hdlc

OSPF process.Xi. conditions for establishing a neighbour: The IP address of both interfaces in the chain is the same network, the subnet mask Same MTU Certified by In the same area In the case of special areas, such as stubs and Nssa, all routers in this area need to be configured. Hello and dead Time consistent Consistent network type 12: OSPF Network type Broadcast Type network: The election of the DR, the link layer protocol is Ethernet, the def

application of the polynomial:Figure 2 PPP frame formatFigure 3 Mac frame formatas can be seen from figures 2 and 3, CRC-16 is applied to PPP frames (16-bit Crc-ccitt for HDLC links) and CRC-32 to Mac frames. Moreover, CRC-32 is more reliable than CRC-16. ----------------------------------------------------------------------------------- The dividing line of God ------------ ------------------------------------------------------------------This secti

, HDLC, PPP, STP, Frame relay, etc., and the device in use, such as a switch switch, belongs to this layer. Network layer: The network layer is responsible for routing, grouping, and reorganizing data between subnets. The unit of data transfer in this layer is a packet (packet). The specifications that belong to this layer are IP, IPX, RIP, OSPF, ICMP, IGMP, and so on.Devices that are actually in use, such as routers, belong to this layer.Transport La

Hierarchy name function Agreement Application tier (Application layer) Responsible for implementing all application-related functions, corresponding to the upper three layers of the OSI reference Model FTP (File Transfer Protocol) HTTP (Hypertext Transfer Protocol) DNS (domain Name Server protocol) SMTP (Simple Mail Transfer Protocol) NFS (Network File System protocol) The Transport layer (Transport layer) Responsible for providing reliable

ISO's Open Internet model (OSI)The OSI (open System Interconnection) Open Systems Interconnect model is a network tiering model defined by ISO (International Organization for Standardization), a total Seven layers .1. Physical layers (physical layer) : The physical layer defines the specifications for all electronic and physical devices, providing a physical medium for the transfer of the upper layer, with bits (bit) in the data Transfer unit. The specifications belonging to the definition of t

OSI (open System Interconnection), open Systems Interconnect Reference Model. From bottom to top seven-tier model features and their representative protocols: Physical Layer (physical) : Specifies the mechanical, electrical, functional, and process characteristics that activate, maintain, and close communication endpoints. This layer provides a physical medium for the upper level protocol to transmit data. bit, bit. Typical protocol representatives: eia/tia-232, eia/tia-499, v.35, v.24, RJ45

TCP/IP is synonymous with a set of protocols, and it also includes many protocols that make up the TCP/IP protocol cluster.TCP/IP protocol cluster is divided into four layers, IP is located in the second layer of the Protocol cluster (corresponding to the third layer of OSI), TCP is located in the third layer of the Protocol cluster (corresponding to the fourth layer of OSI).TCP and IP are the middle two layers of TCP-IP protocol cluster, which is the core of the whole protocol cluster, which pl

In the OSI Reference Model, from bottom to top, each layer accomplishes different, targeted functions. 1. Physical layer (physical layers)The physical layer specifies the mechanical, electrical, functional, and process characteristics that activate, maintain, and close communication endpoints. This layer provides a physical medium for the upper level protocol to transmit data. in this layer, the unit of data is called the bit (bit). Typical canonical representatives belonging to the physical lay

, the International Organization for Standardization (ISO) introduced the "Open Systems Interconnection Reference Model" in 1978, the famous OSI/RM model (open system Interconnection/reference Model). It divides the communication protocol of the computer network architecture into seven layers, from bottom to top: the physical layer (Physics layer), the data link layer, the network layer, the Transport layer (Transport layer), Session layer, Presentation layer (Presentation layer), Application la

attachment node in a packet-switched network . Rs-232-c are usually used for x. 21 interface. The link access layer defines the data transfer as a frame sequence. The protocol used is a balanced link access discipline (Lap-b), which is part of the Advanced Data Link Control (HDLC) protocol. The lap-b is designed for Point-to-point connections. It provides frame structure, error checking, and flow control mechanisms for asynchronous balanced mode sess

