INTERNET DRAFT J.M.Pullen
Expiration: 25 April 1997 George Mason University
Ravi Malghan
COMSAT Incorporated
Lava K. Lavu
George Mason University
25 November 1996
A Simulation Model for IP Multicast with RSVP
<draft-pullen-ipv4-rsvp-00.txt>
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Abstract
This document describes a detailed model of IPV4 multicast with
RSVP that has been developed using the OPNET simulation package
but could be ported to any descrete event simulation package
with procedures defined in the C language. The model was
developed to allow investigation of performance constraints on
routing but should have wide applicability in the Internet
multicast/resource reservation community. We are making this
model publicly available with the intention that it can be used
to provide expanded studies of resource-reserved multicasting.
1. Background
The successful deployment of IP multicasting [1] and its availability in
the Mbone has led to continuing increase in real-time multimedia
Intermet applications. Because the Internet has traditionally supported
only a best-effort quality of service, there is considerable interest
to create mechanisms that will allow adequate resources to be reserved
in networks using the Internet protocol suite, such that the quality
of real-time traffic such as video and voice can be sustained at
specified levels. The RSVP protocol [2] has been developed for this
purpose and is the subject of considerable ongoing implementation
efforts. Although the developers of RSVP have used simulation in their
design process, no simulation of IPmc with RSVP is generally available
for analysis of the performance and prediction of the behavior of these
protocols. The simulation model described here was developed to fill
this gap, and is explicitly intended to be made available to the
IETF community.
2. The OPNET Simulation Environment
The Optimized Network Engineering Tools (OPNET) is a commercial
simulation product of the MIL3 company of Arlington, VA. It employs a
Discrete Event Simulation approach that allows large numbers of
closely-spaced events in a sizable network to be represented accurately
and efficiently. OPNET uses a modeling approach where networks are
built of components interconnected by perfect links (which can be
degraded at will). Each component's behavior is modeled as a state-
transition diagram. The process that takes place in each state is
described by a program in the C language. We believe this makes the
OPNET-based models relatively easy to port to other modeling
environments. Perhaps more importantly, given the widespread
availability of OPNET, it makes them highly efficient so that extended
period of network behavior can be simulated in considerable detail, even
for large networks.
The folowing sections describe the state-transition models and process
code for the IPmc and RSVP models we have created using OPNET.
3. IP Multicast Model
The state-transition diagrams for the IPmc model are available at
http://bacon.gmu.edu/qosip/igmp {In the postscript
version we will include them at this point.}
The following processing takes place in the indicated modules.
Each subsection below describes in detail each layer in the host and
the router with the help of the corresponding OPNET network layer or
node layer or the process layer starting from physical layer.
3.1.1 Address format
The OPNET IP model has only one type of addressing denoted by "X.Y"
where X is 24 bits long and Y is 8 bits long. The X indicates the
destination or the source network number and Y indicates the
destination or the source node number. In our model X = 500 is
reserved for multicast traffic. For multicast traffic the value of Y
indicates the group to which the packet belongs.
3.1 Network Layer
Fig 6.1 describes an example network topology built using the OPNET
network editor. This network consists of two backbone routers BR2,
BR4, three area border routers BR0, BR1, BR3 and six subnets F0,
through F5. As OPNET has no full duplex link model, each connecting
link is modeled as two simplex links enabling bi-directional traffic.
3.1.1 Attributes
The attributes of the elements of the network layer are:
a. Area Border Routers and Backbone routers
1. IP address of each active interface of each router
(network_id.node_id)
2. Service rate of the IP layer ( packets/sec)
3. Transmission speeds of each active interface (bits/sec)
b. Subnets
1. IP address of each active interface of the router in the subnet
2. IP address of the hosts in each of the subnet.
3. Service rate of the IP layer in the subnet router and the hosts.
c. Simplex links
1. Propagation delay in the links
2. the process model to be used for simulating the simplex links
(this means whether animation is included or not).
3.1.2 FDDI Subnets
Fig 6.2 shows the FDDI ring in a subnet and a Ethernet in a subnet.
Both of the subnets will have one router and one or more hosts. The
routers in the subnet are included to route the traffic between the
FDDI ring or Ethernet in the corresponding subnet and the external
network. The subnet router is connected on one end to Ethernet or
FDDI ring and generally connected to an area border router on another
interface (the subnet routers are connected to more than one backbone
router). In the Ethernet all the hosts are connected to the bus
and in FDDI ring the hosts are interconnected as illustrated in
figure 6.2.
