>At 05:57 PM 6/25/01, Michael L. Williams wrote:
>>It seems interested to note that no one has mentioned that IPX not only
>>performs addressing and path determination (layer 3) but can also act as
>>it's own conectionless transport too (layer 4) like UDP......
I suspect that Novell applications that are appropriate for
connectionless transport tend to use the NetBIOS datagram service
rather than raw IPX.
>
>The IPX layer identifies a source and destination socket in addition to
>source and destination layer-3 addresses, but it is still a layer-3
>protocol in my opinion. AppleTalk DDP also identifies sockets, but it's
>layer 3 also. IPX and DDP have the same job as IP. IP identifies the next
>layer up also. It has its protocol type field.
And the equivalent of socket ID, of course, is in TCP or UDP, which
are identified by the IP protocol type field. Other values of IP
protocol type include ICMP, OSPF, EIGRP, etc.
>
>IPX RIP does path determination.
As does NLSP.
>
>> IPX does HAVE
>>to use SPX for transport.....
>
>Not sure if that was a typo, but IPX does NOT have to use SPX for
>transport. Most packets in an IPX network do not have an SPX header.
>
>>so IPX is really a Layer3 & 4 protocol
>
>Perhaps what you are getting at is the extra glue between NetWare Core
>Protocol and IPX that does things like sequencing and acknowledging.
>Protocol analyzers, such as Sniffer and EtherPeek, decode this as part of
>NCP. Novell documentation does not put it with IPX. (I have the IPX
>functional specification but not any formal NCP documentation). Perhaps
>some books put it with IPX.
It's my understanding that NCP runs on top of a NCP-specific reliable
transport called Packet Exchange Protocol (PEP), which runs over IPX.
PEP is part of the largely confidential NCP specification.
The way I look at Novell is that there are three APIs:
Application layer: NCP
Session layer: NetBIOS
Transport layer: SPX
Resource location is defined for NCP with SAP/GNS, with the NetBIOS
name service for NetBIOS, and is undefined for SPX.
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http://www.groupstudy.com/form/read.php?f=7&i=9878&t=9045
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