QoS over IP Networks

1
QoS over IP Networks

• Dave Olshefski
• Candidacy Exam, 12/8/99

2
Overview

• Motivation for QoS in the network
• Flow specification
• Flow separation
• Resource reservation
• Solving the scaling problem
• Management
• Interesting research issues

3
Top Three reasons for QoS in the Network

• Ensure mission critical applications are
  allocated the resources they need.
• Multimedia/realtime applications can only operate
  within a certain range of service.
• Service providers wish to increase revenues
  through premium pricing and competitive
  differentiation of services

4
What is a service?

• End users concerned with response time cost
• Better than Best Effort for webserver
• 1 Mbps, to any point in net, over 1Mbps gets BE
• Leased Line Emulation from point A to B
  (realtime)
• 100 Kbps, A to B, over 100 Kbps get dropped
• Media Playback from point A to B (adaptive)
• 100Kbps sustained, 100Kbps max burst at peak rate
  of 200 Kbps, A to B, excess burst traffic over
  sustained rate given lower priority in class,
  non-conforming traffic etc..

5
Characterize a Flow ltr,b,p,m,Mgt
r constant token rate (bps)
p max peak rate
variable rate input
b token bucket depth
input queue
burst
leaky bucket depth
6
Weighted Round Robin (WRR)
Queue A
WA
Bandwidth assurances iff mean packet size per
flow is known
Queue B
Packet Scheduler
WB
No delay assurances
Queue C
WC
Wi number of packets to service during turn
7
Weighted Fair Queuing (WFQ)
Queue A
WA
Bandwidth and delay assurances
t0
Packet Scheduler
Queue B
WB
Simulates bit-by-bit WRR Sorted list expensive
to maintain
t1
Queue C
WC
t2
Wi number of bits to service during turn
8
Deficit Round Robin (DRR)
Queue A
QADA
Bandwidth assurances but no delay bounds
Queue B
Packet Scheduler
QBDB
Queue C
QCDC
IF (quantumdeficit) gt packet length THEN
send packet deficit - length ELSE deficit
quantum
9
Router Traffic Conditioning
Queue A
Queue B
Multifield Classifier
data
Queue C
BE

• 5-tuple classification ltsrc IP, src port, dest
  IP, dest port, prot idgt
• queue per microflow scaling problem
• How is this configured??

10
ReSource reserVation Protocol
R3
R5
R4
R6
R2

• PATH
• Follows routing path (router alert)
• Carries Tspec for generated traffic
• Soft state left in each router (prev hop)
• Nodes on path advertise capabilities
• All nodes are equivalent

R7
R1
H1
H2
11
RSVP
R3
R5
R4

• RESV
• Hop-by-hop
• Carries Tspec for reservation
• Admission decision made at each node

R6
R2
R7
R1
H1
H2
12
Diff-serv Backbone
IR
ER
CR
BR
BR
Aggregation region single field classification
and class-based queuing
R6
R1
RSVP Stub
RSVP Stub
H1
H2
13
Ingress router to DS domain
Queue A
Queue B
MF Classifier Marker
data
Queue C
5-tuple to DSCP mapping
Multiple field -gt Single field i.e.
microflow-gtclass of service
14
Core router in DS domain
Queue A
Queue B
BA Classifier
Packet Scheduler
data
Queue C
Single field classification No policing, shaping,
dropping
15
Aggregate Region
RSVP Region
RSVP Region
H1
IR
CR
ER
H2
BR
BR
RSVP_E2E_IGNORE to H2
PATH to H2
PATH to H2
RSVP PATH w/DSCP for aggregate
RESV to IR for aggregate
RESV from H2
RESV from H2
RESV from H2
Aggregate RSVP
16
Variations

• Partial path reservations w/incremental updates
• Bottleneck reservations
• reserve if needed else use BE
• Sender initiated reservations

17
RSVP Stub
Multicast Problem
BR
H3
ER
Diff-serv Backbone
IR
CR
ER
BR
BR
R6
R1
RSVP Stub
RSVP Stub
H1
H2
18
Windows 2000/98
QoS-Enabled Application
Traffic Management Application
GQoS
TC API
Winsock2.dll
RAPI
RSVP.exe
Protocol Stack
Kernel Traffic Control
Packet Scheduler
GPC API
Network Card Driver
19
Winsock 2 API

• WSAStartup()
• WSAEnumProtocols(NULL, Protocols, bufferSize)
• WSASocket(, Protocolsi, )
• WSAConnect(, FlowSpecs, )
• WSAGetQoSByName(socket,RSVP,FlowSpec)
• WSAIoctl(socket, SIO_SET_QOS, , Qos2, )