FDDI provides general purpose networking at 100 Mb/sec transmission
rates for large numbers of communicating stations configured in a ring
topology. Use of ring bandwidth is controlled through a timed token
rotation protocol, wherein stations must receive a token and meet
with a set of timing and priority criteria before transmitting frames.
In order to accommodate network applications in which response times
are critical, FDDI provides for deterministic availability of ring
bandwidth by defining a synchronous transmission service. Asynchronous
frame transmission requests dynamically share the remaining ring
bandwidth.
3.1.3 Ethernet subnets
Ethernet is a bus-based local area network (LAN) technology. The
operation of the LAN is managed by a media access protocol (MAC) which
has been standardized by the IEEE under the name 802.3. The role of
this MAC protocol is to provide efficient and fair sharing of the
communication channel connecting the stations of the LAN.
3.2 Node layer
This section discusses the internal structure of the hosts and routers
with the help of node level illustrations built using the Node editor
of OPNET.
3.2.1 Basic elements
The basic elements of a node level illustration are
a. Processor nodes: Processor nodes are used for processing incoming
packets and generating packets with a specified packet format.
b. Queue node: Queue nodes are a superset of processor nodes. In
addition to the capabilities of processor nodes, queue nodes also
have capability to store packets in one or more queues.
c. Transmitter and Receiver nodes: Transmitters simulate the
link behavior effect of packet transmission and Receivers simulate the
receiving effects of packet reception. The transmission speed is an
attribute of the transmitter and receiving speed is an attribute of
the receiver. These values together decide the transmission delay of a
packet.
d. Packet streams: Packet streams are used to interconnect the above
described nodes.
e. Statistic streams: Statistic streams are used to convey
information between the different nodes Processor, Queue, Transmitters
and Receivers nodes respectively.
3.2.2 Host description
The host model built using OPNET has a layered structure which is very
similar to the TCP/IP protocol suite. Fig 6.3 shows the node level
structure of a FDDI host.
a. MAC queue node: The MAC interfaces on one side to the physical
layer through the transmitter (phy_tx) and receiver (phy_rx) and also
provides services to the IP layer. Use of ring bandwidth is
controlled through a timed token rotation protocol, wherein hosts must
receive a token and meet with a set of timing and priority criteria
before transmitting frames. When a frame arrives at the MAC node, the
node performs one of the following actions:
1. If the owner of the frame is this MAC, the MAC layer destroys the
frame since the frame has finished circulating through the FDDI
ring.
2. if the frame is destined for this host, the MAC layer makes a
copy of the frame, decapsulates the frame and sends the
descapsulated frame (packet) to the IP layer. The original frame
is transmitted to the next host in the FDDI ring.
3. if the owner of the frame is any other host and the frame is not
destined for this host, the frame is forwarded to the adjacent
host.
b. ADDR_TRANS processor node: The next layer above the MAC layer is
the addr_trans processor node. This layer provides service to the IP
layer by carrying out the function of translating the IP address to
physical interface address. This layer accepts packets from the IP
layer with the next node information, maps the next node information
to a physical address and forwards the packet for transmission. This
service is required only in one direction from the IP layer to the MAC
layer. Since queuing is not done at this level, a processor node is
used to accomplish the address translation function.
c. IP queue node: The next layer in the hierarchy is the IP layer. IP
layer provides service for the layers above which are the different
higher level protocols by utilizing the services provided by the MAC
layer. For packets arriving from the MAC layer, the IP layer
decapsulates the packet and forwards the information to an upper layer
protocol based upon the value of the protocol ID in the IP header.
For packets arriving from upper layer protocols, the IP layer obtains
the destination address, calculates the next node address from the
routing table, encapsulates it with a IP header and forwards the
packet to the addr_trans node with the next node information.
The IP node is a queue node. It is in this layer that packets incur
delay which simulates the processing capability of a host and
queueing for use of the outgoing link. A packet arrival to the IP
layer will experience delay when it finds another packet already being
transmitted, plus possibly other packets queued for transmission. The
packets arriving at the IP layer are queued and operates with a first-
in first-out (FIFO) discipline. The queue size, service rate of the
IP layer are both promoted attributes, specified at the simulation
run level.
d. IGMP processor node: The models described above are standard
components available in OPNET libraries. We have added the host
multicast protocol model IGMP_host, the router multicast model IGMP,
and the unicast best-effort protocol model UBE.
