CSC 2231 Review of CoDoNS

CoDoNS is proposed to provide automatic configuration, failure resilience,
as well as load balancing for Internet name service. Its basic idea is to
exploit DHT to decouple the name management from the physical location of
servers, and use a proactive caching layer to reduce lookup latency.

However, the main deficiency of this design is that they simply consider
name service as a query to a storage pair (domain name, server IP
addresses). This assumption hurts the flexibility of hierarchy legacy DNS,
that has already evolved into a service with flexible policies and dynamic
name resolution. For instance, each legacy DNS server can be independently
configured to only reply some specified clients, and it can hide internal
domain to the outside. More importantly, current CDN techniques are based
on dynamic domain name resolution of legacy DNS to select servers in
network proximity and load distribution. Although CoDoNS may be able to
associate these complex policies with names and support wise server
selection based on other out of band mechanisms, these concerns greatly
increase its implementation complexity.

CoDoNS works like a big cache of domain names. But its granularity of
replication strategies seems too coarse. It replicates an object at level
i to all nodes with i matching prefix digits. With the increase of level
i, the number of replications increases by multiplying the base of DHT
identifier so that it cannot set the number of replicas within (the
number of objects with i-1 matching prefix digits, the number of objects
with i matching prefix digits). This may waste the storage space and
incur more overhead of updates.

CoDoNS achieves O(1) lookup by aggressive replication. This strategy not
only consumes a large amount of storage space, but is not suitable for
frequent information propagation since it involves many replicas to update.
Moreover, CoDoNS still inherits shortcomings of DHT, for instance, it
cannot effectively deal with load imbalance in a heterogeneous network.

In brief, CoDoNS brings the convenience of automatic configuration by
sacrificing the flexibility of trusted hosts delegation of legacy DNS.
Received on Thu Nov 10 2005 - 09:26:56 EST