Routers Architecture

1
Routers Architecture

• ELG 4183
• Prepared to
• Luis Orozco-Barbosa
• Ph.D. Professor
• By
• Reham Gabr1537395
• Mohamed El Abriki1964565

2
Introduction

• Used for the interconnection of several networks
  that can be different types Ethernet, Token
  ring...
• Route according to the logical addresses (ex IP)
  and not according to the physical addresses (ex
  MAC (Medium Access Control)).
• A router is multi - protocols (network) IP, IPX,
  AppleTalk, etc..

3

• Cover layers 1 to 3 of the OSI model.

4

• Routers possess a connection on each of networks
  
• The router R interconnects networks A and B.
• The role of the R router is to transfer on the B
  network, packets circulating on the network A and
  intended to the B network and vice versa.

Network B
Network A
Router
5
(No Transcript)
6
Router Components

• Memory
• Interfaces and configuration

RAM
NVRAM
Flash
ROM

• IOS
• Programs
• Tables and Tampon
• Active config file
• EXEC

• Startup Diagnostic
• Bootstrap program

• IOS

• config file
• Startup-config

7
Addressing Mode

• Network layer
• Protocols the most used within the LAN
• IP (Internet Protocol) used as well in
  Intranet that in Extranet or Internet (under
  Windows or under Unix)
• IPX (INTERNETWORK PACKET EXCHANGE) essentially
  used by NetWare of Novel
• Hierarchical addressing mode a relation exists
  between addresses neighboring equipments

8
IP Classes
9
Address Resolution Protocols

• Link Problem between the addresses in network
  and link
• Inexistent under IPX because the MAC address is
  contained in the IPX address of all nodes
• Primordial under IP because there is no relations
  exists between the IP addresses and MAC of an
  equipment
• ARP protocol (Address Resolution Protocol) to
  make the relation between an address known IP and
  a MAC address to determine.
• RARP protocol (Reverts Address Resolution
  Protocol) permits to a station to determine to
  the starting its IP address from its MAC address
  (the IP address is searched for on a server of
  RARP addresses)

10
ARP Principle

• All equipment possesses an ARP table where it
  preserves the links between MAC addresses and all
  IP equipments already consulted
• This ARP table is constructed automatically when
  one MAC address of an equipment recipient is
  unknown

11
Routers Architecture

• Current Internet routers are often implemented
  with a monolithic approach.
• The kernel contains a centralized protocol stack
  that is difficult to maintain.
• Nevertheless, new protocols or versions of
  existing protocols are being introduced all the
  time.

12
Problems

• Kernels with a centralized protocol stack must be
  recompiled, relinked, and rebooted, causing a
  disruption of service
• Monolithic implementations do not allow easy
  association between flows and stack modules that
  are supposed to act on them

13
Problems continued

• Coupling the various protocols in a unique stack
  is in contrast with the traditional layered view
  of networking subsystems.
• The core subsystems tend to be stable over time,
  therefore modifying upper layers should be easier.

14
A Possible Solution (EISR)

• EISR stands for Extended Integrated Services
  Router.
• Its a new architecture based on dynamically
  loadable modules that implement protocols (or
  portion of it) and that can be bound to specific
  flows to provide support
• Better support for network management
  applications such as monitoring and statistics
  gathering.

15
Generic Router Architecture
input interface
output interface
Inter- connection Medium (Backplane)
RI
R0
B
C
C
16
Three Router Architectures

• Output queued
• Input queued
• Combined Input-Output queued

17
Generic Architecture of a High Speed Router Today

• Combined Input-Output Queued Architecture
• Input/output speedup lt 2
• Input interface
• Perform packet forwarding (and classification)
• Output interface
• Perform packet (classification and) scheduling
• Backplane
• Point-to-point (switched) bus speedup N
• Schedule packet transfer from input to output

18
Router Architecture
19
input interface
output interfaces
1
Backplane
Data out
15
Data in
Set scheduling (QoS) state
forward engines
Network processor
Control data (e.g., routing)
20
Router Architecture Data Plane

• Line cards
• Input processing can handle input links up to
  2.4 Gbps (3.3 Gbps including overhead)
• Output processing use a 52 MHz FPGA implements
  QoS
• Forward engine
• 415-MHz DEC Alpha 21164 processor, three level
  cache to store recent routes
• Up to 12,000 routes in second level cache (96
  kB) 95 hit rate
• Entire routing table in tertiary cache (16 MB
  divided in two banks)

21
Router Architecture Control Plane

• Network processor 233-MHz 21064 Alpha running
  NetBSD 1.1
• Update routing
• Manage link status
• Implement reservation
• Backplane Allocator implemented by an FPGA
• Schedule transfers between input/output interfaces

22
Filter Table Implementation
23
conclusion

• It is feasible to implement IP routers at very
  high speeds
• Programmable routers
• Simple interface
• Data plane routers
• Performance (3 Mpps)
• Fast packet classification
• Robustness
• Static scheduling

24
conclusion

• We presented an extensible and modular software
• architecture for high-performance extended
  integrated
• services routers. This architecture allows code
  modules called plugins to be dynamically loaded
  into the kernel

25
References

• http//cs-www.bu.edu/faculty/matta/Teaching/cs835/
  S00/Slides/dario/PaperHTML/slide0.html
• http//www.tik.ee.ethz.ch/dan/papers/rt_plugins_s
  igcomm98.pdf
• http//www.cs.princeton.edu/nsg/papers/hotos99.pdf
  
• http//www.cs.umd.edu/hollings/papers/lanman99.Pd
  f
• S. Walton, A. Hutton, and J. Touch. High-Speed
  Data Paths in Host-Based Routers.
• IEEE Computer, 31(11)4652, November 1998.
• T. Lammle, S. Odom, K. Wallace, CCNP Routing
  63-110 (2000)

26
Questions

• 1. Which of the following subnet will support 50
  IP addresses?
• A. 255.255.255.240
• B. 255.255.255.0
• C. 255.255.255.192
• D. 255.255.255.224
• Answer (B C)
• 255.255.255.240gt(256-240-2 14hosts)
• 255.255.255.0gt(256-0-2 254hosts)
• 255.255.255.192gt(256-192-2 62hosts)
• 255.255.255.224gt(256-224-2 30hosts)
• 2. What is the problem with the IP protocol and
  what was the remade for this problem (explain)?
• Answer slide 9
• 3. What are the problems facing Internet routers?
• 4. Provide a possible solution for the internet
  router problems.
• 5. What are the three types of router
  architecture?