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Internet-The Next Generation:
Developments in Internet
Networking Technologies
Slide 1
Outline
• Background
• Best-Effort Architecture
• Emerging Architectures
• Conclusions
• References
Slide 2
Background
• Origins of today’s Internet
– US Dept. of Defense DARPA projects (1960-70’s)
– Evolved from defense to research to commercial
• What is the Internet?
– Hierarchical, global network of communicating hosts
– Hosts have addresses, routers interconnect hosts
– Routers perform packet switching, “best-effort” service
• What is IP (Internet Protocol)?
– Suite of protocols/framework to control routers/hosts
– Addressing, routing, registration, etc.
Slide 3
Background
Sample Network
Residential Internet
(modem access)
Campus
LAN
Corporate
networks
Mux
Eth
IP network
domains
IP routers perform
hop-by-hop packet
forwarding
Intra-domain
OSPF routing
Various router link technologies
(SONET/SDH, ATM, FR)
Inter-domain BGP
routing (red)
Slide 4
Background
• Tremendous growth of IP-based networks
– Worldwide deployment, many TCP/IP applications
– Hosts is growing exponentially, only few “on-line”
– Improving, cheaper “end-user” access technologies
Link speeds increasing (cable, DSL, wireless)
– “Capacity requirements doubling per 4 months” (1999)
– Becoming crucial to economic/national infrastructure
• Changing networking paradigms: “circuit to packet”
– Packet data volume has overtaken voice volume
– Shift from “data over voice” to “voice over data”
– “Convergent network” philosophy
I.e., “One network carries all (data, voice, video)”
Slide 5
Background
Relative Traffic
Data traffic on large carrier
networks exceeds voice
circuit traffic (1998-1999)
Internet applications:
web browsing/caching,
ftp, telnet (exponential
growth scales)
Residential, business
trunked voice circuits
(linear growth scales)
Packet
data
Voice
1997
1998
1999
Time
2000
2001
Slide 6
Background
• Traditional IP user applications
– Initial “data” applications (telnet, ftp, email,web)
– “Non-realtime” applications, no service guarantees
E.g., Web (ftp) transfer can take 1ms or 10 sec
• New, emerging IP user applications
– Recently, new “real-time” applications
E.g., voice (IP telephony), IP video
– Future explosion of “multi-media” applications
E.g., Internet gaming, tele-commuting/conferencing
– Applications need services “guarantees”
E.g., Voice<10 ms delay, video<100 ms delay
Slide 7
Background
• Challenges
– Internet must evolve to support new applications
– IP protocols must support service guarantees
I.e., packet delay, loss, jitter
– Must also support today’s IP protocols/applications
I.e., “Backwards compatibility” requirement
• New solutions are required
– “Intelligent” switching technologies
I.e., Selective processing of traffic flows/types
– Capable of supporting large, diverse user base
I.e., Commonly termed “scalability”
– Various proposals have been made
Slide 8
Best-Effort Architecture
• Represents traditional Internet architecture
– “Hop-by-hop” forwarding (routing decision per packet)
– Very rudimentary packet buffering capabilities
“First-in-first-out” (FIFO), G/G/1 model
– Routing protocols for packet route control (static)
Open-shortest-path-first (OSPF) intra-domain
Border-gateway protocol (BGP) inter-domain
• Best suited for “non-realtime” data applications
– High delay tolerance (e.g., ftp, email)
– Reliability via higher-layer transport (TCP/IP)
– Works well for lightly-loaded networks
I.e., Reduced packet losses, delays
Slide 9
Best-Effort Architecture
Traditional IP Network Hierarchy
Transport control, reliable
transfer functions
User Applications
Traditional “best-effort”
layer three addressing,
routing, packet forwarding
TCP/UDP (Transport)
“Best-effort”
services (e.g., webbrowsing, ftp, telnet)
IP (Network)
Variety of data and
link layer technologies
(costs, complexity)
ATM
FR
SONET Ethernet
SONET
SONET
Hardware (electronic
buffering processing or
SONET-type optoelectronic switching)
Physical Layer
Slide 10
Best-Effort Architecture
• Inadequate service definition
– Basic queueing gives no “quality of service” (QoS)
E.g., bandwidth (capacity), delay, loss, etc.
