Achieving Multimedia QOS over Hybrid IP/PSTN
Infrastructures:
IP Traffic and Congestion Control
April 26, 2001
Susumu Yoneda
Japan Telecom Information &
Communication Labs
Japan Telecom
Information & Communication Labs
Outline

IP Transfer Capabilities







Service models
Traffic descriptors
Conformance definitions
QoS commitments
Generic Traffic & Congestion Controls
Specific Mechanisms e.g., Diffserv, MPLS
Conclusion
2
IP Transfer Capabilities:
ITU-T SG13 Draft Rec. Y.iptc



Dedicated Bandwidth (DBW) IP Transfer
Capability
Statistical Bandwidth (SBW) IP Transfer
Capability
Best-Effort (BE) IP Transfer Capability
IP Transfer Capability: a set of network capabilities provided
by IP based network to transfer a set of IP packets under a
given classification.
3
Service Models &
Traffic Descriptors
DBW
SBW
BE
Service
Model
Conforming Packets
Assure the negotiated QoS
Non-conforming Packets
Discarded
Conforming Packets
Delivered corresponding to the
associated QoS
Non-conforming Packets
Delivered within the limits of
available resources
All Packets
Forwarded by use
of available
resources
Traffic
Descriptors
Peak Rate,
Peak Bucket Size,
The maximum allowed
packet size
DBW’s descriptors +
Sustainable Rate, Sustainable
Token Bucket Size
The maximum
allowed packet size
4
Conformance Definitions &
QoS Commitments
DBW
SBW
BE
Conformance
Definition
Packet Arrival
Conforming to the
GBRA(Rp,Bp)
Packet Length
Not exceed the
maximum allowed
packet size
Packet Arrival
Conforming to the peak
GBRA(Rp,Bp) and the
sustainable GBRA(Rs,Bs)
Packet Length
Not exceed the maximum
allowed packet size
Packet Length
Not exceed the
maximum allowed
packet size
QoS
Commitments
Specified Loss and
Delay commitments
Include IP QoS Class
0 and 1
Specified Loss commitment
Include IP QoS Class 2
No absolute
commitment
5
Generic Traffic & Congestion
Controls

Traffic Control Functions







Network Resource Management
Admission Control
Parameter Control
Packet Marking
Traffic Shaping
Packet Scheduling
Congestion Control Functions


Packet Discard Control
Routing (Proposed)
6
Differentiated Services
[DiffServ]

Two standard per hop behaviors (PHBs) defined
that effectively represent two service levels


Expedited Forwarding (EF): A single codepoint
(DiffServ value). EF minimizes delay and jitter and
provides the highest level of aggregate quality of
service. Any traffic that exceeds the traffic profile
(which is defined by local policy) is discarded.
Assured Forwarding (AF): Four classes and three
drop-precedences within each class (so a total of twelve
codepoints). Excess AF traffic is not delivered with as
high probability as the traffic “within profile,” which
means it may be demoted but not necessarily dropped.
7
Diffserv Functions (1)
•Classifier
•Behavior Aggregate (BA): Uses only the Diffserv Code Point (DSCP) value
•Multi-Field (MF): Uses other header info (like protocol, or port numbers,
etc.)
•Marker
•Adds DSCP when none exists
•Adds DSCP as mapped from RSVP reservation
•Changes to Map from DSCP to IP TOS, or back
•Changes DSCP as local policy dictates
8
Diffserv Functions (2)
• Meter
• Accumulates statistics, and provides the inputs to
conditioning
• Conditioner
• Provides queue selection and treatment, policing
(shaping traffic) by adding delay or dropping packets in
order to conform to the traffic profile described in the
SLA with destination or source (depending whether this
is an egress or ingress point).
• Authenticates the traffic for admission control.
9
MPLS Mechanisms


At the first hop router in the MPLS network, the router
makes a forwarding decision based on the destination
address (or any other information in the header, as
determined by local policy) then determines the
appropriate label value -- which identifies the Forwarding
Equivalence Class (FEC) -- attaches the label to the
packet and forwards it to the next hop.
At the next hop, the router uses the label value as an index
into a table that specifies the next hop and a new label. The
LSR attaches the new label, then forwards the packet to the
next hop.
10
MPLS Routing protocols
Start with existing IGP’s




OSPF
IS-IS
BGP-4
Distribute topology
information only
Enhance to carry constraint data


OSPF-TE
IS-IS –TE
Constraint data
Link capacity,Link utilization
Resource class
Priority
Pre-emption etc
Constraint based routing is the key to Traffic Engineering
11
Label Distribution Protocols

LDP

CR-LDP

RSVP-TE
Hop by Hop routing
Ensures routers agree on bindings between
FEC’s and the labels.
Label paths follow same route as
conventional routed path
Explicit constraint based routing
Route determined by ingress LSR based
on overall view of topology, and constraints
Traffic engineering
CoS and (QoS)
fast (50ms) rerouting
12
MPLS Shim Header Structure
MPLS "shim" headers
...
Layer 2 Header
Label
Exp. S
4 Octets
Label Switching
Look up inbound label + port (+Exp)
to determine
outbound label + port + treatment
TTL
IP Packet
Label:
Exp.:
S:
TTL:
20-bit value, (0-16 reserved)
3-bits Experimental ( ToS)
1-bit Bottom of stack
8-bits Time To Live
Header operations
Swap (label)
Push (a new header)
Pop (a header from stack)
MPLS encapsulations are also defined for ATM and Frame relay.
13
Hierarchy via Label stack
= Network scalability
Layer 2 Header
Within each domain
the IGP simply needs
to allow the Boarder
(ingress) routers to
determine the
appropriate egress
boarder router
Reducing drastically
size of routing table in
transit routers
Label 3
Label 2
Label 1
IP Packet
MPLS Domain 1
MPLS Domain 2
MPLS Domain 3
14
Dynamic-Bandwidth Setting
traffic
time
Link traffic monitor and dynamic-bandwidth setting.
15
Conclusion


Provide a summary of Y.iptc: IP Transfer
Capabilities, Service models, Traffic descriptors,
Conformance definitions, QoS commitments
How does it work with many other existing traffic
engineering mechanisms?


Traffic engineering as well as congestion controls
would work well when traffics are effectively
monitored and conformance is checked.
Utilize Y.iptc for the conformance monitoring purposes.
16