Does it have to be that complicated? Thoughts on a next-generation Internet Henning Schulzrinne...

Does it have to be that complicated? Thoughts on a next-generation Internet

Henning SchulzrinneInternet Real Time Laboratory

Computer Science Dept., Columbia University, New York

http://www.cs.columbia.edu/IRT

COMSWARE (Jan. 2006) 2

Overview

• The transformation in keynote “big pictures”

• The transition in cost metrics• What has made the Internet

successful?• Some Internet problems • Simplicity wins• Architectural complexity• New protocol engineering


Philosophy transition

One computer/phone,many users

One computer/phone,one user

Many computers/phones,one user

anywhere,any time

any media

right place (device),right time,right media

~ ubiquitous computing

mainframe erahome phone

party line

PC eracell phone era


Evolution of VoIP

“amazing – thephone rings”

“does it docall transfer?”

“how can I make itstop ringing?”

1996-2000 2000-2003 2004-

catching upwith the digital PBX

long-distance calling,ca. 1930 going beyond

the black phone


Transition in cost balance• Total cost of ownership

– Ethernet port cost $10– about 80% of Columbia CS’s system support

cost is staff cost• about $2500/person/year 2 new PCs/year• much of the rest is backup & license for spam

filters • Does not count hours of employee or son/daughter

time• PC, Ethernet port and router cost seem to have

reached plateau– just that the $10 now buys a 100 Mb/s port

instead of 10 Mb/s


What has made the Internet successful?• 36 years approaching mid-life crisis time

for self-reflection next generation suddenly no longer

finds it hip• Transparency in the core

– new applications• Narrow interfaces

– socket interface, resolver• HTTP and SMTP messaging as

applications– prevent change leakage

• Low barrier to entry– L2: minimalist assumptions– technical: basic connectivity is within– economical: below $20?

• Commercial off-the-shelf systems– scale: compare 802.11 router vs. cell

base station

Ethernet

web server


IP “hourglass”

email WWW phone...

SMTP HTTP RTP...

TCP UDP…

IP

ethernet PPP…

CSMA async sonet...

copper fiber radio...Steve Deering, IETF Aug. 2001


User issues (guesses)• Lack of trust

– small mistakes identity gone– waste time on spam, viruses, worms, spyware, …

• Lack of reliability– 99.5% instead of 99.999%– even IETF meeting can’t get reliable 802.11 connectivity

• Lack of symmetry– asymmetric bandwidth: ADSL– asymmetric addressing: NAT, firewalls client(-server)

only, packet relaying via TURN or p2p• Users as “Internet mechanics”

– why does a user need to know whether to use IMAP or POP?

– navigate circle of blame


Technical infrastructure issues• Sensor networks

– addressing mechanisms not suitable geographic addressing, self-routing packets

– TCP model– partial and temporal connectivity

• Mobile ad-hoc networks (MANET– address acquisition?

• Mobile networks (e.g., plane [Connexion], train, car, …)

– routing granularity: each plane a BGP AS?– network merging and splitting


Technical infrastructure issues• Multi-homing and mobility

– address vs. locator issues• Large-scale Internet

– secure routing– routing scaling (60,000 AS)

• Architecture– standardization delays now routinely 3-5

years for minor extensions– resistance to change at ≤ L4– difficulty in deploying new applications:

• Internet service = outbound port 80 and 443


What has gone wrong?• Familiar to anybody who has an old house…• Entropy

– as parts are added, complexity and interactions increase• Changing assumptions

– trust model: research colleagues far more spammers and phishers than friends• AOL: 80% of email is spam

– internationalization: internationalized domain names, email character sets

– criticality: email research papers transfers $B and dial “9-1-1”

– economics: competing providers• “Internet does not route money” (Clark)

• Backfitting– had to backfit security, I18N, autoconfiguration, …

Tear down the old house, gut interior or more wall paper?


