What might be difference between sslvpn and site-site vpn . Which one among two is secure and it's significance
Those two have nothing to do with each other.
Site-to-site refers to what you are connecting. In this case, you are connecting two networks. The opposite of site-to-site would be "mobile access" or sometimes called "road warrior": connecting a single device to a network.
It doesn't make sense to talk about security, because this simply talks about what is at the two ends of the VPN.
SSL VPN refers to how you are connecting, i.e. the technology used for implementing the VPN. Or, more precisely, it refers to an entire family of technologies for implementing VPNs. The only thing these have in common is that they somehow, in some way, shape, or form, use SSL somewhere in their protocol. (Actually, one would hope they use TLS and not SSL.) They range from VPNs literally using HTTPS in the browser to tunnel only web traffic to something like OpenVPN, which merely uses the building blocks provided by TLS to build its own protocol on top. The most popular alternative to SSL VPNs (and an international, open standard) would be IPSec, but there are many, many others, both open and proprietary.
It doesn't make sense to talk about security, because this is such a large and diverse family, and security depends on the precise protocol, implementation, configuration, and deployment.
Actually, the way you phrased it in your question, it doesn't really make sense to talk about "secure" at all. Security is always relative to a threat model. If you don't have defined your threat model, then the term "secure" simply doesn't even make sense.
There's IPsec and there are many VPN protocols based on SSL/TLS. The former is more popular for site-to-site and the latter for mobile access - but you can use them either way, SSL VPN and site-to-site are not at all mutually exclusive.
Since there's no one SSL VPN, you can't say which is more secure. Any decent encryption using AES-128 CGM with SHA128 or better can be considered "secure" (ie. not possible to brute force in several thousand years' time).
Both SSL & IPsec site-site have they own significants coming to SSL vpn vpn provides confidentiality, authentication, integrity of data traversing through It uses both symenttric and asymmetric key algorithms (both private and public key infrastructure).; Digital certificate is used to authenticate SSL VPN connectivity is always intiàted from client-side , it is also referred to as remote access VPN
Comming to site -site vpn is secure tunnel is created between two organisation allowing to share the resource on secure tunnel data is provided with confidence, integrity, authentication
IPsec (internet protocol security) Protocol of ipsec are ESP & AH
Confidential =encrypting packets by encryption algorithms (AES,DES,3DES)
Integrity =sha algorithm
Authentication =preshared key
In IPsec Site -Sites VPN traffic can be initiated bidirectionally Another supporting protocol which is always associated with IPsec is isakmp(internet security Associated key management protocol) Isakmp is purely dedicated to transfer the security key from one device to another Isakmp works on UDP port no :500`
Phase 1 negotiation to exchange pràposal or security associations among peers to create a tunnel(main mode)
Phase 2 negotiation to exchange propoßl or security associations for protecting actually payloads (quick mode)
1) keys are used to create tunnel
2) tunnel is used to exchange keys
3) keys are used to encrypt data