washington washington university in st louis [email protected] endsystem support for network...

WashingtonWASHINGTON UNIVERSITY IN ST LOUIS

[email protected]

Endsystem Support for Network Virtualization

Fred Kuhns

2WashingtonWASHINGTON UNIVERSITY IN ST LOUIS

Fred Kuhns - 04/20/23

Overview• Network Diversification:

– Virtual network (vNet): distinct vNets coexist within a common physical network– Diversification layer: common substrate to share physical resources and provide isolation– vNet is composed of one or more virtual routers (VR) interconnected by virtual links. Virtual routers

and links are direct corollaries to their physical counterparts … Network resources are virtualized.– An end-system implements vNet protocols and provides connectivity services within a virtualized

network protocol environment (virtual end-system). The virtual end-system provides mechanisms for protocol implementation, resource control and isolation.

• Diversification layer provides two levels of abstraction (i.e. two core services):– Substrate: encapsulate existing layer 1 and layer 2 technologies and provide a single, consistent

framework for implementing virtualized links and routers.substrate link: abstraction to provide similar behavior as a point-to-point connection between communicating end points. Provides isolation services to different virtual networks using a common substrate link.substrate router: A physical device which forwards network traffic based on its vNet membership. Provides sharing and isolation services to disparate vNets and hosts virtual routers.

– Virtual: framework providing a simple model and set of interfaces for implementing virtual networks. The model defines virtual routers, end-systems and links. The goal is for virtual inks to and routers to behave similar to their physical counterparts.virtual link: simulates the behavior of a dedicted point-to-point link interconnecting virtual end points (virtual routers and/or virtual end systems). A virtual link is implemented by one or more substrate links. virtual router: implements a particular vNet’s routing logic. The underlying substrate router provides the necessary isolation and resource management functions.



vNet Discussion• Develop examples/scenarios

– intranet (no routing) use existing model

– internet (routing) use diversified networking model

– use Ethernet and virtualized IP as running example

• Model: Simple– network devices interconnected through simplex, point-to-point links.

– common link layer protocol used for delivering packetized data to neighbor (not end-to-end but hop to hop)

• Achieving this model– context: shared heterogeneous physical network, links and packet

switches (aka packet routers)

– objectives: • partition physical resources into virtual links and routers

• isolation mechanisms for virtualized resources

• bind virtualized resources to network instances



Context: Network Diversification (vNets)

substrate router

virtual router

substrate link

virtual link

virtual end-system



Simulates Star Topology for Substrate Links

…

switched LAN

VLANX1

Internetworking over a diversified networkSubstrate function with Ethernet: • Substrate links: use VLANs to provide the equivalent

of a virtualized “wire” connecting an endsystem to a specific substrate router.

• Sharing and Isolation: - All vNet traffic use assigned VLANs- Use priority queuing (802.1P/Q)- All intranet traffic uses lower priority queues.

• Resource management:- LAN: Use admission control (static or dynamic) to

provide bandwidth guarantees to vNet traffic.- End system: Substrate layer on end-system enforce

per VLAN and per vNet bandwidth constraints• Virtual links: In this simple example there is exactly

one virtual link for each substrate link.

• Each host to substrate router connection is assigned a distinct VLAN. So N hosts implies N VLANs on Ethernet.

• Alternative is to define one VLAN tree for each protocol suite (i.e. vnet).

VLANX2 VLANXN

vNetX

VR1



vNetX

VR1

Traffic isolation with priority aware substrate

Ethernet Hubwith High and LowPriority TX queues

vNet traffic to Highotherwise Low

…

HighLow

HighLow

HighLow HighLow

vNet traffic (internet)

Local traffic (intranet)

Local control/management;Legacy internet traffic

all vNet traffic



Substrate Link as a VLAN Tree

…

VLANX

ethernet switched LAN

Internetworking over a diversified networkSubstrate function with Ethernet: • Substrate links: The VLAN creates a tree

interconnecting all end-systems to the substrate router. Substrate end-point then uses the VLAN tag and source/destination address to realize the logical point-to-point substrate link.

• Sharing and Isolation: - no change from substrate star topology. The only

difference is the shared VLAN domain. Scheme provides traffic isolation.

• Resource management:- Same

• Virtual links: Same.



