Download Lect 5 - ICN

Internet of Things
Amr El Mougy
Alaa Gohar
Information-Centric Networks
Mobile Data Traffic
Video Data Traffic
Dealing with the Growth in Internet Traffic
• Global IP traffic is expected to exceed 1.4 Zettabytes by the end of 2017
• Over 80% of this traffic will be video
• Solution: shift the load away from the traditional client-to-server
connection pattern
• Proposed solutions: Caching (web caching and content delivery networks)
and peer-to-peer networks
• The idea is to exploit storage and processing capabilities readily existing in
the Internet to speed up data transfer and reduce latency
• Both ideas work at the application layer, where latency is already high
Content Distribution over the Internet
DOES NOT SCALE
Tier 1 Networks
ISPs
IRTF Open Meeting @ IETF-81
Why Not?
• URLs and IP addresses are overloaded with locator and identifier
functionality
– Moving information = changing it‘s name => 404 file not found
• No consistent way to keep track of identical copies
– No consistent representation of information (copy-independent)
• Information dissemination is inefficient
– Can‘t benefit from existing copies (e.g. local copy on client)
– No “anycast”: e.g., get “nearest” copy
– Problems like Flash-Crowd effect, Denial of Service, …
Why Not?
• Can’t trust a copy received from an untrusted node
– Security is host-centric
– Mainly based on securing channels (encryption) and trusting servers
(authentication)
• Application and content provider independence
– CDNs focus on web content distributions for major players
– What about other applications and other players?
Information-Centric Networks (ICN)
Today’s Internet
Focus on
nodes
In today’s Internet,
accessing information is
the dominating use case!
Information Centric Network
Focus on
information objects
Evolution
Web
CDN
• Considering important requirements
– Accessing named resources – not hosts
– Scalable distribution through replication and caching
– Good control of resolution/routing and access
P2P
• With ubiquitous caching
– But for all applications
– And for all users and content/service providers
– Use off path caching and on path (in-network)
caching
Information-Centric Networks (ICN)
• Apart from routing protocols that use a direct identifier of nodes,
networking can take place based directly on content.
• Content can be collected from the network, processed in the network,
and stored in the network
• Goal is to provide a network infrastructure capable of providing
services better suited to today’s application requirements:
– content distribution & mobility
– more resilience to disruption and failures
• We look next at such content-based networking and data aggregation
mechanisms.
Networking Evolution
• Traditional networking
– Host-centric communications addressing end-points
• Information-centric networking
– Data-centric communications addressing information (e.g., data in context).
– Decoupling in space – neither sender nor receiver need to know their
partner.
– Decoupling in time – “answer” not necessarily directly triggered by
“question”, asynchronous communication.
Example: Content Distribution
Example: Content Distribution
Example: Content Distribution
Example: Content Distribution
Example
• 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.
How is it Done?
• Approach
– Named Data Objects (NDOs)
– in-network caching
– multi-party communication through replication
– decoupled senders from receivers
• Architectural questions
– How do we address information?
– How do we obtain information?
– How do we route information?
ICN Communication Model
Dissemination networking
• Data is requested 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)
Digital Signature
Content-Based Security
• Name-content mapping verification via per-data packet signature
– Data packet is authenticated with digital signature
ICN trust establishment by associating
content namespaces w/ public keys
ICN Stack
(1) Van Jacobson, et al, Networking Named Content, CoNEXT 2009
•
•
•
•
•
Change of network abstraction from “named host” to “named content”
Security built-in: secures content and not the hosts
Mobility is present by design
Can handle static as well as dynamic content
Use of 2 messages: Interest and Data Objects
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’.
• ICN has the same character: it can run over anything, including
IP, and anything can run over ICN, including IP.
Naming
• Solution 1: Name the data
– Flat, not human readable identifiers
• 1DB76EB8DFD6B0b92A293AADC8421830BDE73CB6
– Hierarchical, meaningful structured names
• /nytimes/sport/baseball/mets/game022414/
• Solution 2: Describe the data
– With a set of tags
• baseball, new york, mets
– With a schema that defines attributes, values and relations among
attributes
Using Names in CCN
• 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.
Basic ICN forwarding
• Consumer ‘broadcasts’ an ‘interest’ over any & all available
communications media:
get ‘/rutgers/ECE544/Lecture06-14.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 ‘/rutgers/ECE544/presentation.pdf/p1’ <data>
Basic ICN 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).
Publish/Subscribe Communications
• One of the most important communication patterns in ICN
• Publishers are decoupled from subscribers in time and space
• Publishers inform a special network node (for example a content
broker) that they will generate a particular type of content
• Subscribers inform the network of their
interest in this content (once, periodic,
event-based, etc.)
• The network forwards content either
from publisher or the nearest cache
On-Path Caching
**A. Ioannou and S. Weber, “A Survey of Caching Policies and Forwarding Mechanisms in Information-Centric Networking,” IEEE Communications Surveys and Tutorials, Vol. 18, No. 4, 2016.
Caching
• Storage for caching NDOs is an integral part of the ICN service.
• All nodes potentially have caches; requests for NDOs can be
satisfied by any node holding a copy in the cache.
