NetworkingRead Chapter 9 Linux network utilitiesfinger, ftp, host, hostname, mesg, rcp, rlogin, rsh, scp, sftp, slogin, ssh, talk, telnet, users, w, walla, who, write, ...1NetworkingImportant to know common network terminologyhow networks are builthow to talk to other people on the networkhow to use other computeras on the network2NetworkingLocal Area NetworksSimplest LAN 3NetworkingLocal Area NetworksEthernet (Standardized as IEEE 802.3)You have seen the RJ45 connectors4NetworkingBridgesBridge passes Ethernet message between different segments of the network as if both segments were a single Ethernet cable.Used when one has to go beyond the allowed length of a single section fo wire 5NetworkingRoutersRoute traffic to where it is needed. Or, does not route messages where they are not needed. Example of 4 networks: now argue router vs bridge6NetworkingGatewayHigh-capacity routers7InternetworkingPacket Switching and Circuit SwitchingCircuit Switching establish, maintain and terminate dedicated circuite.g., traditional telephone networksPacket Switchingnetwork nodes send messages that are split up into small packetspackets get routed from source to destination8InternetworkingPacket Switching IssuesHow big are the packetsHow do packets get routed, all along the same route or notWhat if packets get lost, arrive out of orderWhat if packet sizes changeWho’s packet is it?9InternetworkingMost of the Internet revolves around:Transmission Control Protocols (TCP/UDP)Internet Protocol (IP)10CS420/520 Axel Krings Sequence 17LAN Protocols in ContextInternetworkingInternet Protocol IPv4 Header12InternetworkingIP Address Formats13InternetworkingSo what network are we? 129.101.153.11714CS420/520 Axel Krings Sequence 19Page IP Addresses - Class B• Start with binary 10• Range 128.x.x.x to 191.x.x.x• Second Octet also included in network address• 214 = 16,384 class B addresses• All allocatedInternetworkingIPv6extended addressing128-bit addresses but that is not all, e.g., security, ...16NetworkingNamingWhat associations exist? hostname, IP address, MAC addressaddress resolution protocol (arp)-bash-3.2$ /sbin/arp -abender.cs.uidaho.edu (129.101.153.101) at 00:0E:0C:69:7B:E7 [ether] on eth0bunyan.cs.uidaho.edu (129.101.153.110) at 00:D0:B7:B6:C1:5C [ether] on eth0varanid.cs.uidaho.edu (129.101.153.119) at 00:03:BA:5C:48:0E [ether] on eth0granite.cs.uidaho.edu (129.101.153.125) at 00:03:BA:5C:48:17 [ether] on eth0-bash-3.2$ 17NetworkingRoutingDynamic routingStatic routing18NetworkingSecurityUser Authenticatione.g., login with username and passworde.g., remote procedure callRPC: execute a command, say date on another computer commet:~ krings$ rsh eternium.cs.uidaho.edu dateworks if one establishes “machine equivalence” this is defined in .hosts filecan also be done in /etc/hosts.equiv19NetworkingSecurityData EncryptionExampleuse telnet to connect to other computer and all communication is in clear-text --- outch!use secure shell, e.g., based on Open Secure Socket Layer OpenSSL20NetworkingPorts and Common ServicesServices like ftp, mail or http use TCP or UDP /etc/services shows the ports and their servicestake a look Linux interprocess communication allows you to communicate with other programs at a known IP address and port. See Chapter 12 “Systems Programming”21NetworkingNetwork Usersusers, list the users on the local hostwho, like users except that it gives you more informationw, like who except that it gives you even more informationhostname, displays your local host's namefinger, gives information about specific users22NetworkingCommunication with Network Userswrite, allows you to send individual lines to a user, one at a timetalk, allows you to have an interactive split-screen two-way conversationwall, allows you to send a message to everyone on the local hostmail, allows you to send mail messages23NetworkingDistributing Datarcp (remote copy) and scp (secure copy) allow you to copy files between your local Linux host and another remote Linux or UNIX host.ftp (file transfer protocol or program) and sftp (secure ftp) allow you to copy files between your local Linux host and any other host (possibly non-Linux) that supports FTP (the File Transfer Protocol). ftp is thus more powerful than rcp.uucp (unix-to-unix copy) is similar to rcp, and allows you to copy files between any two Linux or UNIX hosts.24NetworkingDistributing Datasftpsftp eternium.cs.uidaho.eduConnecting to eternium.cs.uidaho.edu... **************************************************************** * WARNING: To protect the system from unauthorized use and to * * ensure that the system is functioning properly, activities * * on this system are monitored recorded and subject to audit. * * Use of this system is expressed consent to such monitoring * * and recording. Any unauthorized access or use of this system * * is prohibited and subject to criminal and civil penalties. * ****************************************************************[email protected]'s password: sftp> ? [check out the commands displayed with the “?” option]25NetworkingDistributed Processingrlogin and slogin, which allow you to log in to a remote Linux or UNIX host rsh and ssh, which allow you to execute a command on a remote Linux or UNIX hosttelnet, which allows you to execute commands on any remote host that has a telnet server26Networkingrlogin how does it work?rlogin asks for password -l option is used to specify username other than current oneif remote hosts has local host in /etc/rhosts file then no passwd needed what are the advantages or disadvantages of this?what is the difference to telnet?similar but less customizable, connects only to unix hostswisdom: telnet and rlogin should be avoided. Use ssh and slogin27Networkingrlogin how does it work?rlogin asks for password -l option is used to specify username other than current oneif remote hosts has local host in /etc/rhosts file then no passwd what are the advantages or disadvantages of this?what is the difference to telnet?similar but less customizable, connects only to unix hostsWord of wisdom: telnet and rlogin should be avoided! Use ssh and
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