The IGMP_host node is a process node. Packets are not queued in this
layer. IGMP_host provides unique group management services for the
multicast applications utilizing the services provided by the IP
layer. IGMP_host maintains a single table which consists of group
membership information of the application above the IGMP layer. The
function performed by the IGMP_host layer depends upon the type of
the packet received and the source of the packet.
The IGMP_host layer expects certain type of packets from the
application layer and from the network:
1. Accept join group requests from the application layer (it can be
one or more applications): IGMP_host maintains a table which
consists of the membership information for each group. When a
application sends a join request, it requests to join a specific
group N. The membership information is updated. This new group
membership information has to be conveyed to the nearest router and
to the MAC layer. If the IGMP_host is already a member of this
group (i.e. if another application above the IGMP_host is a member
of the group N), the IGMP_host does not have to send a message to
the router or indicate to the MAC layer. If the IGMP_host is not a
member currently, the IGMP_host generates a join request for the
group N (this is called a "response" in RFC 1112) and forwards it
to the IP layer to be sent to the nearest router. In addition the
IGMP_host also conveys this membership information to the MAC layer
interfacing to the physical layer through the OPNET "statistic
wire" connected from the IGMP_host to the MAC layer so that the MAC
layer begins to accept the frames destined for the group N.
2. Accept queries arriving from the nearest router and send responses
based on the membership information in the multicast table at the
IGMP_host layer: A query is a message from a router inquiring each
host on the router's interface about group membership information.
When the IGMP_host receives a query, it looks up the multicast
group membership table, to determine if any of the host's
applications are registered for any group. If any registration
exists, the IGMP_host schedules an event to generate a response
after a random amount of time corresponding to each active group.
The Ethernet example in Fig 6.4 and the description in the
following section describes the scenario.
(See Fig 6.4, An example Ethernet architecture.) The router R
interfaces with the Ethernet on one interface I1 and H1, H2, H3
are the hosts on the Ethernet. To illustrate this let us assume
that the hosts H1 and H3 are members of group N1 and H2 is a member
of group N2. When the router sends a query, all the hosts receive
the query at the same time t0. IGMP_host in H1 schedules an event
to generate a response at a randomly generated time t1 (t1 >= t0)
which will indicate the host H1 is a member of group N1. Similarly
H2 will schedule an event to generate a response at t2 (t2 >= t0)
to indicate membership in group N2 and H3 at t3 (t3 >= t0) to
indicate membership in group N3. When the responses are generated,
the responses are sent with destination address set to the
multicast group address. Thus all member hosts of a group will
receive the responses sent by the other hosts in the Ethernet who
are members of the same group.
In the above example if t1 < t3, IGMP_host in H1 will generate a
response to update the membership in group N1 before H3 does and H3
will also receive this response in addition to the router. When
IGMP_host in H3 receives the response sent by H1, IGMP_host in H3
cancels the event scheduled at time t3, since a response for that
group has been sent to the router. To make this work, the
events to generate response to queries are scheduled randomly, and
the interval for scheduling the above described event is forced to
be less than the interval at which router sends the queries.
3. Accept responses sent by the other hosts in the subnet if any
application layer is a member of the group to which the packet is
destined. The Ethernet example in Fig 6.4 described the function
to be performed when a IGMP_host receives the response sent by
other hosts in the subnet.
4. Accept terminate group requests from the Application layer. These
requests are generated by application layer when a application
decides to leave a group. The IGMP_host updates the group
information table and from now on will not send any response
corresponding to this group (unless any other application is a
member of this group). When a router does not receive any response
for a group in certain amount of time on a specific interface, the
membership is canceled for that group on that interface.
e. Unicast best-effort (UBE) processor node: This node is used model a
best effort traffic in the Internet based on the User Datagram Protocol
(UDP). The objective of this node is to model the background traffic in
a network. This traffic does not use the services provided QOSPF or
RSVP. UBE node aims to create the scenarios observed in a network
which has one type of application using the services provided by
QOSPF, RSVP to achieve specific levels of QoS and the best effort
traffic which uses the services provided by only the underlying IP.