The CRC is based on a checksum of modulo 2 operations.N=k+r.n is the length of the CRC code, K is the number of bits of the information code, and R is the number of bits of the checksum code.2 R-Square >=k+r+1 (correct).4 Useful information (1100) as a cyclic encoding, choose to generate a polynomial g (X) = 1011.1. Move the information bit to the left r bit, i.e. add R 0 after the information bit.Get 1100000.2. Use 1100000 pairs of G (X) for modulo 2 to divide.Get the remainder 010.3. Modulo 2

A few words to master subnet mask, IP address, host number, network number, network address, broadcast address1, 191.172.16.10.33/27 in the/27 that is, the subnet mask is 255.255.255.224 that is 27 full 12. From the subnet mask 255.255.255.252 to obtain its network bit is 30 bits, so only the remaining 2-bit master, the host bit of all zeros for the network address, the host bit all 1 is the broadcast address, the remaining host number is the host address range3. Public address is the responsibi

reliable data transmission services for data transmission without errors. The unit of data in the data link layer is frame ). The specifications defined in this layer include SDLC, HDLC, PPP, STP, and Frame Relay. actually used devices, such as switch switches, belong to this layer. Q Network layer: the network layer is responsible for routing, grouping, and restructuring data between subnets. The unit of data transmission in this layer is packet ).

value is PVID = 1.Therefore, set the pvid to the vlanid and the vlan that can be interconnected as untagged. Huawei vro Switch configuration command: vro command[Quidway] displayversion; displays version information[Quidway] displaycurrent-configuration; displays the current configuration[Quidway] displayinterfaces; display interface information[Quidway] displayiproute; displays route information[Quidway] sysnameaabbcc; change the Host Name[Quidway] superpasswrod123456; set the password[Quidway

, and Point-to-MultiPoint ). Broadcast Multi-Channel Access networks such as Ethernet, Token Ring, and FDDI. NBMA networks such as Frame Relay, X.25, and SMDS. Point-to-Point networks such as PPP and HDLC. The specific structure is shown in the following figure. Comparison between OSPF and RIP: Limitations of r00001 arising from the use of large networks: 1. 15 hop limitations of RIP, routes with more than 15 hops are considered inaccessible. 2. RIP c

The relationship between the router and the network layer the main purpose of the router is to connect multiple networks and forward data packets to their own network or other networks. Because the main forwarding decision of a vro is based on layer-7 IP data packets (that is, based on the destination IP address), The vro is considered as a layer-7 device. The process of making a decision is called routing. When the router www.2cto.com receives the packet, it checks its destination IP address. I

HubLayer 2: Data Link Layer) Based on the bit stream service provided by the physical layer, data links between adjacent nodes are established, and data frames (frames) are transmitted without errors on the channel through error control, and action series on each circuit are carried out. 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 detection, and re-

, AFP, and NCP 5 session layers such as ASAP, TLS, ssh, ISO 8327/CCITT x.225, RPC, NETBIOS, ASP, WinSock, BSD sockets 4. Transport Layer, such as TCP, UDP, RTP, sctp, SPX, ATP, and IL 3 network layers such as IP, ICMP, IGMP, IPX, BGP, OSPF, Rip, IGRP, VPN, ARP, RARP, and X.25 2. data link layer, such as Ethernet, Token Ring, HDLc, frame relay, ISDN, ATM, 802.11 WiFi, FDDI, and PPP 1 physical layer such as wire, radio, fiber optic, and carrier pigeon T

supports the following network interfaces: Lo Local loopback interface. Each machine has this interface with the IP address 127.0.0.1. Ethn (n> = 0) Ethernet interface. N is an integer starting from 0. Eth0 is the first Ethernet interface and eth1 is the second network interface. Fddin (n> = 0) FDDI (optical fiber distributed digital interface) interface, where n is an integer starting from 0. Pppn (n> = 0) PPP (Point-to-Point Protocol) interface, where n is an integer starting from 0. Slin (n>

://sec.chinabyte.com/170/11012670.shtml Http://book.51cto.com/art/200807/81191.htm Http://www.2cto.com/net/201112/112743.html Network Layer: Protocol: IP (Internet Protocol): network Protocol ARP (Address Resolution Protocol): Address Resolution ProtocolRARP (Reverse Address Resolution Protocol): Reverse Address Resolution ProtocolICMP (Internet Control Message Protocol): Internet Control Message ProtocolIGMP (Internet Group Manage Protocol): Internet Group Management ProtocolBOOTP (Bootstrap):