ipv4 octets

cps = 100 2 flags = IPv4} the server_args line is used to configure the storage location of server files, that is, when tftp transmission is performed, all files are searched from this folder Step 1: modify the permissions of the required folder. The folder to be modified is the folder that stores the server file mentioned in the previous step. take my configuration file as an example to create a folder (sudo mkdir/tftpboot ), then, you can set it to

. Chapter 1 Introduction Studying the source code of a large project is like entering a new world with its own customs and language. It is useful to learn some major local customs in advance and try to communicate with the local residents instead of avoiding them. This chapter describes some common programming modes and techniques that you will often encounter in some network code. If possible, I encourage you to try to use a user space tool to interact with some code on a specific network. I

[3adb99eb4207ae5256632eecb8f8b4855])/* + OK indicates that the command is successful, and the subsequent information varies with the Server */ C: USER bripengandre/* plaintext authentication */ S: + OK core mail C: PASS Pop3world/* Send email password */ S: + OK 654 message (s) [30930370 byte (s)]/* authentication successful, transfer to processing status */ C: LIST 1/* display the information of the first email */ S: + OK 1 5184./* The first mail size is 5184 bytes */ C: UIDL 1/* return the un

the content to #/et C/default/tftpd-hpa TFTP_USERNAME = "tftp" TFTP_DIRECTORY = "/tftpboot" # This is the working directory of your tftp server. Modify it by yourself. Note that when creating a working directory, it is recommended to modify the permission to 777. Run the sudo chmod 777/tftpboot TFTP_ADDRESS = "0.0.0.0: 69" TFTP_OPTIONS = "-l-c-s" Step 4th: Enter xinetd. d folder (cd xinetd. d) check whether there is a tftp file. If not, create a new file. If yes, check whether the content is co

. confecho "net. ipv4.tcp _ syncookies = 1 ">/etc/sysctl. confsysctl-p # modify the configuration file vi/etc/login. defsPASS_MAX_DAYS 90 # maximum number of days for creating a user's password PASS_MIN_DAYS 0 # minimum number of days for creating a user's password PASS_WARN_AGE 7 # Number of days for reminding new users of Password Expiration PASS_MIN_LEN 9 # Minimum Password Length: 9-5. restrict which accounts can switch to root1) # vi/etc/pam. d/s

no # adjust yes # adjust no # Compression delayed # ClientAliveInterval 0 # Prepare 3 # ShowPatchLevel no # UseDNS yesuseno # Do not use DNS # PidFile/var/run/sshd. pid # MaxStartups :30:100 # PermitTunnel no # ChrootDirectory none # no default banner path # Banner none # override default of no subsystemsSubsystem sftp/usr/libexec/openssh/sftp-server # Example of overriding settings on a per-user basis # Match User anoncvs # X11Forwarding no # AllowTcpForwarding no # ForceCommand cvs server Res

packets. 1000 2000 /proc/sys/net/core/somaxconn Defines the length of the maximum listening queue for each port in the system, which is a global parameter. 128 2048 /proc/sys/net/core/optmem_max Represents the size of the maximum buffer allowed for each socket. 20480 81920 /proc/sys/net/ipv4/tcp_mem Determine how the TCP stack should reflect memory usage, and each

. conf. It usesVariable = ValueTo set the value. The specified value is set after the system enters multi-user mode. Not all variables can be set in this mode.The sysctl variable is usually set as a string, number, or Boolean. (Boolean1To indicate 'yes', use0To 'no ').Sysctl-W kernel. sysrq = 0Sysctl-W kernel. core_uses_pid = 1Sysctl-W net. ipv4.conf. Default. accept_redirects = 0Sysctl-W net. ipv4.conf. De

= Poplib. Pop3_ssl (self.pophost) self.mailLink.set_debuglevel (0) self.mailLink.user (self.username) Self.mailLink.pass_ (Self.password) self.mailLink.list () print u ' login success! ' Except Exception as E: print u ' login fail! ' + str (e) quit () When you log in to a mailbox, it's natural that we need to provide a username and password, as shown in the code above, which is very simple to use.After the login mailbox is successful, we can use the list method to get mail inform

