QoS for Real Time Applications over Next Generation Data Networks Project Status Report: Part 1 June 2, 2000 http://www.engr.udayton.edu/faculty/matiquzz/Pres/QoS.pdf University of Dayton Mohammed Atiquzzaman Jyotsna Chitri Faruque Ahamed Hongjun Su Haowei Bai
Ohio State University Raj Jain Mukul Goyal Bharani Chadavala Arindam Paul Chun Lei Liu Wei Sun Arian Durresi Mohammed Atiquzzaman, University of Dayton, Email:
[email protected]
NASA Glenn Will Ivancic
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Outline of Talk n n n n
Present state of the Interent. QoS approaches to future data networks. Research Issues. Progress to date: Ÿ Ÿ Ÿ Ÿ Ÿ
Task 1: DS over ATM Task 2: IS over DS Task 3: ATN Task 4: Satellite networks Task 5: MPLS
n Conclusions.
Mohammed Atiquzzaman, University of Dayton, Email:
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Current Internet n TCP/IP glues together all the computers in the Internet. n TCP/IP was designed for terrestrial networks. n TCP/IP does not Ÿ offer QoS to real time applications, or Ÿ perform well in long delay bandwidth networks.
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Efforts to provide QoS in Internet n n n n n
Integrated Services (IS) Differentiated Services (DiffServ) Explicit Congestion Notification (ECN) Multiprotocol Label Switching (MPLS) Asynchronous Transfer Mode (ATM)
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Integrated Services n RSVP to reserve resources during connection setup. n End-to-end QoS guarantees. n A router has to keep information about all connections passing through the router. n Gives rise to scalability problem in the core routers.
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RSVP Signaling
PATH message
DATA Sender
Router1 Router1
Router2 Router2
Receiver
RESV message
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RSVP Signaling n Reserves a portion of link bandwidth in each router n The sender sends a PATH message with resource requirements for a flow. n Receiver responds with a RESV message n Each router processes the RESV to reserve the required resources requested by the sender. n Routers can modify the QoS parameters of the RESV message if enough resources are not available to meet the requirements. n Each router in the entire path confirms the end-to-end reservation for the flow.
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IS Service Classes n Guaranteed Load Service Ÿ Low end-to-end delay, Jitter, Loss. Ÿ Highest priority service.
n Controlled Load Service Ÿ Network should forward the packets with queuing delay not greater than that caused by the traffic’s own burstiness (RFC 2474). Ÿ Performance similar to that of an unloaded network. Ÿ Traffic specifications from the Tspec.
n Best Effort
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Differentiated Services n Similar traffic are grouped into classes. n Resources reserved for classes. n QoS provided to classes. Ÿ QoS to individual connections is an open research issue.
n QoS maintained by: Ÿ Classification Ÿ Traffic policing ú Metering, dropping, tagging Ÿ Traffic shaping
n Per Hop Behavior (PHB) Ÿ Specifies QoS received by packets i.e. how packets are treated by the routers. Mohammed Atiquzzaman, University of Dayton, Email:
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Asynchronous Transfer Mode n Strong QoS guarantees; suitable for real time applications. n High cost prohibits use at the edge network or to the desktop. n Currently used at the core of the Internet.
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Next Generation Internet n Routers at the edge network will not need to carry too many connections Ÿ IS can be used at the edge network.
n Core network needs to carry lot of connections. Ÿ Combination of DS, ATM and MPLS at the core.
n Satellite/Wireless links Ÿ Remote connectivity and mobility.
Mohammed Atiquzzaman, University of Dayton, Email:
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Research Issues n n n n
Service mapping between networks. Loss and delay guarantees. Interoperability among edge and core technologies. Interoperability with Aeronautical Telecommunications Network (ATN). n Operation in satellite environment having high delay and loss.
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Task 1
Prioritized Early Packet Discard
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Asynchronous Transfer Mode (ATM) n Service Classes Ÿ Constant Bits Rate (CBR) Ÿ Available Bit Rate (ABR) Ÿ Unspecified Bit Rate (UBR)
n CLP in cell header Ÿ Determines loss priority of packets
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Differentiated Services n Service Classes Ÿ Premium Service: emulates leased line Ÿ Assured Service Ÿ Best Effort ServiceData Packet
n Various levels of drop precedence. Ÿ Need to be mapped to ATM when running DS over ATM. Ÿ Could be possible mapped to the CLP bit of ATM cell Voice Packet header.
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DS over ATM n Possible Service Mappings Ÿ Premium Service à ATM CBR service. Ÿ Assured Service à ATM UBR service with CLP=0 Ÿ Best Effort à ATM UBR service with CLP=1 n DS packets are broken down into cells at the DS-ATM gateway Ÿ Drop precedence mapped to CLP bit
n Buffer Management at ATM switches Ÿ Partial Packet Discard (PPD) Ÿ Early Packet Discard (EPD)
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Prioritized EPD n DS service classes can use the CLP bit of ATM cell header to provide service differentiation. n EPD does not consider the priority of cells. n Prioritized EPD can be used to provide service discrimination. n Two thresholds are used to drop cells depending on the CLP bit.
Mohammed Atiquzzaman, University of Dayton, Email:
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Buffer Management Schemes n EPD
n PEPD T
N
HT
0
λ
N
µ
•QL < T
λ
µ
Accept all packets.
•T ≤ QL < N
•LT ≤ QL < HT
Discard all new incoming packets.
•Discard all.
0
•QL