The UBE node generates traffic to a randomly generated IP address
so as to create congestion in the network. The packets generated
are sent to the IP layer which routes the packet based upon the
information in the routing table. The attributes of the UBE node are:
1. Session InterArrival Time (IAT) : is the variable used to schedule
an event to begin a session. The UBE node generates a
exponentially distributed random variable with mean Session IAT and
begins to generate data traffic at that time.
2. Data IAT: When the UBE generates data traffic, the interarrival
times between data packets is Data IAT. A decrease in the value of
Data IAT increases the severity of congestion in the network.
3. Session-min and Session-max : When the UBE node starts generating
data traffic it remains in that session for a period which is
uniformly distributed between Session-min and Session-max.
e. Application processor node: The application layer consists of one
or more application nodes which are process nodes. These nodes use
the services provided by lower layer protocols IGMP, RSVP and IP. The
Application layer models the requests and traffic generated by
Application layer programs. Attributes of the application layer are:
1. Session IAT: is the variable used to schedule an event to begin a
session. The Application node generates a exponentially
distributed random variable with mean Session IAT and begins to
generate information for a specific group at that time and also
accept packets belonging to that group.
2. Data IAT: When Application node generates data traffic, the inter
arrival time between the packets uses Data IAT variable as the
argument. The distribution can be any of the available
distribution functions in OPNET.
3. Session-min and Session-max: When an application joins a session
the duration for which the application stays in that session is
bounded by Session-min and Session-max. A uniformly distributed
random variable between Session-min and Session-max is generated
for this purpose.
4. NGRP: This variable is used by the application generating multicast
traffic to bound the value of the group to which an application
requests the IGMP to join.
3.2.3 Router description
There are two types of routers. A router in a subnet and a backbone
router. A subnet router has all the functions of a backbone router
and in addition also has a interface to the underlying subnet which
can be either a FDDI network or a Ethernet subnet. In the following
section the subnet router will be discussed in detail. Fig 6.5 shows
the node level model of a subnet router.
a. The queueing technique implemented in the router is a combination
of input and output queueing. The nodes rx1, rx2, rx3 and rx4 are the
receivers connected to incoming T1 links. The router in Fig 6.5 has a
physical interface to the FDDI ring, which consists of the queue node
MAC, transmitter phy_tx, and the receiver phy_rx. The backbone
routers will not have the MAC layer. The services provided and the
functions of the MAC layer are the same as in the host discussed
earlier.
There is one major difference between the MAC node in an subnet router
that in a host. The MAC node in a subnet router accepts all the
multicast packets unlike the MAC in a host which accepts only the
multicast packets for groups of which the IGMP_host. For this reason
the statistic wire from the IGMP to MAC layer does not exist in a
router.
b. Addr_trans: The next layer in the router hierarchy is the
addr_trans processor node which provides the service of translating
the IP address to a physical address. The addr_trans node was has
already been described under the most model.
c. IP layer: The next layer in the hierarchy is the IP layer which
provides services to the upper layer transport protocols and also
performs routing based upon the information in the routing table. The
IP layer maintains two routing tables and one group membership table.
d. The tables used by the router model are:
1. Unicast routing table: This table is a single dimensional array,
which is used to route packets generated by the UDP process node in
the hosts. If no route is available to a particular IP address,
the corresponding entry is set to a default route in the array.
2. Multicast routing table: This table is a N by I array where N is
the maximum number of multicast groups in the model and I is the
number of interfaces in the router. This table is used to route
multicast packets. The routing table in a router is set by a upper
layer routing protocol which for this project is the QOSPF layer.
When the IP layer receives a multicast packet with a session_id
corresponding to a session which is utilizing the QOSPF and RSVP,
it looks up the multicast routing table to obtain the next hop.
3. Group membership table: This table is used to maintain group
membership information of all the interfaces of the router. This
table which is also an N by I array is set by the IGMP layer
protocol. The QOSPF (or any routing protocol) uses this
information in the group membership table to calculate and set the
routes in the Multicast routing table.
e. Sub-queues: The IP layer has three sub queues built in it,
which implement queuing based upon the priority of arriving packets
from the neighboring routers or the underlying subnet. The
architecture of the router queues is illustrated in Fig 6.6.
