Transcript Packet Data Evolution

Packet Data Evolution
S. Wood Nov. 2006
Copyright 2006 Modern Systems Research
Networking Local Area Networks
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Became popular with LAN’s (Ethernet @ 10Mbit)
How do you connect 2 LAN’s together?
Many LAN’s??
High Speed?? (100Mbit)
Internet??
Networking Software
DEC, 3COM, Banyon, Novel, Microsoft
• Bridges, Switches, Routers
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Internet
• Uses IP routing
• No support for QOS
– QOS assigns priority to certain payloads
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Packet traffic “Bursty” by nature
Congestion often occurs
Congestion causes packet loss / delays
Higher level protocols provide restoration of lost &
damaged packets
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Inside the Internet
• User pays service provider for service
• Service provider pays higher level service provider
• Peering arrangements:
– service providers agree to “share” access to users
• Internet Routing
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IP Routing
• IP (v.4) Address = 32 bits, 4 bytes
• Static Hierarchal Routing
Class A (256 sub-address Class Bs)
Class B (256 sub-address Class Cs)
Class C (256 Users)
Users (256)
Addresses assigned based on agreements between service providers
• Subnet mask on router tells it what block or part of block to look at
• Dynamic Routing: users may move around requiring the network to
“look” for a user
• Routing Protocols allows routers to communicate to find the best path
to forward packets
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Routing Protocols
• Allows routers to work together to find the best path to a
user or a group of users
• Protocol examples:
– OSPF, RIP, BGP ,IGP, RSVP
• Common attributes:
– Use Static parameters to calculate route
example: latency based on distance
– Some protocols are “link state”
Flood network with Link State Advertisements (LSA)
• Routing protocols do NOT take into account dynamic
parameters
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Dynamic Parameters
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Congestion
Intermittent Nodes & Links
Packet flows
QoS
Policies
Packet loading
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Congestion control
• Most internet problems relate to congestion
Some Solutions:
• Network Traffic Engineering:
– identify the source of the congestion
– provide additional bandwidth to fix specific problem.
• Identify heavy users (e.g. Gamers) and:
– get them to pay for more bandwidth
– apply flow constrictors
• Over provision bandwidth (again and again)
• QOS based routing
• Apply admission controls
– “Block new traffic until congestion subsides”
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Packet Quality of Service
• QoS
– Quality of Service
– QoS based routing has been with us for several years
– diff-serv (Differenciated Services) is a QoS Architecture
• Some QoS routers use:
– “Weighted Fair Queuing (WFQ)”
• Congest means there are too many packets to be
transmitted over a given path.
• WFQ provides an orderly means for discarding packets to
bring the bandwidth down to what can be transmitted. All
sources lose some packets with WFQ. Some sources lose
more packets than others
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Packet QoS (cont)
• Hard QoS:
– Packets are organized into flows
– Each flow is assigned a class of service
– When congestion occurs, bottom classes are discarded
first. Higher classes are unaffected
• Currently 4 classes have been identified
– Voice, Video, Priority data, Best effort
• Today's routers assign QoS based on the port used. All
packets arriving at that port share the same class of service.
• Next generation routers assign QoS based on packet flows
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IP Routing – Open Issues
• Currently includes no QOS guarantees
• IP routing software can crash under heavy
congestion
• Latency not deterministic
• No admission control
• No ability to perform load balancing
• Internet routing protocols do not take into account
dynamic parameters such as congestion
• Network slow to recognize link or node failures
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Internet Today
L4
TCP
UDP
L3
Standard Router
Packet
Data
Network
IP
Packet Flows
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No QoS
Congestion takes down network
Variable Latency
No TDM Voice
Network Traffic Engineering needed
Not Secure
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Security
Internet Security Threats
• Denial of service attacks
• Phishing
• Spam
• Mal ware
• Viruses and worms
IP networks use in band signaling
• Internet vulnerable to new generation of “Blue Boxes”
• Users can modify internet packets to:
– Upgrade QOS
– Spoof source / destination
– Modify address at will
Next Generation Routing
• New routers are being developed to correct the issues in current
routing protocols
• Flow-based routing:
– Packet flows are groups of similar packets traveling together
sequentially
• Examples:
– Voice, Streaming Video, File transport
• Flow based routers must:
– Sort packets into flows
– Buffer each flow
– Implement policy/QoS rules to each flow
– Forward packets
• Examples of companies building next generation routers:
– Caspian Networks, Anagran
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Next Generation Routing:
The Hard Part
• When IP addressed packets arrive at the router,
they all look the same. The router must move up
the protocol stack to layer 4 sort the packets into
flows (Deep Packet Analysis).
