交通控制(文件)
【正文】 foreseeable work services ?Should not rely on AAL protocols that are work specific, nor higher level application specific protocols ?Should minimize work and end to end system plexity Timings Considered ?Cell insertion time ?Round trip propagation time ?Connection duration ?Long term ?Determine whether a given new connection can be acmodated ?Agree performance parameters with subscriber Traffic Management and Congestion Control Techniques ?Resource management using virtual paths ?Connection admission control ?Usage parameter control ?Selective cell discard ?Traffic shaping Resource Management Using Virtual Paths ?Separate traffic flow according to service characteristics ?User to user application ?User to work application ?Network to work application ?Concern with: ?Cell loss ratio ?Cell transfer delay ?Cell delay variation Configuration of VCCs and VPCs Allocating VCCs within VPC ?All VCCs within VPC should experience similar work performance ?Options for allocation: ?Aggregate peak demand ?Statistical multiplexing Connection Admission Control ?First line of defence ?User specifies traffic characteristics for new connection (VCC or VPC) by selecting a QoS ?Network accepts connection only if it can meet the demand ?Traffic contract ?Peak cell rate ?Cell delay variation ?Sustainable cell rate ?Burst tolerance Usage Parameter Control ?Monitor connection to ensure traffic cinforms to contract ?Protection of work resources from overload by one connection ?Done on VCC and VPC ?Peak cell rate and cell delay variation ?Sustainable cell rate and burst tolerance ?Discard cells that do not conform to traffic contract ?Called traffic policing Traffic Shaping ?Smooth out traffic flow and reduce cell clumping ?Token bucket Token Bucket ATMABR Traffic Management ?Some applications (Web, file transfer) do not have well defined traffic characteristics ?Best efforts ?Allow these applications to share unused capacity ?If congestion builds, cells are dropped ?Closed loop control ?ABR connections share available capacity ?Share varies between minimum cell rate (MCR) and peak cell rate (PCR) ?ARB flow limited to available capacity by feedback ?Buffers absorb excess traffic during f
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鄂ICP備17016276號-1