Juniper J-4350-JB-SC Datasheet download pdf (Page 4)

Session-Based Forwarding Without the

Performance Hit

In order to optimize the throughput and latency of the combined

router and firewall, Junos OS implements session-based

forwarding, an innovation that combines the session state

information of a traditional firewall and the next-hop forwarding

of a classic router into a single operation. With Junos OS, a

session that is permitted by the forwarding policy is added to

the forwarding table along with a pointer to the next-hop route.

Established sessions have a single table lookup to verify that the

session has been permitted and to find the next hop. This efficient

algorithm improves throughput and lowers latency for session

traffic when compared with a classic router that performs multiple

table lookups to verify session information and then to find a next-

hop route.

Figure 3 shows the session-based forwarding algorithm. When a

new session is established, the session-based architecture within

Junos OS verifies that the session is allowed by the forwarding

policies. If the session is allowed, Junos OS will look up the next-

hop route in the routing table. It then inserts the session and the

next-hop route into the session and forwarding table and forwards

the packet. Subsequent packets for the established session

require a single table lookup in the session and forwarding table,

and are forwarded to the egress interface.

Figure 3: Session-based forwarding algorithm

Figure 4: The distributed enterprise

Security Policy Evaluation

and Next-Hop Lookup

Forwarding for

Permitted Trac

Ingress

Interface

Session Initial

Packet Processing

Table

Update

Disallowed by

Policy: Dropped

Egress

Interface

Session and

Forwarding Table

PSTN

Service Provider

SIP Soswitch

Service Provider

SIP Soswitch

PSTN

SRX210

SRX240

POPPOPPOP

Clear channel T-1

Data (B8ZS)

Channelized T-1

Voice (AMI)

PBX

EX4200 EX4200

LARGE OFFICE

HEAD QUARTERS BRANCH BRANCH

EX4200/EX2200 EX3200/EX2200

Fax Fax

EX3200/EX2200

FIXED MOBILE SITE

(Mobile – 3G)

SMALL OFFICE

Cellular

Wireless

DSL

SRX100

Mobile

SRX210

INTERNET

SRX650

SRX240

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Juniper J-4350-JB-SC Datasheet Page 4

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