VanLUG Email Archive
IP Masq is suitable for Linux because thats all it does, masquarde IP
connections, and only for TCP/IP.
NAT is a generic term to mean taking any protocol and exchanging the data
over to another protocol.
--Vincent Janelle "MCSE = Must Consult Someone Experienced"
--http://random.gimp.org --mailto:random@gimp.org
On Wed, 7 Oct 1998, Curt Sampson wrote:
> On Tue, 6 Oct 1998, Vincent Janelle wrote:
>
> > Ip Masq does just IP to IP with port translation.
> > NAT means that it takes one protocol and translates it to another. Last I
> > checked, Linux didn't translate IPX -> TCP/IP.
> > At least, thats what #unix on efnet managed to agree too.
>
> Interesting. You guys had better run over and tell Cisco, then.
> Here, from their Frequently Asked Questions about NAT document
> (found at http://www.cisco.com/warp/public/458/41.html) is their
> definition of NAT:
>
> Q: What is NAT?
>
> A: Network Address Translation (NAT) is designed for IP address
> simplification and conservation, as it enables private IP
> internetworks that use nonregistered IP addresses to connect
> to the Internet. NAT operates on a router, usually connecting
> two networks together, and translates the private (not globally
> unique) addresses in the internal network into legal addresses
> before packets are forwarded onto another network. As part of
> this functionality, NAT can be configured to advertise only
> one address for the entire network to the outside world. This
> provides additional security, effectively hiding the entire
> internal network from the world behind that address. NAT has
> the dual functionality of security and address conservation,
> and is typically implemented in remote access environments.
>
> Note that their definition even explicitly covers translation to
> a single address, which Linux folks refer to as `IP Masquerading.'
> Incidently, I searched their entire website for that term and came
> up with nothing; it appears that they don't use it at all.
>
> When Cisco does need to distinguish between NAT to multiple addresses
> and NAT that translates everything down to a single address (a
> distinction they rarely make), the call the latter PAT, for Port
> Address Translation. I believe Cisco to be the only company that
> makes this distinction and uses a separate term for it.
>
> Bay Networks explicitly says that NAT refers to translating to a
> single address. On
>
> http://support.baynetworks.com/library/tpubs/html/router/nautica/nrs41/117237AB/J_23.HTM
>
> they say:
>
> Network Address Translation (NAT) is a method for translating
> an internal IP address or network into a single globally unique
> IP address.
>
> Ascend just qualifies its use of NAT if they want to explicitly
> specify one or the other. From http://www.ascend.com/faqs/50/445.html:
>
> Multiple IP address NAT, or one to one NAT is available in
> release 4.6ci17 or later. Single IP address, or one to many
> NAT is available in release 5.0ai16 or later. You are able to
> choose between the two methods of NAT in release 5.1a or later.
>
> 3com uses NAT to refer to translation to a single address on the page
> http://support.3com.com/infodeli/tools/bridrout/oc/INTERNAT.HTM:
>
> With the NAT feature enabled, you can use your own private set
> of IP addresses that will be translated to the single IP address
> which gets assigned to your OfficeConnect during connection
> negotiation
>
> A search of all three of these vendors' sites turned up no use of
> the term "IP masquerading" (I actually searched for "masq*" where
> I could.)
>
> The RFCs don't make this distinction; the only mention of single-address
> translation that I could find is in RFC 2391, where they say only
>
> NATs have traditionally been been used to allow private network
> domains to connect to Global networks using as few as one
> globally unique IP address.
>
> So still, lacking one shred evidence to the contrary, I'm going to
> insist that "IP masquerading" is a term used only by Linux users
> for a distinction not made in the outside world, and that is not
> generally known to non-Linux users.
>
> cjs
> --
> Curt Sampson <
> 604-257-9400 De gustibus, aut bene aut nihil.
> Any opinions expressed are mine and mine alone.
> The most widely ported operating system in the world: http://www.netbsd.org
>
>