Link State Protocol Design by Jignesh Patel Palanivel Rathinam Vishwesh Tendolkar

Overview Representation of routers and networks Assumptions Routing protocol packets Implementation requirements Protocol data structures Implementation issues Protocol headers

Representation of routers and networks

Assumptions

Routing protocol packets

Implementation requirements

Protocol data structures

Implementation issues

Protocol headers

Representation of routers and networks Each router will be a process identified by a unique id No configuration files - command line arguments Port numbers play the role of interfaces 2000 2001 3000 RA RB RC

Each router will be a process identified by a unique id

No configuration files - command line arguments

Port numbers play the role of interfaces

Contd. The command line arguments for the above network topology is Router RA 2000 2001 Router RB 2000 3000 Router RC 2001 3000 Constraints: If a new node is to be added or an existing node is to be deleted, should restart the router process

The command line arguments for the above network topology is

Router RA 2000 2001

Router RB 2000 3000

Router RC 2001 3000

Constraints: If a new node is to be added or an existing node is to be deleted, should restart the router process

Assumptions No hierarchical routing All route processes run on the same machine Routing computation is decoupled from the protocol

No hierarchical routing

All route processes run on the same machine

Routing computation is decoupled from the protocol

Routing protocol packets There are five types of packets. Each packet is identified by the packet type in common header Type 1 packet – Hello Type 2 packet – Database Description Type 3 packet – Link state request Type 4 packet – Link state update Type 5 packet – Link state acknowledgment

There are five types of packets. Each packet is identified by the packet type in common header

Type 1 packet – Hello

Type 2 packet – Database Description

Type 3 packet – Link state request

Type 4 packet – Link state update

Type 5 packet – Link state acknowledgment

Implementation requirements Thread Timers Single-shot Interval – avoid synchronization by adding small random values LSA type – Router LSA List manipulation primitives

Thread

Timers

Single-shot

Interval – avoid synchronization by adding small random values

LSA type – Router LSA

List manipulation primitives

Protocol data structures Router ID – 32 bit number Routing table Interface list Interface data structure Type IP interface address IP interface mask Hello interval Router dead interval Delay Hello timer – fires hello packets every hello interval Neighbor router

Router ID – 32 bit number

Routing table

Interface list

Interface data structure

Type

IP interface address

IP interface mask

Hello interval

Router dead interval

Delay

Hello timer – fires hello packets every hello interval

Neighbor router

Contd. Interface data structure Interface output cost – expressed in link state metric Retransmit interval – number of seconds between LSA retransmissions Interface state (DOWN/UP) Interface state machine DOWN UP Interface up

Interface data structure

Interface output cost – expressed in link state metric

Retransmit interval – number of seconds between LSA retransmissions

Interface state (DOWN/UP)

Interface state machine

Contd. Neighbor list Neighbor data structure State Inactivity timer – single-shot timer whose length is router dead interval Master/slave Database description sequence number Last DD packet received (DD header) Neighbor ID – router ID of neighboring router – this is learned after receiving the hello packet Neighbor IP address

Neighbor list

Neighbor data structure

State

Inactivity timer – single-shot timer whose length is router dead interval

Master/slave

Database description sequence number

Last DD packet received (DD header)

Neighbor ID – router ID of neighboring router – this is learned after receiving the hello packet

Neighbor IP address

Contd. List of router LSA (this is the link state information/database. This is generated for each router in the network) Link state retransmission list Link state request list

List of router LSA (this is the link state information/database. This is generated for each router in the network)

Link state retransmission list

Link state request list

Contd. Neighbor state machine DOWN INIT EX-START 2-WAY EXCHANGE LOADING FULL HELLO RECEIVED ONE-WAY RECEIVED TWO -WAY RECEIVED NEGOTIATION DONE EXCHANGE DONE LOADING DONE

Neighbor state machine

Contd. Routing table structure Destination type Destination ID Address mask Cost Next hop – router ID

Routing table structure

Destination type

Destination ID

Address mask

Cost

Next hop – router ID

Implementation issues We are not using TCP based connection for information exchange, although some routing protocols use it (BGP) Raw IP cannot be used to make processes communicate on the same machine. Since Raw IP is void of any transport layer protocol and hence the ports, processes should use the protocol number in IP to identify packets destined to them. This approach is not feasible UDP although unreliable helps communication between multiple processes through ports. Also UDP has a built in checksum calculation

We are not using TCP based connection for information exchange, although some routing protocols use it (BGP)

Raw IP cannot be used to make processes communicate on the same machine. Since Raw IP is void of any transport layer protocol and hence the ports, processes should use the protocol number in IP to identify packets destined to them. This approach is not feasible

UDP although unreliable helps communication between multiple processes through ports. Also UDP has a built in checksum calculation

Contd. Our link state protocol uses UDP for its communication Presentation layer is binary Java is used as the programming language

Our link state protocol uses UDP for its communication

Presentation layer is binary

Java is used as the programming language

Protocol headers The link state protocol is layered. It has a common header which is given below Version # = 1 Type = {1,…5} Packet length (no. of words including header) Router ID = R1

The link state protocol is layered. It has a common header which is given below

Contd. Packet format for the hello protocol Hello Interval = 10msec Dead time Interval = 5sec Neighbor list = {R2,R3,R1} …

Packet format for the hello protocol

Contd. All link state messages share a common header which is depicted below Age = 5 Sequence number = 3 Link state ID = 2000 Advertising Router = R1

All link state messages share a common header which is depicted below

Contd. The link state advertisement includes information about the link and cost metric. We have used the metric from EIGRP to include delay, bandwidth and reliability # links = 1 Link ID = R1 Link Data = 2000 Metric = w1 * cost + w2* delay + w3* bandwidth

The link state advertisement includes information about the link and cost metric. We have used the metric from EIGRP to include delay, bandwidth and reliability

Contd. Link state updates. When a router receives a link state request packet during database synchronization or a multiple LSAs from neighbors, it sends a LSU. The packet format is shown below # LSAs = 1 Link state advertisements …

Link state updates. When a router receives a link state request packet during database synchronization or a multiple LSAs from neighbors, it sends a LSU. The packet format is shown below

Contd. The database description packet is shown below Interface MTU = 512 M I M/S UNUSED DD SEQUENCE NUMBER = time of day LSA HEADER

The database description packet is shown below

Questions / Suggestions ?/ !

?/ !

References RFC 2328, OSPF v2 Routing in the Internet – by Christin Hieutema CS526 Manuscript – Dr. Deep Medhi & Karthik Ramaswamy

RFC 2328, OSPF v2

Routing in the Internet – by Christin Hieutema

CS526 Manuscript – Dr. Deep Medhi & Karthik Ramaswamy