Integrated Services

1
Integrated Services RSVP

• Types of pplications
• Basic approach in IntServ
• Key components
• Service models

2

• Application types
• Elastic applications
• old-fashioned applications
• Tolerant playback applications.
• One-way video streaming, one-way broadcast
• Delay and delay jitter (Figure 2.1)
• Removing jitter with play-out buffer (Figure 2.2)
• Latency .vs. fidelity
• Intolerant playback applications data need to be
  delievered in real-time
• Two way conversations (stringent delay
  constraint).

3

• Design objective of IntServ
• Preserve datagram model of IP networks
• Support resource reservation and QoS guarantees
  for multimedia applications
• Protect multimedia traffic from being affected by
  regular TCP traffic and vice verse
• Basic approach similar to tele. Networks
• Before sending, sender describes the traffic and
  resource requirement and sends the request to the
  network.
• The request goes through the network hop-by-hop,
  each hop will check its resources to decide
  whether to reject or accept the request.
• If everyone says ok, the sender will be notified
  and can start send data along the reserved path.

4

• Key components in IntServ (Figure 2.4)
• Control plane
• QoS routing agent (QoS routing)
• Can be difficult.
• Admission control
• Reservation setup agent (RSVP)
• Resource reservation table
• Data plane
• Flow identification
• Packet scheduler

5

• Admission control
• To decide whether to accept a new request (done
  at each router in IntServ).
• Parameter based
• A set of parameters is used to characterize
  traffic flows.
• The admission control agent computes the required
  resources based on the parameters.
• Difficult to model the traffic.
• Measurement based
• Measure the actual traffic load for admission
  control.
• Probabilistic in nature, no hard guarantees.
• Trade-off between resource guarantees and
  resource utilizations.
• Common algorithms simple sum, measured sum,
  acceptance region, equivalent bandwidth.

6

• Flow Identifications
• Identify to which flow a packet belong to
• An IP flow is identified by five fields source
  IP address, destination IP address, source port,
  destination port, protocol ID five-tuple
• The flow identification agent must compare the
  five-tuple of a packets to all five tuples in the
  reservation table.
• Requres fast hardware if performed at wire speed
• 64 byte packets arrive in a 622Mbps line back to
  back in less than 1us.

7

• Service Models
• What users can ask and what commitments the
  network can commit.
• Flow model in IntServ
• Described by a leaky bucket
• Token rate ( r ) 1bps 40tbps
• Token-bucket depth (b) 1 B to 250GB
• Peak traffic rate (p) 1bps 40tbps
• Minimum policed unit (m) packets of size lt m
  bytes will be counted as m bytes.
• Maximum packet size (M)
• What is leaky bucket?
• Guaranteed Service and Controlled load Service

8

• Guaranteed Service (RFC 2212)
• For applications requiring fixed delay bound and
  a bandwidth guarantee
• Control the maximum queuing delay
• Guarantees that packets will arrive within a
  certain time and will not be discarded because of
  queue overflows
• No control on minimal or average delay (what
  about jitter?)
• No packet fragmentation is allowed.
• Guaranteed service is invoked by a sender
  specifying a traffic descriptor (Tspec) and a
  service specification (Rspec)
• Rspec has two parameters Service rate ( R ) and
  Slack Term ( S)

9

• Worst case queuing delay for guaranteed service
• ((b-M)(p-R)) / (R (p-r)) (MCtot)/R Dtot
  if pgtRgtr
• (MCtot) / R Dtot if (R gtp gt r)

10

• Controlled load service (RFC 2211)
• Provides unloaded network conditions
• Closely approximates traditional best-effort in a
  lightly loaded or unloaded network environment
• Intended for adaptive applications
• Priority service with admission control
• No fragmentation, packets must comply to MTU