In more detail…• Deployment problems• Layer creep• Simple and universal wins• Scaling in human terms• Cross-cutting concerns, e.g.,

– CPU vs. human cycles• we optimize the $100 component, not the

$100/hour labor– introspection– graceful upgrades– no policy magic


The transformation of protocol stacks

application

network

transport

presentationsession

link

physical

H. Zimmermannca. 1980

application

IP

TCP

802.3

physical

Internetca. 1995

application

IP

TCP

SOAPHTTP

PoS, ATM

physical

MPLS, PoE

IP-in-IP

Internetca. 2005


Cause of death for the next big thing

QoS multi-cast

mobile IP

active networks

IPsec IPv6

not manageable across competing domains

not configurable by normal users (or apps writers)

no business model for ISPs

no initial gain

80% solution in existing system (NAT)

increase system vulnerability


Simple wins (mostly)• Examples:

– Ethernet vs. all other L2 technologies– HTTP vs. HTTPng and all the other hypertext attempts– SMTP vs. X.400– SDP vs. SDPng– TLS vs. IPsec (simpler to re-use)– no QoS & MPLS vs. RSVP– DNS-SD (“Bonjour”) vs. SLP– SIP vs. H.323 (but conversely: SIP vs. Jabber, SIP vs.

Asterisk)– the failure of almost all middleware– future: demise of 3G vs. plain SIP

• Efficiency is not important– BitTorrent, P2P searching, RSS, …


Measuring complexity• Traditional O(.) metrics rarely helpful

– except maybe for routing protocols• Focus on parsing, messaging complexity

– marginally helpful, but no engineering metrics for trade-offs

• No protocol engineering discipline, lacking– guidelines for design– learning from failures

• we have plenty to choose from – but hard to look at our own (communal) failures

– re-usable components• components not designed for plug-and-play• “we don’t do APIs” we don’t worry about whether a

simple API can be written that can be taught in Networking 101


Measuring complexity• Conceptual complexity

– can I explain the protocol operation in one class?

– e.g., counter examples PIM-SM, MADCAP, OSPF• Observable vs. hidden

– one side can see, without “god box”– hidden state and actions increase information

complexity• unknown variables can have any state

• Number of system interfaces– see BISDN, 3GPP, NGN, …


Possible complexity metrics• new code needed (vs. reuse) less likely to be buggy or have

buffer overflows– e.g., new text format almost the same– numerous binary formats– security components

• new identities and identifiers needed• number of configurable options + parameters

– must be configured & can be configured (with interop impact)

– discoverable vs. manual/unspecified– SIP experience: things that shouldn’t be configurable will be– RED experience: parameter robustness– mute programmer interop test: two implementations, no

side channel• number of “left-to-local policy”

– DSCP confusion• start-up latency (“protocol boot time”)

– IPv4 DAD, IGMP


Democratization of protocol engineering• Traditional Internet application protocols (IETF et al.):

– one protocol for each type of application:• SMTP for email, ftp for file transfer, HTTP for web

access, POP for email retrieval, NNTP for netnews, …• slow protocol development process• re-do security (authentication) for each• each new protocol has its own text encoding

– similarity across protocols: SMTP-style headers» Content-Type: text/plain; charset="us-ascii"; format=flowed

– large parsing exposure new buffer overflows for each protocol

• Separate worlds:– most of the new protocols in the real world based on WS– IETF stuck in bubble of one-off protocols more fun!

• re-use considered a disadvantage• insular protocols that have local cult following (BEEP)


The transformation of protocol design• One application, one protocol common infrastructure for

new application• Old model:

– RPC for corporate “one-off” applications– custom protocols for common Internet-scale applications

• Far too many new applications– and not enough protocol engineers– network specialist application specialist– new IETF application protocol design takes ~5 years

• Many of the applications (email to file access) could be modeled as RPC

custom text

protocol

(ftp)

RFC 822 protocol

(SMTP, HTTP, RTSP, SIP, …)

use XML for protocol bodies

(IETF IM & presence)

SOAP and other XML protocols

ASN.1-based

(SNMP, X.400)


Why are web services succeeding(*) after RPC failed?

• SOAP = just another remote procedure call mechanism– plenty of predecessors: SunRPC, DCE, DCOM, Corba, …– “client-server computing”– all of them were to transform (enterprise) computing,

integrate legacy applications, end world hunger, …• Why didn’t they?• Speculation:

– no web front end (no three-tier applications)– few open-source implementations– no common protocol between PC client (Microsoft) and

backend (IBM mainframes, Sun, VMS)– corporate networks local only (one site), with limited

backbone bandwidth

(*) we hope


Why did web services succeed after RPC failed?

