"Priscilla Oppenheimer" wrote in message
[EMAIL PROTECTED]">news:[EMAIL PROTECTED]...
> 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......
>
> 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.
Doesn't IPX do more than just addressing, etc? Everything I've always read
tells me that IPX can actually act as it's own connectionless transport
protocol. Here are some things I've read that imply this. Tell me if this
stuff is misleading or if I'm just reading it wrong:
"SPX extends IPX connectionless datagram service by providing a facility for
reliable connection oriented deliverly".
"IPX (Internetwork Packet Exchange) is a peer-to-peer protocol. It was
derived from the XNS Internet Datagram protocol. IPX is a connectionless
protocol. It's only concern is internetwork addressing and intranode
addressing (sockets). IPX completely relies on the network hardware for the
actual node addressing. " (i.e. it uses the MAC address to complete an
address)
"IPX is a datagram-based, connectionless protocol. Datagram-based,
connectionless protocols do not require an acknowledgment for each packet
sent. Packet acknowledgment, or connection control, must be provided by
protocols above IPX"
"IPX accomplishes these and other Network-layer tasks with the help of RIP,
SAP, and NLSP"
Wouldn't all of these statements imply that IPX can be it's own transport,
and therefore be considered Layer 4 as well?
> IPX RIP does path determination.
Doesn't IPX RIP simply act as a routing protocol like IP RIP? Aside from
allowing routing to share routes, IPX RIP doesn't actually perform the path
determination does it? (i.e. the router still looks in the routing table at
routes for path determination whether they're static, redistributed, or
learned via IPX RIP)
"By default, the Cisco IOS software redistributes IPX RIP routes into
Enhanced IGRP, and vice versa."
Please clarify, because I don't know tons about IPX/SPX and how they divy up
the functions of path determination, etc. that well......
> > 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.
You're right, it was a typo =) However, from my (again, limited)
understanding, most everyday communications over IPX/SPX would need reliable
transport (communications for login to servers, getting files and running
applications from servers, etc..) and would need the SPX for reliability,
correct?
Thanks!
Mike W.
Message Posted at:
http://www.groupstudy.com/form/read.php?f=7&i=9874&t=9045
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