THE GEOMORPHIC VIEW OF NETWORKING: A NETWORK MODEL AND ITS USES

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1 THE GEOMORPHIC VIEW OF NETWORKING: A NETWORK MODEL AND ITS USES Pamela Zave AT&T Laboratories Research Florham Park, New Jersey, USA Jennifer Rexford Princeton University Princeton, New Jersey, USA

2 THE CLASSIC INTERNET ARCHITECTURE this architecture has succeeded (beyond most peoples wildest dreams) in fostering innovation and shaping the world we live in however, it is now widely agreed that it does not meet society s present and future requirements security dependability mobility scalability quality of service resource management APPLICATION LAYER TRANSPORT LAYER NETWORK LAYER LINK LAYER PHYSICAL LAYER the trend is toward a more pluralistic architecture with multiple, customized protocol stacks

3 A REAL EXAMPLE headers in a typical AT&T packet (12 instead of 4) Application HTTP TCP IP IPsec IP GTP UDP security HTTP being used as a transport protocol (! ) because it is the only way to traverse NAT boxes and firewalls cellular service (mobility, QoS, billing) IP MPLS MPLS multiple layers of resource management Ethernet

4 A REAL EXAMPLE: WHAT ARE THE PROBLEMS? COMMUNICATION SERVICES Application HTTP TCP IP IPsec IP GTP UDP IP MPLS MPLS Ethernet we need... a broader range of services security appropriate to each application... so that all applications can be developed easily and efficiently DESIGN PRINCIPLES this is not the most efficient way to satisfy the stakeholders requirements! 15 load-balancing algorithms apply to each packet; each designed and analyzed in isolation we need principles that apply to all levels, produce modular and predictable behavior SOFTWARE DEVELOPMENT we need to develop all this custom software through code re-use and code generation

5 A NEW LAYER MODEL: MEMBERS, ROUTING, AND member a process, which is merely a locus of state and control with the potential for autonomous action name FORWARDING unique and persistent within the layer LAYER A B C D E link a communication channel forwarding protocol enables members to send messages to one another, using the links routes often there is not a link between every pair of members; routes tell the forwarding protocol how to reach one member from another over the existing links, with forwarding by intermediate members routing algorithm maintains the routes as links change over time

6 A NEW LAYER MODEL: COMMUNICATION SERVICES channel an instance of a communication service session a communication channel (as are links) session protocol implements an end-to-end communication service, on top of the basic, fundamentally unreliable, message delivery provided by the forwarding protocol session LAYER a b link d e from the perspective of one layer, sessions are more convenient than links they have longer reach; might be more reliable, better-behaved (with FIFO delivery), with guaranteed performance, etc.

7 A NEW LAYER MODEL: THE USES HIERARCHY OVERLAY (higher layer) A when an overlay uses an underlay, a link in the overlay is implemented by a session in the underlay link E registration relates an overlay member to the underlay member that it is using on the same machine UNDERLAY (lower layer) a b session d e members on the same machine communicate reliably through its operating system to set up this link/session: A sends request to a a looks up registration of E, finds e a sends request to e e sends request to E

8 A NEW LAYER MODEL: THE MAJOR COMPONENTS PROTOCOLS every member must participate STATE can be centralized or distributed across the members in any way ALGORITHMS can be centralized or distributed across the members in any way session protocol where members are registered in underlays registrations of overlay members in this layer members attachments locations sessions member algorithm attachment algorithm location algorithm forwarding protocol links routes link algorithm routing algorithm

9 A NEW LAYER MODEL: SCOPE AND LEVEL layers are arranged in a uses hierarchy, which defines levels the scope of a layer is the set or class of processes that could be members application process APPLICATION LAYERS INTERNET CORE (IP, TCP, UDP) 1 IP interface of machine 2 this describes the classic Internet architecture in terms of the new layer model or geomorphic view LANs 1 2 gateway Ethernet interface

