RSVP is a network control protocol that allows applications to request different qualities of service for their data flows. It works with routing protocols to implement reservations across a network without requiring migration to a new routing protocol. RSVP supports both unicast and multicast sessions, with three service levels - best effort, rate sensitive, and delay sensitive. It uses soft state to dynamically maintain reservations in response to changes in network conditions or routing.

1. Introduction to QoS
Protocols and RSVP
Jayaprakash.N

2.  The goal :
◦ Provide some level of predictability and control beyond
the current IP “best-effort” service

3.  Performance attributes
◦ Service availability
◦ Delay
◦ Delay variation (jitter)
◦ Throughput
◦ Packet loss rate
 Vary according to Service Level Agreement (SLA)

4.  ReSerVation Protocol (RSVP)
 Multi Protocol Labeling Switching (MPLS)
 Subnet Bandwidth Management (SBM)

5.  a network-control protocol that enables Internet
applications to obtain differing qualities of service
(QoS) for their data flows.
 different applications have different network
performance requirements.
 Applications like,
◦ e-mail - require reliable delivery but not timeliness of
delivery
◦ videoconferencing, IP telephony - Data delivery must be
timely but not necessarily reliable

6.  RSVP is not a routing protocol
 works in conjunction with routing protocols
 implementing RSVP in an existing network does not
require migration to a new routing protocol
 Researchers at USC (ISI) and Xerox’s PARC
conceived RSVP.
 IETF specified an Open version in RFC 2205

7.  Data Flows
 Quality of Service
 Session Startup
 Reservation Style
 Soft State Implementation
 Architecture and Protocol
 Messages
 Packet Format

8.  a data flow is a sequence of datagrams that have the
same source, destination and quality of service.
 flow specification - a data structure used by hosts to
request special services from the internetwork.
 describes the level of service requirement ( one of 3
traffic types)
◦ Best-effort
◦ Rate-sensitive
◦ Delay-sensitive

9.  Best-effort traffic
◦ applications require reliable delivery of data regardless of
the amount of time needed to achieve that delivery.
◦ Eg. File transfer, transaction traffic
 Rate-sensitive traffic
◦ a guaranteed transmission rate from its source to its
destination.
◦ Eg. H.323 videoconferencing (Constant Rate)
 Delay-sensitive traffic
◦ timeliness of delivery and that varies its rate accordingly
◦ Eg. MPEG-II video (averages about 3 to 7 Mbps)

10.  designed to manage flows of data rather than make
decisions
 Data flows consist of discrete sessions between specific
source and destination
 Sessions are identified by the following data:
destination address, protocol ID, and destination port.
 RSVP supports both unicast and multicast simplex
sessions.

11.  an attribute determine the way in which data
interchanges are handled by participating entities
(routers, receivers, and senders)
 used to specify the QoS by,
◦ Hosts (to request a QoS level from the network)
◦ Routers (deliver QoS requests to other routers along the
path(s))
 maintains the router and host state to provide the
requested service.

12.  To initiate an RSVP multicast session, a receiver first
joins the multicast group using IGMP.
 In unicast session, unicast routing serves function of
IGMP.
 Sender sends RSVP path message to IP destination
address.
 The receiver application receives a path message and
send reservation-request messages with desired flow
descriptors using RSVP.
 After the sender application receives a reservation-
request message, the sender starts sending data
packets.

13.  a set of control options that specify a number of
supported parameters
 supports two major classes of reservation:
◦ distinct reservations
 install a flow for each relevant sender in each session
◦ shared reservations
 used by a set of senders that are known not to interfere with each
other

14.  distinct and shared RSVP reservation-style types in
the context of their scope,
RSVP Supports Both Distinct Reservations and Shared Reservations

15.  Wildcard-Filter Style
◦ a single reservation is created into which flows from all
upstream senders are mixed.
◦ size is the largest of the resource requests for that link from
all receivers
 Fixed-Filter Style
◦ a distinct reservation request is created for data packets from
a particular sender
◦ scope is determined by an explicit list of senders
◦ The total reservation on a link for a given session is the total
of the FF reservations for all requested senders

16.  Shared-Explicit Style
◦ a shared reservation environment with an explicit reservation
scope
◦ the set of senders is specified explicitly by the receiver making
the reservation

17.  a soft state refers to a state in routers and end nodes
 updated by certain RSVP messages
 Permits dynamic group membership changes and
adapt to changes in routing
 To maintain a reservation state, RSVP tracks a soft
state in router and host nodes

18.  The RSVP soft state is created and must be
periodically refreshed by path and reservation-request
messages.
 If no matching refresh messages arrive before the
expiration timeout, the state is deleted.
 also can be deleted by an explicit teardown message
 When a route changes, the next path message
initializes the path state on the new route.
 When state changes occur, RSVP propagates those
changes from end to end within an RSVP network
without delay

20.  Packet classifier: determines the route and QoS
class for each packet
 Admission control: determines whether the node has
sufficient available resources to supply the required
QoS
 Policy control: determines whether the user has
administrative permission to make the reservation.
 Packet scheduler: manages the various queues to
guarantee the required QoS (resources like CPU time
or buffers)