20

• WSAStartup()
• numProtocols WSAEnumProtocols(NULL, Protocols,
  bufferSize)
• For (i 0 i lt numProtocols i)
• if (Protocolsi.dwServiceFlags1
  XP1_QOS_SUPPORTED)
• (Protocolsi.dwServiceFlags1
  XP1_CONNECTIONLESS)
• (Protocolsi.iAddressFamily
  AF_INET)
• (ProtocolsI.iProtocol
  IPROTO_UDP))
• s WSASocket(FROM_PROTOCOL_INFO,
  // address family
• 
  FROM_PROTOCOL_INFO, // socket type
• 
  FROM_PROTOCOL_INFO, // protocol
• 
  Protocolsi, 0, WSA_FLAG_OVERLAPPED)
• WSAConnect(s, (sockaddr
  )RemoteHost, sizeof(RemoteHost),
• NULL,
  NULL, Qos, RESERVED)
• ..

21
Service Level Agreement

• constraints on source and destination points
• out of profile actions
• marking and shaping services provided
• encryption services
• authentication mechanisms
• pricing and billing
• availability/reliability, refunds,
  re-negotiation/cancellation
• static or dynamic

22
Negotiation During RSVP Signaling
Aggregate Region
RSVP Region
RSVP Region
H1
IR
CR
ER
H2
BR
BR

• Each node on path adds its fee to the
  charge/price as the reservation is propagated
  from end to end.
• Iteration not well supported

23
Bandwidth Broker Negotiation
SLA/COPS
SLA/COPS
BB/PDP
IR
ER
CR
BR
BB/PDP
BR
BB/PDP

• Hierarchical
• Inter-domain
• Intra-domain
• With OSPF, BB can determine price from demand

RSVP
RSVP
R6
R1
H1
H2
24
H1
MPLS
BR
BR
BR
BR
BR
BR
BR
BR
H2
MPLS encapsulation at ingress -gt de-encapsulation
at egress Routing QoS
25
Market
BB
PDP
BB
BB
IR
ER
CR
BR
PDP
BR
PDP

• Negotiation more efficient
• Matching alg. (social welfare)
• Fairness controls

RSVP
RSVP
R6
R1
H1
H2
26
Management Console
PAPI
Policy Server
BB
Policy DB
CPC
LDAP
COPS
PDP
PDP
Border Router
PEP
Proxy
SNMP
Border Router
PEP
LPDP
Border Router
27
Research Issues

• Aggregation
• Expanding/collapsing regions
• dynamic or static SLAs
• Integrating policy, pricing and measurement for
  admissions control/marketing decisions
• Market mechanisms and product definition
• Matching algorithms
• Advanced reservations (pre-emption)
• Pricing (holding, usage, congestion)

28
Research Issues

• Adaptive applications
• Temporal scaling (sampling rate)
• Spatial resolution (image size)
• Layering (video)
• Advance Reservations adapting to price
  fluctuations and availability over time.
• Bandwidth CPU, memory disk space
• Server farms, web hosting
• VPNs, VANs, active networks

29
Questions
30
Pricing/Charging

• Reservation charge
• Usage based charging
• Congestion charging
• Pre-emption vs. selling back unused bandwidth

31
Reservation Styles

• Fixed filter
• Distinct reservations from each source to dest
• Shared Explicit
• Specified sources share the same reservation
• Wildcard filter
• All sources share the same reservation

32
IP-SEC

• DS codepoint not encrypted
• incoming IP-SEC packets cant be multi-field
  classified
• may have to rely on DS codepoint marking in hosts
• IP-SEC hides dst address? Difficult to provide
  quantitative services without knowing the egress
  point.

33
DSCP remarking between domains
BR
BR
R6
R1
RSVP Stub
RSVP Stub
H1
H2
34
Controlled Load

• Approximate BE under unloaded conditions
• Most packets receive little/no queuing delay but
  no delay/jitter assurances
• No micro-flow packet reordering
• ltr,b,p,M,mgt
• Out-of-profile share BE

35
Guaranteed Service

• Firm guarantees on delay bound and minimum
  bandwidth
• No jitter, min or avg delay assurances
• Apps with hard real-time requirements
• Out-of-profile gets dropped

36
Assured Forwarding Group

• Four classes
• Each class receives a certain amount of resources
• Within each class there are three drop
  precedence's
• No micro-flow packet reordering
• No delay/jitter assurances
• ltr,b,p,M,mgt
• Approximates Controlled Load

