Lecture 1 - Intro Flashcards
What do traditional communication networks consist of?
- Hosts
- Switches/Routers
Switches compromise of control logic for communications
- Coordination on how to forward packets
What does the modern networking system consist of?
Services Provider
- Server or host of application software
– e.g., Web Server, E-Mail, Data-Base, Cloud Storage and Compute, Video, Audio, …
Users
- Interconnect via access facilities
– E.g., DSL, WiFi, WiMAX, LTE
- Access applications and content
How to specify (what measurements) what is needed within a modern networking ecosystem
Quality of Service (QoS)
- Measurable traffic characteristics
Quality of Experience (QoE)
- Subjective measures that may depend on traffic characteristics
Both need to be negotiated between
- End User
- Service Provider
What’s the difference between QoS and QoE?
QoS does not account for user’s perception of
- Network performance
- Service quality
QoS and QoE are important motivation for network innovations
Quality of Service (QoS) is the well-defined and controllable behavior of a system with respect to quantitative parameters.
Quality of experience (QoE) is a measure of the delight or annoyance of a customer’s experiences with a service (e.g., web browsing, phone call, TV broadcast)
QoE usually depends on QoS (typically linearly)
Define some metrics that may be within QoS.
- Latency
- Latency Jitter
- Throughput
- Rate Jitter
- Packet Loss
- Availability
- Out-of-order-rate
What is the backbone of Network technologies ?
IP
- Provide connectivity to external networks and users
Explain Edge Router/Aggregation Routers
- At the periphery of an IP backbone
- Connectivity to external networks and users
- Examples:
– WAN with MPLS/EVPN/IPSec
– Ethernet LAN
Explain the network structure/layout
Often organized in three tier-hierarchy
- Access network
- Distribution network
- Core network
Tasks
- Local devices can access the network
– E.g. LAN, Campus
- Interconnection of multiple access networks
- Aggregate traffic to the core network
- Interconnection of geographically dispersed distribution networks
Explain Intermediate systems and what they do.
Intermediate Systems (routers/switches) can typically process layer 2-4 information, e.g.:
- MAC header (L2)
- IP header (L3)
- TCP header (L4)
To forward packers/frames/etc. in the network
Comprises three main concepts:
- Routing
- Forwarding
- Queueing/Buffering
What is routing?
Routing (algorithm) - A successive exchange of connectivity information between routers. Each router builds its own routing table based on collected information.
What is Forwarding?
Forwarding (process) - A switch- or router-local process which forwards packets towards the destination using the information given in the local routing table.
What is Queueing?
Queueing:
- Policies to discard/prioritize packets
– E.g. telephony over best effort Internet traffic
What layers are the key of internet success
Under means the above was built on that
Applications
Reliable (or unreliable) transport
Best-effort global packet delivery
Best-effort local packet delivery
Physical transfer of bits
What are the challenges and problems of traditional networking?
Problems of traditional networking infrastructure:
- Limited flexibility
- Increasing Switch/Router complexity
- Separation of networks and applications
- No easy adaptation to new networking protocols
- Hardcoded, monolithic network functions
- cost for unneeded functionality
-…
Adressing these limitations is the key motivation of SDN!
Explain the limited flexibility problem with traditional networking
Switches and routers are closed “black” boxes
Support some standard protocols and maybe proprietary protocols of manufacturer
No easy changes without support of manufacturer
- Network protocols seem to be “hard-coded”
Due to the complexity, even if the switch/router hardware and software is open, adding new network protocols and functions is hard due to complexitty
Explain the increasing Switch/Router complexity problem with traditional networking.
