Internet Protocols for QoS Support
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Transcript of Internet Protocols for QoS Support
Internet Protocols for QoS Support
Protocols and the TCP/IP Suite Internet Protocols for QoS Support
Chapter 2 Protocols and the TCP/IP Suite
Introduction Modern internet applications demand services not
provided by a best-effort service model The TCP/IP infrastructure
has been enhanced to address the need increased capacity and data
rates efficient multicasting techniques (Chap. 15) QoS capabilities
added (Chap. 17) Protocols are required to support the QoS
enhancements to the infrastructure: RSVP for reservation and
admission control MPLS for traffic engineering RTP for real-time
application support Chapter 18:Protocols for QoS Support Chapter 2
Resource Reservation (RSVP)
Protocols and the TCP/IP Suite Resource Reservation (RSVP) Internet
resource reservation characteristics (RFC 2205) similar, but
fundamentally different from that used in connection-oriented
networks such as ATM, frame relay soft state at routers:reserved
resources expire unless refreshed there is no connection setup or
teardown on which to base hard state maintenance end systems must
periodically renew their requests (default: every 30 sec.) Chapter
18:Protocols for QoS Support Chapter 2 RSVP Design
Characteristics
Protocols and the TCP/IP Suite RSVP Design Characteristics Unicast
and Multicast (design point) Simplex Receiver-initiated reservation
Maintains soft state Different reservation styles Transparent
operation through non-RSVP routers Support for IPv4 and IPv6
Unicast and Multicast Simplex Receiver-initiated reservation
Maintains soft state Different reservation styles Transparent
operation through non-RSVP routers Support for IPv4 and IPv6
Chapter 18:Protocols for QoS Support Chapter 2 Receiver-Initiated
Reservation
Protocols and the TCP/IP Suite Receiver-Initiated Reservation
Source-initiated reservations are inadequate for multicasting
different members of same group may have different resource
requirements if transmission flow is divided into sub-flows, not
all members need all sub-flows if multiple sources are transmitting
for same group, receiver may want to select source In general, QoS
needs of different receivers may differ due to equipment, link
speed, processing speed/power or other differences Sender provides
traffic characteristics, but receiver requests desired QoS Chapter
18:Protocols for QoS Support Chapter 2 Protocols and the TCP/IP
Suite
Soft State Values associated with a given flow is temporarily
cached at the router based on end-system reservation Routing for
that flow is subject to change End systems must periodically
refresh the state information Routers discard states not refreshed
within specified time limit If a new route becomes the preferred
route for the flow, end systems provide the reservation information
to the new routers on the route Chapter 18:Protocols for QoS
Support Chapter 2 RSVP Data Flow Concepts
Protocols and the TCP/IP Suite RSVP Data Flow Concepts How are
flows of data identified? Session identifies a flow by its
destination (unicast or multicast) Destination IP address IP
protocol identifier (e.g., TCP or UDP) Destination port number
Flowspec describes the QoS parameters Service class Tspec:traffic
characteristics of the flow (average rate, peak rate, maximum burst
size) Rspec:QoS reservations specification of the flow (for
Guaranteed Service) Filter specification defines the packets in a
flow Source IP address (minimal) UDP/TCP source port number
(optional) other fields (based on application) Flow Descriptor
Chapter 18:Protocols for QoS Support Chapter 2 Example: Treatment
of Packets at Router
Protocols and the TCP/IP Suite Example:Treatment of Packets at
Router Packet is checked to see if it is in a defined flow 2.Packet
in flow is granted the appropriate QoS for that flow 3.Packets are