10 CLASSIC LAYERS OR OSI REFERENCE MODEL THE GEOMORPHIC VIEW OF NETWORKING there is a fixed number of levels the scope of each layer is global, so layer = level each layer/level has a specialized function there can be any number of levels some layers have small or local scopes each layer is a microcosm of networking, containing all the basic components (state components and mechanisms)

11 WE CALL THIS THE GEOMORPHIC VIEW OF NETWORKING BECAUSE THE COMPLEX ARRANGEMENT OF LAYERS RESEMBLES THE EARTH S CRUST

12 HOW CAN THE GEOMORPHIC VIEW HELP? SIMPLICITY NO MORE TUNNELS the only encapsulation is inter-layer encapsulation NO MORE ARGUING ABOUT NAMES vs. IDENTIFIERS vs. LOCATORS vs. ADDRESSES each layer has exactly one name space, designed for the purposes of the layer (whatever you wish to call the names) the goal is to describe architectures with fewer, better-understood mechanisms rather than many ad hoc mechanisms whose interactions we do not understand hopefully, there will be no constraints on which architectures can be described

13 HOW CAN THE GEOMORPHIC VIEW HELP? GENERALIZATION the same basic mechanism is used for different purposes in different layers so all layers can benefit from the same general theories and possibly even implementations routing is vestigial APPLICATION LAYER user service purpose of routing is security CLOUD LAYER browser security filter server purpose of routing is reachability INTERNET LAYER host router host router host

14 HOW CAN THE GEOMORPHIC VIEW HELP? UNDERSTANDING THERE ARE TWO DISTINCT PATTERNS FOR MOBILITY a discovery enabled by the geomorphic view BENEFITING LAYER DYNAMIC ROUTING MOBILITY A B SESSION-LOCATION MOBILITY as the attachments of a member change, its links change, and the routing algorithm must find new routes to it layer state components that change: attachments links routes a a1 a2 LAYER IMPLEMENTING MOBILITY LAYERS WHERE ATTACH- MENT CHANGES b1 b2 b1 b2 as the session endpoint in the overlay changes its location in this layer, the session state changes to match it layer state components that change: locations sessions

15 HOW CAN THE GEOMORPHIC VIEW HELP? A DESIGN HAS ONLY ONE CORRECT DESCRIPTION AN ORGANIZED SPACE OF POSSIBLE DESIGNS CAN BE GENERATED DESIGN COMPARISON picture shows a scalable design for mobility of routers as well as endpoints (a previously unsolved problem) generated within a mobility design space application work session bus company router b00 b30 layer implements dynamic routing mobility for bus active when bus moves, does nothing with individual devices on bus registration when laptop is on the bus b35 port on bus LAN registration when laptop is elsewhere layer implements session-location mobility for laptop active when laptop moves on and off bus, not when bus moves

16 HOW CAN THE GEOMORPHIC VIEW HELP? FORMALIZATION WE HAVE A FORMAL MODEL OF LAYERS AND LAYER COMPOSITION (the uses hierarchy) IN ALLOY this model becomes more complete as we use it to investigate more issues FOR EXAMPLE, WE HAVE A COMPLETE MODEL OF DYNAMIC ROUTING AND SESSION-LOCATION MOBILITY this model has been used to prove that dynamic routing and sessionlocation mobility are compositional within a layer: they co-exist and work without interference layer implements dynamic routing mobility for bus layer implements session-location mobility for laptop

17 SUMMARY WE NEED MULTIPLE, CUSTOMIZED PROTOCOL STACKS WITH... better communication services design principles code generation and re-use THE GEOMORPHIC VIEW OF NETWORKING IS A USEFUL TOOL IT OFFERS... simplicity generalization understanding design comparison formalization Isn t this all too low-level for middleware and service-oriented architecture? NO! For example, mobility is everywhere you look. FINANCIAL APPLICATION LAYER my employer s payroll link used for direct deposit my bank account BANKING LAYER if I change banks, the direct deposit of my paycheck should still work bank A ident bank B ident