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    Add as FriendA Differentiated Services Architecture for the Internet

    by: Rogers

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    1 : A Differentiated Services Architecture for the Internet References - K. Nichols, V. Jacobson, L. Zhang - D. Clark, J. Wroclawski Presented by Liping Zhang
    2 : Overview Introduction Two different service types: implementation and problems Two-bit differentiated services architecture Problems with end-end bandwidth allocation based on level of marked traffic Discussion
    3 : Introduction Why do we need differentiated services? Different users Different applications Service allocation For example, one goal of assured service is to allocate the bandwidth of the Internet to different users in a controlled way during periods of congestion
    4 : How to describe a service What is provided to the customer E.g., 1 Mbps, continuously available To where is this service provided A single destination A group All nodes on local provider Everywhere Level of assurance provided to service What level of performance uncertainty can user tolerate
    5 : Two distinct service types Assured service D. Clark Premium service V. Jacobson
    6 : Assured service Provide different levels of best-effort service at times of network congestion Expected capacity “In” packets unlikely to be dropped “Out” packets - no assurance Queuing Best effort
    7 : Mechanism for assured service Host First-hop Counter Counter Out- and in- dropper RIO scheme, packets are treated preferentially Marking packets according to the service profile
    8 : RIO algorithm RED - Random Early Detection Packets dropped with low but increasing probability as queue grows; instead of waiting until it is full and dropping all new packets RIO Run two RED algorithms for “in” and “out” with different dropping frequencies
    9 : Premium service Fundamentally different Internet best effort service - high priority traffic has its own queue in routers Shaped, hard-limited to provisioned peak rate No bursts are injected into net Virtual wire, available whenever needed Regular flow pattern, no queuing Shared, with best-effort
    10 : Mechanism for premium service Host First-hop Intra-network Router H-Q: premium, no dropping L-Q: best effort, dropping on congestion
    11 : Two-bit differentiated services architecture Deploying both services More bits available in IP header, why not both Forwarding path mechanisms Leaf routers Input interface: a traffic profile Output interface: two queues (HQ, LQ) Intermediate routers Only have forwarding function Border routers A Profile Meter at the input interface
    12 : Traffic flow from end-host to ISP Host First-hop Router Internal Router Border Router Border Router ISP Company A 1 2 3
    13 : Forwarding path primitives General classifier In leaf routers, transport-level signature matching Bit-pattern classifier Performs a two-way decision based on bit-pattern Bit setter A- and P-bits must be set or cleared in several places Priority queues Shaping token bucket At the leaf router for Premium traffic Policing token bucket At border router, for both P and A services
    14 : Block diagram of leaf router input functionality Packet Classifier Clear A&P bits Forwarding Engine Marker N Marker 1 Arriving packet Best Effort Flow1 Flow N
    15 : Markers to implement the two different services Wait for token Test if token Set A bit Set P bit Packet Input Packet Input Y N
    16 : Router output interface for two-bit architecture Low-priority High-priority P-bit set? If A-bit set? Inc a_cnt RIO queue management If A-bit set? dec a_cnt No
    17 : Border router input interface Profile Meters Is packet marked ? Token available ? Clear A bit Token Available Drop Packet Forwarding Engine N N Y Y P set A set Not marked
    18 : Passing configuration information Request to the leaf router Average rate, burst, service type (P or A) Ways of passing the message RSVP, SNMP, network administrator Authenticating the sender
    19 : Architectural framework for marked traffic allocation Preconfiguring of usage profiles is practical Paying for level of service that is always available Allocation follows organizational hierarchies Each organization must be responsible for its DM Only bilateral agreements work
    20 : Bandwidth Brokers (BB) Roles Allocating and controlling bandwidth shares Responsibilities Parcel out a region’s marked traffic allocation and set up the leaf routers within the local domain Managing messages sent across boundaries to adjacent region BBs
    21 : Examples A statically configured example with no BB message exchanged A statically configured example with BB messages exchanged Dynamic allocation and additional mechanism
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    30 : RSVP and BBs Existing bilateral relations between BBs of adjacent trust regions are necessary for resource allocation A few bits in the packet header are used to mark the service class RSVP resource setup: hop-by-hop Use RSVP between two adjacent ISPs (BB1/BR1 and BB2/BR2)
    31 : Discussion Extensibility of the current 2-bit architecture Service allocation for multicast Who should request the service Sender or receiver Deployment issues Security issues
    32 : 2-bit differentiated services architecture Providing Controlled-Load and Guaranteed service P service for C-L service A constrained case of C-L service P service for G service The service model of P service fits G service model

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