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http://www.arl.wustl.edu/arl
Extreme NetworkingAchieving Nonstop Network Operation Under Extreme Operating Conditions
DARPA PI Meeting, July 23-26, 2002
2 - Jonathan Turner - July 24, 2002
Project Overview Motivation
»data networks have become mission-critical resource»networks often subject to extreme traffic conditions»need to design networks for worst-case conditions» technology advances making extreme defenses
practical Extreme network services
»Lightweight Flow Setup (LFS)»Network Access Service (NAS)»Reserved Tree Service (RTS)
Key router technology components»Super-Scalable Packet Scheduling (SPS)»Dynamic Queues with Auto-aggregation (DQA)»Scalable Distributed Queueing (SDQ)
3 - Jonathan Turner - July 24, 2002
Switch Fabric
IPP
OP
P
FPX
SPC
TI
IPP
OP
P
FPX
SPC
TI
IPP
OP
P
FPX
SPC
TI
IPP
OP
P
FPX
SPC
TI
IPP
OP
P
FPX
SPC
TI
IPP
OP
PFPX
SPC
TI
ControlProcessor
Prototype Extreme RouterField Programmable Port Ext.
NetworkInterfaceDevice
ReprogrammableApplication
Device
SDRAM128 MB
SRAM4 MB
Field Programmable Port Extenders
Smart Port Card
Sys.FPGA
64MB
Pentium
Cache
NorthBridge APIC
ATM Switch Core
Transmisson Interfaces
Embedded Processors
4 - Jonathan Turner - July 24, 2002
Resource Reservation in Internet? Bandwidth reservation can provide dramatically
better performance for some applications. Obstacles to resource reservation in Internet.
» distaste for signaling protocols» perceived complexity of IntServ+RSVP» requires end-to-end deployment» little motivation for service providers
How to get resource reservation in Internet?» keep it simple
focus on top priorities - one-way unicast flows avoid complex signaling - leverage hardware routing
mechanisms
» make it useful when only partially deployed» provide motivation for ISPs to deploy it
5 - Jonathan Turner - July 24, 2002
10 Mb/s available 5 Mb/s
available
2 Mb/s availabl
e
5 Mb/s available
20 Mb/s availabl
e
20 Mb/s availabl
e
Basic LFS Operation
One way, unicast setup with partial reservation.»complete reservations locally when bandwidth released
Optional ack returned by far-end access router. Reservation may terminate explicitly or time out. May alter reserved bandwidth but no re-routing.
A
B
Reserve 8 Mb/s to B
Select best next hop
Reserve bandwidth
Select path and attempt to reserve
Select path and reserve
Complete reservatio
n
6 - Jonathan Turner - July 24, 2002
Soft Reservations Basic LFS provides firm reservations.
»user guaranteed bandwidth until releases Can extend to provide soft reservations as well.
»soft reservation can be adjusted by the network as traffic changes
»can be intermixed with firm reservations to provide a firm minimum, plus more bandwidth as available
Uses of soft reservation.»apps. that need guaranteed minimum and can
sometimes use more, but can adjust use to what’s available
»more rapidly responding congestion control for traditional best-effort traffic
7 - Jonathan Turner - July 24, 2002
Basic IP Option for LFS
length op. Rrateflags Arate code
IP header(fixed part)
trace
IP payload
Code identifies LFS option. Operations
» request firm reservation» request soft reservation» release state
Flags» sender status request» sender network status request» public network status request» intra-domain status request» congested path
Rrate: requested rate. Arate: allocated rate. Trace used by each domain to
track usage.
Allocated rate stored at “last hop” router for status generation
F.P. rates with 4 bit mantissa, 4 bit exponent.» specify rates from 64
Kb/s to 4 Gb/s , 6% “granularity”
8 - Jonathan Turner - July 24, 2002
Use of Trace Field
Network providers need to monitor LFS usage for network management and accounting purposes.» trace field used by ingress router of each domain to
mark LFS packets with domain-specific identification»egress router of each domain maintains record of each
LFS flow, including copy of trace field»end-to-end records created through off-line accounting
resolution mechanisms
domain U domain V domain WX
Y
Z
B
A
X
Y
Z
acct. record[A,B,..] thru X
acct. record[A,B,..] thru Z
acct. record[A,B,..] thru Y
9 - Jonathan Turner - July 24, 2002
Status Reporting
Basic LFS option supports sender status and trace field for accounting.
Network providers likely to want more.»sender net status allows LFS service verification»public net status allows “end-to-end” status check» intra-domain status for verifying local status »each “extra” status report requires insertion of
requestor’s IP address, increasing LFS option length
ISP Vrcvr. LAN
sender LAN ISP U
sender status
sender net status
public net status
intra-domain status
10 - Jonathan Turner - July 24, 2002
Partial Deployment Receivers need not be LFS-aware.
