The Post-PC Era: It’s About The Services

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The Post-PC Era:It’s About The Services

Randy H. KatzComputer Science Division

Electrical Engineering and Computer Science DepartmentUniversity of California, Berkeley

Berkeley, CA 94720-1776

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Presentation Outline• Heterogeneity in Devices and Networks• A New Service Architecture: SAHARA• Reachability as a Service• New Directions• Summary and Conclusions

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The Old Days

All will demand broadbandInternet connectivity

Shape of Things Today: Diverse Appliances and

Devices

Game ConsolesPersonal Digital Assistants

Digital VCRsCommunicators

Smart TelephonesE-Toys

… and 10BaseT won’t be sufficient

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Ever More SophisticatedMobile Phones

• Graphical UI/Joystick control• Voice dialing, voice recognition,

voice recorder• Integrated digital camera w/

640 x 480 res image capture• IR + Bluetooth + Phone2Phone

+ Phone2PC• Java-support for 3rd party apps• WAP + High-speed data over

GSM + HSCSD + GPRS• But often you need to compute!

Screen. Keyboard. StorageNokia 7650Nokia 7600

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High-tier

Low-tier

High Mobility Low MobilityWide Area

Local Area

Promise: Ubiquitous Connectivity

• Seamless data mobility among local and wide-area wireless networks via Mobile IP handoff

– Two orthogonal technologies:» High speed data over cellular for high mobility,

wide-area coverage» Even higher speed data over WLAN hot spots for

low mobility, local area coverage

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Network Services: Communications

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Network Services: Access

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Best Implementation Method:the Internet Programming Model

• Service composition across the network– Network-aware Distributed System architecture

• Bottlenecks near edge, not core– Service deployment points close to where used– Service implementation topology-aware

• Enabled by:– Computing embedded in communications fabric:

distributed, wide-area, topology-aware– Emerging class of programmable network

elements– Per session characterization, processing,

prioritization, monitoring, management, billing

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AccessNetworks

Core Networks

Internet Connectivity and Processing

Transit Net

Transit Net

Transit Net

PrivatePeering

NAPPublic

Peering

InternetDatacenter

PSTNRegionalWirelineRegionalVoiceVoice

CellCell

Cell

CableModem

LANLANLAN

Premises-based

WLANWLANWLAN

Premises-based

Operator-based

H.323Data

Data

RAS

Analog

DSLAM

H.323

Hot Spots

PNE

PNE

PNE

PNEPNE

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Composed Applications:Universal In-box – Message type (phone,

email, fax)– Access network (data,

telephone, pager)– Terminal device (computer,

phone, pager, fax)– User preferences & rules– Message translation & storage

Separate end device andnetwork from end-to-endcommunications service:indirection via compositionof translators with access

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Private Brand NetOperator (MVNO)

Single LocationNetwork Operator

(SLN)Single LocationNetwork Operator

(SLN)CooperativeNetworking

Full ServiceNetworkOperator


Challenge: Single Operator vs. “Virtual” Composed Operator

Premises-basedAccess


Single LocationNetwork Operator

(SLN)

SLN Aggregator

WISP Aggregator

RevenueSharing

Single Sign-onUnified Billing

Billing, ECommerceAuthentication

Inter-site Mobility

VPN Operator, Client-Software

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Challenge: Multiple “Operators”

Coordination Issues• Top-Down vs. Bottom-Up Network Deployment– Operator vs. aggregator/virtual operator models– Neighborhood cooperative mesh networks

• Security– Blurring of distinction between public & private networks: rogue

APs – Interoperation among service/access providers– End-to-end considerations in untrusted infrastructure– Authorization and billing for multi-party services

• Resource Management– Unlicensed but ignore coordination at the cost of performance– Radio resource planning and allocation

• Service Creation and Personalization Platform– Intelligent edge services: service and policy management, user

mobility and profiling, charging and billing– Deployments enabled by edge-network programmable network

elements

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Challenge: Agile or Fragile Networking?

• Baltimore Tunnel Fire, 18 July 2001– “… The fire also damaged fiber optic cables, slowing Internet

service across the country, …”– “… Keynote Systems … says the July 19 Internet slowdown was

not caused by the spreading of Code Red. Rather, a train wreck in a Baltimore tunnel that knocked out a major UUNet cable caused it.”

