CSE 588 - Spring 2002 - Transcription

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Naming Systems
    DNS
        what are the biggest problems in DNS
            insertion capability
                failure
            context sensitivity 
            generality / mechanism
                (Akami, Napster, Distributed Director)
            politics
                name allocation - haphazard
            time (cost) for missing name 
            failover time 
 
            "Poison a DNS cache"
                authoritative server may be secure, but proxies not
                attacker can trigger lookup, and send reply as through
                    were authoritative server - because no authentication
                    between authoritative server and proxies
                fix?? 
                    IPsec - if control protocol
                    preload data 
 
            security - probably biggest issue for most 

 

    Freenet
    Chord
    LDAP
 
Is peer to peer file sharing something that a naming system should 
support?
    probably beter to leave naming system simple, and put other 
    functionality on top of it.
    Possibly still use DNS, and build on top of (different from Freenet 
and 

Chord).
 



what applications of naming?


features goals
    performance
        fast lookup 
        fast update
        search
 
    scalability
    clients / servers
        large # hosts
        # names
        # lookups
        updates to hosts and names

    reliable
        accuracy
        availability
 
    Simplicity
        low layer simple - build functionality on top
        vs.
        implement rich functionality into product
 
    ubiquity
    portability
 
    security
        authentication of updates
        only authorized updates / restricted?
        plausible deniability / secrecy
        Access control for lookup
 
    management overhead
        delegation
        no centralization
 
    context sensitive naming
        flexible (aliases)
 
        many-to-many mapping 
            BoA              --} server A
            bank of American --} server B ....
 
    API
        lookup 
        context-based (wildcard)
            on keyword, not data
        do we want to support webcrawl, google type searches?
 
        example: want to find all printers in Seattle. 
                DNS doesn't support easily
        does naming service become a generic DB - with SQL-like support
        reverse lookup
        triggers (eg notification when change occurs)
 
 

    Applications
        IP lookup
        updates
        Reverse Lookups
        non-hierarchical naming? 
        Object location 
 
is something like Google a solution to the file sharing problem?
put files on webserver, let google do search, build the context-based data

 
How build system
    DNS (example, as in book, with hierarchy of servers)
    how make scalable?
        caching - every time go to root server, cache partial result
            .edu
            washington.edu
            cs.washington.edu
            www.cs.washington.edu (actual webpage)
        long timeouts 
            invalidate (digression on cache coherency)
                directory-based invalidation cache coherence
            use TTL on data
        replicate (root servers) - possibly with single IP addr
        partition data among root servers (or hash)
 
    update
        just need to change table at relevant level
        parallel servers to zone transfers - some latency on update
 
    could system be modified to support searching?
        not easily. need to go through entire tree to find data
 
Akamai
    returns different results from root server searches based on 
    source of request (points to local proxy)
    long TTL at root server (hours), short TTL at proxy (seconds)
    how build geographic list of IP addresses?
        do you care about geography, rather than network distance
    most routers have location as part of name 
 

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