»web site may use LFS to reserve bandwidth for streaming media - users benefit, even without LFS-aware hosts
Issues with non-contiguous LFS domains.» route changes may create “orphan reservations”»no simple way to determine status reporter
No support for non-contiguous LFS domains.»LFS router forwarding to a non-LFS router (or host) strips
LFS option and implements status reporting status report includes IP address of reporting router, letting
sender know how far the reservation went Public IP carrier can accept LFS option from client
networks (LAN) even if client net is not LFS-aware. Clients may use tunnel to access LFS service.
11 - Jonathan Turner - July 24, 2002
Regulating LFS Use - Net Access Svc
Permitting unconstrained access to LFS creates big security vulnerability.
Limit use to authorized users. Limit number of reservations and amount of
reserved bandwidth by authorized users.»access router keeps record and enforces limits»complication - user may use LFS from multiple locations
maintain records in distributed set of servers - each server keeps records for some fraction of the users - use hashing to select
Access router needs means to identify user.»host IP address insufficient (DHCP, NAT)»encryption-based authentication (IPSEC)
Combine access control with usage accounting. What special issues arise with multiple domains?
12 - Jonathan Turner - July 24, 2002
LFS Video Demo Configuration
Wavelet-coded video with and without LFS.» competing datagram traffic» with no reservation, lost packets cause poor video quality» with reservation, high quality preserved
video source
cross traffic
sources
cross traffic sinks
video sink
100 Mb/s links
13 - Jonathan Turner - July 24, 2002
Video Demo - No Reservation
video flow - no reservation
datagram cross traffic flow 1
datagram cross traffic flow 2
video source cross traffic sources all sinks
14 - Jonathan Turner - July 24, 2002
Video Demo - With Reservation
video flow - with reservation
datagram cross traffic flow 1
datagram cross traffic flow 2
video sink cross traffic sinks
15 - Jonathan Turner - July 24, 2002
Competing LFS Flows
no reservations
flow 1 - no reservation
flow 2 - reservation added
flow 3 - no reservation
reservation for flow 2 sources
sinks
sink 2
sink 1
16 - Jonathan Turner - July 24, 2002
Partial Reservation
flow 1 - partial reservation made
sink 1
flow 2 source 1
sink 3
17 - Jonathan Turner - July 24, 2002
Completing Partial Reservation
flow 1 - completes partial reservation
sink 1
sink 3
flow 2 - drops reservation
18 - Jonathan Turner - July 24, 2002
Addition of Flow 3 Reservation
sink 3
flow 3 - adds reservation
sink 2
19 - Jonathan Turner - July 24, 2002
Performance of LFS at Single Link
m = number of flows link can carry exponential session times for flows, infinite queue
1.E-16
1.E-14
1.E-12
1.E-10
1.E-08
1.E-06
1.E-04
1.E-02
1.E+00
0.00 0.05 0.10 0.15 0.20 0.25t (unit = average service time)
Pr{
dela
y>t}
m=50
100
200
400
load=.7
OC-48 link can carry 200 flows
of 12 Mb/s
very few flows
experience any delay
Pareto distributed session times
make little difference
20 - Jonathan Turner - July 24, 2002
Sensitivity to Load and Hop Count
1.E-12
1.E-11
1.E-10
1.E-09
1.E-08
1.E-07
1.E-06
1.E-05
0.00 0.05 0.10 0.15 0.20 0.25
t (unit = average service time)
Pr{
dela
y>t}
load=.7
m=200
hops=1 4 16
1.E-16
1.E-14
1.E-12
1.E-10
1.E-08
1.E-06
1.E-04
1.E-02
1.E+00
0.00 0.05 0.10 0.15 0.20 0.25
t (unit = average service time)
Pr{
dela
y>t}
load=.9
.8
.6
.7
m=200
at 90% load, less than 1 flow in 100 delayed
more than 12% of session time
delay probability scales linearly with number of
hops
21 - Jonathan Turner - July 24, 2002
Overload Performance
0.5
0.6
0.7
0.8
0.9
1.0
0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2
offered load
"carr
ied
load
" no buffer
infinite buffer
m=50
100
200
400
1.E-04
1.E-03
1.E-02
1.E-01
1.E+00
0.50 0.60 0.70 0.80 0.90 1.00 1.10 1.20
offered load
Fract
ion
"R
eje
cted
"
infinite buffer
m=50 100 200 400
no buffer
with infinite buffer, no sessions get
small delays (10%)
with no buffer most sessions still
succeed
buffer reduces rejection fraction
at low loads
22 - Jonathan Turner - July 24, 2002
Summary LFS provides simple reservations for QoS.
»no complex signaling, wire speed setup» limited deployment can be broadly beneficial»support for usage monitoring & accounting gives
network providers a motivation to deploy service Network access service for regulating usage.
»preliminary specification has been developed»uses IPSEC for host/user authentication
Performance analysis, simulation study underway.
Routing issues.»evaluate QoS routing with multiple-choice forwarding» link state distribution for inter-domain routing» inter-domain routing policies