– “PSINet, Verizon, WorldCom and AboveNet were some of the bigger communications companies reporting service problems related to ‘peering,’ methods used by Internet service providers to hand traffic off to others in the Web's infrastructure. Traffic slowdowns were also seen in Seattle, Los Angeles and Atlanta, possibly resulting from re-routing around the affected backbones.”

– “The fire severed two OC-192 links between Vienna, VA and New York, NY as well as an OC-48 link from, D.C. to Chicago. … Metromedia routed traffic around the fiber break, relying heavily on switching centers in Chicago, Dallas, and D.C.”

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Evolution of Internet

• Diversity of devices and access networks– Wireless overlays provide continuum of connectivity– Increasing importance of “services” to mitigate

diversity/provide new functionality and customization– Global services via managed composition– Enabled by processing embedded in the network

interconnect, locally and globally• Multiple service providers/admin domains

– No single operator deploys the global service– But can a reliable service be deployed by multiple,

uncoordinated providers?• Overcoming the reliability bottlenecks

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The SAHARA Project• Service• Architecture for• Heterogeneous• Access,• Resources, and• Applications

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SAHARA Goals• New mechanisms, techniques for end-to-

end services w/ desirable, predictable, enforceable properties spanning potentially distrusting service providers

• Architecture for service composition and inter-operation across separate administrative domains, supporting peering and brokering, and diverse business, value-exchange, access-control models

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Exploits the New Opportunities

• New things you can do inside the network• Connecting end-points to “services” with

processing embedded in the network fabric• “agents” not protocols, executing inside the

network• Location-aware, data format aware• Controlled violation of layering necessary!• Distributed architecture aware of network

topology• No single technical architecture likely to

dominate: think overlays, system of systems

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IsolatedIntra-cloud

serviceTraditional

unicastpeering

Administrativedomain

Admindomain

Administrativedomain

AdmindomainAdmin

domain

Overlays:Creating New Interdomain Services

• Deploy new services above the routing layer– E.g., interdomain multicast management and peering– E.g., alternative connectivity for performance, resilience

Planet-Lab

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Layered Reference Model for Service Composition

IP Network

Enhanced Links(Intra-domain)

Enhanced Paths(Inter-domain)

End-to-End NetworkWith Desirable Properties

Middleware Services

Applications Services

End-User Applications

Conn

ectiv

ityPl

ane

Appl

icatio

nPl

ane

Serv

iceCo

mpo

sitio

n

OverlayNetwork“Links”

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Routing as a Composed Service• Composable Interdomain Routing: BGP

– Complex policy interactions yield non-optimal routes– Slow convergence to routing changes render parts of the IP

address space unreachable for tens of minutes at a time– Vulnerabilities to malicious attacks and unintentional mistakes

• Routing as a Reachability “Service”– Implementing paths between composed service instances,

e.g., “links” within an overlay network– Multi-provider environment, no centralized control

• Desirable Enhanced Properties– Performance: controlled loss and bandwidth guarantees

(OverQoS)– Reliability: detect reachability failure, faster convergence– Security: verify believability of routing advertisements

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Overlay Approach for Achieving Desirable Performance: OverQoS

• Embed QoS functionality in Internet via Overlays

– Overlay nodes implement QoS functions– No support needed from IP routers

• Challenges– Nodes not connected to congested points– Have no control over cross-traffic– Cannot avoid losses (reducing sending rate doesn’t help!)

• Why Overlays?– Previous QoS architectures not deployed globally– Overlay-model empowers third-party providers to provide

some form of QoS

Lakshmi Subramanian, Hari Balakrishnan, Ion Stoica

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OverQoS Method

Entry Node

Exit Node

Overlay Traffic

Redundant Traffic

N-TCP pipe

• Step 1: Aggregate Loss and Bandwidth Control

Flow 2

Flow 1

Scheduler Rate Ctrl

• Step 2: Distribute b/w and loss among flows

Lakshmi Subramanian, Hari Balakrishnan, Ion Stoica

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OverQoS Method

OverlayNode

OverlayNode

OverlayNode

Flow 1

Flow 2 Flow 3

• Step 3: Provide QoS guarantees (b/w,loss) to a flow “bundle” by “stitching” guarantees on overlay links

• Step 4: Perform QoS-routing of multiple flows with different requirements on overlay network

• Used successfully to support Counterstrike gameLakshmi Subramanian, Hari Balakrishnan, Ion Stoica

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Agility in Response to Route Changes:Internet Converges Slowly

• Convergence Times [Labovitz et al.]– Theory: O(n!) (n: number of ASes)– Practice: linear with the longest backup path length– Measurement: up to 15 minutes

• Why so slow?– BGP protocol effects: path exploration– Route flap damping!?

