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CS 145A Case Study: Simplified BGP Finite State Machine Netlab.caltech.edu/course Today Brief Introduction of routing protocols An example of Finite State Machine Lab 3 What does the Internet look like? Example: (/sbin/traceroute) C:\>tracert cwis.usc.edu

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today
Today
  • Brief Introduction of routing protocols
  • An example of Finite State Machine
  • Lab 3
what does the internet look like
What does the Internet look like?
  • Example: (/sbin/traceroute)

C:\>tracert cwis.usc.edu

Tracing route to cwis.usc.edu [128.125.253.146]

1 <1 ms Jorgensen-RSM-44.caltech.edu [131.215.44.253]

2 <1 ms Booth-border.ilan.caltech.edu [131.215.254.254]

3 <1 ms CalREN-Caltech.caltech.edu [192.41.208.49]

4 <1 ms JPL--CIT.POS.calren2.net [198.32.248.5]

5 1 ms UCLA--JPL.POS.calren2.net [198.32.248.1]

6 1 ms ISI--UCLA.POS.calren2.net [198.32.248.29]

7 2 ms USC--ISI.POS.calren2.net [198.32.248.25]

8 3 ms rtr43-c2-gw.usc.edu [128.125.251.66]

9 2 ms rtr-gw-1.usc.edu [128.125.254.1]

10 2 ms cwis.usc.edu [128.125.253.146]

necessary information 1
Necessary Information (1)
  • Where shall I pass the packet, for a given destination IP address? – Routing Table
  • Exmaple:

[weixl@orchestra:~]> route

slide11
How?
  • Manually add/delete routing entries
  • Automatically exchange routing information between routers.
routing protocol
Routing Protocol

A: hi, are you there?

B: yes.

A: Can I tell you a piece of news?

B: Sure.

A: I have a way to get to www.usc.edu.

B: ok. I will send you all the packets that are going to www.usc.edu.

B: Hi, Can I tell you some news, too?

A: Yes!

B: I can connect to all the machines in “cs.caltech.edu”

A: ok. I will send you all the packets that are going to “cs.caltech.edu”.

……

routing protocol13
Routing Protocol

A to C: hi, are you there?

...

A to C: hi, are you there?

A to B: I think C is down. And from now on, I cannot contact USC.

B: OK. I will try other paths when I get packets for USC.

routing protocol14
Routing Protocol
  • Good: Efficiently broadcast up-to-date routing information
  • Bad: Rumor may be broadcast efficiently, too.
  • Argument: If the majority is good…
  • The algorithm should be correct in distributed environments.
routing protocols
Routing Protocols
  • Autonomous System
routing protocols16
Routing Protocols
  • Inside Autonomous System: Embrace the Freedom!
  • RIP (Routing Information Protocol)
  • OSPF (Open Shortest Path First)
  • Between Autonomous System (Exterior Gateway Protocol): More consideration…
  • BGP (Border Gateway Protocol)
border gateway protocol 4
Border Gateway Protocol-4
  • Inter-Autonomous System Communication
  • Propagate Path Information
  • Support Policy
  • Incremental Updates
  • Assume reliable transmission (TCP)
  • http://www.ietf.org/rfc/rfc1771.txt
bgp packets
BGP Packets
  • Packets Format:
    • 0-15th Byte: FF (hexadecimal)
    • 16-17th Byte: Unsigned number, Length of the Packet (>=19)
    • 18th Byte: Packet Type:
      • 1 OPEN
      • 2 UPDATE
      • 3 NOTIFICATION
      • 4 KEEPALIVE
    • 19th Byte to the end of the Packet: Routing Data
detailed specification
Detailed Specification
  • http://www.ietf.org/rfc/rfc1771.txt Appendix I (page 47)
lab 3 task
Lab 3 - Task
  • Implement a (simplified) simplified BGP Finite State Machine:
  • Ignore the timers
  • Ignore the details of Routing Data
lab 3 requirements
Lab 3 - Requirements
  • The implementation is based on TCP.
  • The implementation is able to actively connect to multiple machines and it is able to accept requests from multiple machines.
  • The implementation allows at most one connection from one machine (identified by IP / hostname).
  • For each connection, the implementation implements the Lab3 Finite State Machine.
lab 3 details
Lab 3 - Details
  • A program “server”
  • Read from a file called “server.conf”. Format of “server.conf”:
  • (1st line:) Listen_Port Connection_Num(N)
  • (2nd line:) IP_1 Port_1
  • (…)
  • (N+1st line:) IP_N Port_N
  • The server should read from “server.conf”, listen to Listen_Port for new connection, at the same time, actively connect the specified machines (IP_1:Port_1, IP_2:Port_2, … IP_N:Port_N)
lab 3 possible problems
Lab 3 - Possible Problems
  • Implementation of Finite State Machine
  • Check the errors (including operation errors and Packet errors)
  • Multiple connections from the same machine
lab 3 tips
Lab 3 - Tips
  • Re-Use the codes in Lab 1
  • How to implement the Finite State Machine?
  • “if … then…”
  • “State transition table”
  • How to test?
  • Incremental Development
  • DON’T START AT THE LAST MOMENT!
lab 328
Lab 3
  • Due: Dec 1st (Sunday) 23:59:59
  • Email: weixl@caltech.edu
  • Grading
  • TA hours:

Tue / Thu (20:00 – 22:00) JRG 170

Except: Nov.19 / Nov.21