Cs 552 Computer Networks Quality Of Service

Wildcard Filter: Inefficient Resource Utilization Example

• H1 reserves 3B; wants to listen from all senders simultaneously
• Problem: reserve 3B on (S3:S2) although 2B sufficient!

• S1

• S2

• S3

• H2

• H1

• H5

• H4

• H3

• (3B,*)

• (3B,*)

• (3B,*)

• sender

• receiver

Fixed Filter Example

• Receivers: H2, H3, H4, H5; Senders: H1, H4, H5
• Routers maintain state for each receiver in the routing table

• S1

• S2

• S3

• H2

• H1

• H3

• sender

• receiver

• H5

• H4

• sender+receiver

• NextHop Sources
• H1 S2(H5, H4)
• H2 H1(H1), S2(H5, H4)

Fixed Filter Example

• H2 wants to receive B only from H4

• S1

• S2

• S3

• H2

• H1

• H3

• sender

• receiver

• H5

• H4

• sender+receiver

• (B,H4)

• (B,H4)

• (B,H4)

• (B,H4)

Dynamic Filter Example

• H5 wants to receive 2B from any source

• S1

• S2

• S3

• H2

• H1

• H3

• sender

• receiver

• H5

• H4

• sender+receiver

• (B,H4)

• (B,H4)

• (B,H4)

• (2B,*)

• (B,H4)

• (B,*)

• (B,*)

Soft State

• Per session state has a timer associated with it
• path state, reservation state
• State lost when timer expires
• Sender/Receiver periodically refreshes the state
• Claimed advantages
• no need to clean up dangling state after failure
• can tolerate lost signaling packets
• signaling message need not be reliably transmitted
• easy to adapt to route changes
• State can be explicitly deleted by a Teardown message

Tear-down Example

• H4 leaves the group
• H4 no longer sends PATH message
• State corresponding to H4 removed

• S1

• S2

• S3

• H2

• H1

• H3

• sender

• receiver

• H5

• H4

• sender+receiver

• (B,H4)

• (B,H4)

• (B,H4)

• (2B,*)

• (B,H4)

• (B,*)

• (B,*)

Tear-down Example

• H4 leaves the group
• H4 no longer sends PATH message
• State corresponding to H4 removed

• S1

• S2

• S3

• H2

• H1

• H3

• sender

• receiver

• H5

• sender+receiver

• (2B,*)

• (B,*)

• (B,*)

RSVP Soft-state

• RSVP control messages need to be sent periodically
• State will disappear if not refreshed
• Periodic state refresh every t sec (30 sec)
• If no refresh within n*t (n=3) , delete state
• RSVP messages sent as router-alert message
• Intermediate routers intercept packets and update state accordingly

Soft State (cont)

• Per session state has a timer associated with it
• Path state, reservation state
• State lost when timer expires
• Sender/Receiver periodically refreshes the state, resends PATH/RESV messages, resets timer
• Claimed advantages
• No need to clean up dangling state after failure
• Can tolerate lost signaling packets
• Signaling message need not be reliably transmitted
• Easy to adapt to route changes
• State can be explicitly deleted by a Teardown message

RSVP and Routing

• RSVP designed to work with variety of routing protocols
• Minimal routing service
• RSVP asks routing how to route a PATH message
• Route pinning
• addresses QoS changes due to “avoidable” route changes while session in progress
• QoS routing
• RSVP route selection based on QoS parameters
• granularity of reservation and routing may differ
• Explicit routing
• Use RSVP to set up routes for reserved traffic