• More speculation:– Corba, DCOM, SunRPC: no real security story

• had custom-made security instead of TLS– Many initially designed for LAN only

• e.g., use of UDP, service naming by ports only– Limited language support

• e.g., no PHP or Perl support for Corba– Limited platform support

• DCOM = Microsoft• Corba = all-but-Microsoft


Technical challenges for web services• Resistance to common protocol

infrastructure• “Yet another RPC fad”• SOAP overhead = the price of

generality:– SOAP envelope– inefficient binary encoding

(images, etc.) compared to MIME multipart

– klumsy load-balancing and redundancy

– inefficient implementations• high start-up costs

• XML problems– XML schema hard to work with– Namespace clutter– hard to extend among multiple

independent parties ( RelaxNG)• can only do <any ##other>

servlets

SOAP

PHP


Emerging light-weight alternatives• Many SOAP services, but public services are often

XML-RPC only– or even HTTP POST

• Examples:– eBay, Amazon, Google– Ajax

• Reasons?– SOAP envelope adds modest value– Scripting languages have– REST principles: identify objects by URL in

request, not by identifier in RPC body• easier dispatch to PHP/Ruby/… scripts


Time for a new protocol stack?• Now: add x.5 sublayers and overlay

– HIP, MPLS, TLS, …• Doesn’t tell us what we could/should do

– or where functionality belongs– use of upper layers to help lower layers (security

associations, authorization)– what is innate complexity and what is entropy?

• Examples:– Applications: do we need ftp, SMTP, IMAP, POP, SIP, RTSP,

HTTP, p2p protocols?– Network: can we reduce complexity by integrating

functionality or re-assigning it?• e.g., should e2e security focus on transport layer

rather than network layer?– probably need pub/sub layer – currently kludged locally

(email, IM, specialized)


NSF “Green Field” approach• US National Science Foundation (NSF) working on new

funding thrust next-generation Internet– idea: incremental components new architecture– vs. traditional “brown field” approach

• Two major components– GENI: large-scale experimental testbed for testing next-

generation ideas• building on PlanetLab (hundreds of public-access

servers) p2p, CDN, measurement infrastructures• probably offers circuits (optical or virtual with

bandwidth guarantees)• ~$300M (not yet allocated)

– FIND:• regular research program within NETS ($15m)• prepare architecture designs


NSF: FIND and GENI, cont’d• Fundamental notions:

– not constrained by existing Internet architecture• Difficulties:

– not coordinated too many moving pieces?– no single research team can do everything– point optimization: Internet for – benchmarks missing

• how do you compare architectures?• are there quantifiable requirements?• are there metrics to compare different

approaches?• Cynic’s prediction based on the past:

– IPv6: “you’ll get security, QoS, autoconfiguration, mobility, …”

– IPv4: “good ideas, I’ll do those, too”


(My) guidelines for a new Internet• Maintain success factors,

such as– service transparency– low barrier to entry– narrow interfaces

• New guidelines– optimize human cycles,

not CPU cycles– design for symmetry– security built-in, not

bolted-on– everything can be

mobile, including networks

– sending me data is a privilege, not a right

– reliability paramount– isolation of flows

• New possibilities:– another look at circuit

switching?– knowledge and control

(“signaling”) planes?– separate packet

forwarding from control– better alignment of costs

and benefit– better scaling for Internet-

scale routing– more general services


More “network” services• Currently, very specialized and limited

– packet forwarding– DNS for identifier lookup– DHCP for configuration

• New opportunities– packet forwarding with control– general identifier storage and lookup

• both server-based and peer-to-peer– SLP/Jini/UDDI service location ontology-based

data store– network file storage for temporarily-

disconnected mobiles– network computation translation, relaying– trust services ( IRT trust paths work)


Security• More than just encryption!• Need identity and role-based certificates• May want reverse-path reachability (bank customer)

asking user network

user do I know this person? is he a likely sender of spam?is this really a bank?

am I connected to a “real” network or an impostor?

network

is this a customer? is this BGP route advertisement legitimate?