The queue with index 0 has the highest priority. When a packet
arrives at the IP node, the packets are inserted into the appropriate
sub-queue based on the priority of their traffic category: resource-
reserved traffic, best effort traffic, or control traffic. A non-
preemptive priority is used in servicing the packets. After the
servicing, packets are sent to the one of the output queues q_1
through q_I or the MAC. The packets progress through these queues
until the transmitter becomes available.
f. Attributes of the IP node are:
1. Unique IP address for each interface (a set of transmitter and
receiver constitute an interface).
2. Service rate: the rate with which packets are serviced at the
router.
3. Queue size: size of each of the sub queues used to store incoming
packets based on the priority can be specified individually
g. Output queues: The output queues perform the function of queuing
the packets served by the IP layer when the transmitter is busy.
A significant amount of queuing takes place in the output queues only
if the throughput of the IP node approaches the transmission capacity
of the links. Attribute of the queue node are:
1. Queue size: size of the queue in each queue nodes.
3.2.4 IGMP implementation at a router
The next layers in the hierarchy level are the IGMP for implementing
multicasting, the routing protocol, and RSVP for providing specific
QoS setup.
a. IGMP Node: The IGMP node implements the IGMP protocol as defined in
RFC 1112. The IGMP node at a router is different from the one at a
host. The functions of the IGMP node at a router are:
1. IGMP node at a router sends queries at regular intervals on all it's
interfaces.
2. When IGMP receives a response to the queries sent, IGMP updates the
multicast Group membership table in the IP node.
3. Every time the IGMP sends a query, it also updates the multicast
group membership table in the IP node if no response has been
received on for the group on any interface, indicating that a
interface is no longer a member of that group. This update is done
only on entries which indicate an active membership for a group on a
interface where the router has not received a response for the last
query sent.
4. The routing protocol (which we have implemented as QOSPF, see
companion paper) uses the information in the Group membership table
to calculate the routes and update the multicast routing table.
5. When the IGMP receives a query (an IGMP at router can receive a
query from a directly connected neighboring router), the IGMP node
creates a response for each of the groups it is a member of on all
the interfaces except the one through which the query was received.
4. RSVP model
The current version of the RSVP model supports only fixed-filter
reservation style. The state-transition diagrams for the RSVP model are
available at
http://bacon.gmu.edu/qosip/rsvp
The following processing takes place in the indicated modules.
4.1 RSVP APPLICATION
4.1.1 Init
Initializes all variables and load the distribution functions
for Multicast Group Id's, termination of the session. Transit
to Idle state after completing all the initializations.
4.1.2 Idle
This state has transitions to four states, Arr, Join, Data_Send and
EndSim. It transit to Arr state upon Packet Arrival, transit to
Join state when the Join interrupt was true, transit to Data_Send
state when the Send_Data interrupt was true, transit to EndSim state
when simulation ends.
4.1.3 Arr
In this state if a data packet arrives the application will
increment the Data Received counter, and if a Session message
from Local RSVP daemon arrives it update it's Registered
Session directory. After completing these functions it will return
to the idle state.
4.1.4 Join
The Application will send a session call to local RSVP
daemon and once it receives the session Id from the Local
daemon it makes a sender or receiver call. The multicast
group id is selected randomly from a uniform distribution.
While doing a sender call the application will write all its
sender information in a global session directory.
If the application is acting as a receiver it will check for
the sender information in the session directory for the
multicast group that it wants to join to and makes a receive
call to the local RSVP daemon.
Along with these two calls it makes a IGMP join call.
If the application chooses to terminate the session it
was registered to, it will send a release call to the
local RSVP daemon and a terminate call to IGMP daemon.
After completing these functions it will return to the idle state.
4.1.5 Data_Send
Creates a data packet and send it multicast destination
that it selects. It update a counter to keep track of how many
packets that it had sent. This state on default returns to
Idle state.
4.1.6 EndSim
This state gives statistics of how many packets have
received and how many packets have been sent.
4.2 RSVP ON ROUTER
4.2.1 Init
This state calls a function called RouterInitialize which
will initialize all the router variables. This state will go to
Idle state after completing these functions.
4.2.2 Idle
Idle state transit to Arr state upon receiving a packet.
4.2.3 Arr
This state checks for the type of the packet arrived and
calls the appropriate function depending on the type of message
received.
a. PathMsgPro: This function was invoked by the Arr state when a path
message is received.
1. It first checks for a Path state block which has a
matching destination Address and if the sender port or sender address
or destination port does not match the values of the Session object
of the Path state block, it sends an path error message and returns.
