ip switching and gigabit routers
DESCRIPTION
IP Switching and Gigabit Routers. Shlomi Malki Nachman Cohen. Topics. Motivation. Gigabit Routers. IP Switching: flow classification. implementation. GSMP/IFMP. Conclusion. Gigabit Routers. Multigigabit Routers. IP/ATM. Cell Switch Router (CSR). IP Switching. NetStart GigaRouter. - PowerPoint PPT PresentationTRANSCRIPT
Jump to first page
IP Switching and
Gigabit Routers
Shlomi Malki
Nachman Cohen
Jump to first page
2
Topics
Motivation. Gigabit Routers. IP Switching:
flow classification. implementation. GSMP/IFMP.
Conclusion.
Jump to first page
3
Jump to first page
4
Jump to first page
5
Jump to first page
6
Gigabit Routers
Multigigabit Routers. IP/ATM. Cell Switch Router (CSR). IP Switching. NetStart GigaRouter.
Jump to first page
7
Getting Up to gigabitRouter
Average packet size on internet is 2000 bits.
Therefore must forward 500 Kpps per Gbps of traffic.
Replace shared bus by switch fabric. Separate processor performs routing
function and scales with number of peers. Not with bandwidth.
Increase forwarding performance with multiple parallel forwarding engines.
Jump to first page
8
Jump to first page
9
Gigabit Router Components
Line Card Contains the physical layer
components. Switch Fabric
Used to interconnect the various components of the gigabit router.
Jump to first page
10
Forwarding Engine Inspects packets headers. Determines to which outgoing
line card they should be sent. Rewrites the header.
Network Processor Runs the routing protocols. Compute the routing table. Handle network management.
Gigabit Router Components (1)
Jump to first page
11
ATM Overview
CELL Vs PACKET. Segmentation & Reassemble. Connection Oriented. Virtual Channel, VCI. Virtual Path, VPI. Label Swapping.
Jump to first page
12
Switch Fabric
Offers much higher aggregate capacity then the conventional backplane bus.
Implementation: crossbar. ATM.
Jump to first page
13
Switch Fabric (1)
ATM advantage: Standard H/W. QoS. Multicast.
ATM disadvantage: Cell oriented. Connection oriented.
Jump to first page
14
Forwarding Engine
Location within the router: Physically separate component. Integrated with either the line card
or the network processor. At IP Switching most data need no
forwarding engine interference. Whereas routers always requires at least one forwarding engine.
Jump to first page
15
Design of the Forwarding Engine
As we already saw we must forward 500 kpps per Gbps of traffic.
Two approaches to achieve this rate: the silicon forwarding engine. High speed general purpose
processor with destination address caching.
Jump to first page
16
Silicon Design Design
Silicon hardware. Memory
16 byte for each IPv4 route table entry. 250,000 routers. TOTAL: 4 Mbytes.
Forwarding capability memory accesses per route = 1+logN. 10 ns SRAM. 200 ns for full lookup. TOTAL: 5 Mpps. ( enough for 10 Gbps )
Jump to first page
17
Processor with caching Design
Design A 415 MHz general purpose processor
with internal cache. Internal cache: least recently used of
9000 IPv4 destination address. Memory
Additional external memory of 8 Mbytes (holds the complete routing table).
Forwarding capability 11 Mpps - all requests are at cache. Multicast - handle by the full routing table.
Jump to first page
18
Design of the Forwarding Engine
Silicon Design Processor with caching Design
Design Silicon hardwareA 415 MHz general purposeprocessor with internal cache
Memory 4 MBAdditional 8 MB (for a completerouting table of several hundredthousand routes)Forwarding
Capability5 Mpps on average 10Gbps of traffic
11 Mpps if all the requesteddestinations in the cache
AdvantageMaintains itsmaximum forwardingrate regardless past
Maintains its full forwarding rate ifat least 60% chance the requiredstination address has been seen in
Disadvantage Fixed SolutionDebate regarding the use of caching(locality).
Jump to first page
19
Forwarding engine - summarize Sufficient to offer a simple, best-
effort packets forwarding. Additional functionality required of
the next generation of routers (multicast, QoS differentiation, firewall filtering, etc.)
Needs to base the routing decision on more fields in the packets header.
Jump to first page
20
IP Switching
Can used any higher level IP functionality.
Uses the concept of a flow (a sequence of packets that are treated identically by possibly complex routing function).
Uses an ATM switch as the switch fabric.
Jump to first page
21
Jump to first page
22
ATM as Switch Fabric
The 3 approaches that uses ATM as Switch Fabric are: IP/ATM. Cell Switch Router (CSR). IP Switching.