21.  process initiation begins when an RSVP daemon
consults the local routing protocol(s) to obtain routes.
 A host sends IGMP messages to join a multicast group
and RSVP messages to reserve resources along the
delivery path(s).
 Each router passes incoming data packets to a packet
classifier and packet scheduler.
 A QoS request, originating in a receiver host
application

22.  Protocol then is used to pass the request to all the
nodes (routers and hosts) along the reverse data
path(s) to the data source(s).
 At each node, the RSVP program applies a local
decision procedure called admission control and
policy control.
 If control succeeds, sets the parameters to obtain the
desired QoS
 If admission control fails at any node, the program
returns an error indication to the application that
originated the request.

23.  impossible to deploy RSVP or any new protocol at
the same moment throughout the entire Internet.
 when two RSVP-capable routers are interconnected
via non-RSVP routers
 Non-RSVP is incapable of performing resource
reservation
 but can provide acceptable and useful real-time
service
 RSVP supports tunneling, which occurs
automatically through non-RSVP routers.

24.  Tunneling requires RSVP and non-RSVP routers to forward
path messages toward the destination using local routing table
 a path message traverses a non-RSVP router, the path message
copies carry the IP address of the last RSVP-capable router.
 Reservation-request messages are forwarded to the next
upstream RSVP-capable router.

25.  Supports four basic message types,
 Reservation-Request Messages
◦ sent by each receiver host toward the senders.
◦ must be delivered to the sender hosts to set up appropriate
traffic-control parameters.
 Path Messages
◦ sent by each sender along the unicast or multicast routes
◦ A path message is used to store the path state in each node.
◦ The path state is used to route reservation-request messages
in the reverse direction.

26.  Teardown Messages
◦ remove the path and reservation state without waiting for
the cleanup timeout
 Path-teardown messages
 Reservation-request teardown messages
 Error and Confirmation Messages
◦ Path-error messages
◦ Reservation-request error messages
 Admission Failure
 Bandwidth unavailable
 Service not supported
◦ Reservation-request acknowledgment messages

27.  RSVP message header fields are comprised of the following:
◦ Version—A 4-bit field indicating the protocol version number (currently
version 1).
◦ Flags—A 4-bit field with no flags currently defined.
◦ Checksum—A 16-bit field representing a standard TCP/UDP checksum
over the contents of the RSVP message
◦ Length—A 16-bit field representing the length of this RSVP packet in
bytes.
◦ Send TTL—An 8-bit field indicating the IP time-to-live (TTL) value with
which the message was sent.

28. ◦ Type—An 8-bit field with six possible (integer) values.
◦ Message ID—A 32-bit field providing a label shared by all fragments of
one message
◦ More fragments (MF) flag—Low-order bit of a 1-byte word with the
other 7 high-order bits specified as reserved. MF is set on for all but the
last fragment of a message.
◦ Fragment offset—A 24-bit field representing the byte offset of the
fragment in the message

29.  RSVP is a transport layer protocol that enables a
network to provide differentiated levels of service to
specific flows of data.
 different application types have different performance
requirements.
 RSVP acknowledges these differences and provides
the mechanisms necessary to detect the levels of
performance required by different applications.

30.  Is it necessary to migrate away from your existing
routing protocol to support RSVP?
 Identify the three RSVP levels of service?
 What are the two RSVP reservation classes, and how
do they differ?
 How can RSVP be used through network regions that
do not support RSVP?

31. Thank You

32.  MPLS is a packet forwarding technology which uses
labels to make data forwarding decisions.
 With MPLS, the Layer 3 header analysis is done just
once (when the packet enters the MPLS domain). Label
inspection drives subsequent packet forwarding.
 MPLS provides these beneficial applications:
◦ Virtual Private Networking (VPN)
◦ Traffic Engineering (TE)
◦ Quality of Service (QoS)
◦ Any Transport over MPLS (AToM)
 Additionally, it decreases the forwarding overhead on the
core routers. MPLS technologies are applicable to any
network layer protocol.

33.  A label is a short, four byte, fixed length, locally
significant identifier which is used to identify a
Forwarding Equivalence Class (FEC).
 The label which is put on a particular packet
represents the FEC to which that packet is assigned.
◦ Label - Label Value (Unstructured), 20 bits
◦ Exp - Experimental Use, 3 bits; currently used as a Class of
Service (CoS) field.
◦ S - Bottom of Stack, 1 bit and TTLTime - to Live, 8 bits

34.  Applies to the Data Link Layer (OSI layer 2)
 Makes LAN topologies (e.g. Ethernet) QoS-enabled
◦ Fundamental requirement
◦ All traffic must pass through at least one SBM-enabled
switch
 SBM Modules
◦ Bandwidth Allocator (BA)
◦ Hosted on switches
 Performs admission control
◦ Requestor Module (RM)
◦ Resides in every end-station
◦ Maps Layer 2 priority levels and the higher-layer QoS
protocol parameters

35. Thanks