1. NamingCS-4513, D-Term 20071 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 20072 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 20073 Naming (continued) Applies to Files Machines (aka hosts) Services (remote and local) People Places Things (objects) …

4. NamingCS-4513, D-Term 20074 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 20075 Fundamental Tricotomy Names Addresses Routes (aka paths)

6. NamingCS-4513, D-Term 20076 Fundamental Tricotomy Names (Abstract) strings or other data types 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

7. NamingCS-4513, D-Term 20077 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

8. NamingCS-4513, D-Term 20078 Example — a File Name — index.html Address — inode #54321 Route (path) — /csopt1/cs4513/public_html/d07/index.html

9. NamingCS-4513, D-Term 20079 Example — a computer Name— ccc3.wpi.edu Address — 130.215.36.150 Route — Nobody bothers with this today due to IP routing In pre-internet days:– mit!umass!wpi!ccc3

10. NamingCS-4513, D-Term 200710 Example — a Web Page Name — CS-4513 Home Page Address — inode #54321 Route — http://www.cs.wpi.edu/~cs4513/d07

11. NamingCS-4513, D-Term 200711 Example — Remote Object Name — Gutenberg (a print server) Address — ??? Route — rmi://garden.wpi.edu:1099/Gutenberg

12. NamingCS-4513, D-Term 200712 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

13. NamingCS-4513, D-Term 200713 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 When you hand an address to a system, it already knows how to find it. E.g., an IP address

14. NamingCS-4513, D-Term 200714 Addresses vs. Paths When you hand an address to a system, it already knows how to find it. E.g., and IP address When you hand a path (i.e., a route) to a system, you are giving it a sequence of things it knows how to find Iterative or recursive follow Step-by-step

15. NamingCS-4513, D-Term 200715 Naming Systems we all know Unix/Linux file names URL’s on the World Wide Web Types and objects in a C++ or Java program Computers attached to the Internet …

16. NamingCS-4513, D-Term 200716 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

17. NamingCS-4513, D-Term 200717 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”)

18. NamingCS-4513, D-Term 200718 Issue — Finding Objects that Move Forwarding pointers

19. NamingCS-4513, D-Term 200719 Objects that Move (continued) Redirection

20. NamingCS-4513, D-Term 200720 Objects that Move (continued) Mobile IP

21. NamingCS-4513, D-Term 200721 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

22. NamingCS-4513, D-Term 200722 Hierarchical Resolution of Flat Names

23. NamingCS-4513, D-Term 200723 Caching

24. NamingCS-4513, D-Term 200724 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

25. NamingCS-4513, D-Term 200725 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

26. NamingCS-4513, D-Term 200726 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)

27. NamingCS-4513, D-Term 200727 Familiar Structured Naming Systems Unix/Linux/Windows file systems Domain Name System (DNS) for Internet nodes and services …

28. NamingCS-4513, D-Term 200728 Other Topics in Structured Naming Systems Aliases Mounting and mount points …

29. NamingCS-4513, D-Term 200729 Attribute-based Naming Directories store (attribute, value) pairs Multiple values for same attribute May be combined with hierarchical structure

30. NamingCS-4513, D-Term 200730 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

31. NamingCS-4513, D-Term 200731 Questions?