Serval: Software Defined Service-Centric Networking

transcript

Serval: So*ware Defined Service-‐Centric Networking

Jen Rexford Erik Nordstrom, David Shue, Prem Gopalan,

Rob Kiefer, Mat Arye, Steven Ko, Mike Freedman

Princeton University

serval-‐arch.org

Internet of the 1970s

Network designed for accessing a specific host.

IMP 0 h1

h3 PDP-‐11

SDS Sigma SDS 940

UCLA Stanford

*p, telnet

Service-‐Centric Networking

Users agnosWc of actual service instance and its locaWon

Challenges: MulWplicity and Dynamism

• Service with dynamic pool of replicas – Challenge: keep service resoluWon up-‐to-‐date

Replicated Web Service

Load Balancer

Failure Internet

• IaaS with dynamic traffic demand – Challenge: migrate VMs to balance network load

VM MigraWon

Internet

• Mobile end-‐hosts with mulWple interfaces – Challenge: seamless service access across virtual migraWons and physical mobility

Cellular Provider

Enterprise Network

Physical Mobility

MulW-‐ Homing

Transit Provider

SupporWng Modern Services

• Defining “the right” abstracWons – Service naming

– Service-‐level events – Common APIs

• SeparaWng control and data – Programmability through a well-‐defined data plane – Policy/control through a flexible control plane

Service-‐Centric AbstracWons

• Service = group of processes with same funcWonality – Have: IP address + port number – Problems: Slow DNS failover due to caching, inefficient and costly stateful load balancers with fate sharing

– Want: Service names with a group abstracWon that hide composiWon and locaWon

• Flow = dynamic service communicaWon context – Have: Five-‐tuple, bound to interface and locaWon – Problems: ConnecWons break when addresses change – Want: Flow names decoupled from locaWon and underlying communicaWon interface

A Clean Role SeparaWon in the Stack

• Naming the right things at the right level – What you access (serviceID), over which flows (flowIDs), and at which service instance (IP address)

TCP/IP Serval

Transport demux (IP + port)

Network forward (IP)

forward (IP)

ApplicaWon bind (IP + port) bind (serviceID)

Service Access

demux ( ) serviceID flowID

Service Names (ServiceID)

• Different granulariWes of services – EnWre distributed Web service – Replicated parWWon in back-‐end storage – Set of peers distribuWng a common file

• ServiceIDs allocated in blocks – Ensures global uniqueness – Enables prefix-‐based aggregaWon

• ServiceID carried in network packets – Service-‐level rouWng – Late-‐binding to a service instance

AcWve Sockets

• ApplicaWons should operate on service names

connect(fd, serviceID) bind(fd, serviceID) listen(fd)

Network stack must resolve service to instance for client

Network stack must adver6se service for server

SeparaWng Control and Data

Kernel Network Stack

ApplicaWon Socket

Service Control API

ServiceID Ac;on Sock/Addr

Service Table

bind(X) close() Control-‐Plane Protocol

• Service controller • DNS or other database • OpenFlow controller

Dest Address Next Hop

IP Forwarding Table

(un)register X

Data Plane: The Service Table

ServiceID Ac;on Rule State

Prefix A FORWARD Send to addr A1

Prefix B FORWARD Send to [A2, A3, A4]

Prefix C DEMUX Send to listening sock s

Prefix D DELAY Queue and noWfy service

controller

Prefix E DROP

* FORWARD Send to A5

The Service Table (SIB)

controller

Prefix E DROP

controller

Prefix E DROP

controller

Prefix E DROP

controller

Prefix E DROP

Ad hoc Service Discovery

* FORWARD 192.168.1.255

connect(X) 2

* X a 1 SRC

DST SYN

a 1 b 3 SRC

DST SYN-ACK

a 1 c 4 SRC

DST SYN-ACK

Service-‐Level Forwarding

Kernel Network Stack

FlowID Socket

Flow Table

ServiceID Ac;on Sock/Addr

Service Table

Dest Address Next Hop

IP Forwarding Table

Service-‐level Forwarding

Load Balancing Example

Service Access

X d,e * a

Transport

e X a 1

b X a 1 SRC

a 1 e 2 SRC

e X a 1

Transport

FlowID Socket

Flow Table Service Access

Network a1 a2

flowID fC2

IP interfaces

Socket s

flowID fC1

Flow demux’d by unique local flowID, not “5 tuple”

ApplicaWon

ConnecWons with MulWple Flows

MigraWon and MulWpath

sC sS fS1 fC1

fS2 fC2

Host C Host S

Local flowID

Local Interface

Remote Interface

fC1 a1 a3

fC2 a2 a4

Socket Descriptor

Remote ServiceID Cntrl Seq # Local

flowIDs Remote interfaces

SC X seqC fC1, fC2 a3, a4

sC sS fS1 fC1

fS2 fC2

Host C Host S

Socket State

Local flowID

Local Interface

Remote Interface

fC1 a1 a3

fC2 a2 a4

Socket Descriptor

Remote ServiceID Cntrl Seq # Local

flowIDs Remote interfaces

SC X seqC fC1, fC2 a3, a4

sC sS fS2

fS1 fC1

Host C Host S

Socket State

Prototype

• End-‐host network stack – Linux kernel module

– BSD sockets with AF_SERVAL protocol family – AF_INET sockets can be accessed simultaneously

• Legacy middleboxes / NATs handled via encap.

• Translator for incremental deployment – Unmodified apps and end-‐hosts – Serval apps with unmodified services

CompeWWve Performance

ApplicaWons are Easy to Port

Example ApplicaWons

• Server replicas – MulWple Mongoose servers

– Balancing load over live server instances

• Key-‐value store parWWon – MulWple Memcached servers

– RouWng requests to parWWons based on the key

• MigraWng flows – Load balancing across network interface cards – MigraWng virtual machines across layer-‐3 networks

Making Service Management Easier

Controller

Managing Switches and Services

• Switch and service state similar – FIB: <layer 2-‐3 mask | ACTION | STATE> – SIB: <service prefix | ACTION | STATE>

• So*ware Defined Networking – OpenFlow focuses on layer-‐2/3 – Serval extends to hosts, services

• Read events and write rules – With FIB: packets, topology changes, flow counters – With SIB: host/interface changes, service instance changes, connecWon/host/service staWsWcs

Controller

Switches

Ongoing Research

• SDN to the edges – Joint end-‐host and switch control

• So*ware-‐defined service resoluWon – Leveraging legacy systems like DNS and rouWng – Ad hoc, local service discovery

• So*ware-‐defined path selecWon – MulWpath and interface migraWon in datacenter – Interface selecWon and migraWon on mobile devices

serval-‐arch.org

Papers, demos, source code (GPL) online

Serval: Software Defined Service-Centric Networking

Technology