Network Routing Protocols andAdvanced Topics

Network Routing Protocols

Link & Frame Detail

Distributed Software Module

Node Software Applications

Exercise 3 - Client/Server Network

Packet Switching and Network Operation

Routing Protocols– Static and adaptive routing algorithms for packet switching– Metrics based on user-defined penalties, measured delays,

or composite metrics

Routing Classes– Routing protocols using shortest path metrics are a

function of routing class– Allows different classes of traffic to take different routes

Packet Routing Strategies

Define Backbone Properties

Backbone Properties

Backbone Routing Protocols

Shortest Measured Delay Routing Parameters

Shortest Measured Delay

The shortest path through the network based on a delay metric where the metric used for each port is the average delay experienced by packets transmitted on the port

The packet delay measurement covers the interval from when a packet enters an output buffer until the packet completes transmission (I.e. transmission queue)

The shortest path calculation is performed periodically and after each node/link failure or restoration causing the routing tables to be updated according to the most recent delay measurements

Vulnerable to oscillations if used with datagram routing– The route that was good for one interval can look bad after the next

interval because too much traffic used it– Can use % deviation and multipath routing to reduce this effect– Sessions using connection-oriented routing are not as vulnerable

because the sessions typically last longer than routing update interval

Common Routing Protocol Parameters

Routing update interval (seconds)– Routing table update interval for adaptive routing algorithms– Updates occur instantaneously in the model– Use traffic sources on the node in order to model broadcasting of

routing table updates

Deviation % for multiple shortest paths– All routes having a metric within X% of the best route’s metric are

regarded as equivalent and traffic is load balanced among the equivalent routes

– When X=0, no ties are declared and only the best route is chosen

Connection-oriented routing for sessions– Session information packets are transmitted over virtual circuits

Packet Routing Classes

Add New Packet Routing Class

Packet Routing Class Parameters

Packet Routing Class Parameters (continued)

Hop Limit– Maximum number of hops that traffic of this class can take between

source and destination

Session Retry Interval (minutes)– Invoked if session setup packet is blocked or lost enroute– Another session setup packet is generated and transmitted after this

delay

Reroute Connections– Connection-oriented sessions routed across links that fail are

automatically rerouted

IGRP Metric– Composite metric used for IGRP routing protocol only– These parameters only apply to traffic classes that are routed with

the IGRP protocol

Session Source Routing Class

Edit Routing Classes

RIP Minimum Hop Routing

RIP Minimum Hop

Routing Information Protocol– Routing algorithm commonly used with TCP/IP– Known as a “distance-vector” algorithm

Treats all links as equivalent and minimizes the number of hops in an end-to-end path

Shortest path calculation performed globally at start of simulation and after each node/link failure or restoration

Hop limits are enforced both in the shortest path calculation and also when routing individual packets

True RIP does not support multipath routing - the % deviation is provided only as a modeling convenience

Link State Shortest-Path-First Routing

Link State Shortest-Path-First

IS-IS (Intermediate System - Intermediate System) and OSPF (Open Shortest-Path-First) are both Link-State-Path-First routing algorithms

IS-IS is used with OSI nets while OSPF is used with TCP/IP integrated IS-IS can be used with either

Routing metric can vary by link and by routing class

Comnet III model includes an arbitrary penalty or weight that varies by routing class, but does not include a traffic dependent component of the metric (use minimum penalty path routing to introduce a traffic dependent component)

Can prohibit a routing class of traffic from using a link by assigning a negative penalty value

Shortest path calculation is performed at start of simulati9n and whenever there is a change in node or link states

Typically much smaller routing update traffic than with RIP

Edit Penalty for Routing Class

Accept Penalty Table

Opposing Port Packet Routing Penalty Table

Minimum Penalty Routing

Minimum Penalty Path

Shortest path through the network based on variable penalties where each port is assigned an arbitrary penalty table

The penalty table assigned to a link port determines the penalty value which can vary by routing class and by the level of congestion on the link as well

Can prohibit a routing class of traffic from using a link for certain (or all) congestion levels by assigning a negative penalty value

The shortest path calculation is performed periodically and after every failure/restoration event using the current metrics assigned to a port

Each port points to a penalty table, which allows different nodes connected to the same link to see different penalties for the link

The model has a list of penalty tables -- typically a different table for different categories of links (e.g. more desirable links have lower penalty values)

Edit Congestion Threshold

Edit Routing Class Penalty

IGRP Routing

IGRP Routing Parameters

IGRP Model Interior Gateway Routing Protocol - A model of Cisco’s routing protocol