» Delay convergence of relatively stable routes» Unexpected interaction between flap damping and

convergence

Morley Mao, Ramesh Govindan, George Varghese

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Flap Damping (RFC2439)

• Suppress routes that change too frequently– For each peer, per

destination, keep penalty value, increase for each route change (aka “flap”)

– Exponential decay

• Parameters:– Fixed: Penalty increment– Configurable: half-life,

suppress-, reuse-threshold, max suppressed timeReuse threshold

Time

Pena

lt y

Suppress threshold

Exponentially decayed

)'()()'( ttetPtP


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Selective Route Flap Damping• Flaps occur due to certain topologies among

routers causing triggered announcements and withdrawals– Not toy scenarios!

• Approach: ignore flap sequences indicating path exploration—these likely to trigger more changes in near future

• Redefine a flap:– “Any route change is considered a flap” “must alter direction

of route preference value change, relative to flaps”– Flaps due to withdrawal: increasing AS_Path lengths, route

value keeps decreasing• Morley Mao Ph.D. dissertation (AT&T Labs)


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• Stability achieved through flap damping [RFC2439]• BUT unexpected:flap damping delays

convergence!

Topology: clique of routers

Selective flap damping– Duplicate suppression: ignore flaps

caused by transient convergence instability

– Eliminates undesired interaction without sacrificing stability

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Can You Depend on Your Routes? BGP Route Verification

• BGP is highly vulnerable!– Allows ASes to propagate invalid routes that deviate

from actual Internet topology– Critical implications for performance and correctness

» Misconfigured routers cause long outages• Drop packets (“blackholes”)• Roughly 6% of misconfigurations cause reachability

problems» Malicious routers cause even greater damage

• Misroute or eavesdrop on traffic• Impersonate destinations• Collude with other nodes to make detection difficult

Lakshmi Subramanian, Ion Stoica, Volker Roth, Scott Shenker

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“Listen” and “Whisper”• One approach: route verification with PKI

authentication– Deployment has been difficult– Political issues with single PKI: who controls it?

• Alternative: route consistency testing to detect suspicious ASes– Listen: “Passive” TCP-probing

» Modified nodes watch TCP traffic to detect reachability problems» No modifications to BGP, incrementally deployable» Ineffective for detecting malicious hosts: can’t distinguish between

genuine and malicious hosts– Whisper: Advertisements sent consistent with those received

» Route advertisement invalid if AS-PATH does not match its propagation path (Mao: true for 8% of observed paths!)

» Use redundant net connectivity to verify route consistency


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Detection Scenarios


CNN

Browser

Browser

MaliciousNode

Internet

No detectionin this case

BrowserCNN

Browser

Alarm Alarm and Avoid

Adversarial Router onthe Regular Path

IsolatedAdversary

Adversary AnnouncingMany Invalid Routes

CNN

Browser

Reuters

Browser

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Whisper (aka “Telephone”)

• Alternative Whisper Protocols– Loop Whisper, (Weak/Strong) Split Whisper– Vary in ability to detect malicious behavior given acceptable

levels of false positive rate

Verifier

Originator

IntermediaryIntermediary’

Route Propagation

Advertisements

Verifier

Originator

IntermediaryIntermediary’

Loop Testing

Advertisements


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The OASIS Project•Overlays and •Active •Services for •Internetworked •Storage

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New Opportunity:“The Computer is the

Network”• Emergence of Programmable Network Elements

– First Gen Network Appliances, Directors– Storage Virtualizers, Intrusion Detectors, Traffic Shapers, Server

Load Balancers, MIE accountants– Next Gen: Third Party Programmable beyond rules

• Generalized PNE programming and control model– Generalized “virtual machine” model for this class of devices– Retargetable for different underlying implementations

• Apps of Interest– Network Services: L7 switching, firewalls, intrusion and infected

machine detection, storage virtualization, network monitoring and management, etc.

