2019 term 3 TELE3118: Network Technologies Week 5: Network Layer Control plane: SDN and SNMP Some slides have been taken from: qComputer Networking: A Top Down Approach Featuring the Internet, 7 th edition. Jim Kurose, Keith Ross. Addison-Wesley, 2016. All material copyright 1996-2016. J.F Kurose and K.W. Ross, All Rights Reserved. qComputer Networks, 5 th edition. Andrew S. Tanenbaum. Prentice-Hall, 2010.
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2019 term 3 TELE3118: Network Technologies · 2019-10-15 · Software defined networking (SDN) Network Technologies 5c-2 nInternet network layer: historically has been implemented
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2019 term 3TELE3118: Network Technologies
Week 5: Network Layer Control plane: SDN and SNMP
Some slides have been taken from:qComputer Networking: A Top Down Approach Featuring the Internet, 7th edition. Jim Kurose, Keith Ross. Addison-Wesley, 2016. All material copyright 1996-2016. J.F Kurose and K.W. Ross, All Rights Reserved.qComputer Networks, 5th edition. Andrew S. Tanenbaum. Prentice-Hall, 2010.
Software defined networking (SDN)
5c-2Network Technologies
n Internet network layer: historically has been implemented via distributed, per-router approachq monolithic router contains switching hardware,
runs proprietary implementation of Internet standard protocols (IP, RIP, IS-IS, OSPF, BGP) in proprietary router OS (e.g., Cisco IOS)
q different “middleboxes” for different network layer functions: firewalls, load balancers, NAT boxes, ..
n ~2005: renewed interest in rethinking network control plane
Recall: per-router control plane
5c-3Network Technologies
Individual routing algorithm components in each and every router interact with each other in control plane to compute forwarding tables
RoutingAlgorithm
dataplane
controlplane
4.1 • OVERVIEW OF NETWORK LAYER 309
tables. In this example, a routing algorithm runs in each and every router and both forwarding and routing functions are contained within a router. As we’ll see in Sec-tions 5.3 and 5.4, the routing algorithm function in one router communicates with the routing algorithm function in other routers to compute the values for its forward-ing table. How is this communication performed? By exchanging routing messages containing routing information according to a routing protocol! We’ll cover routing algorithms and protocols in Sections 5.2 through 5.4.
The distinct and different purposes of the forwarding and routing functions can be further illustrated by considering the hypothetical (and unrealistic, but technically feasible) case of a network in which all forwarding tables are configured directly by human network operators physically present at the routers. In this case, no routing protocols would be required! Of course, the human operators would need to interact with each other to ensure that the forwarding tables were configured in such a way that packets reached their intended destinations. It’s also likely that human configu-ration would be more error-prone and much slower to respond to changes in the net-work topology than a routing protocol. We’re thus fortunate that all networks have both a forwarding and a routing function!
Values in arrivingpacket’s header
1
23
Local forwardingtable
header
0100011001111001
1101
3221
output
Control plane
Data plane
Routing algorithm
Figure 4.2 ♦ Routing algorithms determine values in forward tables
M04_KURO4140_07_SE_C04.indd 309 11/02/16 3:14 PM
Recall: logically centralized control plane
5c-4Network Technologies
A distinct (typically remote) controller interacts with local control agents (CAs) in routers to compute forwarding tables
dataplane
controlplane
Remote Controller
CA
CA CA CA CA
Software defined networking (SDN)
5c-5Network Technologies
Why a logically centralized control plane?q easier network management: avoid router
n intent framework: high-level specification of service: what rather than how
n considerable emphasis on distributed core: service reliability, replication performance scaling
SDN: selected challenges
5c-22Network Technologies
n hardening the control plane: dependable, reliable, performance-scalable, secure distributed systemq robustness to failures: leverage strong theory of
reliable distributed system for control planeq dependability, security: “baked in” from day one?
n networks, protocols meeting mission-specific requirementsq e.g., real-time, ultra-reliable, ultra-secure
n Internet-scaling
Network management & SNMP
5c-23Network Technologies
n autonomous systems (aka “network”): 1000s ofinteracting hardware/software components
n other complex systems requiring monitoring, control:q jet airplaneq nuclear power plantq others?
"Network management includes the deployment, integration and coordination of the hardware, software, and human elements to monitor, test, poll, configure, analyze, evaluate, and control the network and element resources to meet the real-time, operational performance, and Quality of Service requirements at a reasonable cost."
Infrastructure for network management
5c-24Network Technologies
managed devicemanaged device
managed device
managed device
definitions:
managed devicescontain managed
objects whose data is gathered into a
Management Information Base
(MIB)
managingentity data
managing entity
agent data
agent data
networkmanagement
protocol
managed device
agent data
agent data
agent data
SNMP protocol
5c-25Network Technologies
Two ways to convey MIB info, commands:
agent data
managed device
managingentity
agent data
managed device
managingentity
trap msgrequest
request/response mode trap mode
response
SNMP protocol: message types
5c-26Network Technologies
GetRequestGetNextRequestGetBulkRequest
manager-to-agent: “get me data”(data instance, next data in list, block of data)
Message type Function
InformRequest manager-to-manager: here’s MIB value
SetRequest manager-to-agent: set MIB value
Response Agent-to-manager: value, response to Request