) self.mailLink.user (self.username) Self.mailLink.pass_ (Self.password) self.mailLink.list () print u ' login success! ' Except Exception as E: print u ' login fail! ' + str (e) quit ()When you log in to a mailbox, it's natural that we need to provide a username and password, as shown in the code above, which is very simple to use.After the login mailbox is successful, we can use the list method to get mail information for

. The Nth message is specified as N. In POP3 commands and responses, the message number and length are in decimal format. The following is a summary of the above three commands: 　 Command Format Parameters Restrictions Response Example User Name Specifies the mailbox string, which is critical to the server Only when the user and PASS commands fail or are in the "OK" status + OK: valid email address;-Err: invalid email address C: User mroseS: + OK mrose i

allowed to be sent to a queue when each network interface receives a packet at a rate that is faster than the rate at which the kernel processes these packets. 1000 2000 /proc/sys/net/core/somaxconn Defines the length of the maximum listening queue for each port in the system, which is a global parameter. 128 2048 /proc/sys/net/core/optmem_max Represents the size of the maximum buffer allow

Two key transition technologies of metropolitan Area Network IPv6 transition Technology--nat444 and ds-lite, what are the basic factors to be considered when choosing two kinds of transition technologies? This blog post will give you a detailed description of the rationale for both technical solutions and how to deploy them later. The large number of broadband users in the metropolitan area Network is the main force that consumes the network IPV4 add

With the depletion of IPv4 addresses, IPv6 is necessary for application. However, most networks around the world are still using IPv4, so the transition from IPv6 to IPv4 must be gradual, which is a relatively slow process, in this case, we need to use the IPv6 Tunneling Technology to connect the IPv4 network with the

The network is called a network because of its large system and there are no isolated islands. With the use of IPv6, there is a small island in the network. In order to connect networks of the two protocol versions, we need to use the IPv4/IPv6 Tunneling mechanism to accomplish this arduous task. How can we achieve this? Next we will explain in detail the tunneling technology. Tunneling Technology Before an IPv6 network completely replaces an

In order to better integrate IPv4 and IPv6 protocols, we have adopted many technologies for intercommunication between the two networks. First, let's introduce the tunneling technology. And some related transitional technologies. Tunneling Technology Before an IPv6 network completely replaces an IPv4 network, some access network technologies first have an IPv6 protocol stack. Generally, in the early stage o

[IPv6] Detailed description of ISATAP tunnel technologyI. Basic ConceptsISATAP (Intra-SiteAutomatic Tunnel Addressing Protocol)ISATAP is an IPv6 transition mechanism that is easy to deploy and use. In an IPv4 network, we can easily deploy ISATAP. First, you need a V4/V6 dual-stack PC. Then, you need a vro that supports ISATAP, the ISATAP router can be anywhere in the network, as long as the PC can ping it (of course, you need to know the

package as if it didn't receive the package, the REJECT will send a "Destination Unreachable" icmp request to the Request Host while dropping the package. Ping host A on host B. At this time, we will find that the response speed of the "Destination Unreachable" icmp packet is very timely. Run the following command on host: Echo "1000">/proc/sys/net/ipv4/icmp_destunreach_rate That is, an "Destination Unreachable" icmp packet is returned every 10 se

ISATAP is an IPv6 transition mechanism that is easy to deploy and use. In an IPv4 network, we can easily deploy ISATAP. First, you need a V4/V6 dual-stack PC. Then, you need a vro that supports ISATAP, the ISATAP router can be anywhere in the network, as long as the PC can ping it (of course, you need to know the IPv4 address of the router ). Next, we can deploy isatap on the vro to support ISATAP dual-stac

running. Available kernel parameters are in the/proc/sys directory. It includes some advanced options for TCP/IP stacks and virtual memory systems, which allows experienced administrators to improve system performance. You can use sysctl to read more than five hundred system variables. the conf setting is a sysctl still circulating on the network. conf optimizes the configuration of sysctl. conf setting # disable the packet filtering function. net. ipv4