Multiple Substrate Links

VLANdgram

VLANmed

VLANhigh


…

Internetworking over a diversified networkSubstrate function with Ethernet: • Substrate links: Three VLAN trees are used for all

virtual net traffic to/from a substrate router: - Low priority: default for best-effort traffic- Medium priority for virtual nets with soft

performance requirements (average bandwidth)- High priority for isochronous or low-delay,

interactive applications• Sharing and Isolation: See above.• Resource management: See above• Virtual links: Same.



Multiple vNets per Host

…

VLAN1 VLAN2 VLAN3

VLI VLI VLI

The full model:• Substrate link: connects end-system to substrate router.

Virtualization of a physical cable or wire. A packet enters one end, exists the other and is opaque within.

- Simplex or Duplex?• Substrate interface: end-system abstraction

- Ethernet: <interface, VLAN, dst_addr>- tunnel: MPLS, IP, IPsec, L2TPv3, GRE, AToM- Layer 2: ATM, others?

• Virtual link: Logical interconnection (virtual wire) of adjacent vNet nodes.

- Point-to-point, Simplex or Duplex?• Virtual interface: end-system abstraction representing

one end of a virtual link. Substrate defines mechanism for multiplexing onto common substrate link. For example a virtual link identifier (VLI) in a substrate header

- Simplex or Duplex?

VLAN tag and dst addridentify substraterouter. VLI tagused to router pkt

ether addr/vlan

ether addr/vlan

ether addr/vlan

ethernet LAN

substrate interface

virtual interface

substrate interfaces

virtual interface

VR1

VLIVLI

VR1



Multiple next hop VRs

VLANA1

vNetX

VR1

vNetX

VR2

vNetX

VR3

VLANA2 VLANA3

Host Amember of

vNetX and vNetY


Multiple Next Hop Virtual Routers:• Substrate link: per end-system, substrate router pair.• Substrate interface: three substrate interfaces:

SI1 = <eth0, VLANXA1, enetAddrSR1>SI2 = <eth0, VLANXA2, enetAddrSR2>SI3 = <eth0, VLANXA3, enetAddrSR3>

• Virtual link: Logical point-to-point connection between virtual end-system and access virtual router. Since we model a point-to-point link there is no need for link addresses.

• Virtual interface: Representation of virtual link on the end-system. The substrate assigns a per substrate link, virtual link identifier (VLI) for each virtual link.

VI1 = <SI1, VLI1>VI2 = <SI1, VLI2>VI3 = <SI2, VLI1>VI4 = <SI3, VLI1>

enetAddrSR1

enetAddrSR2 enetAddrSR3enetAddrA

substraterouter 1

substraterouter 2

substraterouter 3

vNetY

VR1

VLI1 VLI2

VLI1 VLI1



Substrate Interface:Directly connected: destination IP address + ARP = enet addrGateway: (Gateway’s IP + ARP = enet addr) + VLAN

Virtual Interface:Directly connected: Not used, model only for internetworkingGateway: VLI assigned by substrate. How is this integrated into the current ARP/route interface?

VLI VLI

IP

TCP/IP as an Example Protocol

…

destination

prefix

gateway

(router address)

virtual interface

substrate

interfacell_info

192.168.12.0/24 0.0.0.0 eth0 ARP

*

(default)192.168.12.254

vint0

(eth0,VLAN,ethDst)VLI

vNet Protocl = IP

eth0standard ethernet

Interface

ethernet device

VLANX

direct connect

ethernet LAN

VLAN

VLI

Substrate RouterSR1

ethernetdest. addr

vint0

VLANX

eth0

vNetframework



Using Tunnels for the substrate layer• Need to look into the various tunneling approaches/protocols.

How can we leverage these?– MPLS and MPLS VPNs

– Generic Routing Encapsulation (GRE): RFC 2784

– Point-to-point tunneling protocol (PPTP)

– Secure VPN

– Any transport over MPLS (AToM)

– IP tunnel

– IPsec VPNs

– Layer 2 Tunneling Protocol version 3 (L2TPv3)• version3 is a draft standard

• RFC 2661: Layer 2 tunneling protocol

– 802.1Q Tunneling: Cisco 802.1Q-in-Q VLAN Extension Services

• What about MPLS over IP tunnels: what was done there?