– Network storage, iSCSI support– Streaming media transcoding/adaptation– Billing, accounting, stream customization for Mobile Network Edge

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Proliferation of Network Appliances

In-the-Network Processing: the Computer IS THE Network

F5 Networks BIG-IP LoadBalancerWeb server load balancerPacketeer PacketShaper

Traffic monitor and shaper

Ingrian i225SSL offload appliance

Network Appliance NetCacheLocalized content delivery platform

Nortel Alteon Switched FirewallCheckPoint firewall and L7 switch

Cisco IDS 4250-XLIntrusion detection system

Cisco SN 5420IP-SAN storage gateway

Extreme Networks SummitPx1L2-L7 application switch

NetScreen 500Firewall and VPN

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OASIS Vision• Problem

– Common programming/control environment for diverse network elements to realize full power of “inside the network” services and applications

• Approach– Software toolkit and VM architecture for PNEs, with

retargetable optimized backend for diverse appliance-specific architectures

• Current Focus – Network health monitoring, protocol interworking and packet

translation services, iSCSI processing and performance enhancement, intrusion and worm detection and quarantining

• Potential Impact– Open framework for multi-platform appliances, enabling third

party service development– Provable application properties and invariants; avoidance of

configuration and “latest patch not installed” errors

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Generic PNE Architecture

InterconnectionFabric

Inpu

t Por

ts

Outp

ut P

orts

BuffersBuffersBuffers

TagMem

CPCPCPAP

ActionProcessor

CPCPCPCP

ClassificationProcessor

Rules &Programs

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OASIS Testbed• Programmable Networking

Testbed– Alteon Filter Programmable

Level 7 Switches» Next generation significantly

more third party programmable

– 2 x Enterprise Class Routers– (Many) 1U PCs

• In discussion– Nortel + IBM on Blade Center

Storage Servers for UDCs– Cisco IOS Next Generation (ION)

Programmable Packet Filters

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SAHARA• Evolve Internet architecture better supporting

multi-network/multi-service provider model– Dynamic environment, many service providers & service

instances– Achieve desirable properties across multiple, potentially

distrusting (Internet) service providers– Exploit PlanetLab infrastructure to construct wide-area

prototype• Routing as a composed service

– Essential for successfully connecting applications endpoints in a distributed network environment

» QoS through Overlays: loss and bandwidth guarantees» Enhanced route reliability through fast convergence» Security: BGP Verification/Detection + Containment

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New Service ArchitectureIntegrated Communications and Processing

• Increasing diversity of interconnected devices• Increasing importance of “services” to mitigate

diversity/provide new functionality and customization– Refocus from performance to reliability/dependendabilty

• Enabled by processing embedded in the network interconnect, locally and globally– “Active networking” is real

• Global services via managed composition– Role of multiple service providers and administrative domains– Separation of services from connectivity via overlays– No single operator deploys the global service– Predictable performance and end-to-end reliability

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The Post-PCEra:

It’s About the Services

Randy H. Katz

Thank You!

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AnyQuestions

?

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The Post-PC Era:It’s About The Services

Randy H. KatzComputer Science Division

Electrical Engineering and Computer Science DepartmentUniversity of California, Berkeley

Berkeley, CA 94720-1776

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Controlled-Loss Virtual Link (CLVL)

• Two parameters:– Statistical bound on loss rate, q (<= p; typically << p)– Capacity, c(t), possibly time-varying

• Can prove: if offered load < c(t), then loss rate < q

• How is c(t) determined?– Given f(t) to be the redundancy factor: c(t) = b(t)( 1- f(t))

Buffer mgmt &Scheduling & Traffic regulator

Coderc(t), q De-

coderb(t), p(t)

Flow 1

Flow 2

Flow n

OverQos Nodecontrol planeCLVL

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Characterizing the Internet Hierarchy from Multiple Vantage

Points• Customer-Provider Relationships

– Customer pays provider for Internet access– AS exports customer’s routes to all neighbors– AS exports provider’s routes only to its customers

• Peer-to-Peer Relationships– Peers exchange traffic between their customers – Free of charge (assumption of even traffic load)– AS exports a peer’s routes only to its customers

Sharad Agarwal. Lakshmi Subramanian, Jennifer Rexford

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These Relationships Matter!• Useful for:

– Placement of servers for content distribution– Selection of new peers or providers for an AS– Analyzing convergence properties of BGP– Installing route filters to protect against misconfiguration– Understanding basic structure of the Internet

• Knowing the AS graph is Not Enough– Interdomain routing is not shortest-path routing– Some paths not allowed (e.g., transit through a peer)– Local preference of paths (e.g., prefer customer path)– Node degree does not define the Internet hierarchy