– No service differentiation possible
– Router processing speeds become bottleneck
I.e., “Layer 3” IP address-lookup ( O(log2(N) )
– Static routing causes network congestion
• Inefficient interworking with multiple “lower-layers”
– Layered model approach (SONET/SDH, ATM, FR)
Added maintenance/operations costs, complexity
– Counter to convergent networks trend
Slide 11
Best-Effort Architecture
FIFO Queueing Node (Edge)
Constant inter-packet
timing, fixed packet size
Time
IP Router
Outgoing (combined) flows:
voice timing very distorted
Voice packet stream (phone call)
Time
Variable inter-packet timing,
variable packet sizes
FIFO queue, voice and data
packets mix (G/G/1 model)
Fixed router
transmission link speed
Time
Data packet stream (web transfer)
Incoming (individual) traffic
flows to IP router queue
Slide 12
Best-Effort Architecture
FIFO Queueing Network
User connection flows (e.g.,
TCP/IP or UDP session, dotted
lines) buffered in same queues
Router B
Router D
Router A
Full-IP address lookup, single
aggregate with large interference
between multiple flows
Router C
Slide 13
Emerging Architectures
• Revamp IP protocols/architecture
– New service definitions for “integrated” services
“Everything over IP networks” (voice, video, data)
– Basic idea is to “separate out” different traffic types
I.e., Treat “realtime” different from “non-realtime”
– Large focus in Internet Engineering Task Force (IETF)
• Multiple proposals have emerged:
– Integrated Services (IntServ) proposal
– Differentiated Services (DiffServ) proposal
– Multi-Protocol Label Switching (MPLS)*
*Emerging as comprehensive solution
Slide 14
Emerging Architectures: IntServ
• Detailed, advanced service definitions
– Multiple service categories
Best-effort:
Like “best-effort” Internet
Controlled-load:
Lightly-loaded Internet
Guaranteed:
Firm bounds (capacity, delay)
• Router requirements
– Advanced, fast packet classification/processing
I.e.,IP-address lookup, complex buffering/scheduling
– Admission control, scheduling, buffer management
– Advanced resource control signaling (RSVP protocol)
For set-up and take-down of flow reservations
– Requires policy control (who makes reservations?)
Slide 15
Emerging Architectures: IntServ
Per-Flow Queueing Node (Edge)
Constant inter-packet
timing, fixed packet size
IP IntServ Router
Outgoing (combined) flows:
limited voice timing distortion
Time
Flow 1
Time
Voice packet streams
Variable inter-packet timing,
variable packet sizes
Flow 2
Flow 3
Fixed link speed
Flow 4
Per-flow bandwidth scheduler
gives capacity guarantees
(hardware complexity: tracking,
processing/computing)
Time
Time
Data packet streams
Time
Per-flow buffering, voice and data
packets separated (G/G/n model)
Slide 16
Emerging Architectures: IntServ
Per-Flow Queueing Network
User connection flow (e.g.,
TCP/IP or UDP session)
IntServ Router B
IntServ Router D
IntServ Router A
Per-flow buffering and
scheduling, complexity increases
with number of traversing flows
IntServ Router C
Slide 17
Emerging Architectures: IntServ
• Shortcomings and concerns
– Per-user flow storage/processing for QoS at routers
I.e., Potentially millions of flows at any time
– Hardware complexity: storage, scheduling, monitoring
E.g., Very fast (bounded) IP-address lookup times
– Software complexity: RSVP protocol
– Does not “scale”, i.e., if number of flows very large
Note: Same problem as ATM technology
– Traffic engineering limitations
• Current status/developments
– Complexity concerns have led to DiffServ proposal
– RSVP being modified to suit DiffServ and MPLS
Slide 18
Emerging Architectures: DiffServ
• Simplify per-flow model to per-class
– Arrange (mark) user flow packets into classes
“Class of service” (CoS) indicated in IP header
– Perform “per-class” control (buffering, scheduling)
Via standardized “per-hop behaviors” (PHBs)
– Much less complex than “per-flow” IntServ approach
I.e., O(# of classes) vs. O(# of flows)
• Router requirements
– Edge classification/metering (“mark” ToS byte header)
– PHB resource mappings (% bandwidth,priority,buffer)
E.g., Advanced buffer control (RED schemes)
– No signaling, “fixed” service level agreements (SLAs)
Slide 19
Emerging Architectures: DiffServ
Per-Class Queueing Node (Edge)
Constant inter-packet
timing, fixed packet size
Time
Time
Voice packet streams
IP DiffServ Router
Class 1
1 1
Variable inter-packet timing,
variable packet sizes
Time
Data packet streams
1
1
Class 2
2
Time
Outgoing (combined) flows:
moderate voice timing distortion
Time
Fixed link speed
2
Per-class bandwidth scheduler
(reduced complexity)
DiffServ classification maps multiple
flows to fewer classes (two shown) by
“marking” ToS byte in IPv4 header
Slide 20
Emerging Architectures: DiffServ
Per-Class Queueing Network
User connection flows (e.g.,
TCP/IP or UDP session, dotted
