html5-img
1 / 18

Network Services

Network Services. Section Overview. Client-Server Model Network Ports, Services and Daemons Network Protocols Viewing Active Ports Common Server Daemons. TCP/IP Protocol Stack. Application (FTP, HTTP, DNS). Transport Layer (TCP,UDP). Network Layer (IP). Link Layer (Device Drivers).

vianca
Télécharger la présentation

Network Services

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Network Services

  2. Section Overview • Client-Server Model • Network Ports, Services and Daemons • Network Protocols • Viewing Active Ports • Common Server Daemons

  3. TCP/IP Protocol Stack Application (FTP, HTTP, DNS) Transport Layer (TCP,UDP) Network Layer (IP) Link Layer (Device Drivers) Physical Layer (media)

  4. Client-Server Model Server Client Makes a request Request fulfilled Listens for incoming requests

  5. Network Ports • Enables processes to communicate with each other across a network • 64K possible ports • Privileged ports • < 1024 reserved for system use only • Correspond to well-known services • /etc/services

  6. /etc/services Service-name port/protocol aliases Examples: ssh 22/tcp smtp 25/tcp mail www 80/tcp http www-http imaps 993/tcp syslog 514/udp

  7. Running Network Servers • Stand-alone Daemon • Each started via rc script • Always running • Listens (binds) to the service port • Uses resources even when idle • inetd “Super-daemon” • Listens to many ports • Starts daemon when request is received • Daemon shuts down when finished • /etc/inetd.conf

  8. /etc/inetd.conf • service_name: Service name • sock_type: • stream (tcp) • dgram (udp) • raw (direct IP) • proto: protocol used (/etc/protocol) • flags: wait, nowait • user: User to run daemon as • server_path: Full path to daemon program • args: Command line arguments to daemon

  9. Xinetd • Replacement for inetd • Enhancements • Access Control • Resource based limits • Logging (Success and Failure) • Default:/etc/xinetd.conf • Service Specific: /etc/xinetd.d

  10. /etc/xinetd.conf defaults { instances = 60 log_type = SYSLOG authpriv log_on_success = HOST PID log_on_failure = HOST cps = 25 30 } includedir /etc/xinetd.d

  11. Example xinetd service /etc/xinetd.d/imaps: service imaps { disable = no socket_type = stream wait = no user = root server = /usr/local/sbin/imapd groups = yes flags = REUSE IPv6 }

  12. Windows Service Management • Microkernel – Everything a service • Administrative tools -> Services • Service Options • Startup Type: Automatic, Manual, Disabled • Log On: Which user to run service as • Recovery: What to do on failure • Dependencies: Which services does this one depend upon

  13. Settings for: First Failure Second Failure Subsequent Failures Counter Reset (Days) Options: Take no Action Restart the Service Run a program Restart the Computer Windows Service Recovery

  14. Network Protocols • Service request/response syntax • Often uses English commands • Request For Comments (RFC) • Documentation for protocols and practices • Each revision its own number • May have a second classification • For Your Information (FYI) • Best Common Practices (BCP) • Standards (STD)

  15. Viewing Active Ports • netstat –a – Ports in use • Source/destination addresses and ports • Protocol used • State • LISTEN • ESTABLISHED • lsof –i :service – Process using port • tcpdump – View network traffic

  16. Resource Sharing Daemons • Network File System (NFS) • nfsd • mountd • Line Printing Daemon (lpd) • Samba • smbd – Microsoft file and print sharing • nmbd – Microsoft name resolution

  17. Internet Daemons • telnetd – Remote Access • ftpd – File transfer • Berkeley-R Daemons • sshd – Secure Shell • Electronic Mail • sendmail/postfix – Receiving email • imapd, popd – Remote email access • httpd – Web

  18. Infrastructure Daemons • named – DNS • dhcpd – Dynamic Host Config Protocol • nisd/ldapd – Directory Services • fingerd – User information • xntpd – System time synchronization • routed/gated – Routing • Firewall

More Related