0

So I have an ad-hoc network made of 5 nodes. Assume that each node has a physical broadcast range of 1 arrow (nearest neighbor)

A <--> B <--> C <--> D <--> E

The IP addresses are:

192.168.2.5 192.168.2.6 192.168.2.7 192.168.2.8 192.168.2.9

If I set the TTL to 1 and send a multicast packet from node C, the packet should reach B and D because they are within the broadcast range of C.What I'm wondering is if nodes A and E receive the packet as well? Or will the packet not be forwarded to them?

I'm using some raspberry pi's which are using the linux rtl8192cu driver in ad-hoc mode and I'm wondering whether or not they would be propagate the multicast packets to other nodes within the network if they are all on the same subnet (due to physical constraints some of the radios are not within each others transmission radius).

IE I have a node C which is able to ping B and D. It is my understanding that if I send a multicast packet to a certain address/port that all nodes within the transmission range of the node which sent the packet should at least have a chance of receiving the packet. What I'm not sure of is whether that packet also gets forwarded.

I couldn't seem to find a concrete answer anywhere. Help is much appreciated!

  • What you have is not an ad hoc network, which by definition in the IEEE 802.11™-2012 consists of only two stations. At best, you have some sort of mesh of individual ad hoc networks. The answer to your question is going to depend on how you have created the mesh. – Ron Maupin Jan 26 '17 at 19:05
  • 4.3.2 The independent BSS (IBSS) as an ad hoc network The IBSS is the most basic type of IEEE 802.11 LAN. A minimum IEEE 802.11 LAN may consist of only two STAs. Since the BSSs shown in Figure 4-1 are simple and lack other components (contrast this with Figure 4-2), the two can be taken to be representative of two IBSSs. This mode of operation is possible when IEEE 802.11 STAs are able to communicate directly. Because this type of IEEE 802.11 LAN is often formed without preplanning, for only as long as the LAN is needed, this type of operation is often referred to as an ad hoc network. – Ron Maupin Jan 26 '17 at 19:07
  • 1
    Ron I appreciate the response. I took a look at the IEEE 802.11 document. The sentence states "A minimum IEEE 802.11 LAN may consist of only two STAs". By them stating "minimum" I infer that you can create a larger network of more than two STA's with IBSS. With that interpretation we could further infer that an ad hoc network may contain more than two nodes? Correct me if I'm wrong but the document never states something to the likes of "An ad hoc network consists of a maximum of two communicating nodes" – zac Jan 26 '17 at 19:36
  • No, that is incorrect. The minimum with only two stations is an ad hoc network. Beyond the minimum, you need an access point. A station radio can only associate with a single device, either another station or an access point. You can create a mesh, but that requires some non-standard stuff. – Ron Maupin Jan 26 '17 at 19:39
  • 1
    Ron I'm looking into this topic more and it is not supporting your argument. In history Ad Hoc and Mesh networks seem to have been used interchangeably. Ad Hoc is usually used to describe the fact that there is no infrastructure to the network. There is nothing I can find that defines mesh and ad hoc as the way you describe. Also there are many, many academic research papers that you will find using the term "ad hoc" which refer to networks upwards of 10, 20, or 100+ nodes. They all refer to this as ad hoc. See ietf.org/mail-archive/web/manet/current/msg05889.html as well. – zac Jan 26 '17 at 19:48
0

IBSS (the 802.11 standard's name for what's typically called an ad hoc network) has no provision for relaying packets, so all nodes must be in radio range of all other nodes.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.