• Need to Know Relationship between AS Pairs

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Underlying AS Structure

• Peer-peer relationships hard to infer– Mislabeling P-P edge as P-C does not

change valid path into invalid– Heuristics to detect P-P edges

• Some unusually relationships– Siblings providing mutual transit– Backup relationship for failed connectivity– Misconfigured conventional relationships– Detect cases by analyzing “invalid” paths

• Access to large path set is hard– Exploit BGP routing tables from multiple

vantage points (10 public BGP tables)

April 200111K ASs

24K edges20 AS’sInner Core

129 AS’s

Outer Core897 AS’s

Transit Core

Regional ISPs971 AS’s

Customers8898 AS’s

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Policy Management for BGP

• Integrate BGP with Policy Agent control plane

– Improved BGP convergence through explicit fail over policies

– Constrained routing for performance or trust reasons

– Traffic discrimination, low quality vs. high quality connectivity or fair use issues

– Load balancing outbound and inbound flows for multi-homed ASs

– Sharad Agarwal’s Ph.D. thesis (Sprint ATL)

AS AS

ASAS

AS

PA

PA

PA

PA

PA

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Policy Control Architecture for InterAS RoutingSharad Agarwal

• Tremendous growth in multi-ISP connectivity– But slow failover & weak traffic balancing– Bogus announcement & static peering problems

• Approach : separate policy control architecture– BGP not designed for such issues– Explicit negotiation, traffic & peering intelligence– More flexibility, control, verification

• Impact : media / application service providers, users

– Available connectivity– Manageable congestion

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Tomography-based Overlay Network Monitoring

Yan Chen• Given n end hosts on an

overlay network and O(n2) paths, how to select a minimal subset of paths to monitor so that the loss rates/latency of all other paths can be inferred.

• Approach: select a basis set of k path segments that completely describe all O(n2) paths (k = O(n))

– Select and monitor k linearly independent paths to compute the loss rates of basis set

– Infer the loss rates of all other paths• Find > 97% lossy paths with < 5% false positive

Overlay Network Operation Center

topology

End hosts

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Performance Characteristics of TCP Throughput for Peer Selection in

Peer-to-Peer NetworksWeidong Cui

• Problem– How to select the optimal peer for download from a

set of candidates• Approach

– Evaluate performance of various probing techniques: RTT-based, size-based, time-based

– Investigate the relationship between probing parameters and various download file sizes

• Impact– Improve the performance of p2p networks

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Underlay Optical NetworksTal Lavian

• Problem – Radical mismatch between the optical transmission world and the

electrical forwarding/routing world. Currently, a single strand of optical fiber can transmit more bandwidth than the entire Internet core.

– Mismatch between L3 core capabilities and disk cost. With $2M disks (2PB) can fill the entire core internet for a year

• Approach – Service architecture interacts with the optical control, provides

applications a dedicated, on-demand, point-to-point optical link that is not on the public Internet

• Current Focus – Grid Computing, OGSA, MEMs, 10GE, Optical technologies– OmniNet testbed in Chicago, which will be connected to major

national and international optical networks • Potential Impact

– Enabling technology for Data-Intensive applications (multi Terabytes)

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Estimating Shared Congestion Among Internet Paths

Sridhar Machiraju• Problem

– Given two paths in the Internet, estimate the fraction of packet drops at shared points of congestion (PoCs) using probe flows along the paths

• Approach– Count correlated (simultaneous) packet drops of two

probe flows (UDP or TCP)– “Inflate” the fraction using delay jitter correlation

• Applications using path diversity e.g., multimedia streaming, parallel downloads, etc.

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Routing Dynamics in Simultaneous Overlay Networks

Mukund Seshadri• Problem: When is “greedy” overlay-level route selection

unstable/inefficient, when multiple such overlay networks interact?

• Motivation: why will many overlay networks be deployed?– Due to pure Overlay Network protocols (RON[3], Detour[4], ESM[5])– Due to deployment of overlay primitives (“Path reflection”, i3-arch.)

• Model and Focus: Overlays make independent decisions; no info. shared.

– Size: 50-100 overlay networks; 10-100 nodes each.– App: Multimedia streams, long-lived, need bandwidth level + stability

• Impact: simple design principles to ease deployment of multiple overlay networks

– Randomization of route selection improves stability and loss-rates.» With high path sharing, variation in link b/w, loaded links, low cross-

traffic.– Random-subset method improves stability even more, with comparable loss-

rate, and lower measurement overhead.

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The Post-PC Era: It’s About The Services