On Fri, 02 May 2003 at 06:20:58PM +0200, Peter Ondraska wrote: > Doesn't TCP/IP have only at most 4 layers? In the OSI model there are 7 Layers. TCP/IP takes up only two of them (3 & 4). Layer 1 - Physical - Cat5, Fiber, etc. Layer 2 - Datalink - Ethernet, FDDI, etc. Layer 3 - Network - IP, IPX, etc. Layer 4 - Transport - TCP, UDP, XPX, ICMP, IGMP, (the list goes on and on). Layer 5 - Session - HTTP, SMTP, POP3, SSH, NNTP, etc. Layer 6 - Presentation - GIF, HTML, etc. Layer 7 - Application - Layer for communicating with the user. So, to answer your question, yes TCP only acts at layer 4, but when one looks at networking as a whole it goes up much farther than layer 4. Layer 4 and down is usually the concern of the O/S. -- Phillip Hofmeister Network Administrator/Systems Engineer IP3 Inc. http://www.ip3security.com PGP/GPG Key: http://www.zionlth.org/~plhofmei/ wget -O - http://www.zionlth.org/~plhofmei/key.txt | gpg --import -- Excuse #71: Someone is standing on the Ethernet cable causing a kink in the cable
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