• Once sorted, The flows must be ordered and
assigned QoS and policy constraints.
• When done properly, the network can give priority
to voice or video when congestion occurs. Some
technologies such as MPLS already support QoS
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Internet With A Flow Based Router
L4
TCP
UDP
L3
Flow Based
Router
Flow Based
Packet
Data
Network
IP
Packet Flows
• Expensive (Flow Based Routers needed throughout the
network)
• Congestion can still take down Packet Switches (must be
Traffic engineered)
• Does not support TDM voice
• Not secure
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Label Switching
TDM Voice
• Used in DACS (1980’s)
– DACS is a digital access cross connect
– Uses a time slot interchanger
– Each DS0 (64kb data channel) can be considered as a
packet; it has both a payload (8 bits) and an address
(from the framing)
– The old address is used to reference the new address in
the cross connect.
– Path and setup software ran separately from the cross
connect hardware
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Label Switching
Frame Relay (early 1980’s)
• WAN Data Network service offered by
telecommunications carriers
• Desirable, since it was tarriffed for less money
than voice services
• Typically used T1’s
• Each pack was variable length and had a short
label
• Used bits to encode priority on each packet
(congestion control)
• Slower and less efficient than later IP routing
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Label Switching
ATM (mid 1990’s)
• Stands for Asynchronous Transfer Mode
• Considered next level for ISDN
• Supported both Voice and several data formats
– AAL1 through AAL5
• Uses 53 byte cells (5 byte address, 48 byte payload)
• Intended to be used on SONET
• Fundamental Switching very simple, Transport and setup
become complex
• Supports hard QOS. Switching very reliable. Adopted by
most carriers
• Went out of favor with the introduction of gigabit Ethernet
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Label Switching
MPLS
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Stands for Multi Protocol Label Switching
4 byte label, variable length payload
Used with SONET up to 40 Gbit/S
Considered very reliable since switching is
done by hardware
• Uses internet routing protocols
• Considered next transport technology for
carriers
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What is MPLS?
• MPLS: Multi-Protocol Label Switching
• A short 20 bit label is attached to the front of each packet.
A label is good for one hop only!
• When a packet is forwarded by a Label Switch Router
(LSR), the next hop is assigned and the label is updated.
• LSR’s are very fast, some even operate at 40Gbit/sec rate.
• Labels can be stacked; A MPLS packet can have it’s label
stack “pushed” or “popped” instead of simply being
translated at each LSR.
• The path taken by the labeled packets is called a “label
Switched Path” or LSP
• The path is fixed and can traverse several nodes.
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LSP Programming
• Label Switched Paths are usually built from the
destination to the source.
• A special protocol called LDP (Label Distribution
Protocol) exists for this purpose.
• IP routing protocols are used to determine the best
path and build the LSP.
• Building LSP’s this way can be problematical and
slow.
• Many carriers choose to use network Traffic
Engineering to build and manage LSP’s
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What is Network Traffic
Engineering?
• Network Traffic Engineering is the
computer simulation of a data network in
order to ensure that congestion is avoided
and the best links are chosen to carry the
data flows between nodes.
• Part of Network Traffic Engineering is to
set up redundant paths if a priority path was
to fail
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Why do Network Traffic
Engineering?
• Large carriers have found that engineered networks are
more efficient and robust
• Most carriers use MPLS on backbone systems.
• MPLS works best when engineered.
• The internet bubble generated a glut of bandwidth.
