Practical implications of OSI vs TCP/IP networking.

Question

Hi.

I'm supposed to be setting up a 'geolocation based', ipv6, wireless mesh network to run on google android.

I found what seems to be a good app to support the meshing: http://www.open-mesh.net/wiki/batman-adv

"Batman-advanced is a new approach to wireless networking which does no longer operate on the IP basis. Unlike B.A.T.M.A.N, which exchanges information using UDP packets and sets routing tables, batman-advanced operates on ISO/OSI Layer 2 only and uses and routes (or better: bridges) Ethernet Frames. It emulates a virtual network switch of all nodes participating. Therefore all nodes appear to be link local, thus all higher operating protocols won't be affected by any changes within the network. You can run almost any protocol above B.A.T.M.A.N. Advanced, prominent examples are: IPv4, IPv6, DHCP, IPX."

But other members in my team has said it's a no-go because it operates on OSI, rather than TCP/IP. This was the first I'd heard of OSI, and I'm wondering how much of a problem this is? What are the implications for mesh network apps that can be developed on top of it? Considering the android is relatively new, we don't need to worry too much about compatibility with existing apps, so does it matter?

I haven't spent a lot of time working with networks, so please put in noobmans terms.

Answer 1

"ISO/OSI Layer 2" does not mean the OSI protocols. It refers to the "Seven Layer" model of network stacks. It means the Data Link layer.

The layers are: Physical, Data Link, Network, Transport, Session, Presentation, Application.

Answer 2

OSI is a model not a protocol like IP and TCP. What your team seem to be saying is that the mesh won't be using IP. I suspect they are wrong as the text you have quoted states the BATMAN protocol is capable of supporting IP & IPv6 and if that is the case you'd need a very strong reason to use anything else.

Answer 3

They're probably referring to the OSI model, which is a commonly-used way of distinguishing between network layers. I'm not sure it's a useful way of looking at things, but it's taught in every networking course on the planet.

OSI level 2 is the data link layer, which operates immediately above the actual physical level. Basically, it's in charge of flow control, error detection, and possibly error correction. The data link layer is strictly "single hop". It's only concerned about about point-to-point data transfers, not about multi-hop transfers or routing.

If they're actually referring the OSI networking protocal itself, run screaming as fast as you can. OSI was notoriously hard to implement, and I've never heard of an actual working installation. See the Wikipedia article for the gory details.

Answer 4

"You can run almost any protocol above B.A.T.M.A.N. Advanced, prominent examples are: IPv4, IPv6, DHCP, IPX."

"But other members in my team has said it's a no-go because it operates on OSI, rather than TCP/IP. "

The other members in your team are confused by the buzzword-fest in BATMAN.

The "IP" of TCP/IP is IPv4 (or IPv6). So BATMAN supports TCP/IP directly and completely.

There's no conflict of any kind. Just confusion.

Answer 5

The OSI model and the OSI protocols are different.

The OSI model is a way of breaking things down: physical, link, network, transport, session, presentation, application. OSI protocols are protocol implementations that map directly to those layers in the model.

The model is a way of looking at things. It mostly makes sense, but it breaks down at the higher levels. For example: what does a presentation layer really do?

During the '90s, OSI was (in some circles) thought to be the future, but was actually the downfall of some companies, and wasted the resources of many others. For example, DECnet Phase V was Digital's insanely complex implementation of an OSI stack that met government OSI requirements, but was run over by the TCP/IP steamroller.

The test is: What are the bytes on the wire? In this case it is UDP over IP, not the OSI equivalent, which was CLNP.

Having said all that, if it is a layer two protocol, it will probably have scalability problems because it is a layer two protocol. Fine for a small number of nodes, but if you're trying to get scale, you need a better solution.