handled (queued and serviced) per QoS parameters Chapter
18:Protocols for QoS Support Chapter 2 RSVP Reservation
Operation
Protocols and the TCP/IP Suite RSVP Reservation Operation
Source(s)/ Senders(s) RSVP Reservation (RESV) Messages
Destination(s)/ Receiver(s) Router Reservation actions at router:
Admission control verify requested resources are available Policy
control verify permissions Set up classifier and scheduler to
provide requested Q0S Forward request upstream (aggregate as
required) Chapter 18:Protocols for QoS Support Chapter 2 Protocols
and the TCP/IP Suite
RSVP Operation R1, R2, R3, R4:forwarding routers G1, G2,
G3:multicast receivers S1, S2: multicast senders Chapter
18:Protocols for QoS Support Chapter 2 Protocols and the TCP/IP
Suite
Reservation Styles How resource reservations are aggregated/merged
for multiple receivers in the same multicast group Two options,
specified in the receivers reservation requests Reservation
attribute: reservation is shared over flows from multiple senders,
or distinct for each sender Sender selection: explicit list or
wildcard Three reservation styles are defined Chapter 18:Protocols
for QoS Support Chapter 2 RSVP Styles - Reservation Attributes and
Sender Selection
Protocols and the TCP/IP Suite RSVP Styles - Reservation Attributes
and Sender Selection per session per sender Fixed-Filter: Specifies
a distinct reservation for each sender and an explicit list of
senders Symbolic representation: FF(S1{Q1}, S2{Q2}, )
Shared-Explicit: Specifies that a single resource reservation is to
be shared by an explicit list of senders Symbolic representation:
SE(S1, S2, {Q}) Wildcard-Filter: Specifies that a single resource
reservation is to be shared by all senders to this address Symbolic
representation: WF(*{Q}) Chapter 18:Protocols for QoS Support
Chapter 2 Reservation Styles: Example
Protocols and the TCP/IP Suite Reservation Styles: Example S1 S2 S3
Router with RSVP capability Multicast Group Sources Multicast Group
Receivers Chapter 18:Protocols for QoS Support Chapter 2 RSVP
Protocol Mechanisms
Protocols and the TCP/IP Suite RSVP Protocol Mechanisms Two basic
message types: Resv: propagates upstream from receivers to
establish router soft states (resource reservations) for a
multicast group, merging as required.Message carries a merged
flowspec. Path: issued by senders to establish reverse-hop
(upstream) path back to a source from group members Chapter
18:Protocols for QoS Support Chapter 2 Protocols and the TCP/IP
Suite
QoS Protocols (cont.) Chapter 2 Multiprotocol Label Switching
Protocols and the TCP/IP Suite Multiprotocol Label Switching
MPLS:The intelligence of routing with the performance of switching.
Chapter 18:Protocols for QoS Support Chapter 2 Multiprotocol Label
Switching
Protocols and the TCP/IP Suite Multiprotocol Label Switching MPLS
Goal: provide ATM-like traffic management and QoS within IP-based
networks Reality:provides an approach which reduces per-packet
processing required at routers, thereby enhancing IP routing
performance Significant new capabilities are introduced in MPLS:
support for connection-oriented QoS Traffic engineering VPN support
multiprotocol support RFC 3031 issued in January 2001 Chapter
18:Protocols for QoS Support Chapter 2 Protocols and the TCP/IP
Suite
MPLS in Practice High-speed IP backbones Legacy ATM networks
MPLS-capable ATM networks Optical networks Frame relay networks
Most prevalent usage is for transporting IP data over these
networks with low overhead/latency, often to implement a VPN for IP
traffic Chapter 18:Protocols for QoS Support Chapter 2 Protocols
and the TCP/IP Suite
MPLS in Practice improves packet-forwarding performance in the
network MPLS enhances and simplifies packet forwarding through
routers using Layer-2 switching paradigms. MPLS is simple, which
allows for easy implementation. MPLS increases network performance
because it enables routing by switching at wireline speeds.