(At present in our application we are not sending any error
messages, we are printing this error message on to console).
2. If a PSB is found whose Session Object and Sender Template
Object matches with that of the path message received, the current
PSB is made as forwarding PSB.
3. Search for the PSB whose session and sender template matches
the corresponding objects in the path message and whose incoming
interface matches the IncInterface. If such a PSB is found and the
if the Previous Hop Address, Next Hop Address, and SenderTspec
Object doesn't match that of path message then the values of path
message is copied into the path state block and path refresh
needed flag is turned on. If the Previous Hop Address, Next Hop
Address of PSB differs from the path message then the Resv Refresh
Needed Flag is also turned on, and the Current PSB is made equal
to this PSB.
4. If a matching PSB is not found then a new PSB is created and
and Path Refresh Needed Flag is turned on, and the Current PSB
is made equal to this PSB.
5. If Path Refresh Needed Flag is on, Current PSB is copied into
forwarding PSB and Path Refresh Sequence is executed. To execute
this function called PathRefresh is used. Path Refresh is sent to
every interface that is in the outgoing interfaces list of
forwarding path state block.
6. Search for a Reservation State Block whose filter spec object
matches with the Sender Template Object of the forwarding PSB and
whose Outgoing Interface matches one of the entry in the forwarding
PSB's outgoing interface list. If found then a Resv Refresh message
to the Previous Hop Address in the forwarding PSB and execute the
Update Traffic Control sequence.
b. PathRefresh: This function is called from PathMsgPro. It creates the
Path message sends the message through the outgoing interface that is
specified by the PathMsgPro.
c. ResvMsgPro: This function was invoked by the Arr state when a Resv
message is received.
1. Determine the outgoing interface and check for the PSB whose
Source Address and Session Objects match the ones in the Resv
message.
2. If such a PSB is not found then send a ResvErr message saying
that No Path Information available (At present we are not
implementing this message and just printing this error message on
to console).
3. Check for the incompatible styles and process the flow
descriptor list to make reservations, checking the PSB list for
the sender information. If no sender information is available
through the PSB list then send an Error message saying that No
Sender information. For all the matching PSB's found, if the
Refresh PHOP list doesn't have the Previous Hop Address of the PSB
then add the Previous Hop Address to the Refresh PHOP list.
4. Check for matching Reservation State Block (RSB) whose Session
and Filter Spec Object matches that of Resv message. If no such
RSB is found then create a new RSB from the Resv Message and set
the NeworMod flag On. Call this RSB as activeRSB. Turn on the Resv
Refresh Needed Flag.
5. If a matching RSB is found, call this as activeRSB and if the
FlowSpec and Scope objects of this RSB differ from that of Resv
Message copy the Resv message Flowspec and Scope objects to the
activeRSB and set the NeworMod flag On.
6. Call the Update Traffic Control Sequence. This is done by
calling the function UpdateTrafficControl
7. If Resv Refresh Needed Flag is On then send a ResvRefresh
message for each Previous Hop in the Refresh PHOP List. This was
done by calling the ResvRefresh function for every Previous Hop in
the Refresh PHOP List.
d. ResvRefresh: this function is called by both PathMsgPro and
ResvMsgPro with RSB and Previous Hop as input. The function constructs
the Resv Message from the RSB and sends the message to the Previous
Hop.
e. PathTearPro: This function was invoked by the Arr state when a
PathTear message is received.
1. Search for PSB whose Session Object and Sender Template Object
matches that of the arrived PathTear message.
2. If such a PSB is not found do nothing and return.
3. If a matching PSB is found, a PathTear message is sent to all the
outgoing interfaces that are listed in the Outgoing Interface list
of the PSB.
4. Search for all the RSB whose Filter Spec Object matches the Sender
Template Object of the PSB and if the Outgoing Interface of this
RSB is listed in the PSB's Outgoing interface list delete the RSB.
5. Delete the PSB and return.
f. ResvTearPro: This function is invoked by the Arr state when a
ResvTear message is received.
1. Determine the Outgoing Interface.
2. Process the flow descriptor list of the arrived ResvTear message.
3. Check for the RSB whose Session Object, Filter Spec Object matches
that of ResvTear message and if there is no such RSB return.
4. If such an RSB is found and Resv Refresh Needed Flag is on send
ResvTear message to all the Previous Hops that are in Refresh PHOP
List.
