a tutorial overview with a voice over ip slant · 2007-03-05 · cisco systems, inc. 1 of 24 etsi...
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1 of 24
IP
es:
r IP Slant
Cisco Systems, Inc.
ETSI Workhop on Voice overJune 9, 1999
Kathleen [email protected]
Differentiated Servic
A Tutorial Overview with a Voice ove
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Differentiated Services
del is an approach lly deployable way
s
ges maximal
rking on the
de up of of which is
Kathleen Nichols — ETSI Workshop: Differentiated S
Cisco Systems, Inc.
• The differentiated services architectural moto delivering QoS in a scalable, incrementathat:
› keeps control of QoS “local”
› pushes work to the edges and boundarie
› requires minimal standardization, encourainnovation
• The IETF Differentiated Services WG is wo“minimal standardization” part of this
• Diffserv’s model is based on an Internet maindependently administered domains, eachconnected to at least one other
3 of 24ervices
An Architectural Framework based on Clouds and
s are regions of control,
ay’
Kathleen Nichols — ETSI Workshop: Differentiated S
Cisco Systems, Inc.
Boundaries
Follows the structure of today’s Internet: Cloudrelative homogeneity in terms of administrativetechnology, bandwidth, etc.
‘Me’
‘Not-me-1’
‘Not-me-2’
‘Far Aw
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Clouds within Clouds
Kathleen Nichols — ETSI Workshop: Differentiated S
Cisco Systems, Inc.
Telecommuters
‘Me’
Training
Tele-commuters
Remote Site
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QoS and Clouds
to some locally
aries of clouds and
ndary
s is confined to ents where clouds
Kathleen Nichols — ETSI Workshop: Differentiated S
Cisco Systems, Inc.
• Within a cloud, QoS is allocated according determined set of rules
• Almost all the work is confined to the boundcovered by a set of rules
• Rules might not be symmetric across a bou
• QoS information exchanged between cloudboundaries and covered by bilateral agreemhave different owners
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Advantages of Model Based on Clouds
nistered regions of
technology might
p and evolve
ility
esn’t need to be ost nodes can be ection-oriented state for every yable or scalable
Kathleen Nichols — ETSI Workshop: Differentiated S
Cisco Systems, Inc.
• Clouds can map to the independently admithe Internet
• Architecturally agnostic: within a cloud any be used to deliver QoS
• Signaling agnostic and signaling can develo
• Possibility of multiple paths increases reliab
• QoS can be deployed in only one cloud, dosignaled per connection, and the state in mreduced considerably as compared to connapproaches which tie up resources, requireconnection and are not incrementally deplo
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Scalability through Aggregation
s to handle
ing QoS may be of rules which
they are to receive
al with the small track of every h
Kathleen Nichols — ETSI Workshop: Differentiated S
Cisco Systems, Inc.
• Fundamental to the diffserv approach is:
› there are a relatively small number of waypackets in the forwarding path
› the number of traffic conversations requirquite large and subject to a wide range devolve from policy
• Packets are grouped by the forwarding behaviorwithin a cloud
• Nodes in the center of a network only have to denumber of traffic aggregates rather than keepingseparate traffic conversation that passes throug
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Aggregation and Conversations
gates and are
dual conversations ame marking. Any tion
t the behavior performance for regate
Kathleen Nichols — ETSI Workshop: Differentiated S
Cisco Systems, Inc.
• The per-conversation state is kept at the edges
• Flows or conversations are classified into aggre“conditioned” to meet the rules of that aggregate
• Packets are not marked for the “services” indivimay be receiving. Many services may use the sviable service must make sense under aggrega
• Don’t distinguish between flows, so the treatmenaggregate receives should not result in differentdifferent traffic compositions of the behavior agg
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“Minimal Standardization”: IETF RFC 2474
e packet’s et in IPv4 and the its 0-5 as a
into a table of
arding treatment o that behavior from, for
ally assigned and point to behavior
000000-111000
Kathleen Nichols — ETSI Workshop: Differentiated Ser
Cisco Systems, Inc.