supports QoS and CoS for service differentiation MPLS uses
traffic-engineered path setup and helps achieve service-level
guarantees. MPLS incorporates provisions for constraint-based and
explicit path setup. supports network scalability MPLS can be used
to avoid the overlay performance problem associated with meshed
IPATM networks. Chapter 18:Protocols for QoS Support Chapter 2
Protocols and the TCP/IP Suite
MPLS in Practice integrates IP and ATM in the network MPLS provides
a bridge between access IP and core ATM. MPLS can reuse existing
router/ATM switch hardware, effectively joining the two disparate
networks. builds interoperable networks MPLS is a standards-based
solution that achieves synergy between IP and ATM networks. MPLS
facilitates IPover-synchronous optical network (SONET) integration
in optical switching. MPLS helps build scalable VPNs with
traffic-engineering capability. Chapter 18:Protocols for QoS
Support Chapter 2 MPLS Terminology Summary
Protocols and the TCP/IP Suite MPLS Terminology Summary Chapter
18:Protocols for QoS Support Per RFC 3031 Chapter 2 Protocols and
the TCP/IP Suite
MPLS Operation using an interior routing protocol (like OSPF),
establish a path (LSP) in advance for a given FEC and establish the
QoS parameters for the FEC.Labels are assigned for each FEC. the
egress LSR strips the label and forwards the packet to its final
destination packets entering at ingress LSR are assigned to an
appropriate FEC and a label is attached at each LSR along the LSP,
the incoming label is removed and an outgoing label is attached
Chapter 18:Protocols for QoS Support Chapter 2 Protocols and the
TCP/IP Suite
MPLS Operation Chapter 18:Protocols for QoS Support Chapter 2
Protocols and the TCP/IP Suite
MPLS Operation MPLS FEC can be determined by a number of
parameters: source/destination IP addresses port numbers IP
protocol ID DS codepoint IPv6 flow label Forwarding between LSRs
requires only simple mapping between label values and next hop
addresses note:labels have local significance only A particular PHB
can be assigned for a given FEC at each LSR Chapter 18:Protocols
for QoS Support Chapter 2 MPLS Advantages over Network Layer
Forwarding
Protocols and the TCP/IP Suite MPLS Advantages over Network Layer
Forwarding MPLS forwarding can be done by high-speed switches that
may not be capable of IP packet analysis/handling Forwarding
behavior (the LSP) can be based on information other than that in
the IP header Forwarding behavior can be based on network ingress
point FEC determination can be arbitrarily complex since it is done
only once at ingress Paths for traffic can be engineered in advance
to balance load traffic or provide different levels of serviced for
different FECs Chapter 18:Protocols for QoS Support Chapter 2 MPLS
Packet Forwarding
Protocols and the TCP/IP Suite MPLS Packet Forwarding Label
stacking? Chapter 18:Protocols for QoS Support Chapter 2 MPLS Label
Format & Placement
Protocols and the TCP/IP Suite MPLS Label Format & Placement
Data Link Frame IEEE 802 MAC Frame ATM Cell Frame Relay Frame
Chapter 18:Protocols for QoS Support Chapter 2 Protocols and the
TCP/IP Suite
MPLS Path Selection Traffic Engineering Class of Service Chapter
18:Protocols for QoS Support Chapter 2 MPLS Path (Route)
Selection
Protocols and the TCP/IP Suite MPLS Path (Route) Selection Two
options specified in RFC 3031: hop-by-hop routing makes use of
ordinary routing protocols, like OSPF does not readily support
traffic engineering or routing based on policy/priority explicit
routing single designated LSR, usually an ingress or egress LSR,
specifies all LSRs in a route for a given FEC with loose explicit
routing only some of the LSRs are specified Chapter 18:Protocols
for QoS Support Chapter 2 MPLS Label Distribution
Protocols and the TCP/IP Suite MPLS Label Distribution RFC 3031
does not define or depend on a specific label distribution protocol
several are defined MPLS-LDP (RFC 3036) RSVP-TE (RFC 3209) MPLS-BGP
MPLS-RSVP-TUNNELS Labels are distributed (bound) in a downstream
path of LSRs in an LSP Labels must be unique on each hop between
pairs of LSRs )local significance) Recent focus of IETF efforts
Chapter 18:Protocols for QoS Support Chapter 2 Real-Time Transport
Protocol (RTP)
Protocols and the TCP/IP Suite Real-Time Transport Protocol (RTP)
Chapter 2 Real-Time Traffic Flow
Protocols and the TCP/IP Suite Real-Time Traffic Flow Real-Time
Distributed Application: Source generates data stream at a constant
rate One or more destinations must deliver that data to an
application at the same constant rate Chapter 18:Protocols for QoS
Support Chapter 2 Protocols and the TCP/IP Suite
Time relationship of real-time traffic Real-time traffic requires
preservation of the time relationship between packets of a session.
