content centric networking based on van jacobson’s slide decks uichin lee kaist kse

Content Centric Networking

Based on Van Jacobson’s slide deckshttp://www.ccnx.org/

Uichin LeeKAIST KSE

http://www.ccnx.org/

http://www.ccnx.org/

Talk Plan

• A Brief History of Networking (+Motivation)• Node Model• Routing• Transport

A Brief History of Networking

• Generation 1: the phone system (focus on the wires)

• Generation 2: the Internet (focus on the endpoints)

• Generation 3? dissemination (focus on the data)

The Phone System is not about phones, it’s about connecting wires to

other wires

• The utility of the system depends on running wires to every home & office

• The wires are the dominant cost• Revenue comes from dynamically constructing

a path from caller to callee

A business model built on side effects

• For a telco, a call is not the conversation you have with your mom in Phoenix, it’s a PATH between two end-office line cards

• A phone number is not the name of your mom’s phone, it’s a program for the end-office switch fabric to build a path to the destination line card

Some ways to build paths

Switchboard coordinate(AT&T Operators, 1959)

Sequential switch sequencing(Strowger stepper)

Structural problems with phone systems

• Path building is non-local and encourages centralization and monopoly

• Calls fail if any element in path fails so reliability goes down exponentially as the system scales up

• Data can’t flow until a path is set up so efficiency decreases when setup time or bandwidth increases or holding time decreases

Gen 2: packet switching

• Change point view to focus on endpoints rather than paths

• Data sent in independent chunks and each chunk contains the name of the final destination

• (Transitivity) If node gets a chunk for a different destination, tries to forward it using static configuration or distributed routing computation

Don Davies, 1963

Paul Baran, 1964

Packet switching used the existing wires, it just used them differently

In 1964 these ideas were ‘lunatic fringe’ — anyonewho knew anything about communicationsknew this could never work

ARPAnet September, 1971

ARPAnet

• The ARPAnet was built on top of the existing phone system– It needed cheap, ubiquitous wires– It needed a digital signaling technology (but not

anything like the state of the art)

At the outset, the new network looked like an inefficient way to use the old network

The rest of the research community put enormous effort into the details of circuit switched data. In the end it didn’t matter

The CATENET and TCP/IP

• Packet switching worked so well that by 1973 everyone wanted a network

• Each was done as a clean slate so they didn’t interoperate

• Since Paul had already abstracted out all the topological details Vint realized that a common encapsulation & addressing structure could glue together arbitrary networks

Bob Kahn, 1973

Vint Cerf, 1973

Multinetwork Demonstration 1977

TCP/IP wins

• Adaptive routing lets system repair failures and hook itself up initially.

• Reliability increases exponentially with system size.

• No call setup means high efficiency at any bandwidth, holding time or scale.

• Distributed routing supports any topology and tends to spread load and avoid a hierarchy’s hot spots.

TCP/IP issues

• “Connected” is a binary attribute: you’re either part of the internet and can talk to everything or you’re isolated.

• Becoming part of the internet requires a globally unique, globally known IP address that’s topologically stable on routing time scales (minutes to hours).– connecting is a heavy weight operation– the net doesn’t like things that move

• Like the phone system before it, TCP/IP solved the problems it set out to solve so well that even today it’s hard to conceive of an alternative.

• TCP/IP’s issues don’t reflect an architectural failing but rather its massive success in creating a world rich in information & communication.

• When TCP/IP was invented there were few machines and many users per machine. Today there are many machines and many machines per user, all with vast amounts of data to be synchronized & shared.

• And that creates an entirely new class of problem . . .

• The raison d’être of today’s networking, both circuit switched and TCP/IP is to allow two machines to have a conversation

• The overwhelming use (>99% by most measurements) of today’s networks is for a machine to acquire named chunks of data (like web pages, or email messages)

Acquiring named chunks of data is not a conversation, it’s a “dissemination” (the computer equivalent of “Does anybody have the time?”)

In a dissemination the data matters, not the supplier

It’s possible to disseminate via conversation and get the data as a side effect, But:

• Security is an afterthought. Channels are secured, not data, so there’s no way to know if what you got is complete, consistent or even what you asked for.

• It’s inefficient (hotspots, poor reliability, poor utilization).• Users have to do the translation between their goal & its

realization and manually set up the plumbing to make things happen.

Dissemination networking

• Data is request by name, using any and all means available (IP, VPN tunnels, multicast, proxies, etc).

• Anything that hears the request and has a valid copy of the data can respond.

• The returned data is signed, and optionally secured, so its integrity & association with name can be validated (data centric security)

Content Centric Networking (CCN): Goals

• Create a simple, universal, flexible communication architecture that:– Matches today’s communication problems– Matches today’s application design patterns– Is at least as scalable & efficient as TCP/IP– Is much more secure– Requires far less configuration

Universal?

• Any architecture that runs over anything is an overlay (IP is an overlay).

• IP started as a phone system overlay; today much of the phone system is an IP overlay. System theorists would say ‘IP is universal’.

• CCN has the same character: it can run over anything, including IP, and anything can run over CCN, including IP.

• And CCN has a simpler, more general relationship with lower layers than IP.

There are two waysto view CCN

• a ‘universal’ middleware• an IP for content

The difference between these isdeployment time horizon

IP to “chunks of named content”• Strategy: exploit multiple simultaneous connectivities for data delivery

(e.g., ethernet, 3G, WiFi) due to its simpler relationship with layer 2

CCN Current Internet

Talk Plan


CCN packets

There are two CCN packet types:interest (similar to http “get”) and data(similar to http response). Both areencoded in an efficient binary XML.

