Database System Engineer - Network Fundamentals test center notes

Chapter V networking basics
    related protocols
        TCP is the fourth layer (transport layer) of the Transmission Control Protocol;
        IP is the third layer (network layer) protocol
        IPSec is the third layer (network layer) VPN protocols
        PPOE work in the second layer 2 (data link layer)
        the SSL security protocol to work on TCP protocol
    FTP transmission needs to establish
        a control connection: file transfer command requested by the client to the server
        2, the data connection: transfer files from the active mode server active connections, passive mode waits for a client to connect to
    a port number
        port number: service process: Note
        20: FTP: file transfer protocol (data link)
        21: the FTP: file transfer protocol (control connection)
        23: TELNET: virtual terminal network
        25: SMTP: simple Mail transfer protocol
        53: DNS: domain Name server
        80: HTTP: hypertext transfer protocol
        110: POP3: Post Office protocol (simple Mail read)
        111: the RPC: remote procedure call
        143: IMAP: interactive access protocol (packet access)
    e-commerce transactions
        can determine the identity of an entity by means of authentication, to prevent one entity pretends to be another entity;
        Combined authentication and authorization, modify the data to others can be prevented from unauthorized destruction;
        protect the confidentiality of information can prevent the information from leaking out of the supervisors in the communication process.
        Lai resistance and prevent a party involved in the transaction of the transaction denied that there had been
    network security technology
        to protect information accessed by the user identification and authentication, user access control, security monitoring systems, computer virus prevention, data encryption
        related technology
            1, the VPN technology
                through the tunnel; two internal network via the public network connection, making it a general network
            2, firewall technology
                type
                    1, packet filtering firewall (screening routers): the route is placed in the internal network, the network layer security
                    2, application proxy firewall
                        is dual-homed host firewall, the security application layer
                    3, the state detection technology firewall: Combining the above two techniques, as for shielding the external network router, bis As host internal network
                    4, screened subnet firewall: set DMZ (demilitarized zone) and made of dual-homed router shielding means
    multimode fiber characteristics of
        low cost, wide core, concentrating, dissipate large inefficient for low-speed communication over short distances.
    The characteristics of single-mode fiber
        High cost, narrow core, needs a laser light source, a small dissipation, high efficiency, for high-speed long-distance communication
    ping command
        determines the user communicates with the external sites
            1, ping127.0.0.1 (local address cycle), if not ping the machine then the TCP / IP protocol does not work
            2, ping + general Description machine does not present a network adapter (NIC / MODEM) fails
    netstat command
        to display TCP, UDP, IP, ICMP protocol-related statistics, generally used for testing of the present machine network connection port
    ARP command
        can examine and modify the local computer's ARP entries and view the ARP cache and resolving address resolution problems is very useful
    Tracert (trace route) is a route-tracing program for determining access to the target IP datagrams taken of the path, you can see which route to connection problems
    DHCP (dynamic host configuration protocol)
        for dynamic allocation of IP addresses the host network, the client uses the first to reach the DHCP server assigns default IP address
    Internet protocol
        TCP / IP protocol: is the core protocols of the Internet protocol, the basic characteristics (logical addressing, routing, domain name resolution protocol, Error detection and flow control)
        the ARP (Address Resolution Protocol) and the RARP (anti-ARP): the ARP translates the IP address to a physical address (MAC address) of
    a network design principles
        1, Advanced: the use of advanced technology
        2, practicality: The object of the mature and reliable technology and equipment used to achieve the effect of
        3, open: the network system using open standards and technologies
        4, economy: cost savings possible to meet the demand on the basis of
        5, HA / by : the system has a high MTBF, such as: financial, securities and other railway