From Data Communication and Networks, Forouzan, 4th Edition Chapter
18:Protocols for QoS Support Chapter 2 Protocols and the TCP/IP
Suite
Jitter (variation in delay) Jitter is introduced due top the
variable component of delay in packet switched networks. From Data
Communication and Networks, Forouzan, 4th Edition Chapter
18:Protocols for QoS Support Chapter 2 Protocols and the TCP/IP
Suite
Timestamp Timestamping packets can allow reconstruction of original
time relationship at the receiver. From Data Communication and
Networks, Forouzan, 4th Edition Chapter 18:Protocols for QoS
Support Chapter 2 Protocols and the TCP/IP Suite
Playback Buffer threshold threshold A playback buffer at the
receiver is used to sequence/time the release of data to the
application. From Data Communication and Networks, Forouzan, 4th
Edition Chapter 18:Protocols for QoS Support Chapter 2 Protocols
and the TCP/IP Suite
TCP/UDP for Real-Time? TCP point-to-point, connection-oriented, so
not suitable for multicast includes retransmission mechanisms for
lost segments, which often conflicts with real-time application
requirement no segment timing information available UDP no segment
timing information available or other general purpose real time
tools Chapter 18:Protocols for QoS Support Chapter 2 Real-Time
Transport Protocol (RTP)
Protocols and the TCP/IP Suite Real-Time Transport Protocol (RTP)
Defined in RFC 3550 to provide mechanisms needed to support
real-time traffic in IP-based networks, primarily to satisfy the
needs of multi- participant multimedia conferences Best suited for
soft real-time communication Lacks mechanisms to support hard
real-time traffic (i.e., traffic with no loss tolerance, minimal
jitter) Closely coupled with the application layer in the Internet
protocol stack (typically, above UDP) Two protocols make up RTP:
RTP, a data transfer protocol (carries the data) RTCP, a control
protocol (carries session/QoS info) Chapter 18:Protocols for QoS
Support Chapter 2 RTP Architecture Concepts
Protocols and the TCP/IP Suite RTP Architecture Concepts From Data
Communication and Networks, Forouzan, 4th Edition Chapter
18:Protocols for QoS Support Chapter 2 RTP Architecture
Concepts
Protocols and the TCP/IP Suite RTP Architecture Concepts
Application-Level Framing recovery from lost data and framing can
be handled at the application layer retransmission may not be
appropriate may be more useful for destination(s) to inform source
about the quality of transmission application often provides data
for retransmission may need to re-compute lost data before sending
may be able to send new data that fixes the consequences of any
lost data flow is broken into ADUs (application data units), e.g.