37
(Weighted) Random Early Detection
Min Threshold
Max Threshold
p1
p0

• P is a function of mean queue length and time to
  last packet drop.
• P increases slowly as queue fills up
• Flows lose packets in proportion to their
  allocated bandwidth
• RIO RED applied to in-profile and out-profile
  queues separately
• Weights(drop probabilities) based on IP-precedence

38
Slots
bandwidth
new intervals
unallocated
allocated
time
demand
time
39
Intervals
bandwidth
new intervals
unallocated
allocated
time
demand
time
40

• hEvent WSACreateEvent()
• While(True)
• rc WSAWaitForMultipleEvents(1, hEvent,
  FALSE, timer, FALSE)
• switch(rc)
• case WSA_WAIT_EVENT_0
• WSAEnumNetworkEvents(s, hEvent,
  events)
• if (events.lNetworkEvents
  FD_QOS)
• WSAIoctl(s, SIO_GET_QOS,
  NULL, 0, Qos2, sizeof(QoS2), )
• if (events.lNetworkEvents
  FD_READ)
• WSARecvFrom(.

41
Windows 2000 Flow Spec

• typedef struct _flowspec
• uint32 TokenRate
  / In Bytes/sec
• uint32 TokenBucketSize
  / In Bytes
• uint32 PeakBandwidth
  / In Bytes/sec
• uint32 Latency
  / In microseconds
• uint32 DelayVariation
  / In microseconds
• SERVICETYPE ServiceType /
  Guaranteed, Predictive,
• 
  / Best Effort, etc.
• uint32 MaxSduSize
  / In Bytes
• uint32 MinimumPolicedSize
  / In Bytes

42
Services

• Qualitative
• relative, measured by comparison
• Traffic service B has a lower drop probability
  than traffic in service A
• arbitrary end points A to ?
• harder to manage predict
• Quantitative
• measured independent of other services
• 90 of traffic delivered at service level C will
  experience no more than 50 msec delay
• between specific end points A to B
• Easier to manage and predict

43
Aggregate Region
RSVP Region
RSVP Region
H1
IR
CR
ER
H2
BR
BR
RSVP PATH from H1 to H2
Using RSVP signaling to establish aggregate
reservation.
Signal ltsrc IP, src port, dest IP, dest
port, RSVP, Tspec gt
44
Aggregate Region
RSVP Region
RSVP Region
H1
IR
CR
ER
H2
BR
BR
Microflow RSVP packets IP Protocol number are
remarked from RSVP to RSVP_E2E_IGNORE by ingress
router. Router Alert is set but CR doesnt
recognize RSVP_E2E_IGNORE.
Signal ltsrc IP, src port, dest IP, dest port,
RSVP_E2E_IGNORE, Tspec gt
45
Aggregate Region
RSVP Region
RSVP Region
H1
IR
CR
ER
H2
BR
BR
Egress router recognizes RSVP_E2E_IGNORE and
resets IP Protocol to RSVP. Packets can now
reserve rest of path IR is seen as the previous
hop so RESV will be addressed to IR.
Signal ltsrc IP, src port, dest IP, dest port,
RSVP, Tspec gt
46
Aggregate Region
RSVP Region
RSVP Region
H1
IR
CR
ER
H2
BR
BR
TSpecs/Flowspecs for microflows are summed. An
RSVP packet for the aggregate is passed from IR
to ER which CR notices. The DSCP is included.
Signal ltsrc IP, src port, dest IP, dest
port, RSVP, Tspec, DSCP gt
47
Aggregate Region
RSVP Region
RSVP Region
H1
IR
CR
ER
H2
BR
BR
Remote host sends a RESV to allocate resources,
hop-by-hop.
Signal ltsrc IP, src port, dest IP, dest
port, RSVP, Tspecgt
48
Aggregate Region
RSVP Region
RSVP Region
H1
IR
CR
ER
H2
BR
BR
ER sends an aggregate RESV to IR. CR routers
perform normal RESV admission control.
Signal ltsrc IP, src port, dest IP, dest
port, RSVP, Tspec, DSCP gt
49
Aggregate Region
RSVP Region
RSVP Region
H1
IR
CR
ER
H2
BR
BR
ER sends the mircoflow RESV to IR (previous hop).
Signal ltsrc IP, src port, dest IP, dest
port, RSVP, Tspec, DSCPgt
50
Aggregate Region
RSVP Region
RSVP Region
H1
IR
CR
ER
H2
BR
BR
IR establishes reservation and sends the
microflow RESV on to source.
Signal ltsrc IP, src port, dest IP, dest
port, RSVP, Tspecgt