DiffServ Document and Link Collection

Technical University of Braunschweig · Computer Science at TU BS · Operating Systems and Computer Networks

Differentiated Services (DiffServ) document and link collection

Links to DiffServ Sites:

The DiffServ Homepage (outdated, mid 1998).
The DiffServ Working group at the IETF.
The DiffServ Mailing List Archive (old).
The current DiffServ Mailing List.
The DiffServ Interest Mailing List Archive
The Implementation Issues of Differentiated Services Mailing List
The QBone Homepage
The Differentiated Services Work Item of the TF-TANT within TERENA
The Internet2 QoS Working Group

Sites related to Bandwidth Broker:

Implementations:

Historical papers (before DiffServ came into being)

Work done at LBNL's Network Research Group

Van Jacobson: Flexible, efficient resource management for datagram networks, talk at Sun Microsystems, October 12, 1993.
Talk about some basics on Classed Based Queueing (CBQ) and link-sharing mechanisms as part of it. Contains a nice clarification on QoS goals and non-goals and what a router is able to do / not to do. Includes the idea to separate resource management from per-packet processing as it was done in routing / forwarding.
Sally Floyd and Van Jacobson: Link-sharing and Resource Management Models for Packet Networks (for electronic versions and an abstract of it, see the CBQ webpage), IEEE/ACM Transactions on Networking, Vol. 3 No. 4, pp. 365-386, August 1995.
Main paper on Classed Based Queueing (CBQ) and hierarchical link-sharing, which should be incorporated into CBQ taking care of preventing starvation of lower-priority traffic

Work done at The MIT's Advanced Network Architecture Research Group

David Clark: Adding Service Discrimination to the Internet (for electronic versions of the paper, see ANA's papers webpage), presented at: Telecommunications Policy Research Conference (TPRC), September 1995.
First preliminary paper on the 'allocated capacity' framework. Describes sharing of bandwidth under network congestion and takes pricing as an issue. Service discrimination is limited to large transfers and to bandwidth, no delay issues discussed. The user's view on a service is a central aspect. The approach described is only useful for elastic applications (non real-time). The target service objective is transfer rate. The whole report is centered around TCP and its congestion mechanisms. It is the first paper I know about that introduced the idea of assured service using tagging packets as in-profile vs. out-of-profile.
David Clark and Wenjia Fang: Explicit Allocation of Best-Effort Packet Delivery Service, IEEE/ACM Transactions on Networking, Vol. 6 No. 4, pp. 362-373, August 1998.
Final paper (for now) on the 'allocated capacity' approach which allocates bandwidth in a controlled way to build differentiated services under congestion. The paper focuses on TCP and the problem that there is no way to tell TCP to send at a certain transmission rate. The only possibility to control the sending rate of TCP is to drop packets. The approach describes the tagging of in-profile packets vs. out-of-profile packets at border routers, dropping out-of-profile packets preferentially under congestion. The necessary information to tag packets is provided via profiles which consist of a traffic specification in terms of bandwidth, of a certain destination and an assurance. This paper especially focuses on the introduction of algorithms for tagging and dropping. The results are evaluated with the use of simulations.
David Clark: Service Allocation Profiles, talk held at the 'Integrated Services' working group meeting (minutes) at the 39th IETF, August 1997.
Talk about service profiles (in terms of in/out-of profile traffic) necessary to configure the profile meters at the border of a DiffServ domain (avoid per-flow signalling). Important: consider the behavior of TCP to load a link. Again important: no over-provisioning of the network.

The genesis of Differentiated Services and its IETF working group

Minutes of the 'Future Directions for Differential Services' BOF (fddifs) from the 38th IETF, April 1997.
Several reports on the customer's view on differentiated services. Nothing really useful IMHO, but at least the very beginning of activities with regard to differentiated services in the IETF.
Minutes of the 'Integrated Services' working group from the 39th IETF, August 1997.
Minutes of the 'Integrated Services' working group from the 40th IETF, December 1997.
This meeting was the real startup to the work done up to now. David Clark, Kathie Nichols, Lixia Zhang, and Van Jacobson presented the basic framework A Combined Approach to Differential Service in the Internet, where the separation of mechanisms (per-hop behaviors) and application services (not only end-to-end) was pointed out first. Also, the separate approaches from Jacobson (Premium Service) and Clark (Assured Service) were putten together here.
Minutes of the 'Differentiated Services' working group from the 41th IETF, March 1998.
The first meeting of the DiffServ working group. Clark's 'mechanism' is now called 'per-hop behavior (PHB)'. Consensus that the working group will define PHBs, but no services (whether end-to-end or anything else).
Minutes of the 'Differentiated Services' working group from the 42th IETF, August 1998.
First appearance of expedited forwarding draft and assured forwarding (AF) draft. Consensus about 4 AF classes and 3 drop preferences per class.
Minutes of the 'Differentiated Services' working group from the 43th IETF, December 1998.
Issues on RSVP and DiffServ will be moved to the issll working group.
Minutes of the 'Differentiated Services' working group from the 44th IETF, March 1999.
First RFC's on the DS Field and the architecture out.
Minutes of the 'Differentiated Services' working group from the 45th IETF, July 1999.
Standardize PHB identification codes for to use in signalling (e.g., RSVP, MPLS). Conceptual model for DiffServ routers for building management software. Management Information Base and Policing Information Base.
Minutes of the 'Deployment Considerations for Implementing Differentiated Services' BOF from the 45th IETF, July 1999.