Consequently only a minor amount of engineering is
needed.
• Automatic path allocation software supplied by vendors
does not do an adequate job.
• Now that extra bandwidth has been used up and
engineering must be done to avoid network crashes
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What is Done?
• Network Traffic Engineering is often done by outside
firms.
• Special network simulation software has been developed
for this purpose.
• Network engineers collect data from carrier on nodes,
links, policy preferences, existing LSP’s, estimated
bandwidth needs for each LSP, latency between nodes,
customer contract requirements, etc.
• Engineers enter collected data into simulation program.
• Program produces a map with traffic loading and latency
for all nodes
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What is Done? (cont)
• A maximim traffic loading value is assigned to each node
(usually 70%)
• Engineers use program to build new LSP’s or change
existing LSP’s to conform to latency and traffic
requirements
• Stress tests are performed on simulated network to find
failures and maximum loading
• Redundant LSP’s are added as a result of the previous
tests.
• When finished, recommendations are made to carriers
• Carriers provision new LSP’s
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Internet Reliability
• Internet reliability is linked to each router
• Router Reliability (MTBF)
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Computer Logic
Power Supply
Routing Software
AC power
100,000 hrs
200,000 hrs
10,000 hrs
40,000 hrs
• Clearly, the routing software reliability is the weakest link
• This is evidenced by the system “crashes” that occur when the network
is overloaded. The network relies on the routing protocols to bypass
effected routers. Because of the delays involved, these crashes will
cause dropped VOIP calls
• MPLS switches are more reliable because the actual switching is done
in hardware.
• Adding QoS can worsen the reliability as it can slow the software
making it easier to crash.
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Internet Availability
• An Internet outage is measured in time. This outage is often shown as
Mean Time To Repair or MTTR.
• 1 – MTTR = Internet Availability generally expressed as a percentage.
• The availability requirement for the PSTN is that it is available
99.999% of the time. It can only be out of service a total of 5.25
minutes a year!
• To achieve this Telcos had to do several improvements over traditional
designs over time:
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Redundant Power (dual 48V battery plants)
Transmission tests through switch matrix before call cut-through
Redundant processor and software throughout
Verification of connection paths before setup
Mechanized Loop Testing (MLT)
All links redundant with hot standby
Triple Redundant Switching Control Processor for SS7 network
• As can be seen, we have a long way to go before we abandon the
PSTN in favor of whatever appears to be cheaper!
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Toward Reliable VOIP
Power
Redundant
Power
Battery
Backup
Network
Switching
Redundant
Processing
DC Switch using
power Hardware
Label
Switching
(MPLS)
(ATM)
Path
Verification
Redundant
Lilnks
Qualilty
Network
Traffic
Admission
Engineering
Control
Fast
Rerout
Excess
Bandwidth
Hard
QOS
Flow
Based
Routing
Congestion
Link
failures
Software
QOS
Route
Flapping
PSTN
QUALITY
VOIP
Traditional
AC Power
Heat
Software
Switching
Many
hops
Power
Switching
Routing
software
Network
Weighted
Fair
Queuing
Quality
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Next Gen Network
Design Objectives
• Make network capable of carrying all forms of data
– TDM Voice
– High Speed Streaming Video
– Internet traffic with QoS
• Make switching function hardware-based
– Speed
– Reliability
– Deterministic throughtput
• Include path building and control in switching functions
• Provide a simple request – grant (layer 4) user interface
• Make a mesh network immune to node and link failures
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Next Gen Network
Design Objectives (cont)
• Network Plug and Play
– Network can operate with no provisioning
– Provisioning can be added to establish policies and QoS
• Self route each path based on :
– Packet flow requirements: (latency, QoS, bandwidth)
– Available nodes / links that meet the requirements
– Service provider policies
• Support Enhanced Services
– Multicasting (Branching & Merging)
– Redundant paths
• OA&M Support (Operation, Administration and Maintenance)
– Direct control of network setup by network engineers
– Real-time network stress testing
– Control alarms for node, link, path failures or congestion
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