• A bit-field in the packet header determines thforwarding treatment. DS field is the TOS octTraffic Class octet in IPv6; within that uses b“codepoint” field (DSCP)
• Codepoints should be looked at as an index packet forwarding treatments at each router.
• This table maps a DSCP to a particular forwor “per-hop behavior” (PHB) that is applied taggregate. PHBs are constructed by vendorsexample, particular queue schedulers
• Behavior for only a few codepoints to be globdiffserv-capable equipment must make codemapping flexible and accessible
• Class Selector Compliant PHBs get DSCPs
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The DSCP and PHBs in Use
lassifiers (both DS and configurable )markers. These can
a particular queue
odepoint ected to occur at
same behavior a “behavior
n, the packet ingress microflow or
Kathleen Nichols — ETSI Workshop: Differentiated S
Cisco Systems, Inc.
• Diffserv-capable equipment will include packet cfield and multiple fields of the IP packet header)traffic conditioners such as shapers, policers, (rebe used to control both selection and entry into
• A packet’s DS field may be marked with a c“anywhere” in the network (but marking expedges and boundaries)
• All packets with the same codepoint get thethus providing aggregation and scalability (aggregate”)
• Marking can be based on microflow identificatiolink, the measured temporal characteristics of aaggregate, etc.
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The EF Per-Hop Behavior (RFC 2598)
ut it is also the one
, can be ism
ets from any urable rate.
dependent of the ansit the node.
rate when r longer than the ed packet at the
Kathleen Nichols — ETSI Workshop: Differentiated S
Cisco Systems, Inc.
This is a forwarding behavior of general use, bmost useful for doing VoIP
In simple terms, it is a rough equivalent of PQimplemented by PQ with some safety mechan
More precisely (from RFC 2598)
“the departure rate of the aggregate’s packdiffserv node must equal or exceed a config
The EF traffic SHOULD receive this rate inintensity of any other traffic attempting to tr
It SHOULD average at least the configuredmeasured over any time interval equal to otime it takes to send an output link MTU sizconfigured rate. “
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Example Implementations of EF PHB
andwidth. BE is
one-half the MTU.
An MTU at thesubscribed rate
Arrival pattern
Priority Queueing
WRR/DRR
Kathleen Nichols — ETSI Workshop: Differentiated S
Cisco Systems, Inc.
Arrival rate is twice the output link bandwidth
EF queue configured to get 25% of the output link bconfigured to get 75% of the output link bandwidth.
Here packets come in only two sizes, the MTU and
EF EF
EF
EF EFBE BE
BE BE
BE EF BE
EF BE BE EF
EF
BE BE BE
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Performance of VoIP using Diffserv’s EF PHB
eams. 10% of traffic f the EF packets, sults due to Y. Kim
24
FQ
R
Kathleen Nichols — ETSI Workshop: Differentiated Ser
Cisco Systems, Inc.
Median Jitter (|(aj-ai)-(dj-di)|) for voice type packet stris EF-marked, 60% gets other “special” treatment. Ohalf are long (1500 bytes), half short (100 bytes). (Reof Cisco)
5 ms
10 ms
15 ms
20 ms
4 8 12 16 20
PQCBWW RRMDR
number of congest T1 hops
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Performance of VoIP using EF PHB (cont)
24
W FQRR
RR
Kathleen Nichols — ETSI Workshop: Differentiated S
Cisco Systems, Inc.
95th percentile of jitter
10 ms
20 ms
30 ms
40 ms
50 ms
60 ms
4 8 12 16 20
PQCBWMD
number of congest T1 hops
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Services in the Diffserv Framework
bout building
behavior
boundaries
daries
e same aggregate
under aggregation
Kathleen Nichols — ETSI Workshop: Differentiated S
Cisco Systems, Inc.
• That covers the forwarding path, but what aservices?