Switches and routers implement a large set of complex protocols
Even redundant protocols like multiple routing protocols
Even protocols that are not needed by the application/customer
Customer pays for hardware resources and functionality that they might not need
- … and still cannot easily implement their own protocols
Name some of the problems within the networking industry (2007)
Features and OS - Routing, management, mobility management, access control, VPNs… Millions of lines of source code, 5400 RFCs, Barrier to entry
Forwarding chip - Billions of gates, Complex, Power Hungry
Closed, vertically integrated, bloated, complex, proprietary
Many complex functions baked into the infrastructure
- OSPF, BGP, multicast, differentiated services, Traffic Engineering, NAT, firewalls, MPLS, redundant layers,…
Little ability for non-telco network operators to get what they want
Functionality defined by standards, put in hardware, deployed on nodes
Explain the separation of network and application problem in traditional networking.
Application view onto the network: “byte pipe” (black box)
Network view onto the application: “load generator” (black box)
Integrated system view would benefit application and network!
- Higher performance of application
- Higher efficiency and utilization of network
Explain the Broadband Network Gateway (BNG) example from slides.
Important Function in Internet Access Scenario
BNG:
- Point to Point Protocol over Ethernet (PPPoE)
- Authentication and Authorization
- Rate Limiting and Traffic Shaping (QoS)
- Packet Forwarding
- Accounting
- One BNG handles many thousands of customers
What are some of the problems with BNG
BNG Problems:
Very specialized key functionality:
- Power hungry and costly
- Expensive
- Complex
What if new functionality is required?
Why not customize the functionality of the BNG and deploy it even on different hardware?
What are the idea and the academic and industry context definition of SDN?
Idea:
Programmable control logic
- Control and Data Plane separation
- Program the entire network (not a single element) (lecture 1 slide 33)
Academic Context definition: Software Defined Networking (SDN) describes the decoupling of Control and Data Plane in Computer Networks. One Control Plane entity serves multiple Data Plane entities (1 to n)
Industry Context: Software Defined Networking (SDN) describes an Architecture, Concept and Methodology that leverages a central Controller to manage, operate, control and monitor Computer Networks. (called Network Softwarization in academia)
What is a control plane in SDN and what are the benefits?
Control plane is a distributed system
Benefits:
- Simplifies implementation of control logic
- Improved control capabilities and flexibility
- Physical controller distribution ensures high availability and scalability
What does the SDN architecture consist of?
SDN architecture consists of
- Control plane (SDN control platform, network services)
- Southbound (e.g. OpenFlow)
- Data Plane (The network infrastructure and connected nodes within)
What does the Management Plane do in SDN?
Handles:
- Configuration
- Monitoring
- Updating
- …
Check slide 40 in lecture 1
What is OpenFlow?
A protocol for remotely controlling the forwarding table of a switch or router (i.e. a Southbound protocol)
It’s an implementation of the SDN idea (one of)
Name benefits of SDN
Leverages increased flexibility
Easy modification of the network logic
- From “hard-coded” logic to exchangeable software
API to “program the network
- Software (application) “defines” the network
High-level programming languages
- For implementation of logic
- To benefit from powerful integrated dev environments
Reduced switch complexity
- Remove control logic from switch and host it on servers
- Preserve same forwarding performance!
– Switch still supports forwarding in hardware
Integrated system: application & network
- Global view onto the system
Reducing the complexity of implementing control logic
- Distribution transparency
What is Network Function Virtualization (NFV)?
Server virtualization
- Masks server resources from server users
— Conserves hardware resources
- Single machine partitioned into multiple, independent servers
- Facilitates load balancing and failure recovery
Can be applied to network functions (this is NFV), e.g.
- Router
- Firewall
- SD-WAN
- …
Need for SDN & NFV:
- How to switch packets between VMs?
Logic for switch, router, firewall and IDS/IPS are running on different VMS and OSs, but same machine, they are controlled using a VM monitor (hypervisor)
What is the difference between whitebox and blackbox switches?
A switch consists of:
- A normal server (CPU, RAM, SSD)
- Normal Network Interface card
- A pecial purpose forwarding chip (ASIC)
On the switch is a software:
- Software is proprietary and same vendor - BLACKBOX
- Software can be chosen and installed by the user - WHITEBOX
