CSE 588 - Spring 2002 - Transcription

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Naming Systems: DNS/FreeNet/LDAP/Chord

Criteria for evaluation and Required Features in an Ideal Naming System
--Performance
    -fast lookups, fast updates, fast Searches
--Scalability
      large number of hosts/clients/names/lookups, ability to handle large updations of hosts/names
--Reliability
      accuracy of information and availability of the service
--Ubiquity of usage -- thru portability
--Less Management overhead
      delegation and decentralization
--Should it have simplicity? with other features like searching at a top layer?
--Security
    Authentication before updates and access control even for lookups
--Flexible naming system
    Naming can be flexible by the context in which it is used
--Possible
    many-many (many-keys-to-many-values) mapping
    
    
    
Ideal APIs for the Naming System Interface
    lookup() with wildcharacters as part of the parameters
          takes the form of a search
    reverselookup()
          returns the key(s) given the values
    update()
    should it support trigger()?
    
    
Must a Naming System have all the functionality of a database as what it really has is a mapping 
of keys and values and applications and desirable functionality like keyword searches and triggers 
are already present?

Applications of a Naming System
  IP Lookup/Updates/Reverse Lookups
  Lookups of data based on keyword searches
  
  

Features of DNS

-Scalable for lookups of names
-Does NOT have fine grained searches and lookups
-Does NOT scale well for fast changing insertions.
-NO context sensitive lookups
-Has long fail-voer times with caching in intermediate proxies


DNS cache can be poisoned by an attacker by passing a lookup request to a proxy and inserting a fake 
response for the key after(or is it before?) the Authoritative Server returns the response. 
DNS exhibits clear problems with lack of security

FreeNet system provides anonymity -- perhaps an important feature in this world of Napster?

Scalability of DNS
-DNS achived scalability thru caching of name-addressing mapping of even partial names in the 
 proxies(and clients).
-There is usually a long timeout before the cache becomes invalid. The Server lists the TTL of each entry
 along with the value it returns for the name and the Root AS store a very long TTL for their entries
-There is a redundancy of servers (replication of data) as well as load balancing of requests coming in.
 Data is also partioned across servers

Zone Transfers happen between load-balanced and replicated servers.
About 60% of the requests to DNS servers today are because of bad clients not using the TTL properly.

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