• Services are built by adding rules to governaggregates:
› initial packet marking
› how particular aggregates are treated at
› temporal behavior of aggregates at boun
• Different user-visible services can share th
• Services must be sensible and quantifiable
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Example: Putting Together an EF-based Service
routers know
Kathleen Nichols — ETSI Workshop: Differentiated Serv
Cisco Systems, Inc.
Natural Question: How do the border and edgewhat to mark?
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Controlling the Boundaries
track of priorities users, projects,
, consult and n information to
an Jacobson).
must authenticate also be
tations remain up
Kathleen Nichols — ETSI Workshop: Differentiated S
Cisco Systems, Inc.
• A repository of of policy is needed to keep and limits on QoS allocations for individual and/or departments.
• An entity needs to receive requests for QoSupdate the database, and send configuratiothe routers, where indicated.
• Call this entity a “bandwidth broker” (BB) (V
• BB is part of the network infrastructure andrequests from users. Some information canconfigured.
• Intradomain policy decisions and implemento each domain.
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Bandwidth Broker in the Enterprise
n, BB configures n (COPS-PR?)
Kathleen Nichols — ETSI Workshop: Differentiated S
Cisco Systems, Inc.
In a static or configured implementatioleaf/edges with soft state informatio
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Requests to a BB and the Result
requests
Kathleen Nichols — ETSI Workshop: Differentiated S
Cisco Systems, Inc.
Here the BB responds to user
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Requests Can Come from Many Sources
g”
Kathleen Nichols — ETSI Workshop: Differentiated S
Cisco Systems, Inc.
“Agnostic about signalin
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What about Voice?
trivial and not
ode sufficient to
ation is within the
router to ensure
Kathleen Nichols — ETSI Workshop: Differentiated S
Cisco Systems, Inc.
Inside a high-bandwidth cloud, VoIP flows are worth tracking
› Assume configured EF at each network nhandle all calls
› When a call is initiated, check if the destincloud
› If so, just admit the call
› May want to set up a classifer on the edgeno “spoofing”
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Voice between (Administratively Same) Clouds
esources, h-rich clouds
red for an EF rate f “busy”
ble - call_bw) >=0?
ed
Kathleen Nichols — ETSI Workshop: Differentiated S
Cisco Systems, Inc.
Track connections only in the areas of limited rboundaries between clouds. For two bandwidtconnected by a low-bandwidth link
› Assume the low-bandwidth link is configuthat gives a sufficiently low probability o(bw_available)
› When a call is initiated, check destination
› If it’s in the other cloud, check: (bw_availa
› If not, refuse call
› If yes, bw_available -= call_bw and proce
23 of 24ervices
Voice across Clouds
limited resources,
te that sufficient to (bw_available)
l_bw) >=0?
ait for reply
and proceed
Kathleen Nichols — ETSI Workshop: Differentiated S
Cisco Systems, Inc.
Locally, track connections only in the areas of tail to “next cloud”.
› Assume the tail is configured for an EF rahandle all outside calls most of the time
› When a call is initiated, check destination
› If it’s “not-me”, check: (bw_available - cal
› If not, refuse call
› If yes, signal/message “next cloud” and w
› If reply is positive, bw_available -= call_bw
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Pointers
ervices Working erv-charter.html. page.
Van Jacobson ilable at: proceedings from s/may98Workshop/
ce about BBs .lbl.gov/papers/
Kathleen Nichols — ETSI Workshop: Differentiated S
Cisco Systems, Inc.
• For information on the IETF Differentiated SGroup, see www.ietf.org/html.charters/diffsThe diffserv RFCs are at the bottom of the
• A talk on diffserv and bandwidth brokers bygiven at the Internet2 QoS workshop is avawww.internet2.edu/media/qos8.ram and thethat workshop are at www.internet2.edu/qo9805-Proceedings.pdf
• A “historical” document that still has relevan(Nichols, Jacobson, and Zhang): ftp://ftp.eedsarch.pdf