Jump to first page
23
ATM as Switch Fabric Incoming flows are mapped onto
ATM VC’s. The IP Switch uses a protocol
IFMP (RFC1953) to propagate the mapping between flow and VCI.
IP/ATM uses a pool of pre-established PVC’s.
CSR uses RSVP protocol (RFC1577)to propagate the mapping between flows and VCI’s.
Jump to first page
24
Flow Classification Flow classification operation is to
select those flows that are to be switched in the ATM switch and those that should be forwarded in the forwarding engine.
Long duration flows - ATM switch. Multicast - ATM switch. Short duration flows - Forwarding
engine.
Jump to first page
25
Flow Classification (1)
IP Switch Controller
Port 0Port 1
Port C
IP Switch Controller
Port 0Port 1
Port C
Jump to first page
26
Flow Classification (2) For the flows selected for
switching, a VC must be established.
IP Switching requires a protocol to distribute the association of flow and VCI label.
The task of cache lookup and packet labeling is propagated upstream to the edge of the network.
Jump to first page
27
Jump to first page
28
Flow Classification - summery IP switch provides high speed
routing by low level switching of flows.
It defines protocol to indicate these flows.
All flows are classified. The forwarding engine is optimized
for flow classification and for forwarding uncached packets.
Jump to first page
29
Jump to first page
30
Forwarding by the IP Switch
Default
IP SwitchController
Default
IP Switch
IP SwitchController
Default
IP Switch
Upstreamdirection
Downstreamdirection
Source Destination
Jump to first page
31
IP Switch Controller
Forwarding by the IP Switch
Default
Port 0Port 1
Default
Upstreamdirection
Downstreamdirection
IFMP Redirect(Flow ID,VPI/VCI=A,lifetime)
VPI/VCI=A
Port Cz
Jump to first page
32
IP Switch Controller
Forwarding by the IP Switch
Port 0Port 1
Default
Upstreamdirection
Downstreamdirection
IFMP Redirect(Flow ID,VPI/VCI=A,lifetime)
VPI/VCI=A
Port C
Default
VPI/VCI=B
IFMP Redirect(Flow ID,VPI/VCI=B,lifetime)
Jump to first page
33
General Switch Management Protocol (GSMP)
Simple master-slave protocol. Switch controller - master. ATM switch - slave.
Unreliable massage transport is assumed between controller and switch for speed and simplicity.
GSMP runs on a single well known virtual channel (VPI 0,VCI 15).
Jump to first page
34
GSMP (1)
The most frequent messages (connection management) are small enough to be a single cell.
Ver Type Result Code
Transaction Identifier
GSMP Message Body
Pad (0-47 octets)
GSMP Message Format
Jump to first page
35
GSMP (2) An adjacency protocol is used to:
Synchronize state across the control link.
Discover the identity of the entity of the far end of the link.
Detect when the far end is changed.
No GSMP massages may be sent across the link until adjacency has been established.
Jump to first page
36
GSMP (3)
GSMP has five type of massages: Configuration. Connection management. Port management. Statistics. Events.
Jump to first page
37
Ipsilon Flow Management Protocol (IFMP) Runs on a point to point link
between two IP switches. The purpose of IFMP is to inform
the transmitting end of a link of the VCI that should be associated with a particular IP flow.
The VCI is selected by the receiving end of the link.
Jump to first page
38
IFMP (1) Two flow types has been defined:
port-pair flow (type 1) - source IP address,destination IP address,source port number,destination port number.
Host-pair flow (type 2) - source IP address,destination IP address.
An IFMP redirect message is sent upstream to inform the transmitter of the association between flow and VCI.
Jump to first page
39
IFMP (2)
Ver IHL TOS TTL
Source IP Address
Protocol
Destination IP Address
Source Port Destination Port
Flow type 1 - Identifier
Ver IHL Rsrvd TTL
Source IP Address
Rsrvd
Destination IP Address
Flow type 2 - identifier
IFMP Redirect MSG
Flow Type
Label
Flow Identifier
Flow ID Lifetime
Jump to first page
40
IFMP (3) A lifetime field specified the length
of time for witch this association of flow and VCI is valid.
The flow redirection must be refreshed.
Flow labeling process occurs independently an concurrently on each link.
The flow classification policy is consistent within an administrative domain.
Jump to first page
41
IFMP (4)
When upstream and downstream links are both labeled for a given flow, that flow is switched directly trough the ATM switch.
When an IP switch accepts a redirection messages it also change the encapsulation.
It allows an IP switch to act as a simple based firewall.
Jump to first page
42
Conclusion
The IP switch is an alternative architecture to the gigabit router.
It uses low level switching of flows. It include a cooperative protocols. Link by link basis decision. All flows are classified. It allows to support multicast, QoS,
Simple firewall filtering.