Application Protocols • SMTP: Simple Mail Transport Protocol • HTTP: Hyper Text Transport Protocol • HTTPS: Hyper Text Transport SSL (Secure) • SNMP: Simple Network Management Protocol • FTP: File Transfer Protocol • Telnet: Interactive login • SSH: Secure Shell telnet • DNS: Domain Name Service
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Application Protocols SMTP: Simple Mail Transport Protocol HTTP: Hyper Text Transport Protocol HTTPS: Hyper Text Transport SSL (Secure) SNMP: Simple Network.
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Application Protocols
• SMTP: Simple Mail Transport Protocol• HTTP: Hyper Text Transport Protocol• HTTPS: Hyper Text Transport SSL (Secure)• SNMP: Simple Network Management Protocol• FTP: File Transfer Protocol• Telnet: Interactive login• SSH: Secure Shell telnet• DNS: Domain Name Service
IP header
• Source and Destination IP addresses
• Type of Service – Selects delivery speeds vs. accuracy
• Protocol (TCP,ICMP, UDP)
• Time to Live (Router hops)
• Identification and Fragment offset– Reassembly of a fragmented datagram
Version Leng Type of Svc Total Length
Identification Flags Frag OffsetTime to Live Protocol Header Checksum
IP Header
Source Address
Destination Address
TCP Header then your data...
TCP fields
• Ports (service identifiers)
• Sequence numbers
• Acknowledgement numbers
• Windowing– More retries (less acks) smaller packets– Less retries (more good data) larger packets
Source Port Destination Port
Sequence Number
Acknowledgement Number
DataOffset
Reserved
FlagsWindow
Checksum Urgent Pointer
Your Data… next 500 octets
TCP Header
Services
• RFC’s (Requests for Comments)• /etc/services or multinet:services.master_server• lists service name and port number• Common (well known) ports:
; ; Hosts file for domain flibble.orac.net.au. ; ;name ttl class type data ; ; Source of authority @ IN SOA solaris.flibble.orac.net.au. root.solaris.flibble.orac.net.au. (
2000050201 ; Serial 10800 ; Refresh - 3 hours 3600 ; Retry - 1 hour 432000 ; Expire - 1 week 86400) ; Minimum - 1 day IN NS solaris.flibble.orac.net.au.
More Config; ; Machines for the flibble.orac.net.au domain ; ;name ttl class type data localhost IN A 127.0.0.1 solaris IN A 10.5.3.1 win95 IN A 10.5.3.21 linux IN A 10.5.3.22 ; ; Aliases ; mail IN CNAME solaris www IN CNAME solaris
More config
; ; Domain mailing addresses ; flibble.orac.net.au. IN MX 10 solaris.flibble.orac.net.au. flibble.orac.net.au. IN A 10.5.3.1
DNS ResolutionWant cc.usu.edu
Top Level DomainServer (resolve .edu)
thingy.usu.edu
resolve usu.eduresolve cc.usu.edu
homeuser.aol.com
USU DNS
• Handled by Network and Computing Services
• thingy.usu.edu webpage for registrations and lookups