Summary• Traditional protocol engineering

– “must do congestion control”– “must do security”– “must be efficient”

• New module engineering– must reduce operations cost– out-of-the-box experience– re-usable components

• most protocol design will be done by domain experts (cf. PHP vs. C++)

• What would a clean-room design look like?– keep what made Internet successful– generalize & adjust to new conditions

Managing (VoIP) Applications – DYSWIS

Henning SchulzrinneDept. of Computer Science

Columbia UniversityJuly 2005


Overview• User experience for VoIP still inferior• Existing network management doesn’t work

for VoIP and other modern applications• Need user-centric rather than operator-

centric management• Proposal: peer-to-peer management

– “Do You See What I See?”• Also use for reliability estimation and

statistical fault characterization


VoIP user experience• Only 95-99.5% call attempt success

– “Keynote was able to complete VoIP calls 96.9% of the time, compared with 99.9% for calls made over the public network. Voice quality for VoIP calls on average was rated at 3.5 out of 5, compared with 3.9 for public-network calls and 3.6 for cellular phone calls. And the amount of delay the audio signals experienced was 295 milliseconds for VoIP calls, compared with 139 milliseconds for public-network calls.” (InformationWeek, July 11, 2005)

• Mid-call disruptions• Lots of knobs to turn

– Separate problem: manual configuration


Diagnostic undecidability• symptom: “cannot reach server”• more precise: send packet, but no

response• causes:

– NAT problem (return packet dropped)?– firewall problem?– path to server broken?– outdated server information (moved)?– server dead?

• 5 causes very different remedies– no good way for non-technical user to

tell• Whom do you call?


Circle of blame

OS VSP

appvendor

ISP

must be a Windows registryproblem re-installWindows

probably packetloss in yourInternet connection reboot your DSL modem

must beyour software upgrade

probably a gateway fault choose us as provider


Traditional network management model

SNMP

X

“management from the center”


Old assumptions, now wrong• Single provider (enterprise, carrier)

– has access to most path elements– professionally managed

• Typically, hard failures or aggregate problems– element failures– substantial packet loss

• Mostly L2 and L3 elements– switches, routers– rarely 802.11 APs

• Indirect detection– MIB variable vs. actual protocol performance

• No real end system management– DMI & SNMP never succeeded– each application does its own updates


Example VoIP: managing the protocol stack

RTP

UDP/TCP

IP

SIP

no routepacket loss

TCP neg. failureNAT time-outfirewall policy

protocol problem

playout errors

mediaecho

gain problemsVAD action

protocol problem

authorizationasymmetric conn (NAT)


Example VoIP: call lifecycle view

get ad

dres

ses

SIP

INVIT

E

get 20

0 O

K

REG

ISTE

R

exch

ange

med

iate

rmin

ate

call

STUN failur

e

auth?registra

r?

outbound

proxy?dest.

proxy?

loss?gain?

silence suppressio

n?


Types of failures• Hard failures

– connection attempt fails– no media connection– NAT time-out

• Soft failures (degradation)– packet loss (bursts)

•access network? backbone? remote access?

– delay (bursts)•OS? access networks?

– acoustic problems (microphone gain, echo)


Examples of additional problems• ping and traceroute no longer works reliably

– WinXP SP 2 turns off ICMP– some networks filter all ICMP messages

• Early NAT binding time-out– initial packet exchange succeeds, but then TCP

binding is removed (“web-only Internet”)\• policy intent vs. failure

– “broken by design”– “we don’t allow port 25” vs. “SMTP server

temporarily unreachable”


“Do You See What I See?”• Each node has a set of active and passive

measurement tools• Use intercept (NDIS, pcap)

– to detect problems automatically• e.g., no response to HTTP or DNS request

– gather performance statistics (packet jitter)– capture RTCP and similar measurement

packets• Nodes can ask others for their view

– possibly also dedicated “weather stations”• Iterative process, leading to:

– user indication of cause of failure– in some cases, work-around (application-layer

routing) TURN server, use remote DNS servers

• Nodes collect statistical information on failures and their likely causes


Failure detection tools

• STUN server– what is your IP address?

• ping and traceroute• Transport-level liveness

– open TCP connection to port

– send UDP ping to port

media

RTP

UDP/TCP

IP


Need failure statistics• Which parts of the network are most

likely to fail (or degrade)– access network– network interconnects– backbone network– infrastructure servers (DHCP, DNS)– application servers (SIP, RTSP,

HTTP, …)– protocol failures/incompatibility

• Currently, mostly guesses• End nodes can gather and

accumulate statistics


Conclusion• Internet middle-aged time for reflection• can we keep what has worked and re-consider the

others?• need to work on control, management and

reflection• opportunity for new building blocks vs. classical

middleware• opportunity

Does it have to be that complicated? Thoughts on a next-generation Internet Henning Schulzrinne...

Documents

Transcript of Does it have to be that complicated? Thoughts on a next-generation Internet Henning Schulzrinne...