle and implementation process of vl

and division operations. The polynomial of CRC code generation is as follows, where CRC-16 and CRC-CCITT generate 16-bit CRC code, while CRC-32 produces 32-bit CRC codeThe receiver divides the number of received binary sequences (including the Information Code and CRC Code) by the polynomial. If the remainder is 0, no error occurs during transmission. Otherwise, the transmission is incorrect, I will not describe its principles here. When the CRC code is calculated using software, the receiver c

the same time, there is no gap between the transmitted characters, that is, the bit synchronization relationship is maintained, and the character synchronization relationship is also maintained. The sender can synchronize the receiver in two ways. In this case, data blocks are treated as data streams, and sequence 01111110 is used as the start and end signs. To avoid confusion caused by sequence 01111110 in the data stream, the sender always inserts an additional 0 in each of the five consecuti

will cause confusion, however, the OSI model is not complex enough to do better work. The following chart tries to display the positions of different TCP/IP and other protocols in the original OSI model: 7 Application Layer Such as HTTP, SMTP, SNMP, FTP, telnet, sip, ssh, NFS, RTSP, XMPP, Whois, ENRP 6 Presentation Layer For example, XDR, ASN.1, SMB, AFP, and NCP 5 Session Layer Such as ASAP, ssh, ISO 8327/CCITT x.225, RPC, NETBIOS, ASP, WinSock, BSD

protocols. PPP protocol details 1. PPP data frame Encapsulation The PPP protocol defines an encapsulation method for data transmitted over a serial link, which is based on the High-Level Data Link Control HDLC) standard. The format of the PPP data frame is 1. A ppp frame starts and ends with a flag character of 01111110. The address field is 1 byte in length, the content is standard broadcast address 11111111, and the control field is 00000011. The

for a period of time. Figure 1 CHAP CHAP has high requirements on the end system because it requires multiple identity questions and responses. This requires a lot of CPU resources, so it is only used in scenarios with high security requirements. Ppp chap configuration 3 CHAP Configuration 3.1 basic PPP Configuration For synchronous serial interfaces, the default Encapsulation Format is HDLCCisco private implementation ). You can use the encapsulation ppp command to change the encapsulation Fo

shutdown Ip address 192.168.1.2 255.255.255.0 Ip nat outside Encapsulation hdlc Ip nat pool bluegarden 192.16.1.10 192.168.50 prefix-length 24 Ip nat inside source list 1 pool bluegarden Router rip Version 2 Network 10.1.8.0 255.255.255.0 Passive-interface Serial 0 Access-list 1 permit 10.1.8.0 0.0.255 ! Ip classless ! Ip route 0.0.0.0 0.0.0.0 Serial 0 No ip http server Snmp-server community public RO No snmp-server location No snmp-server contact !

, maintenance, and exchange of information on physical connections. At this layer, the unit of data is bit ). Representative of typical specifications defined by the physical layer include: EIA/TIA RS-232, EIA/TIA RS-449, V.35, RJ-45, etc. Layer 2: data link layer (DataLinkLayer): establishes data links between adjacent nodes based on the bit stream service provided by the physical layer, and provides Frame transmission without errors through error control, and carries out the action series on e

physical layer:Repeaters, hubs.　　Second layer: Data link layer (datalinklayer)On the basis of providing the bit-stream service in the physical layer, the data link between adjacent nodes is established, and the data frame (frame) is transmitted without error on the channel through error control, and the action series on each circuit is carried out. The data link layer provides reliable transmission on unreliable physical media.　　The functions of this layer include: Physical address addressing,

(1) Various layers of the network Physical layer: RJ45, CLOCK, IEEE802.3 (Repeater, hub, Gateway)- Data link: PPP, FR, HDLC, VLAN, MAC (bridge, switch)- Network layer: IP, ICMP, ARP, RARP, OSPF, IPX, RIP, IGRP, (router)- Transport layer: TCP, UDP, SPX- Session layer: NFS, SQL, NETBIOS, RPC- Presentation layer: JPEG, MPEG, Asii- Application tier: FTP, DNS, Telnet, SMTP, HTTP, WWW, NFS (2) The biggest advantage of the switch is the fast

I. TCP/IP Protocols +- +-+| Http ftp telnet SMTP | DNS | snmp tftp nfs rpc |+- +-+| TCP | UDP |+- +-+| Icmp igmp |+-+ IP +-+ rip OSPF +| Arp/RARP |+- +-+| Ethernet (DIX/802.3) Token Ring (802.5) |++| FDDI X.25 slip ppp (HDLC) |+- +-+ Network Layer IP: Internet Protocol RFC 791 (v4) 1884 (v6)ICMP: Internet Control Message Protocol RFC 792 (v4) 1885 (v6)ARP: Address Resolution Protocol RFC 826.RARP: Reverse Address Resolution Protocol RFC 903IGMP: Inte

[yes]:Use the 100 Base-TX (RJ-45) connector? [Yes]:Operate in full-duplex mode? [No]:Configure IP on this interface? [No]: yesIP address for this interface: 6.0.0.1Number of bits in subnet field [0]:Class A network is 6.0.0.0, 0 subnet bits, mask is/8Configure IPX on this interface? [Yes]:IPX network number [1]:Need to select encapsulation type[0] SAP (IEEE 802.2)[1] Snap (IEEE 802.2 snap)[2] ARPA (ethernet_ii)[3] Novell-ether (Novell ethernet_802.3)Enter the encapsulation type [2]: Serial Inte

I. Summary PPP is a commonly used link protocol in ATM Networks. pppoa based on PPP protocol is indispensable in XDSL modem. This article briefly describes the frame Encapsulation Format of the PPP protocol, and provides a simple PPP encoding and decoding algorithm, hoping to be helpful to the consumers. II. Introduction to the PPP protocol The format of the PPP data frame looks like the iso hdlc (High-Level Data Link Control) standard. Is PPP dataFra

provides a physical media for the upper-layer protocol to transmit data. At this layer, the unit of data is bit ). Representative of typical specifications defined by the physical layer include: EIA/TIA RS-232, EIA/TIA RS-449, V.35, RJ-45, etc. 2. How do I perform each step of the Data Link Layer? The data link layer provides reliable transmission on unreliable physical media. The role of this layer includes physical address addressing, data frame formation, traffic control, data error detectio

these errors can be detected because if the register value is 0, 0 message bytes (or bits) are processed and sentThe memory value remains unchanged. To solve the first two problems, we only need to make the initial value of the Register not 0, and make the following improvements to do_crc:Unsigned short do_crc (unsigned short reg_init, unsigned char * message, unsigned int Len){Unsigned short crc_reg = reg_init;While (Len --)Crc_reg = (crc_reg> 8) ^ crc16_ccitt_table [(crc_reg ^ * message ++)

immediately without establishing a connection. After the data is sent, the connection is released. Therefore, it is simple and flexible to use connectionless data packets for communication. Connection-oriented and connectionless scenarios emphasize the stages of communication. Connection orientation must go through three phases: "establish connection> transmit data> release connection", while no connection has only one phase: "Transfer Data ". Circuit Switching and group switching emphasize