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Exploring Network Naming: Understanding Associations and Resolving Values

Delve into the realm of network naming, discovering how associations between names and values are bound and resolved. Learn about contexts, aliases, and name services such as DNS, Grapevine, and Ethernet cards. Explore Ethernet card naming conventions, DNS structures, and the complexities of name resolution in hierarchically structured zones. Unveil the nuances of DNS servers and the challenges of name resolution, caching, and consistency in the dynamic world of networking.

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Exploring Network Naming: Understanding Associations and Resolving Values

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  1. Naming March 8, 2001

  2. Networks • What is naming? • Associations between some elements in a set of names and some elements in a set of values • Binding - One such association • Name resolution - Determining the value associated with a name • Context - A set of name to value associations • The same name can be bound to different objects in different contexts • Alias - a name that references a value that already has a name

  3. Networks, cont. • Name Services • A service that resolves names in a given context • May or may not be fully automated • Examples: • DNS on the Internet • Grapevine • Ethernet cards • Objectives: speed, availability, scalability

  4. Networks, cont. • Ethernet Card Naming • Each Ethernet Card has a 48-bit name • e.g., C0 39 FB 23 5E 9A • Name used by link-layer to differentiate between other Ethernet cards • Manufacturers get blocks of addresses from a naming authority • Issue - What happens if we run out of names? (How likely is this?)

  5. Networks, cont. • DNS • Domain name - a name associated with an IP address • generically: <name2>.<name1> • <name1> is a top-level domain • <name3>.<name2>.<name1> is a subdomain of <name2>.<name1> • Use hierarchy to reduce complexity and improve scalability of name resolution • Use caching to improve lookup speed and availability • Typically implemented on top of UDP

  6. Networks, cont. • DNS, cont. • Name resolution done hierarchically, split into zones • A zone contains: • Specific info for some hosts in a domain (types) • e.g., A, MX, NS, CNAME • Names of servers providing DNS for sub-domains • Zone governing properties (caching, replication)

  7. Networks, cont. • Name resolution in DNS • Query - ask for a type of info on a domain name • e.g., photo.net MX (mail exchanger) • Start with top-level, well known root DNS server • These root servers service mit.edu, arsdigita.com, ... • Get the name of the DNS server with info about your sub-domain • Resolve the name of the DNS server • Iterate - Send your query to the new DNS server

  8. Networks, cont. • Name resolution in DNS, cont. • Full name resolution takes at least 2 steps • Optimization: Use caching • Three types of DNS servers: authoritative, non-authoritative, caching • Two authoritative servers required for each domain name

  9. Networks, cont. • Name resolution in DNS, cont. • Authoritative server is primary source of info • Non-authoritative servers replicate data in authoritative servers • e.g., 1-2 times per day • Caching servers cache DNS info • Clients must be told whether IP is from authoritative source or not

  10. Networks, cont. • Name resolution in DNS, cont. • No mechanism to guarantee consistency between DNS servers at all times • To address cache consistency, use Time To Live • DNS Server can specify a TTL for a resolved domain name • A caching server invalidates an entry based on its TTL

  11. Networks, cont. • DNS issues • DNS changes can take hours or days to propagate • Partially depends on TTL • Clients must decide how to determine whether an IP address is valid • DNS can be spoofed • Need higher-layer security to ensure you are talking to the right host • Simple errors can create disasters • One small change to a root-level authoritative server can throw the Internet into chaos

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