5. Finally delete the RSB.
g. ResvConfPro: This function is invoked by the Arr state when a
ResvConf message is received. The Resv Confirm is forwarded to the IP
address that was in the Resv Confirm Object of the received ResvConf
message.
h. UpdateTrafficControl: This function is called by PathMsgPro and
ResvMsgPro and input to this function is RSB.
1. The RSB list is searched for a matching RSB that matches the
Session Object, and Filter Spec Object with the input RSB.
2. Effective Kernel TC_Flowspec are computed for all these RSB's.
3. If the Filter Spec Object of the RSB doesn't match the one of the
Filter Spec Object in the TC Filter Spec List then add the Filter
Spec Object to the TC Filter Spec List.
4. If the FlowSpec Object of the input RSB is greater than the
TC_Flowspec then turn on the Is_Biggest flag.
5. Search for the matching Traffic Control State Block(TCSB) whose
Session Object, Outgoing Interface, and Filter Spec Object matches
with those of the Input RSB.
6. If such a TCSB is not found create a new TCSB.
7. If matching TCSB is found modify the reservations.
8. If Is_Biggest flag is on turn on the Resv Refresh Needed Flag flag,
else send a ResvConf Message to the IP address in the ResvConfirm
Object of the input RSB.
4.2.4 pathmsg: The functions to be done by this state are done through
the function call PathMsgPro described above.
4.2.5 resvmsg: The functions that would be done by this state are done
through the function call ResvMsgPro described above.
4.2.6 ptearmsg: The functions that would be done by this state are done
through the function call PathTearPro described above.
4.2.7 rtearmsg: The functions that would be done by this state are done
through the function call ResvTearPro described above.
4.2.8 rconfmsg: The functions that would be done by this state are done
through the function call ResvConfPro described above.
4.3 RSVP ON HOSTS
4.3.1 Init
Initializes all the variables. Default transition to idle state.
4.3.2 idle
This state transit to the Arr state on packet arrival.
4.3.3 Arr
This state calls the appropriate functions depending on the
type of message received. Default transition to idle state.
a. MakeSessionCall: This function is called from the Arr state whenever
a Session call is received from the local application.
1. Search for the Session Information.
2. If one is found return the corresponding Session Id.
3. If the session information is not found assign a new session Id to
the session to the corresponding session.
4. Make an UpCall to the local application with this Session Id.
b. MakeSenderCall: This function is called from the Arr state whenever
a Sender call is received from the local application.
1. Get the information corresponding to the Session Id and create a Path
message corresponding to this session.
2. This packet is sent to the IP layer.
c. MakeReserveCall: This function is called from the Arr state whenever
a Reserve call is received from the local application. This function
will create and send a Resv message.
d. MakeReleaseCall: This function is called from the Arr state whenever
a Release call is received from the local application.This function will
generate a PathTear message if the local application is sender or
generates a ResvTear message if the local application is receiver.
4.3.4 EndSim
This state does not do anything.
4.3.5 Session
This state's function is performed by the MakeSessionCall function.
4.3.6 Sender
This state's function is han by the MakeSenderCall function.
4.3.7 Reserve
This state's function is performed by the MakeReserveCall function.
4.3.8 Release
This state's function is performed by the MakeReleaseCall function.
5. Future work.
We hope to receive assistance from the IPmc/RSVP development
community within the IETF in validating and refining this model.
We believe it will be a useful tool for predicting the behavior
of RSVP-capable systems.
6. References
[1] Deering, "Host Requirements for IP Multicasting", RFC 1112,
August 1989
[2] Braden et. al., "Resource Reservation Protocol Version 1 Functional
Specification", work in progress (draft-ietf-rsvp-spec-14)
November 1996
[3] MIL3 Inc., "OPNET: Optimized Network Engineering Tools, Simulation
Kernel Manual", November 1991
Authors' Addresses
J. Mark Pullen
Computer Science/4A5
George Mason University
Fairfax, VA 22032
mpullen@gmu.edu
Ravi Malghan
COMSAT Laboratories
22300 COMSAT Drive
Clarksburg, MD 20871-9475
rmalghan@bacon.gmu.edu
Lava K. Lavu
C3I Center/4B5
George Mason University
Fairfax, VA 22030
llavu@bacon.gmu.edu
Expiration: 25 April 1997