OS Kernel Block Diagram

configuration: registers, MMU (TLB, cache, VM) bus and peripheralsSystem Exception handlers

ethernet

Socket Interface

UDP RAW IP

IP routes

TCPnTCP2TCP1 …TCP module

clock handlerprocess accountingschedulingtime management

uarteth0

timer

hardware dependent layer

HW interrupt/Exception

hardware independent layer

scheduler

SW int(AST)callout Q

TCPpoll

tasks

task management

openfiles

FS managementbuffercache

ops

File Interface ops

Device independent I/O

Inte

rru

pt P

roce

ssin

gA

ST

Pro

cess

ing

User Space (Applications)

Hardware

Basic I/O Interface

txqueue rxqueue

TC/AST

qdisc

device driver

OS ISR demux

callback

util



User or kernel Space protocols?• Each has pros and cons

• User space protocols:– easier to implement and debug

– easier to introduce new protocols (not tightly dependent on socket layer knowing about the new protocol)

– easier to isolate and protect protocols and apps from each other (leverage process model)

• kernel level protocols– easier to integrate into existing framework (simplifies support for system

interface functions like select/poll)

– simplifies intra-protocol security and protection (since protocol runs within trusted kernel)

– simplifies (well, more direct) kernel demultiplexing to correct protocol context (endpoint)

– increased efficiency



User Space Protocol Implementation• Uncommon outside of high-performance community, they want

zero-copy and specialized demux keys.• Problems: asynchronous processing, life cycle, authentication and

demultiplexing to endpoints– latency in delivering packets (i.e. acks) to user space– increased overhead in per packet processing before a drop/keep decision is

made– processing received acks– timeouts and retransmissions– establishing connections and security: snooping, masquerading– supporting select and poll– protocols where connection may outlive process (TCP’s TIMED_WAIT)– global routing and address resolution tables– global connection tables

• need to know what other ports are being used (locally)• accepting/rejecting new connections



Assumptions

• Assumptions:– Applications using different VNs (or no VN) will need

to communicate using the various IPC mechanisms

– We want to manage all aspects of Network I/O but not the use of other traditional resources (memory, files etc)

– CPU, memory and interface bandwidth controlled at the virtual net granularity

– intra-VN, implementers should have the mechanisms to support QoS and Security

– simple mechanism for adding new protocols/VNs



User Space Protocols

Chandramohan A. Thekkath , Thu D. Nguyen , Evelyn Moy , Edward D. Lazowska, Implementing network protocols at user level, IEEE/ACM Transactions on Networking (TON), v.1 n.5, p.554-565, Oct. 1993

Chris Maeda, Brian Bershad, Protocol Service Decomposition for High-Performance Networking, Proceedings of the 14th ACM Symposium on Operating Systems Principles. December 1993, pp. 244-255.

• Aled Edwards , Steve Muir, Experiences implementing a high performance TCP in user-space, Proceedings of the conference on Applications, technologies, architectures, and protocols for computer communication, p.196-205, 1995

• Kieran Mansley, Engineering a User-Level TCP for the CLAN Network, Proceedings of the ACM SIGCOMM workshop on Network-I/O convergence: experience, lessons, implications, Pages: 228 – 236, 2003



user-space protocols: Global Issues• Routing: Direct packets to/from correct endpoint/interface

– How is traffic demultiplexed and sent to the correct endpoint/process?• In-kernel filters

– Where are the routing tables and how are they maintained?• route fixed when connection established or located in shared memory

• Control: I use IPv4 as an example– Address resolution protocols/tables? – Other control protocols. For example ICMP, IGRP, others?– Where are the routing protocols implemented?

• Management:– Must manage a protocols namespace (for example, port numbers in IPv4).– Common programming technique, allow protocol instance to select local address part

• specify port = 0 and addr = 0 then implementation will assign correct values– Passive connect model?

• In IPv4 a server listens on a port (host:port:proto) for a connection request. To establish a connection a unique (to the endsystem) port number is assigned and new socket allocated.

– socket-oriented system calls must be supported. On UNIX must support non-blocking I/O with select and poll.

– Connection lifetime may outlast process.• For example TCP TIME_WAIT or simply waiting for a final ack or resending if no ack received.

• Security: we must provide sufficient mechanisms for protocol developers– implementations must be able to guard against masquerading and eavesdropping



User Space: Configurations

• Given these global issues there are two likely configurations:– all traffic passes through common protocol daemon in user

space– control daemon implements basic set of control functions while

user library implements majority of data path functions– prior work has shown the latter approach to be superior.