lines) mapped to fewer classes
DiffServ Router B
DiffServ Router D
DiffServ Router A
Per-class buffering/scheduling,
complexity reduced to number of
classes not number of traversing flows
DiffServ Router C
Slide 21
Emerging Architectures: DiffServ
• Traffic aggregation problems
– Class guarantees do not mean flow (user) guarantees
I.e., Flows inside a class can “collide/interfere”
– Good for small data transfers (web browsing)
– Poor performance for real-time flows
• Limited flexibility
– Designed for relatively “static” networks
Network topology, user traffic demands unchanging
– Difficult to change class resource allocations
E.g., Increase/decrease bandwidth per usage levels
– Automated, fast re-adjustment required today
I.e., Need “traffic engineering” applications
Slide 22
Emerging Architectures: MPLS
• Very comprehensive framework
– Decouple packet forwarding from routing
I.e., packet route setup before data transfer
– Major industry focus (main IP networking framework)
• Based upon earlier flow/tag switching proposals
– Assign “tags” to flows, switch based upon “tags”
– Reduced delays for (layer 3) IP address-lookups
– Various tag assignment schemes (measure/control)
• MPLS enables many advanced applications
– Traffic engineering, QoS service guarantees/routing
– Virtual private networks (VPNs)
Slide 23
Emerging Architectures: MPLS
IP-MPLS Network Hierarchy
Transport control, reliable
transfer functions
Layer three “QoS-aware”
routing/packet forwarding
and label-based forwarding,
traffic engineering,
protection/ restoration
User Applications
“QoS-based” applications (IP
voice/video, Internet gaming,
etc.), and traditional “besteffort” applications (web
browsing, ftp, telnet, etc.)
TCP/UDP (Transport)
IP-MPLS (Network/Data)
Hardware (electronic packet
buffering/processing and
even optical switching)
Physical Layer
Slide 24
Emerging Architectures: MPLS
• “Label” and “label switched path” (LSP) concepts
– Label: Identifier/tag used for switching data flows
– LSP: Concatenation of labels, arbitrary granularity
– LSP achieves “virtual circuit”, i.e., logical connection
– Encapsulate IP packets into MPLS packets (header)
– LSP protection, label stacking (flow aggregation)
• Router requirements
– Maintain input/output label tables, “short” label match
– Generic association of labels with local QoS resources
I.e., buffer space, priority, bandwidth
– Signaling protocols to control label assignments
RSVP+extensions, label distribution protocol (LDP)
Slide 25
Emerging Architectures: MPLS
MPLS Label-Switching Node
Constant inter-packet
timing, fixed packet size
Time
IP MPLS Router
Voice distortion dependant upon
MPLS resource control (e.g.,
per-flow or per-class)
Voice packet streams
Variable inter-packet timing,
variable packet sizes
Time
Time
Data packet streams
Label encapsulation,
label swapping
Time
Time
Generic resource
control engine
(buffering,
scheduling)
Fixed link
speed
Label encapsulated user
packets/datagrams (i.e., MPLS
“shim” header)
MPLS packet mapping (via forward
equivalent class, FEC), packet
encapsulation with MPLS header
Slide 26
Emerging Architectures: MPLS
MPLS Network
Label In
Link Out
1
23
3
21
2
15
5
27
…
…
…
…
5
3
1
89
MPLS Router A
Label control
Label
Out
Resource
control
MPLS Router B
Resource
control
Label processing operations
(edge mapping, swapping,
stacking): arbitrary granularity
and resource control
Label-switched paths (incoming
labels overwritten with outgoing
labels after switching, based upon
label table entries)
MPLS Router D
Label control
Link In
Label control
Label Table
Resource
control
User connection flow (e.g.,
TCP/IP or UDP session)
Label control
MPLS Router C
Resource
control
Slide 27
Emerging Architectures: MPLS
• DiffServ implementation via MPLS
– Associate labels (LSPs) with aggregate classes
I.e., Multiple flows (traffic classes) on to same label
– RSVP/LDP can now fill signaling shortcomings
• IntServ implementation via MPLS
– Associate labels (LSPs) with each flow (connection)
I.e., Each user (connection) has unique label (LSP)
– Note: Per-flow complexity, but can “stack” labels
• Extensions to optical networks
– For migration from SONET/SDH technology
– Can apply “label” switching to wavelength switching
Slide 28
Conclusions
• Internet growth forecasted to grow tremendously
– New applications, more bandwidth, more users
– Increasingly integral to corporate/national success
• Traditional “best-effort” IP model is inadequate
– Designed for “latent” data traffic transport (ftp, email)
– No multi-service guarantees (delay, loss, jitter)
– Added costs complexity maintaining multiple networks
I.e., IP, ATM, SONET/SDH, frame relay, etc.
• Emerging advances promise much more
– Service guarantees, traffic engineering, VPNs
– MPLS has emerged as comprehensive framework
Slide 29