• ICN combines caching at the network edge as in P2P and other
overlay networks with in-network caching (e.g., transparent
web caches)
Challenges
• Caching decisions cannot be determined apriori as in CDNs, it is
based on content  may add delay
• Limited cache capacity. Larger caches may introduce more delay
due to extended lookup time
• Deciding on a policy for prioritizing which content to be cached
• Large diversity in content
• How to implement cooperative caching to optimize storage
• Deciding on the popularity of content
• Correlation between content (people with geographical proximity
order similar content)
• Exploiting cached content. How to determine best forwarding paths
from the closest cache to the subscriber
Taxonomy of
Caching
Mechanisms
Probabilistic Caching
• Caching decisions are based on a probability p, which could be fixed or
dynamic
• Fixed probabilistic policies involves no cooperation and thus does not cause
additional overhead
• On the other hand, it does not consider network topology, correlation, or
popularity of content
• RND defines a fixed p for all nodes
• Unicache assigns uniform p =
(1/length of path)
• Leave Copy Everywhere (LCE) assigns p = 1
at all nodes
Probabilistic Caching
• Dynamic policies take into account traffic characteristics, type of content,
and network topology to determine p
• ProbCache tries to store content at nodes that are farther away from the
publisher by calculating
Ttw = 2 seconds
Nx = Nn = 10 seconds
• Where x is the length of the path and y is the number of hops from the
source to a node, Nn is the cache size of n, Nx is the average cache size of a
path, and Ttw is the time for which content should be cached on a path
Graph-Based Caching
• Considers the network topology to decide where to cache
• Edge caching leaves a copy at the last node on a path, where it is closest to
the consumer
• Leave copy down (LCD) leaves a copy one more hop towards the consumer
each time the same content is received, thus capturing content popularity
• However these policies are
static and do not consider the
position of different nodes on
the path relative to
consumers
Graph-Based Caching
• Centrality policies use graph metrics to determine the most possible node
for caching
6
Graph centrality
1/ max 𝑑 𝑚, 𝑛 𝑓𝑜𝑟 𝑎𝑙𝑙 𝑚 ≠ 𝑛
Closeness 𝐶𝑙𝑜𝑠𝐶 =
𝑖
Centrality
9
Degree
Centrality
deg(𝑖)
𝐷𝑒𝑔𝐶𝑖 =
𝑛−1
1
𝑖≠𝑗 𝑑𝑖𝑠 𝑖, 𝑗
4
7
3
5
10
2
Betweenness
Centrality
𝐵𝑒𝑡𝑤𝐶𝑖 =
8
1
𝑠𝑝𝑗,𝑘 𝑖
𝑗≠𝑖 𝑠𝑝𝑗,𝑘
Label-Based Caching
• The objective here is to increase content diversity in the network by
allowing each node to cache only a range of content
• The network topology and the content ranges must be defined apriori
• Must be restricted in scale of an ISP. Otherwise content ranges are difficult
to define
Popularity-Based Caching
• Tries to minimize the cache pollution problem, where one-timer objects are
stored
• One-timer object requests are estimated to lie between 45% and 75% of all
requested content. Thus, the cache pollution problem may be significant
• However, popularity of content also depends on location. Thus we have
local-based policies and path-based policies
• Popularity is decided based on a
content counter
• In path-based policies, the counter is
initialized to “new”
• It does not address the cache pollution
problem effectively
Popularity-Based Caching
• Unlike path-based policies, local-based policies do not require a minimum
of one node to cache any content
• Local-based policies work by observing the popularity of content, and can
be static or dynamic
• Static local-based caching defines a
threshold for the content counter to
start caching any content
• Calculating the threshold is
challenging
• This policy does not adapt the
threshold if conditions change
Popularity-Based Caching
• Dynamic local-based popularity caching observes the popularity within a
time interval ΔT
• Implicit dynamic popularity defines • Explicit dynamic popularity arranges
content in an ordered list of
popularity as the fraction of one the
popularity (counter) of one request to decreasing popularity and stores the
first x objects
the total number of requests
ICN Approaches
**G. Xylomenos, C. Ververidis, V. Siris, N. Fotiou, C. Tsilopoulos, X. Vasilakos, K. Katsaros, and G. Polyzos, ”A Survey of Information-Centric Networking Research,” IEEE Communications Surveys
and Tutorials, Vol. 16, No. 2, 2014.
Named Data Networking (NDN)
– Naming: Hierarchical naming,
single address
– Security: Signed content
– Routing: Longest prefix matching
– Caching: Local or network based
– Content existence knowledge:
Not part of the CCN core
– Producer-consumer meeting:
Propagation of interests
Scalable and Adaptive Internet Solutions (SAIL)
– Naming: Flat-ish naming
– Security: Confidentiality, integrity,
authentication, authorization
– Routing: Name resolution and data
matching can be either coupled or
decoupled
– Caching: Local and network based
– Content existence knowledge: Through
name resolution service
– Producer-consumer meeting: Name
resolution service provide locations
Publish/Subscribe Internet Technology (PURSUIT)
– Naming: Multi-level identifiers
– Security: Signed content
– Routing: (1) Name resolution (2)
Information transfer
– Caching: Network based
– Content existence knowledge:
Registrations in Rendezvous
system
– Producer-consumer meeting:
Rendezvous system provides
location
Data Oriented Network Architecture (DONA)
– Naming: Flat naming
– Security: Signed content
– Routing: Queries are resolved to
locations
– Caching: Network based
– Content existence knowledge:
Through resolution infrastructure
– Producer-consumer meeting:
Resolution infrastructure provides
location