Content-Based Security

• Name-content mapping verification via per-data packet signature– Data packet is authenticated with digital signature

CCN trust establishment by associating content namespaces w/ public keys

Basic CCN forwarding

• Consumer ‘broadcasts’ an ‘interest’ over any & all available communications media:get ‘/parc.com/van/presentation.pdf’

• Interest identifies a collection of data - all data items whose name has the interest as a prefix.

• Anything that hears the interest and has an element of the collection can respond with that data:HereIs ‘/parc.com/van/presentation.pdf/p1’ <data>

Basic CCN transport

• Data that matches an interest ‘consumes’ it.• Interest must be re-expressed to get new data.

(Controlling the re-expression allows for traffic management and environmental adaptation.)

• Multiple (distinct) interests in same collection may be expressed (similar to TCP window).

Internally, CCN names areopaque, structured byte strings

/parc.com/van/cal/417.vcf/v3/s0/0x3fdc96a4...

is represented as a component count then, for each component, a byte count

followed by that many bytes:

7 8: parc.com 3: van 3: cal 32: 3FDC96…

The only assumption CCN makes about names is hierarchical structure.E.g., names or components can be encrypted or contain arbitrary binary data.

…

Using Names

• The hierarchical structure is used to do ‘longest match’ lookups (similar to IP prefix lookups) which helps guarantee log(n) state scaling for globally accessible data.

• Although CCN names are longer than IP identifiers, their explicit structure allows lookups as efficient as IP’s.

(see hashing work by Rasmus Pagh and Martin Dietzfelbinger)

Names and meaning

• Like IP, a CCN node imposes no semantics on names. Meaning comes from application, institution and global conventions reflected in prefix forwarding rules.

For example,/parc.com/people/van/presentations/FISS09

might be the name of a presentation’s data and/thisRoom/projector

the name of the projector it should display on.• The former is a globally meaningful name leveraging the DNS

global naming structure. The latter is local and context sensitive—it refers to different objects depending on the room you’re in.

IP node model

CCN node model

Get /parc.com/videos/WidgetA.mpg/v3/s2

Comparison

Strategy layer(mobility management)

• When you don’t care who you’re talking to, you don’t care if they change.

• When you’re not having a conversation, there’s no conversation state to migrate.

• Multi-point gives you multi-interface for free.• When all communication is locally flow

balanced, your stack knows exactly what’s working and how well.

Quality of Service (QoS)

• In the current Internet, QoS problems are highly localized.

• Roughly half the problems arise from the serial dependencies created by queues.

• The other half are caused the lack of receiver based control of bottleneck links.

• Unlike IP, CCN is local, doesn’t have queues and receivers have complete, fine-grained control.

• But it does aggregate traffic and has face-specific controls on the aggregation.

Talk Plan


• There are many (emerging) ways to do routing, e.g., Small Worlds, Geographic Hyperbolic, Pseudo potential Gradient, Epidemic percolation.

• In general they’re easier to implement and work better for CCN than for IP:– no looping data no convergence issues.⇒– multi-destination state can be approximate (false ⇒

positives ok).– CCN transport model matches routing’s and adds

security.

• I’m only going to talk about embedding CCN in existing Internet routing.– This is an easy evolutionary path (it allows for

immediate, incremental deployment).– It offers some intuition on scaling (same scaling as

IP routing).– The basics are the same for any routing scheme.

Existing link-state routingprotocols can be used, unmodified,

to construct a CCN FIB

A

D

E

F

B

data src advertisement:/parc.com/media/art

data src advertisement: /parc.com/media/art/parc.com/media

/parc.com/media/art/parc.com/media

A, B B

E’s FIB

CCN Router

C

Example: Content Distribution

• Content goes only where there’s interest.

• It takes at most one trip across any link.

• Average latency is minimized.

• Total bandwidth is minimized.

• There’s no routing or control traffic associated with the replicas.

Talk Plan


Transport State

• Conversation transport state is very compact:• One dynamic state variable

(tcp sequence / ack number) conveys what ends know.

• Additional static variable (tcp window) conveys what they want.

Annotated path in CCN nametree serves as transport state

Conventions:• name tree child nodes are lexically ordered• <next> assumed if no relationship specified


• Most recent version of slides for this talk:parc.com/van/talks/mit10-08 <rightmost child>




• Newest version after v2:parc.com/van/talks/mit10-08/v2 <rightmost

sibling> (fails since there is no newer version)




• Newest version after v2:parc.com/van/talks/mit10-08/v2 <rightmost

sibling> (fails since there is no newer version)

• Next available chunk after s1:parc.com/van/talks/mit10-08/v2/s1


Bulk-data transferperformance comparison

Pipeline size (like TCP window size)

Thro

ughp

ut (M

bps)

CCN

TCP

Shared-contentperformance comparison

# of clients

Dow

nloa

d de

lay

CCN

TCP

Wrapup

• CCN node is as simple as an IP node:– same memory requirements– same computational requirements (with option to

increase security)• CCN offers simple, robust, secure single-point

configuration.• CCN does near optimal content distribution. • Network, applications and users all share the

same model of communication.

content centric networking based on van jacobson’s slide decks uichin lee kaist kse

Documents

data slide

callee slide

didnt matter slide

destination line card

existing phone system

wires generation

existing wires

van jacobsons slide