1. NamingCS-4513, D-Term 20081 Naming CS-4513 Distributed Computing Systems (Slides include materials from Operating System Concepts, 7 th ed., by Silbershatz, Galvin, & Gagne, Modern Operating Systems, 2 nd ed., by Tanenbaum, and Distributed Systems: Principles & Paradigms, 2 nd ed. By Tanenbaum and Van Steen)

2. NamingCS-4513, D-Term 20082 Naming One of most difficult issues in all of computing Most large, long-lived systems outgrow their naming subsystems Scalability Global distribution … No general solution

3. NamingCS-4513, D-Term 20083 Naming (continued) Applies to Files Machines (aka hosts) Services (remote and local) People Places Things (objects) …

4. NamingCS-4513, D-Term 20084 Resources Silbershatz §16.5.1, §10.5.2.2, §3.4.2.1, etc. Tanenbaum (Modern Operating Systems) §8.3 (Naming Transparency) Tanenbaum & Van Steen All of Chapter 5

5. NamingCS-4513, D-Term 20085 Class discussion (laptops closed, please) What do we mean by “name”?

6. NamingCS-4513, D-Term 20086 Fundamental Tricotomy Names Addresses Routes (aka paths)

7. NamingCS-4513, D-Term 20087 Fundamental Tricotomy Names (Abstract) strings or data structures that refer to specific entities in a system Addresses Identifiers of places to find the named entities Routes Sequences of names or addresses specifying steps to follow to get to named entities Sometimes called paths

8. NamingCS-4513, D-Term 20088 Example — a Person Name — Jonathan M. Smith Address — 123 Park St., Andover, MA Route — From Andover center, go west 1.2 miles Turn right, then take 3 rd left He lives at the 2 nd house on the right

9. NamingCS-4513, D-Term 20089 Example — a File Name — index.html Address — inode #54321 Route (path) — /csopt1/cs4513/public_html/d08/index.html

10. NamingCS-4513, D-Term 200810 Example — a computer Name— ccc3.wpi.edu Address — 130.215.36.150 Route — IP numbers are converted to routes by network layer of protocol stack Route is a sequence of hops derived from routing tables at each node in network

11. NamingCS-4513, D-Term 200811 Example — a Web Page Name — CS-4513 Home Page Address — inode #54321 Route — http://www.cs.wpi.edu/~cs4513/d08

12. NamingCS-4513, D-Term 200812 Example — Remote Object Name — Gutenberg (a print server) Address — ??? Route — rmi://garden.wpi.edu:1099/Gutenberg

13. NamingCS-4513, D-Term 200813 Names vs. Addresses A name in one context may be an address in another Example:– “Park Street” is (part of) Jonathan Smith’s address “Park Street” is a name of a road in the town

14. NamingCS-4513, D-Term 200814 Names vs. Addresses (continued) When you hand a name to a naming system to resolve, it must … … look it up to find the corresponding object or entity Or resolve it some other way When you hand an address to a system, it already knows how to find it. E.g., an IP address

15. NamingCS-4513, D-Term 200815 Names vs. Addresses (continued) When you hand a name to a naming system to resolve, it must … … look it up to find the corresponding object or entity Or resolve it some other way When you hand an address to a system, it already knows how to find it. E.g., an IP address Most of Chapter 5 of Tanenbaum & van Steen is about resolving names

16. NamingCS-4513, D-Term 200816 Addresses vs. Paths When you hand an address to a system, it already knows how to find it. E.g., an IP address, an i-node of a file system When you hand a path (i.e., a route) to a system, you are giving it a sequence of steps it knows how to follow Iteratively or recursively Hoping it eventually reaches the thing you want!

17. NamingCS-4513, D-Term 200817 Naming Systems we all know Unix/Linux/Windows file names URL’s on the World Wide Web Types and objects in a C++ or Java program Computers attached to the Internet …

18. NamingCS-4513, D-Term 200818 Types of Names in Distributed Systems Flat All names are equivalent in name space Must be globally unique Hierarchical Names (usually) have structure Unique only within immediately containing level Each level resolved within context of next higher level

19. NamingCS-4513, D-Term 200819 Flat Name Spaces Need global directory May be replicated May be partitioned Not (necessarily) tied to location … But many challenges Issues of scaling Imagine 600  10 6 computers attached to Internet (50,000 named “Frodo”)

20. NamingCS-4513, D-Term 200820 Issue — Finding Objects that Move Forwarding pointers

21. NamingCS-4513, D-Term 200821 Objects that Move (continued) Redirection

22. NamingCS-4513, D-Term 200822 Objects that Move (continued) Tanenbaum & van Steen, Fig 5-3

23. NamingCS-4513, D-Term 200823 Hierarchical Approaches –A flat name space with hierarchical administration –Top level domain knows (or can find) all names –Each sub-domain knows subset of names –Local names resolved within own subset –Other names cached as needed

24. NamingCS-4513, D-Term 200824 Hierarchical Resolution of Flat Names

25. NamingCS-4513, D-Term 200825 Caching

26. NamingCS-4513, D-Term 200826 Domain Name System (DNS) Internet names are structured, not flat ccc3.wpi.edu update.microsoft.com Resolution works the same way If a name is cached in local name server, try to use it If not, go to up the hierarchy one level to find a cached entry, etc. Difference is that each level knows only its level –E.g., edu knows wpi but not ccc3

27. NamingCS-4513, D-Term 200827 Structured Naming Systems Names organized into name spaces Names spaces organized into directed graph Leaf nodes represent named entities Interior nodes represent directories Everyone has to know root node

28. NamingCS-4513, D-Term 200828 Structured Naming Systems (continued) Names are really paths through the naming system Relative vs. Absolute Resolution – iterative vs. recursive Iterative – repeatedly contact hierarchy of nodes to resolve parts of the name Recursive – contact your local name space and let it walk the hierarchy (and cache results)

29. NamingCS-4513, D-Term 200829 Familiar Structured Naming Systems Unix/Linux/Windows file systems Domain Name System (DNS) for Internet nodes and services …

30. NamingCS-4513, D-Term 200830 Other Topics in Structured Naming Systems Aliases Mounting and mount points …

31. NamingCS-4513, D-Term 200831 Attribute-based Naming Directories store (attribute, value) pairs Multiple values for same attribute May be combined with hierarchical structure

32. NamingCS-4513, D-Term 200832 LDAP – Lightweight Directory Access Protocol Directory entry stores a bunch of (attribute, value) pairs for some entity Lookup can find entitites by name by attribute by value Implementation OSI X.500 Directory service Microsoft Active Directory Service

33. NamingCS-4513, D-Term 200833 Questions?