RFC 2638 from the

IETF The Internet Engineering Task Force (IETF) is a standards organization for the Internet and is responsible for the technical standards that make up the Internet protocol suite (TCP/IP). It has no formal membership roster or requirements and ...

defines the entity of the Bandwidth Broker (BB) in the framework of

differentiated services Differentiated services or DiffServ is a computer networking architecture that specifies a mechanism for classifying and managing network traffic and providing quality of service (QoS) on modern IP networks. DiffServ can, for example, be used t ...

(DiffServ). According to RFC 2638, a Bandwidth Broker is an agent that has some knowledge of an organization's priorities and policies and allocates

quality of service Quality of service (QoS) is the description or measurement of the overall performance of a service, such as a telephony or computer network, or a cloud computing service, particularly the performance seen by the users of the network. To quantitat ...

(QoS) resources with respect to those policies. In order to achieve an end-to-end allocation of resources across separate domains, the Bandwidth Broker managing a domain will have to communicate with its adjacent

peers Peers may refer to: People * Donald Peers * Edgar Allison Peers, English academician * Gavin Peers * John Peers, Australian tennis player * Kerry Peers * Mark Peers * Michael Peers * Steve Peers * Teddy Peers (1886–1935), Welsh international fo ...

, which allows end-to-end services to be constructed out of purely

bilateral Bilateral may refer to any concept including two sides, in particular: *Bilateria, bilateral animals *Bilateralism, the political and cultural relations between two states *Bilateral, occurring on both sides of an organism ( Anatomical terms of l ...

agreements.

Admission control Admission control is a validation process in communication systems where a check is performed before a connection is established to see if current resources are sufficient for the proposed connection. Applications For some applications, dedicated ...

is one of the main tasks that a Bandwidth Broker has to perform, in order to decide whether an incoming resource reservation request will be accepted or not. Most Bandwidth Brokers use simple admission control modules, although there are also proposals for more sophisticated admission control according to several metrics such as acceptance rate, network utilization, etc. The BB acts as a Policy Decision Point (PDP) in deciding whether to allow or reject a

flow Flow may refer to: Science and technology * Fluid flow, the motion of a gas or liquid * Flow (geomorphology), a type of mass wasting or slope movement in geomorphology * Flow (mathematics), a group action of the real numbers on a set * Flow (psyc ...

, whilst the edge routers acts as Policy Enforcement Points (PEPs) to police traffic (allowing and marking packets, or simply dropping them). DiffServ allows two carrier services apart from the default

best-effort service Best-effort delivery describes a network service in which the network does ''not'' provide any guarantee that data is delivered or that delivery meets any quality of service. In a best-effort network, all users obtain best-effort service. Under b ...

: Assured Forwarding (AF) and Expedited Forwarding (EF). AF provides a better-than-best-effort service, but is similar to best-effort traffic in that bursts and

packet delay variation In computer networking, packet delay variation (PDV) is the difference in end-to-end one-way delay between selected packets in a flow with any lost packets being ignored.RFC 3393 The effect is sometimes referred to as packet jitter, although th ...

(PDV) are to be expected. Out of profile AF packets are given a lower priority by being marked as best effort traffic. EF provides a ''virtual wire'' service with

traffic shaping Traffic shaping is a bandwidth management technique used on computer networks which delays some or all datagrams to bring them into compliance with a desired ''traffic profile''. Traffic shaping is used to optimize or guarantee performance, imp ...

to prevent bursts, strict

admission control Admission control is a validation process in communication systems where a check is performed before a connection is established to see if current resources are sufficient for the proposed connection. Applications For some applications, dedicated ...

(out of profile packets are dropped) and a separate queue for EF traffic in the core routers, which together keep queues small and avoid the need for buffer management. The resulting EF service is low loss, low

delay Delay (from Latin: dilatio) may refer to: Arts, entertainment, and media * ''Delay 1968'', a 1981 album by German experimental rock band Can * '' The Delay'', a 2012 Uruguayan film People * B. H. DeLay (1891–1923), American aviator and ac ...

and low PDV. Hence although loosely a BB allocates bandwidth, really it allocates carrier services (i.e. QoS resources). Bandwidth Brokers can be configured with organizational policies, keep track of the current allocation of marked traffic, and interpret new requests to mark traffic in light of the policies and current allocation. Bandwidth Brokers only need to establish relationships of limited trust with their peers in adjacent domains, unlike schemes that require the setting of flow specifications in routers throughout an end-to-end path. In practical technical terms, the Bandwidth Broker architecture makes it possible to keep state on an administrative domain basis, rather than at every router, and the DiffServ architecture makes it possible to confine per flow state to just the edge or leaf routers. The scope of BBs has expanded and they are now not restricted to DiffServ domains. As long as the underlying QoS mechanism can be mapped to DiffServ behaviour, then a BB can understand it and communicate with its adjacent peers, i.e. the ' lingua franca' of QoS in the

Internet The Internet (or internet) is the global system of interconnected computer networks that uses the Internet protocol suite (TCP/IP) to communicate between networks and devices. It is a ''internetworking, network of networks'' that consists ...

should be DiffServ. There may be more than one BB in a domain, though if there are, RFC 2638 envisages that only one BB will function as the top-level inter-domain BB. * Manages each cloud’s resources (Bandwidth Broker) * Packets are "coloured" to indicate forwarding "behavior" * Focus on aggregates and NOT on individual flows * Policing at network periphery to get services * Used together with Multiprotocol Label Switching (MPLS) and Traffic Engineering (TE) * "Aggregated" QoS guarantees only! * Poor on the guarantees for end-to-end applications

References

Further reading