Admission Control in IP and MPLS Networks

Admission Control in
IP and MPLS
Networks

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Agenda
􀂃 Introduction and CAC Taxonomy

Admission Control: Why?
􀂃 The Over-Provisioning Model: Adjust Network capacity to peak Traffic
􀂃 The TCP Congestion Control Model: Adjust every elastic flow to its share
of Network capacity
􀂃 The Admission Control Model: Reject Flows that don’t fit
􀂃 Many environments live happily through combination of Over-Provisioning
and TCP Congestion Control
e.g. The Internet, Campus networks, …
􀂃 Some environments require Admission Control. Typically, where
– Important Traffic is inelastic (“steep utility curve”), like Voice/Video
– inelastic traffic is in high proportion, like Video in Metro Aggregation
– Determinism is required
e.g. Mobile Phone Trunking, Triple Play, Enterprise WAN, Military Ad-hoc networks
Ensuring Traffic Fits in Network:



Admission Control: What?
􀂃 A technology for:
(i) Deciding which flow fits or doesn’t fit into network.
(ii) Providing explicit notification to Application so it can do the
right thing (e.g send busy tone). Often challenging, as it
requires the “Network” and the “Application” to communicate


Admission Control: How?
Taxonomy for Admission Control

Admission Control
Wireline CAC Requirements
Tight SLA commitments not compatible with call blocking probability of CAC. Requires stringent capacity planning
(and possibly TE like traffic engineering) both in normal and failure conditions
􀃎CAC with feedback to application not needed
Business
Generally provisioned with
sufficient class bw to cope with
peak during working and failure
case
􀃎 CAC not generally needed
In few SPs potential for congestion
in areas of the network both in
working and network failure cases
􀃎 CAC needed in some cases
Potential for congestion both in
working and network failure cases
􀃎 CAC highly needed
VoD
(unicast)
Some requirements for trunk level
admission control (p-mp TE) but
not with feedback to the
application
Generally provisioned with
sufficient class bw to cope with
peak during working and failure
case
􀃎 CAC not needed
Generally provisioned with
sufficient class bw to cope with
peak during working and failure
case
􀃎CAC not generally needed
In a few SPs, potential for
congestion on DSLAM uplink and
Aggregation (very high nb of
channels, HDTV)
􀃎CAC needed in some cases
Today:Video services generally
marketed with total display capacity
below access line rate (e.g. 1 SDTV
port + 1 SDTV/HDTV port on 12Mb/s
line).
# of streams easily limited at the endsystem
or application level
􀃎no additional CAC needed
In the future: Video services could be
marketed with total display capacity
above access line rate (e.g. 2
SDTV/HDTV ports on 12 Mb/s line).
􀃎 integrated CAC solution covering
mcast and unicast needed in future?
Broadcast
video
(multicast)
With the move to NGNs supporting
the integration of the PSTN into IP
networks, adding support for
deterministic admission control is
essential
􀃎 CAC needed in some cases,
generally to cover failures rather
than normal condition
Bw requirements small compared
to video and generally provisioned
with sufficient class bw to cope
with peak during working and
failure case
􀃎 CAC not generally needed
# of calls generally limited at the
application level, i.e. call server, and
bw requirements small compared to
video
􀃎 CAC only needed as part of call
server (eg SBC with on-board PCSCF)
VoIP
ACCESS LINK (last mile) AGGREGATION NETWORK CORE



VoD CAC Requirements in Aggregation
􀂃 Each VoD Stream is big (eg. 1.5-4Mb/s SD, 8-12Mb/s HD)
􀂃 Aggregation network cannot be dimensioned to cope with simultaneous
VoD use by all users
􀂃 Aggregate VoD load is very hard to predict
(unlike aggregate Broadcast Video load)
scales with peak number of simultaneous users
depends on many external variables (service uptake, content attractiveness,
promotions,…)
􀂃 Video encodings intolerant to loss
􀂃 If the aggregate Video load sessions exceeds the capacity, ALL Video
sessions degrade
􀂃 Failures in Aggregation makes problem even worse
CAC Highly Needed for VoD in Aggregation