itmbench: Generalized API for Internet Traffic Managers

Transcription

1 itmbench: Generalized API for Internet Traffic Managers Traffic Controllers as Building Blocks Toward Safely Composing New Network Services Ibrahim Matta Computer Science Department Boston University Joint work with Gali Diamant, Leonid Veytser, Azer Bestavros, Mina Guirguis, Liang Guo, Yuting Zhang, Sean Chen CAMAD 04 Workshop, November 29,

2 Toward a Road System with Traffic Lights! b b b b Alice (Transmission Control Protocol) TCP b c b c c c Bob b c bc c Cathy Goal: more efficient, more predictable 11/29/2004 CAMAD'04 by Ibrahim Matta 2

3 The Internet Traffic Managers (ITM) Architecture Capacity planning The ITM framework Internet Domain Identification programs Traffic characterization Edge-to-edge control Adaptive control control Traffic Core router Control programs Bandwidth control Differentiated control Best Effort Service Traffic Manager (Edge Router) Internet Internet domain Edge-to-edge Traffic Engineering domain Bandwidth Management Packet Classification Intelligent Transmission 11/29/2004 CAMAD'04 by Ibrahim Matta 3

4 TCP Bandwidth Sharing TCP needs a slow start period to probe available bandwidth Congestion window size depends on when packet loss is detected Rate Initial handshake Slow-start Congestion avoidance Time On average, short flows (mice ) transfer at a lower rate than long flows (elephants ) 11/29/2004 CAMAD'04 by Ibrahim Matta 4

5 Elastic TCP-based Tunnels Providing Soft Bandwidth Guarantees to Aggregates sources ITM Elastic tunnel of m TCP-friendly flows ITM receivers Cross traffic adjust m scheduler TCP controller IP monitor measured bandwidth 11/29/2004 CAMAD'04 by Ibrahim Matta 5

6 etcp Controllers Naïve control: m(t +1) = * B b(t) m(t) P control: m(t +1) = K p e(t), e(t) = B * -b(t) PI control: m(t +1) = K p e(t) + Kie(t) Target + - Error Controller Plant Achieved Rate 11/29/2004 CAMAD'04 by Ibrahim Matta 6

7 Simulations Naïve vs PI vs No Control Naïve: - big overshoot - aggressive reaction - not good for highly dynamic environments Bandwidth achieved PI : + more steady + less overshoot + less jitter # active ITM-TCP connections 11/29/2004 CAMAD'04 by Ibrahim Matta 7

8 SaTS: Size-aware TCP Service Allocate tunnel s bandwidth to aggregates of packet Preferential flows with Early divergent Dropping characteristics class-based scheduling Proactively send congestion notification even before queue is full class-based routing preferential dropping (feedback signaling) queue length q High priority Low priority dropping probability p i 11/29/2004 CAMAD'04 by Ibrahim Matta 8

9 Size-threshold Controller Error Target + - Controller Plant Estimated Response Time Size Threshold pm 5am 30 NLANR Trace, Indiana University Optimization constraint: Penalty < 3% pm 2am 11am Gain (%) 11/29/2004 CAMAD'04 by Ibrahim Matta 9

10 itmbench: Generalized API for ITMs itm_mod serves as intermediate layer between applications and TCP/IP stack Other modules register with it to receive service Keeps record of registered applications and transfers packets according to given specifications Currently uses netfilter to interact with stack user space application SaTS_mod itm_mod etcp_mod kernel registration TCP/IP libitm packets itm_queue 11/29/2004 CAMAD'04 by Ibrahim Matta 10

11 Registering with itm_mod Kernel space Applications Kernel modules register directly with itm_mod Each module provides a specific service or implements an application Packets can be dropped, changed or left untouched then re-injected to stack User space applications Register with itm_mod, using libitm itm_queue communicates with itm_mod to receive packets like a regular kernel application itm_queue demultiplexes packets to applications 11/29/2004 CAMAD'04 by Ibrahim Matta 11

12 An Event-driven API A registering application needs to specify functions to handle event: Classify Monitor Process Control 11/29/2004 CAMAD'04 by Ibrahim Matta 12

13 Synchronous Events Use itm_register_hook to register with itm_mod, specifying pointers to functions to be activated on event Current events: packet arrival at different locations of TCP/IP stack: pre-routing, IP-in, IPforward, IP-out, post-routing Application Local-in Local-out Routing Prerouting Forward Postrouting 11/29/2004 CAMAD'04 by Ibrahim Matta 13

14 Asynchronous Events Use itm_register_timer to register with itm_mod, specifying pointers to functions to be activated when timer expires Event is timer-triggered: specify amount of time to wait before event occurs. After handling, can re-register to trigger again at a later time 11/29/2004 CAMAD'04 by Ibrahim Matta 14

15 etcp using itmbench API Packet arriving at source ITM Periodic Control Incoming etcp ACK Classify Monitor update etcp tunnel s goodput Registered client Monitor update etcp tunnel s throughput adjust etcp tunnel s strength Process forward back to client Process encapsulate & send over etcp tunnel 11/29/2004 CAMAD'04 by Ibrahim Matta 15

16 SaTS using itmbench API Packet arriving at source ITM Periodic Control Classify Registered client Monitor update flow s size adjust size threshold Process mark class in packet s header 11/29/2004 CAMAD'04 by Ibrahim Matta 16

17 Food for Thought: Safe Composition Is it safe for an itmbench programmer (e.g. network manager or service provider) to compose API functions or even services? What if a PI controller is replaced by a PID controller? What if multiple bandwidth tunnels are cascaded? What if a SaTS service is cascaded with an etcp tunnel?. etcp controller TCP controller. etcp controller TCP controller SaTS controller. etcp controller TCP controller 11/29/2004 CAMAD'04 by Ibrahim Matta 17

18 Questions? For more information, please check For more WING projects, please check 11/29/2004 CAMAD'04 by Ibrahim Matta 18