At 08:46 PM 6/25/01, Michael L. Williams wrote:
>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:
It's all essentially correct. It is simply describing a very normal layer-3
connectionless protocol that provides transport of datagrams. You could
replace every instance of IPX with IP and it would also be correct. Change
a few words here and there, like SPX -> TCP, and this could be right out of
TCP/IP Illustrated.
>"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 is its own transport. That doesn't make it layer 4. IP is its own
transport. It's not layer 4. There are cases of protocols that run directly
over IP, without TCP or UDP, (ICMP, IGMP, OSPF, IGRP, etc.), just like
there are cases of protocols that run directly over IPX without SPX (NCP,
RIP, SAP).
> > IPX RIP does path determination.
>
>Doesn't IPX RIP simply act as a routing protocol like IP RIP?
Yes.
> 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)
When forwarding frames, the router looks in the routing table for the next
hop. The routing protocol does path determination, at least the way Cisco
uses the term "path determination." The routing protocol learns how to
reach remote networks. But we're just mincing words now.
The bottom line is that Novell protocols aren't anything special. If you
know IP, you can learn IPX. I would say the only weird things are the
sockets in the IPX header (but DDP has sockets too, so that's not unique)
and that the common file-sharing protocol (NCP) runs right on top of IPX.
It does not use SPX. NCP does its own sequencing, acknowledgements, flow
control (with burst mode) even though it is supposedly an application-layer
protocol.
Priscilla
>"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.
________________________
Priscilla Oppenheimer
http://www.priscilla.com
Message Posted at:
http://www.groupstudy.com/form/read.php?f=7&i=9890&t=9045
--------------------------------------------------
FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html
Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