Current papers on Differentiated Service

The signalling: Bandwidth broker (see also UCLA Internet Research Lab)

Van Jacobson: Towards Differentiated Services for the Internet, Bay Networks Architecture Lab, November 25, 1997.
Clarification on QoS: gives QoS to someone while taking it away from someone else. Emphasis on scaling. Use Edge Tagging by David Clark and a 'Bandwidth Broker' to solve remaining problems (with several examples). Several issues on designing a DiffServ network. Important: proper provisioning of the network is not enough, shaping must be done, too!
Kathie Nichols,Van Jacobson, and Lixia Zhang: A Two-Bit Differentiated Services Architecture for the Internet(PS), Request for Comments 2638 (Informational), Internet Engineering Task Force (IETF), July 1999.
Was first submitted as Internet draft in November 1997 and resubmitted unchanged as informational RFC in 1999 to make it referable.
Describes two bandwidth-centered services: Premium Service (first referable occurrence here) and Assured Service and how to provide both using the same set of mechanisms in the forwarding path (outdated, see DiffServ drafts). Premium service completely relies on proper provisioning of the networks whereas Assured Services presents a buffer management approach together with proper provisioning. Important: Best Effort traffic is assumed to remain the bulk of Internet traffic. Scalability is reached by moving most of the complexity to the edge of the network. The paper also introduces first an architecture how to allocate bandwidth to single flows using Bandwidth brokers (also first referable occurrence.) There are several very useful examples of how Bandwidth Broker can be used.
Very good introduction to the two services (Premium and Assured) and to Bandwidth Brokers!
Lixia Zhang: A scalable resource management framework for differentiated services, in: Proceeding of the First Internet2 Joint Applications/Engineering QoS Workshop, Santa Clara, CA, U.S.A., May 1998, pp. 37-39.
Proposes a two-tier hierarchical framework for resource management. Within an administrative domain, a Bandwidth Broker (BB) keeps track of reservation requests from users / applications depending on, for example, the topology within that domain. Between two BB, a special protocol is needed to signal the bilateral Service Level specifications (SLSs).
Frank Reichmeyer, Lyndon Ong, Andreas Terzis, Lixia Zhang, Raj Yavatkar: A two-tier resource management model for Differentiated Services Networks (PDF), Internet draft, Internet Engineering Task Force, November 1998, work in progress.
Proposes a two-tier resource management model for dynamic resource allocations: Within each administrative domain, individual management solutions for internal use should be possible to fit the individual domain's need. The inter-domain management must use a standardized protocol. This approach is similar to the current two-tier routing architecture with BGP as inter domain routing protocol.
Andreas Terzis, Jun Ogawa, Sonia Tsui, Lan Wang, Lixia Zhang: A Prototype Implementation of the Two-Tier Architecture for Differentiated Services, presented at Workshop on QoS Support for Real-Time Internet Applications in conjunction with Fifth IEEE Real-Time Technology and Applications Symposium (RTAS), Vancouver, Canada, June 1, 1999.
Describes a first implementation of the two-tier resource management. The communication between a Bandwidth Broker and an edge router is implemented using COPS, but resources are stored manually within a flow database in the Bandwidth Broker (there is no call-setup signaling).
Ben Teitelbaum: Draft QBone Architecture, Internet2 QoS Working Group Draft, June 1999.
Gives a specification of the QBone Premium Service with absolute, per-flow assurances and focuses on a QBone measurement architecture. Reservation setup is done manually for now.

More overviews on Differentiated Services

Van Jacobson: Differentiated Services for the Internet, talk held at the First Internet2 Joint Applications/Engineering QoS Workshop, Santa Clara, CA, U.S.A., May 1998.
Similar to the talk at Bay Networks. Clarification on QoS, differentiate between services and behaviors. Emphasis on scaling. Use Edge Tagging and a 'Bandwidth Broker'.
Van Jacobson: Differentiated Services for the Internet, in: Proceeding of the First Internet2 Joint Applications/Engineering QoS Workshop, Santa Clara, CA, U.S.A., May 1998, pp. 26-29.
Summarizes the above talk in written form (although not written by Van Jacobson himself). Perhaps the best high-level introduction to Differentiated Services.
John Wroclawski: Evolution of End-to-End QoS: A design philosophy, in: Proceeding of the First Internet2 Joint Applications/Engineering QoS Workshop, Santa Clara, CA, U.S.A., May 1998, pp. 32-36.
Comparison of IntServ and DiffServ, shows commonalities and differences. Premium service is a start, but more services should follow (namely the Allocated Capacity Service), e.g., to support adaptive applications providing a lower bound on QoS. Sender or receiver control of QoS is a matter of what the user chooses. Per-hop behaviors as building blocks for services. Overview on Allocated capacity.

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