• Having all traffic pass through a common protocol daemon => at least one extra copy operation (kernel -> daemon -> user process)

• A better solution is for a daemon to insert relatively simple packet filters in kernel for established connections which directs packets to/filters packets from endpoints.



socket layer

connection filters

User-Space: Passive Open

vnetXcontrol daemon:

(namespace, lifecycle, connections)

vnetX: protocol library

application

ethernet

vnet demux

3. insert incoming andoutgoing filters forvnetX connection

1. connectionrequest (in)

4. new connection

0. listen/accept(passive open)

5. data, establishedconnections

compare against connection specific outgoing filter

use VLI to access incoming filters and use to demux to filter set and/or socket.

data copy

2. ack (out)



User-Space: Active Open

socket layer

connection filters




application

ethernet

vnet demux


4. new connection

0. connect

5. data, establishedconnections

compare against connection specific outgoing filter

data copy

1. connectionrequest (out)

2. ack (in)

use VLI to access incoming filters and use to demux to filter set and/or socket.



socket layer

connection filters

User-Space: Datagram (Connectionless)


application

ethernet

vnet demux


2. new connection(local address)

0. open(any)

3. data establishedconnections

compare against “connection” specific outgoing filter

use VLI to access incoming filters and use to demux to socket. In this case only the local part is used.

data copy

daemon fills in local address and binds to socket. No restrictions on destination





socket layer

connection filters

User-Space: Datagram (Connectionless)


application

ethernet

vnet demux


2. new connection(local and remote)

0. open(local and remote addr)

3. data establishedconnections

compare against “connection” specific outgoing filter

use VLI to access incoming filters and use to demux to socket.

data copy

daemon fills in both local and destination addresses. Destination restricted





socket layer

connection filters

User-Space: App exits




application

ethernet

vnet demux

3. remove filters 1. connectionclose (out)

drop

2. ack (in/out)

TCP enters TIME_WAIT after close



Extensible protocol frameworks in the kernel

• Herbert Bos, Bart Samwel, Safe Kernel Programming in the OKE, Proceedings of the fifth IEEE Conference on Open Architectures and Network Programming, June 2002



OKE• Context: For performance reasons it is useful to permit third parties to load optimized

modules into the kernel• Problem: Third party code is untrusted so loading into kernel will compromise system

security and reliability. Could use safe execution environment like java but incurs expensive runtime checks.

• Solution: create set of mechanisms and policies to permit non-root users to safely load untrusted application modules into kernel space with minimal impact on runtime performance.

– Safety: use a trusted compile to enforce policies (constraints). The constraints are designed to ensure the untrusted module will not adversely affect the kernel (core and loadable modules) or unrelated processes.

– User privileges: Vary enforced constraints based on user privileges (customizable language)– Termination: well defined termination boundaries to protect system state– Enforcement: Static and dynamic checks; language extensions– Ease of use: Familiar development environment using Cyclone (type safe, C extension) and

kernel module.• Contribution: definition of safe kernel programming environment that meets competing

needs:– performance– safety– ease of use– hosted in a commodity OS



Considerations

• Identified areas where modules may impact system behavior1. program correctness: language restrictions for safety and

enforce coding conventions

2. Memory access: static and dynamic enforcement of memory access rules

3. Kernel module access: static and dynamic enforcement of kernel module (interface) access restrictions

4. Resource usage: Bounded (deterministic or limited)



Pushing protocols into the Kernel

• Positives:– All the issues associated with user-space protocol simply go

away. Global tables and lifetime of the kernel

– Performance, efficiency, existing code base

– Enhances intra-Protocol security

– Simplifies integration with existing network I/O subsystems and interfaces

• Negatives: – Isolation: More difficult to isolate system from protocol

instances. Inter-protocol isolation difficult.

– Security: Proving trust/security more difficult

– Implementation and debugging more difficult in kernel



Kernel-Space Protocols

…

ethetnet

TCPnTCP2TCP1 …UDP RAW IP

IP routes

TCP

eth device driver

HW interrupt/Exception

HW Interrupt

SW Interrupt

User Space (Applications)

Hardware

openfiles

FS managementbuffercache

opsFile Interface

I/O Interface

vnet Demux

VLAN

Application(s)

vnet Socket I/O Interfacevnet ops

vnet Protostate tables

/dev/protoX/dev/vnet

udp:porttcp:port rawIP…vnet:epvnet:ep

Socket InterfacePF_VNET PF_INET

eth0

route to interface

TCP/IPvnet Protostate tables …

Rework!

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