Uses a composite routing metric[ K1 * (1010/bandwidth) ] +[ K2 * (1010/bandwidth)/( 256 - (utilization * 255) ) ] +[ K3 * (delay factor) ]

Routing tables are updated periodically (typically every 90 seconds) using current value of metric

Weights K1, K2, K3 and delay factors can vary by routing class. In practice, all weight is often placed on the static components of the composite metric (i.e. K2=0)

Computing the routing metric– bandwidth (bps) is determined by the link in the path that has the minimum bandwidth– utilization is variable– delay factor (units of 10 microseconds) is determined by standard delay parameters

in routing strategy detail by default or by penalty tables if the penalty applied to the port is greater than 1

IGRP uses multipath routing; typically use a very small deviation %

Links

Link Characteristics

Messages are transported– between Processing Nodes and Groups– using Routing Nodes and Switches between LANs

Two links cannot directly connect– Node is required

Takes a message in the form of bytes or packets– reformats it into frames– transfers it to destination node– gives the destination the message in the form of bytes or packets

Proper frame sizes and overheads are built in to the predefined implementations– destination headers on message packets, message checksums, etc.

Link Loading

Frame Parameters

Frame min (bytes)– Minimum size link-level transmission frame– Frames will be padded in order to reach the minimum frame size– Default of zero implies no minimum

Frame max (bytes)– Largest link-level transmission unit– Maximum number of packet bytes = frame maximum - frame overhead– Default of zero implies no maximum

Frame overhead (bytes)– Link-level overhead bytes added to frames prior to comparing the frame to the

minimum frame size– Fractions of a full frame will still incur the full frame overhead

Frame Assembly– Enables assembly of packets from the output queue for a link into a frame

Link Level Transmission Frame

Transmission Frames

PE PE PEProcessingElements

Frames Frames

ApplicationSourceQueue

LocalStoragefor Files

Application Sources & Nodes

Library Command Types

Create Transport Message Command

Message Text Options

Create Setup Session Command

Session Messages

Destination Types

Create Answer Message Command

Accept Command Repertoire

Command Name Detail

Editing “Local” Host Node Commands

Close Local Command Repertoire

Application & Traffic Sources

Process Command Name

Processor Utilization

Accept Process Command Properties

Create Read File Command

File to Access (continued)

Accept Read Command Properties

Accept Command Repertoire

Accept Node Parameter Set

File Size

Create Write File Command

Accept Write File Command Properties

Edit Answer Command

Create Wait For Command

Stop Waiting

Waiting for User-defined State Dependency

Variable Assignment Types

Add New Variable

Accept List of Local Variables

Assignment Expression

Command Name Detail

Macro Command Sequence

Node Command Repertoire

Node Software Capability

Global Commands and Variables

Exercise 3 - Client/Server Network

Replace the Client Session and Server Response Traffic Sources of Exercise 2 with Application Sources and Commands.

Client Workstation Application

In addition to E-Mail, the client workstations still continue to generate a 1000 byte FTP request to the server with an exponentially distributed iteration time (mean of 10 minutes).

The client workstations then wait for a response before they continue processing.

When the server response arrives, the client workstations process the information for 2 seconds and then write a file to a local storage disk. The file size is equal to the server’s answer message size(i.e. A x msg bytes + B).

Try making a global command macro with this sequence of commands.

Execute the global macro in the client application sources.

Server Application

The 100 microsecond server (i.e. processing time per cycle), upon receipt of an FTP request, processes for a random amount of time. The processing time is beta distributed with a minimum of 10000 cycles and a maximum of 40000 cycles. Using the formula (processing time per cycle) * (cycles) = processing time, what does this processing time work out to be on the server?

The server then reads a random sized file from local storage. The size of the file is Poisson distributed with a mean of 10000 bytes.(Hint: Use Poi(10000)).

Finally, the server returns the file to the client with an answer message that is equal in size to the file just read (i.e. A x file bytes + B).

Try making a local command macro with this sequence of commands.

Execute the local macro in the server application source when an FTP request arrives.

Client/Server Node Parameter Sets

Modify the node parameter set for the client workstations so that they have storage disks with 16 millisecond seek times, 200 microsecond transfer rates per sector, and sector sizes of 2048 bytes (i.e. 2 Kbytes).

Modify the server node parameter set so that it has a storage disk with a 10 millisecond seek time, a 100 microsecond transfer rate per sector and a sector size of 16,384 bytes (i.e. 16 Kbytes).

In addition, the processing time per cycle for the server must be set to 100 microseconds.