588 Section 8

Neil Spring

May 25, 1999

Schedule

• Notes

• Homework 3

• Reservations?

Reminders & Notes

• Homework 3 due June 1

• Project 3 or final project will be due June 11– Word documents OK.

• Next week: 422

Homework 3 -1

• Read Reflections on Trusting Trust, by Ken Thompson

• Figure 1 might give you some clues about how to answer this question.

Homework 3 - 2

• Sample denial of service attacks:– syn flooding– name service attacks, possibly pretending map

www.cnn.com to your favorite (ahem) ‘adult entertainment’ site.

– Infrastructure attacks:• smurfing: broadcast icmp echo with a forged source

address

– end host attacks• internet worm

Homework 3 - 3

• Multicast source routing packet header format

• Efficiency: size, complexity– can you get both?

• Evaluation– Could it be deployed?– Would it help?

Homework 3 - 4

• Incompatible routing protocols:

• Two questions– How does it happen?– How do you fix it?

G1

G2

S

R

N1 N2

Homework 3 - 5

• End to end – (i) if lost (ii) how to recover

• If lost should be of the form– the x doesn’t get his update– have to multicast everywhere

• To recover should be of the form– we send the update to x again, x asks for an

update…– pruning is initiated again

Homework 3 - 6

• DNS asynchronous update

• a. write, but read the before image?

• b. to get processor order?

• c. to get total order?

Homework 3 - 7

• Distance vector updates• This is NOT link state, also NOT distance

vector as described in the book:– The initial table contains no 1’s!!!– Routers don’t know about their direct links!!!

• A) tables like on page 167• B) flooding direction might change if a new

route is there

Homework 3 - 8

• Straightforward…

• questions?

Real Time

• Problem: – Want interactive video, audio,– Interactive means buffering (normal

technique) is bad

• Maybe want multicast

• Routers, links fail

• Congestion happens

The Story of RSVP

• Senders deliver flow specifications to receivers, over predictable routes. Receivers send resource reservations back toward the sender. Routers along the way do admission control to decide whether guarantees can be made, then packet scheduling to meet those guarantees.

The Feature Sheet

• Receiver-driven– scalable for multicast– heterogeneity

• Soft-state– tolerates failures, changes– path state - forward, using existing routing– reservation state - reverse path– timeout & refresh

• Filters: differentiate between senders