audio samples, video frames lower layers must preserve ADU
boundaries payload format is specific to the application Chapter
18:Protocols for QoS Support Chapter 2 RTP Architecture
Concepts
Protocols and the TCP/IP Suite RTP Architecture Concepts Integrated
Layer Processing typical layered protocols call for data units to
be sequentially processed by each layer integrated layer processing
allows adjacent layers (application,RTP, transport) of the protocol
stack to be tightly coupled therefore, RTP is not complete by
itself requires application-layer and transport layer capabilities
(and appropriate information in its header) Chapter 18:Protocols
for QoS Support Chapter 2 RTP Architecture Concepts
Protocols and the TCP/IP Suite RTP Architecture Concepts Profile
Specification Document: defines a set of payload type codes and
their mapping to payload formats (e.g., media encodings). May also
define extensions or modifications to RTP that are specific to a
particular class of applications. Typically, an application will
operate under only one profile. E.g. profile for AV application
data may be found in RFC 3551. Payload Format Specification
Documents: define how a particular payload, such as an audio or
video encoding, is to be carried in RTP. Chapter 18:Protocols for
QoS Support Chapter 2 RTP Data Transfer Protocol
Protocols and the TCP/IP Suite RTP Data Transfer Protocol Supports
transfer of real-time data among participants in a RTP session
session is defined by: RTP port#, RTCP port#, participant IP
address Four primary functions are: payload type identification
timestamping data sequencing/synchronizing data mixing/translating
data Chapter 18:Protocols for QoS Support Chapter 2 RTP Data
Transfer Protocol
Protocols and the TCP/IP Suite RTP Data Transfer Protocol Each RTP
data unit must include: source identifiers (who generated data)
timestamp (when data was generated) sequence number (order of data
in a flow) payload format (type of data) RTP relays mixer: combines
data from multiple sources and creates new single data signal
translator: converts input and resends in new format, or replicates
for unicast destinations Chapter 18:Protocols for QoS Support
Chapter 2 RTP Mixers & Translators
Protocols and the TCP/IP Suite RTP Mixers & Translators Mixer
Translator Chapter 18:Protocols for QoS Support Chapter 2 Protocols
and the TCP/IP Suite
RTP Fixed Header Supplied by a mixer Chapter 18:Protocols for QoS
Support Chapter 2 Some Standard Payload Types (see RFC 3551)
Protocols and the TCP/IP Suite Some Standard Payload Types (see RFC
3551) Chapter 18:Protocols for QoS Support Chapter 2 RTP Control
Protocol (RTCP)
Protocols and the TCP/IP Suite RTP Control Protocol (RTCP) Provides
control information and feedback between session participants Each
participant in an RTP session periodically issues an RTCP packet
Uses same underlying transport as RTP (usually UDP) RTCP port # =
RTP session port # +1 Provides four key functions for real-time
traffic management (per RFC 1889) QoS and congestion control Source
identification Session size estimation and scaling Session control
Chapter 18:Protocols for QoS Support Chapter 2 Protocols and the
TCP/IP Suite
RTCP Operation Protocol specifies report packets exchanged between
sources and destinations in real-time flows (max. one every 5 secs,
limit to 5% session traffic) Five report types are defined: Sender
(SR), Receiver(RR), Goodbye (BYE), Source Description (SDES) and
Application specific SR and RR reports contain statistics such as
the number of packets sent, number of packets lost, inter-arrival
jitter, etc. Used to modify sender(s)transmissions and for
diagnostics purposes Chapter 18:Protocols for QoS Support Chapter 2
Protocols and the TCP/IP Suite
RTCP Bandwidth Scaling RTCP attempts to limit its traffic to 5% of
the session bandwidth. Example Suppose one sender, sending video at
a rate of 2 Mbps. Then RTCP attempts to limit its traffic to 100
Kbps (5% of 2 Mbps) RTCP gives 75% ofthis rate to the receivers;
remaining 25% to the sender The 75 kbps is equally shared among
receivers: With R receivers,each receiver gets to send RTCP traffic
at 75/R kbps. Sender gets to send RTCP traffic at 25 kbps.
Participant determines RTCP packet transmission period by
calculating avg RTCP packet size (across the entire session) and
dividing byallocated rate. Chapter 18:Protocols for QoS Support
Chapter 2 Protocols and the TCP/IP Suite
RTCP Formats Sender Report Receiver Report Application-defined
Packet RTCP BYE Source Description Chapter 18:Protocols for QoS
Support Chapter 2 Protocols and the TCP/IP Suite
SDES Types Chapter 18:Protocols for QoS Support Chapter 2