Internet Indirection Infrastructure

Motivation: i3 is an overlay based infrastructure that offers a rendezvous
based communication abstraction to provide services like multicast, anycast
and mobility.

Key Points:

1) It is essentially a Publish-Subscribe-Notify model built on top of Chord.
It decouples receiving form sending.Senders send packets to a id and
receivers subscribe to an id. The infrastructure facilitates the forwarding
of the packet.

2) Such a infrastructure provides mobility, multicast and anycast.
Mobility - Since communication is not connection based between source and
destination, it provides mobility ub updation of the contact information at
the rendezvous server. Both, sender and receiver can thus be mobile
simultaneously.
Multicast - More than one receiver can subscribe to the id.
Anycast - i3 provides anycast by sending the packet to the identifier whose
k-bit prefix matches the anycast group identifier and then forwarding the
packet to identifier that best matches the packet identifier.

3) i3 can provide service composition by sending the packet to a sequence of
ids before finally forwarding it to the destination.
An interesting application is heterogeneous multicast where different
receivers can notify the sequence of ids through which the packet should go
before being forwarded to them. This enables different processing for
different receivers.

4) i3 largely depends on the overlay network over which it is built (Chord
lookup protocol). Thus, i3 benefits as well as limited by the properties of
Chord.

5) Relying on i3 overlay to mange routing for packets introduces the burden
of making it secure and robust. The authors argue that they can do as well
as the current Internet.

6) One problem is that i3 might lead to considerable path inflation as it
would be difficult to provide for shortest path for majority of the end
nodes. Although the authors argue, to reduce latency the address of the
server doing the forwarding can be cached. However, even then it would lead
to some path inflation as providing the shortest path route would be very
difficult in most of the cases. This has serious limitations for time
sensitive applications like streaming, ajax-based appications, VoIP etc.

7) i3 breaks the "connection" paradigm between end hosts. Moreover, i3 makes
the uplink and downlink fairly asymmetric.
This would complicate the behavior of certain applications.

All in all, I think i3 is a cool concept and is useful for certain
applications but has limitations for others.
Received on Thu Nov 23 2006 - 10:10:39 EST